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    Akselsson, K. Aerosol sampling and samplers matched to PIXE analysis 1984 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
    Vol. 3(1-3), pp. 425-430 
    article URL 
    Abstract: The PIXE method constitutes a tool for fast, reliable multi-elemental analysis of small samples. These properties are very attractive in aerosol sciences and in aerosol monitoring programmes. Thus PIXE allows the use of small samplers which are easy to deploy and could be operated for long periods even at more or less remote sites. For working environment aerosols, samplers with time resolution can be, and in a few cases are, designed for personal continuous sampling in the breathing zone. For both practical and economical reasons, PIXE, in many applications, facilitates the gathering of multi-elemental information about aerosols with more detailed size, site and time resolution when compared with conventional techniques. Conditions for maximum exploitation of the PIXE technique in aerosol research are development of suitable samplers, optimal sampling strategies and adequate analytical procedures taking the unique properties of PIXE into consideration. These developmental tasks require intense interactions between several research and development disciplines. In this paper, the state of the art of samplers matched to the PIXE method is reviewed.
    BibTeX:
    @article{Akselsson,
      author = {Akselsson, K.Roland},
      title = {Aerosol sampling and samplers matched to PIXE analysis},
      journal = {Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms},
      year = {1984},
      volume = {3},
      number = {1-3},
      pages = {425--430},
      url = {http://www.sciencedirect.com/science/article/B6TJN-470VFV9-1GJ/2/62b9c693b46b569fa52b99898e6e99df}
    }
    
    Anderson, T.L., Covert, D.S., Wheeler, J.D., Harris, J.M., Perry, K.D., Trost, B.E., Jaffe, D.J. & Ogren, J.A. Aerosol backscatter fraction and single scattering albedo: Measured values and uncertainties at a coastal station in the Pacific Northwest 1999 J. Geophys. Res.
    Vol. 104(D21), pp. 26793-26807 
    article URL 
    Abstract: Light scattering, hemispheric backscattering, and absorption properties of submicrometer and supermicrometer aerosol particles at low relative humidity and 550 nm wavelength are investigated as a function of air mass category during a 2-month campaign at a midlatitude Pacific coastal station at Cheeka Peak, Washington. The main source of uncertainty in single scattering albedo (ω) measurements, namely, the measurement of light absorption, is addressed by the deployment of three identical absorption photometers and by relying on a recent calibration of this device using direct optical measurements. The absorption photometer measurement is corrected for response to light scattering, and measurements of sea-salt aerosol in this campaign provide a partial validation of this correction. Scattering measurements by nephelometry are also corrected for known instrumental nonidealities. Uncertainties stemming from instrumental noise, drift, calibration, and correction factors are propagated to allow comparisons among air mass categories and with other data sets and, ultimately, to constrain the values of ω and other optical properties used in climate models. Marine aerosol over the midlatitude eastern Pacific is found to be weakly absorbing for the sub-μm component and virtually nonabsorbing for the super-μm component (separated at 1 μm, low-relative humidity, aerodynamic diameter). A distinct increase in sub-μm light extinction (especially absorption) observed during 2 days of sustained marine flow appears to be Asian pollution transported across the Pacific. Low levels of gaseous NOx during this period rule out nearby combustion sources, and low levels of particulate Fe, Al, and Si rule out a significant contribution from mineral dust. Excluding this episode, both scattering and absorption properties for marine sampling conditions are similar to those observed in the clean midlatitude Southern Hemisphere (Cape Grim, Tasmania). In general, continental influence, as indicated by trends over the air mass categories, tends to raise the backscatter ratio and lower ω. Light absorption values compared to previous marine and coastal measurements confirm the range of values found by others and the highly variable nature of this quantity.
    BibTeX:
    @article{Anderson1999,
      author = {Anderson, T. L. and Covert, D. S. and Wheeler, J. D. and Harris, J. M. and Perry, K. D. and Trost, B. E. and Jaffe, D. J. and Ogren, J. A.},
      title = {Aerosol backscatter fraction and single scattering albedo: Measured values and uncertainties at a coastal station in the Pacific Northwest},
      journal = {J. Geophys. Res.},
      publisher = {AGU},
      year = {1999},
      volume = {104},
      number = {D21},
      pages = {26793--26807},
      url = {http://dx.doi.org/10.1029/1999JD900172}
    }
    
    Annegarn, H.J., Cahill, T.A., Sellschop, J.P.F. & Zucchiatti, A. Time sequence particulate sampling and nuclear analysis 1988 Physica Scripta
    Vol. 37(2), pp. 282 
    article URL 
    Abstract: A review is given of a series of time-sequence sampling devices for atmospheric particles. The samplers considered are all designed around the sensitive analytical capabilities of Particle Induced X-ray Emission (PIXE) and other charged particle nuclear techniques. Time-sequence samplers, collecting for subsequent chemical (elemental) analysis, are distinguished from automatic devices giving instantaneous readings (optical devices), and automated samplers, which collect multiple samples on discrete substrates. Time-sequence samplers discussed typically sample from 30 to 200 intervals on a single set of substrates. The versatile interpretive possibilities from the multi-elemental, time- and size resolved data are illustrated with examples from industrial hygiene, mesoscale transport, crustal aerosol and visibility studies. Factors that have limited wide-spread acceptance of these samplers are discussed, and suggestions given for further lines of development.
    BibTeX:
    @article{1402-4896-37-2-016,
      author = {H J Annegarn and T A Cahill and J P F Sellschop and A Zucchiatti},
      title = {Time sequence particulate sampling and nuclear analysis},
      journal = {Physica Scripta},
      year = {1988},
      volume = {37},
      number = {2},
      pages = {282},
      url = {http://stacks.iop.org/1402-4896/37/i=2/a=016}
    }
    
    Bateman, A.P., Nizkorodov, S.A., Laskin, J. & Laskin, A. Time-resolved molecular characterization of limonene/ozone aerosol using high-resolution electrospray ionization mass spectrometry 2009 Phys. Chem. Chem. Phys.
    Vol. 11(36), pp. 7931-7942 
    article URL 
    Abstract: Molecular composition of limonene/O secondary organic aerosol (SOA) was investigated using high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) as a function of reaction time. SOA was generated by ozonation of -limonene in a reaction chamber and sampled at different time intervals using a cascade impactor. The SOA samples were extracted into acetonitrile and analyzed using a HR-ESI-MS instrument with a resolving power of 100 000 (/[capital Delta]). The resulting mass spectra provided detailed information about the extent of oxidation inferred from the O : C ratios, double bond equivalency (DBE) factors, and aromaticity index (AI) values in hundreds of identified individual SOA species. The chemical composition of SOA was approximately the same for all size-fractionated samples studied in this experiment (0.05 to 0.5 [small mu ]m range). The SOA constituents quickly reached an average O : C ratio of 0.43, which grew to 0.46 after one hour of additional oxidation of particles by the excess ozone. The dominant mechanism of oligomerization, inferred from high resolution ESI-MS data, was reaction between Criegee intermediates and stable first-generation products of limonene ozonolysis. Although the SOA composition was dominated by various oxidized aliphatic compounds, a small fraction of products appeared to contain aromatic rings. SOA generation was also studied in the presence of UV radiation and at elevated relative humidity (RH). The presence of UV radiation had a negligible effect on the SOA composition. The presence of water vapor resulted in a slight redistribution of peak intensities in the mass spectrum likely arising from hydration of certain SOA constituents. The data are consistent with fast production of the first-generation SOA constituents, including oligomers, followed by very slow aging processes that have a relatively small effect on the average molecular composition on the timescale of our experiments.
    BibTeX:
    @article{Bateman2009,
      author = {Bateman, Adam P. and Nizkorodov, Sergey A. and Laskin, Julia and Laskin, Alexander},
      title = {Time-resolved molecular characterization of limonene/ozone aerosol using high-resolution electrospray ionization mass spectrometry},
      journal = {Phys. Chem. Chem. Phys.},
      publisher = {The Royal Society of Chemistry},
      year = {2009},
      volume = {11},
      number = {36},
      pages = {7931--7942},
      url = {http://dx.doi.org/10.1039/B905288G}
    }
    
    Bench, G., Grant, P.G., Ueda, D., Cliff, S.S., Perry, K.D. & Cahill, T.A. The Use of STIM and PESA to Measure Profiles of Aerosol Mass and Hydrogen Content, Respectively, across Mylar Rotating Drums Impactor Samples 2002 Aerosol Science and Technology
    Vol. 36(5), pp. 642-651 
    article URL 
    Abstract: A method has been developed for measuring profiles of aerosol mass on thin (480 w g/cm 2 ) Apiezon-L coated Mylar films employed in rotating drum aerosol impactor samplers using the ion beam analysis technique scanning transmission ion microscopy (STIM). The greased Mylar films are excellent impaction substrates and possess excellent uniformity in projected density, making them an ideal substrate for STIM analysis. The uniformity in projected density of a film enables STIM with a 3 MeV proton beam to produce profiles of aerosol mass with an accuracy of better than 90% and a mass sensitivity approaching 10 w g/cm 2 . Further, we have extended proton elastic scattering analysis (PESA) to the same films, achieving measurement of an organic surrogate. Although the films contain ∼ 20 w g/cm 2 hydrogen, the spatial uniformity in film hydrogen content enables PESA with a 3 MeV proton beam to produce profiles of hydrogen arising solely from the aerosols with an accuracy to within - 1 w g/cm 2 and a mass sensitivity of ∼ 1 w g/cm 2 . These measurements when combined with synchrotron-x-ray fluorescence (S-XRF) measurements on the same film allow mass closure, sum of species versus measured mass, a key quality assurance protocol, to be approached. All 3 techniques were applied to very fine and ultra-fine particles collected in Fresno, CA, November, 2000 by slotted DRUM samplers. Temporal resolution in the resulting profiles was h 6 h. The dramatic changes in composition versus size and time, and new types of elemental correlations unseen in PM 2.5 filters, will be major assets in correlating aerosols and health impacts, visibility degradation, and the effects of aerosols on climate.
    BibTeX:
    @article{Bench2002,
      author = {Bench, Graham and Grant, Patrick G. and Ueda, Dawn and Cliff, Steve S. and Perry, Kevin D. and Cahill, Thomas A.},
      title = {The Use of STIM and PESA to Measure Profiles of Aerosol Mass and Hydrogen Content, Respectively, across Mylar Rotating Drums Impactor Samples},
      journal = {Aerosol Science and Technology},
      publisher = {Taylor & Francis},
      year = {2002},
      volume = {36},
      number = {5},
      pages = {642--651},
      url = {http://www.informaworld.com/10.1080/02786820252883874}
    }
    
    Bernardoni, V., Cuccia, E., Calzolai, G., Chiari, M., Lucarelli, F., Massabò, D., Nava, S., Prati, P., Valli, G. & Vecchi, R. ED-XRF set-up for size-segregated aerosol samples analysis 2011 X-Ray Spectrom.
    Vol. 40(2), pp. 79-87 
    article URL 
    Abstract: Abstract The knowledge of size-segregated elemental concentrations in atmospheric particulate matter (PM) gives a useful contribution to the complete chemical characterisation; this information can be obtained by sampling with multi-stage cascade impactors. In this work, samples were collected using a low-pressure 12-stage Small Deposit Impactor and a 13-stage rotating Micro Orifice Uniform Deposit Impactor™. Both impactors collect the aerosol in an inhomogeneous geometry, which needs a special set-up for X-ray analysis. This work aims at setting up an energy dispersive X-ray fluorescence (ED-XRF) spectrometer to analyse quantitatively size-segregated samples obtained by these impactors. The analysis of cascade impactor samples by ED-XRF is not customary; therefore, as additional consistency test some samples were analysed also by particle-induced X-ray emission (PIXE), which is more frequently applied to size-segregated samples characterised by small PM quantities. A very good agreement between ED-XRF and PIXE results was obtained for all the detected elements in samples collected with both impactors. The good inter-comparability proves that our methodology is reliable for analysing size-segregated samples by ED-XRF technique. The advantage of this approach is that ED-XRF is cheaper, easier to use, and more widespread than PIXE, thus promoting an intensive use of multi-stage impactors. Copyright © 2011 John Wiley & Sons, Ltd.
    BibTeX:
    @article{Bernardoni2011,
      author = {Bernardoni, Vera and Cuccia, Eleonora and Calzolai, Giulia and Chiari, Massimo and Lucarelli, Franco and Massabò, Dario and Nava, Silvia and Prati, Paolo and Valli, Gianluigi and Vecchi, Roberta},
      title = {ED-XRF set-up for size-segregated aerosol samples analysis},
      journal = {X-Ray Spectrom.},
      publisher = {John Wiley & Sons, Ltd.},
      year = {2011},
      volume = {40},
      number = {2},
      pages = {79--87},
      url = {http://dx.doi.org/10.1002/xrs.1299}
    }
    
    Braaten, D. & Cahill, T. Size and composition of Asian dust transported to Hawaii 1986 Atmospheric Environment (1967)
    Vol. 20(6), pp. 1105-1109 
    article URL 
    Abstract: The 1981 spring dust episode observed at the Mauna Loa Observatory, Hawaii, was studied by particulate size and elemental composition, strengthening its association with Asian sources and establishing its mass median diameter at 1.0 � 0.3 [mu]m. An average mass loading of 400 ng m-3 was observed during the three peak weeks of the episode (5/12/81-6/2/81) for soil-derived elements (Al, Si, K, Ca, Ti, Mn, Fe plus their oxides). Elemental ratios remained very constant in this period, and closely resembled those previously reported in North China dust storms. The size and concentration of sulfur panicles also remained constant during the dust episode periods, while differing strongly from non-dust episode periods for the 8 months before and after the events.
    BibTeX:
    @article{Braaten1986,
      author = {Braaten, D.A. and Cahill, T.A.},
      title = {Size and composition of Asian dust transported to Hawaii},
      journal = {Atmospheric Environment (1967)},
      year = {1986},
      volume = {20},
      number = {6},
      pages = {1105--1109},
      url = {http://www.sciencedirect.com/science/article/B757C-48CFRTV-GR/2/7b0f33eebf4244e843ed614367b78e6e}
    }
    
    Bukowiecki, N., Gehrig, R., Hill, M., Lienemann, P., Zwicky, C.N., Buchmann, B., Weingartner, E. & Baltensperger, U. Iron, manganese and copper emitted by cargo and passenger trains in Z�rich (Switzerland): Size-segregated mass concentrations in ambient air 2007 Atmospheric Environment
    Vol. 41(4), pp. 878-889 
    article URL 
    Abstract: Particle emissions caused by railway traffic have hardly been investigated in the past, due to their obviously minor influence on air quality compared to automotive traffic. In this study, emissions related to particle abrasion from wheels and tracks were investigated next to a busy railway line in Z�rich (Switzerland), where trains run nearly exclusively with electrical locomotives. Hourly size-segregated aerosol samples (0.1-1, 1-2.5 and 2.5-10�[mu]m) were collected with a rotating drum impactor (RDI) and subsequently analyzed by synchrotron radiation X-ray fluorescence spectrometry (SR-XRF). In this way, hourly elemental mass concentrations were obtained for chromium, manganese, iron and copper, which are the elements most relevant for railway abrasion. Additionally, daily aerosol filters were collected at the same site as well as at a background site for subsequent analysis by gravimetry and wavelength dispersive XRF (WD-XRF). Railway related ambient air concentrations of iron and manganese were calculated for the coarse (2.5-10�[mu]m) and fine (<2.5�[mu]m) particle fraction by means of a Mn/Fe ratio investigation. The comparison to train type and frequency data showed that 75% and 60% of the iron and manganese mass concentrations related to cargo and passenger trains, respectively, were found in the coarse mode. The railway related iron mass concentration normalized by the train frequency ranges between 10 and 100�ng�m-3�h iron in 10�m distance to the tracks, depending on train type. It is estimated that the personal exposure next to a busy railway line above ground is more than a magnitude lower than inside a subway station.
    BibTeX:
    @article{Bukowiecki2007,
      author = {Bukowiecki, Nicolas and Gehrig, Robert and Hill, Matthias and Lienemann, Peter and Zwicky, Christoph N. and Buchmann, Brigitte and Weingartner, Ernest and Baltensperger, Urs},
      title = {Iron, manganese and copper emitted by cargo and passenger trains in Z�rich (Switzerland): Size-segregated mass concentrations in ambient air},
      journal = {Atmospheric Environment},
      year = {2007},
      volume = {41},
      number = {4},
      pages = {878--889},
      url = {http://www.sciencedirect.com/science/article/B6VH3-4M57HFX-1/2/5153049f87d9854e65abf9bb1a2c4d6f}
    }
    
    Bukowiecki, N., Lienemann, P., Hill, M., Figi, R., Richard, A., Furger, M., Rickers, K., Falkenberg, G., Zhao, Y., Cliff, S.S., Prevot, A.S.H., Baltensperger, U., Buchmann, B. & Gehrig, R. Real-World Emission Factors for Antimony and Other Brake Wear Related Trace Elements: Size-Segregated Values for Light and Heavy Duty Vehicles 2009 Environmental Science & Technology
    Vol. 43(21), pp. 8072-8078 
    article URL 
    Abstract: Hourly trace element measurements were performed in an urban street canyon and next to an interurban freeway in Switzerland during more than one month each, deploying a rotating drum impactor (RDI) and subsequent sample analysis by synchrotron radiation X-ray fluorescence spectrometry (SR-XRF). Antimony and other brake wear associated elements were detected in three particle size ranges (2.5−10, 1−2.5, and 0.1−1 μm). The hourly measurements revealed that the effect of resuspended road dust has to be taken into account for the calculation of vehicle emission factors. Individual values for light and heavy duty vehicles were obtained for stop-and-go traffic in the urban street canyon. Mass based brake wear emissions were predominantly found in the coarse particle fraction. For antimony, determined emission factors were 11 ± 7 and 86 ± 42 μg km−1 vehicle−1 for light and heavy duty vehicles, respectively. Antimony emissions along the interurban freeway with free-flowing traffic were significantly lower. Relative patterns for brake wear related elements were very similar for both considered locations. Beside vehicle type specific brake wear emissions, road dust resuspension was found to be a dominant contributor of antimony in the street canyon.
    BibTeX:
    @article{Bukowiecki2009a,
      author = {Bukowiecki, Nicolas and Lienemann, Peter and Hill, Matthias and Figi, Renato and Richard, Agnes and Furger, Markus and Rickers, Karen and Falkenberg, Gerald and Zhao, Yongjing and Cliff, Steven S. and Prevot, Andre S. H. and Baltensperger, Urs and Buchmann, Brigitte and Gehrig, Robert},
      title = {Real-World Emission Factors for Antimony and Other Brake Wear Related Trace Elements: Size-Segregated Values for Light and Heavy Duty Vehicles},
      journal = {Environmental Science & Technology},
      publisher = {American Chemical Society},
      year = {2009},
      volume = {43},
      number = {21},
      pages = {8072--8078},
      url = {http://dx.doi.org/10.1021/es9006096}
    }
    
    Bukowiecki, N., Lienemann, P., Zwicky, C.N., Furger, M., Richard, A., Falkenberg, G., Rickers, K., Grolimund, D., Borca, C., Hill, M., Gehrig, R. & Baltensperger, U. X-ray fluorescence spectrometry for high throughput analysis of atmospheric aerosol samples: The benefits of synchrotron X-rays 2008 Spectrochimica Acta Part B: Atomic Spectroscopy
    Vol. 63(9), pp. 929-938 
    article URL 
    Abstract: The determination of trace element mass concentrations in ambient air with a time resolution higher than one day represents an urgent need in atmospheric research. It involves the application of a specific technique both for the aerosol sampling and the subsequent analysis of the collected particles. Beside the intrinsic sensitivity of the analytical method, the sampling interval and thus the quantity of collected material that is available for subsequent analysis is a major factor driving the overall trace element detection power. This is demonstrated for synchrotron radiation X-ray fluorescence spectrometry (SR-XRF) of aerosol samples collected with a rotating drum impactor (RDI) in hourly intervals and three particle size ranges. The total aerosol mass on the 1-h samples is in the range of 10��g. An experimental detection of the nanogram amounts of trace elements with the help of synchrotron X-rays was only achievable by the design of a fit-for-purpose sample holder system, which considered the boundary conditions both from particle sampling and analysis. A 6-�m polypropylene substrate film has evolved as substrate of choice, due to its practical applicability during sampling and its suitable spectroscopic behavior. In contrast to monochromatic excitation conditions, the application of a [`]white' beam led to a better spectral signal-to-background ratio. Despite the low sample mass, a counting time of less than 30�s per 1-h aerosol sample led to sufficient counting statistics. Therefore the RDI-SR-XRF method represents a high-throughput analysis procedure without the need for any sample preparation. The analysis of a multielemental mass standard film by SR-XRF, laboratory-based wavelength-dispersive XRF spectrometry and laboratory-based micro XRF spectrometry showed that the laboratory-based methods were no alternatives to the SR-XRF method with respect to sensitivity and efficiency of analysis.
    BibTeX:
    @article{Bukowiecki2008,
      author = {Bukowiecki, Nicolas and Lienemann, Peter and Zwicky, Christoph N. and Furger, Markus and Richard, Agnes and Falkenberg, Gerald and Rickers, Karen and Grolimund, Daniel and Borca, Camelia and Hill, Matthias and Gehrig, Robert and Baltensperger, Urs},
      title = {X-ray fluorescence spectrometry for high throughput analysis of atmospheric aerosol samples: The benefits of synchrotron X-rays},
      journal = {Spectrochimica Acta Part B: Atomic Spectroscopy},
      year = {2008},
      volume = {63},
      number = {9},
      pages = {929--938},
      url = {http://www.sciencedirect.com/science/article/B6THN-4SNNT5N-1/2/fce3be88d46274252974d76dcf550421}
    }
    
    Bukowiecki, N., Richard, A., Furger, M., Weingartner, E., Aguirre, M., Huthwelker, T., Lienemann, P., Gehrig, R. & Baltensperger, U. Deposition Uniformity and Particle Size Distribution of Ambient Aerosol Collected with a Rotating Drum Impactor 2009 Aerosol Science and Technology
    Vol. 43(9), pp. 891-901 
    article URL 
    Abstract: Rotating drum impactors (RDI) are cascade type impactors used for size and time resolved aerosol sampling, mostly followed by spectrometric analysis of the deposited material. They are characterized by one rectangular nozzle per stage and are equipped with an automated stepping mechanism for the impaction wheels. An existing three-stage rotating drum impactor was modified, to obtain new midpoint cutoff diameters at 2.5 μm, 1 μm, and 0.1 μm, respectively. For RDI samples collected under ambient air conditions, information on the size-segregation and the spatial uniformity of the deposited particles are key factors for a reliable spectrometric analysis of the RDI deposits. Two aerodynamic particle sizers (APS) were used for the determination of the RDI size fractionation characteristics, using polydisperse laboratory room air as quasi-stable proxy for urban ambient air. This experimental approach was suitable for the scope of this study, but was subject to numerous boundary conditions that limit a general use. Aerodynamic stage penetration midpoint diameters were estimated to be 2.4 and 1.0 μm for the first two RDI stages. Additionally, the spatial uniformity and geometrical size distribution of the deposited aerosol were investigated using micro-focus synchrotron radiation X-ray fluorescence spectrometry (micro-SR-XRF) and transmission electron microscopy (TEM), respectively. The size distribution of the particles found on the TEM samples agreed well with the results from the APS experiments. The RDI deposits showed sufficient uniformity for subsequent spectrometric analysis, but in the 2.5–10 μm size range the particle area density was very low. All of the applied methods confirmed the theoretical cutoff values of the modified RDI and showed that compared to other cascade impactors, the determined stage penetration sharpness was rather broad for the individual impactor stages.
    BibTeX:
    @article{Bukowiecki2009,
      author = {Bukowiecki, Nicolas and Richard, Agnes and Furger, Markus and Weingartner, Ernest and Aguirre, Myriam and Huthwelker, Thomas and Lienemann, Peter and Gehrig, Robert and Baltensperger, Urs},
      title = {Deposition Uniformity and Particle Size Distribution of Ambient Aerosol Collected with a Rotating Drum Impactor},
      journal = {Aerosol Science and Technology},
      publisher = {Taylor & Francis},
      year = {2009},
      volume = {43},
      number = {9},
      pages = {891--901},
      url = {http://www.informaworld.com/10.1080/02786820903002431}
    }
    
    Cahill, C.F., Cahill, T.A. & Perry, K.D. The size- and time-resolved composition of aerosols from a sub-Arctic boreal forest prescribed burn 2008 Atmospheric Environment
    Vol. 42(32), pp. 7553-7559 
    article URL 
    Abstract: Aerosols from wildfires are the primary aerosols in the Arctic atmosphere during the summer months. These aerosols occur in large, increasing quantities and impact the sensitive radiative balance in the Arctic. FROSTFIRE, a controlled burn in a Long-Term Ecological Research Area 50�km north of Fairbanks, Alaska, was designed to quantify the impacts of wildfire on sub-Arctic boreal forest ecosystems in permafrost regions. However, it provided a unique opportunity to examine smoke aerosols collected in the middle of a sub-Arctic boreal forest fire. A battery-powered eight-stage aerosol impactor (i.e. a Davis Rotating-drum Unit for Monitoring), mounted at the top of a 10�m meteorological tower in the burn zone, collected size- and time-resolved aerosol samples with 19.45�min resolution for 24�h during the burn. The samples underwent Proton Induced X-ray Emission (PIXE) and Proton Elastic Scattering Analysis (PESA) to determine the sizes and elemental compositions of the collected aerosols. Throughout the fire, the smoke reaching the sampler was strongly monodisperse with most of the aerosol mass in the optically active 0.56-1.15�[mu]m in aerodynamic diameter size range. Fine organics comprised almost all of the mass in this optically active size range and the concentrations of the organics were high throughout the sampling period. However, unlike the fine organics, the potassium concentrations in the smoke decreased exponentially during the sampling period as the fire progressed from an active flaming to a smoldering behavior. The major findings from this field experiment are the dramatic differences in aerosol composition as a function of fire type (i.e.�smoldering or active flaming) and that the largest emission of organics occurs during the smoldering phase, unaccompanied by the potassium emissions often used as a smoke tracer. These results agree with recent laboratory experiments.
    BibTeX:
    @article{Cahill2008,
      author = {Cahill, Catherine F. and Cahill, Thomas A. and Perry, Kevin D.},
      title = {The size- and time-resolved composition of aerosols from a sub-Arctic boreal forest prescribed burn},
      journal = {Atmospheric Environment},
      year = {2008},
      volume = {42},
      number = {32},
      pages = {7553--7559},
      url = {http://www.sciencedirect.com/science/article/B6VH3-4SX3P46-1/2/d2252c8a36267978dc108b57344b8d35}
    }
    
    Cahill, C.F., Rinkleff, P.G., Dehn, J., Webley, P.W., Cahill, T.A. & Barnes, D.E. Aerosol measurements from a recent Alaskan volcanic eruption: Implications for volcanic ash transport predictions 2010 Journal of Volcanology and Geothermal Research
    Vol. 198(1-2), pp. 76-80 
    article URL 
    Abstract: Size and time-resolved aerosol compositional measurements conducted during the 2006 eruption of Augustine Volcano provide quantitative information on the size and concentration of the fine volcanic ash emitted during the eruption and carried and deposited downwind. These data can be used as a starting point to attempt to validate volcanic ash transport models. For the 2006 eruption of Augustine Volcano, an island volcano in south-central Alaska, size and time-resolved aerosol measurements were made using an eight-stage (0.09-0.26, 0.26-0.34, 0.34-0.56, 0.56-0.75, 0.75-1.15, 1.15-2.5, 2.5-5.0, and 5.0-35.0�[mu]m in aerodynamic diameter) Davis Rotating Unit for Monitoring (DRUM) aerosol impactor deployed near ground level in Homer, Alaska, approximately 110�km east-northeast of the volcano. The aerosol samples collected by the DRUM impactor were analyzed for mass and elemental composition every 90�min during a four-week sampling period from January 13 to February 11, 2006, that spanned several explosive episodes during the 2006 eruption. The collected aerosols showed that the size distribution of the volcanic ash fallout changed during this period of eruption. Ash had its highest concentrations in the largest size fraction (5.0-35.0�[mu]m) with no ash present in the less than 1.15�[mu]m size fractions during the short-lived explosive events. In contrast, during the continuous ash emission phase, concentrations of volcanic ash were more significant in the less than 1.15�[mu]m size fractions. Settling velocities dictate that the smaller size particles will transport far from the volcano and, unlike the larger particles, not be retained in the proximal stratigraphic record. These results show that volcanic ash transport and dispersion (VATD) model predictions based on massless tracer particles, such as the predictions from the PUFF VATD model, provide a good first-order approximation of the transport of both large and small volcanic ash particles. Unfortunately, the concentration of particles in different size fractions depends on eruptive style and ash generation processes, so predicting the actual behavior of the ash particles from an eruption requires additional information in real time.
    BibTeX:
    @article{Cahill2010,
      author = {Cahill, Catherine F. and Rinkleff, Peter G. and Dehn, Jonathan and Webley, Peter W. and Cahill, Thomas A. and Barnes, David E.},
      title = {Aerosol measurements from a recent Alaskan volcanic eruption: Implications for volcanic ash transport predictions},
      journal = {Journal of Volcanology and Geothermal Research},
      year = {2010},
      volume = {198},
      number = {1-2},
      pages = {76--80},
      url = {http://www.sciencedirect.com/science/article/B6VCS-50TRX5N-1/2/8263fcc29add54125101d6dc17227f92}
    }
    
    Cahill, T.A. Analysis of air pollutants by PIXE: The second decade 1990 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
    Vol. 49(1-4), pp. 345-350 
    article URL 
    Abstract: Analysis of air pollution by PIXE was the earliest and one of the most successful applications of the technique. In the first decade that followed the pioneering paper of Johansson et al. in 1970 [1], many innovative programs grew up around the technique. By 1980, five of the six largest PIXE groups in the world listed analyses of air pollutants as their most numerous sample type [2], with more than 30000 analyses in the year 1979 alone. The purpose of this article is to examine the role of PIXE in air pollution in the second decade, to see to what degree the bright promises of the 1970s have been realized, to examine the reasons for the successes and the failures, and to attempt to use this information to predict the role of PIXE in the next decade.
    BibTeX:
    @article{Cahill1990,
      author = {Cahill, Thomas A.},
      title = {Analysis of air pollutants by PIXE: The second decade},
      journal = {Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms},
      year = {1990},
      volume = {49},
      number = {1-4},
      pages = {345--350},
      url = {http://www.sciencedirect.com/science/article/B6TJN-470WDGH-FW/2/d76de0f8db872c71603432f4dc1c6d08}
    }
    
    Cahill, T.A. Proton Microprobes and Particle-Induced X-Ray Analytical Systems 1980 Annual Review of Nuclear and Particle Science
    Vol. 30(1), pp. 211-252 
    article DOI URL 
    BibTeX:
    @article{doi:10.1146/annurev.ns.30.120180.001235,
      author = {Cahill, T A},
      title = {Proton Microprobes and Particle-Induced X-Ray Analytical Systems},
      journal = {Annual Review of Nuclear and Particle Science},
      year = {1980},
      volume = {30},
      number = {1},
      pages = {211-252},
      url = {http://www.annualreviews.org/doi/abs/10.1146/annurev.ns.30.120180.001235},
      doi = {http://dx.doi.org/10.1146/annurev.ns.30.120180.001235}
    }
    
    Cahill, T.A., Feeney, P.J. & Eldred, R.A. Size-time composition profile of aerosols using the drum sampler 1987 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
    Vol. 22(1-3), pp. 344-348 
    article URL 
    Abstract: Mie scattering theory imposes strict requirements for both size and compositional information on aerosols associated with visibility degradation. But, at the very clean National Park Service sites where we do such studies, episodes of degraded visibility may be infrequent and of short duration. To meet these needs, an 8 stage impactor of the Battelle/SFU design was mated to rotating drum impaction surfaces of the Lundgren design in a compact and rugged DRUM sampler of Davis design. This unit, three years in development, has been extensively tested using laboratory aerosols and field intercomparisons. The standard unit runs essentially unattended for 14 or 28 days. The samples are analyzed in 2 to 8 hour time segments. Analyses are done by carefully collimated (1 mm, 2 mm) proton beams in a tightly coupled PIXE system, yielding sensitivities of a few . Dramatic shifts in the size distribution of sulfur versus time have been observed, with direct influence on optical extinction. Further, primary smelter effluents have been clearly identified at Grand Canyon NP, but only in the < 0.15 [mu]m size fraction. The DRUM sampler makes excellent use of PIXE capabilities, but can also be analyzed by lasers (Csoot) and [beta]-gauging (mass).
    BibTeX:
    @article{Cahill1987,
      author = {Cahill, Thomas A. and Feeney, Patrick J. and Eldred, Robert A.},
      title = {Size-time composition profile of aerosols using the drum sampler},
      journal = {Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms},
      year = {1987},
      volume = {22},
      number = {1-3},
      pages = {344--348},
      url = {http://www.sciencedirect.com/science/article/B6TJN-470VCHG-M2/2/9fcff511942b7aa6aa1eb498d357801f}
    }
    
    Cahill, T.A. & Wakabayashi, P. Compositional Analysis of Size-Segregated Aerosol Samples 1993
    Vol. 232Advances in Chemistry, pp. 211-228- 
    incollection URL 
    Abstract: Knowing both the size and composition of fine particles in the air is vital for understanding the sources, transport, transformation, effects, and sinks of atmospheric aerosols. However, compositional analysis of such size-segregated aerosol samples poses difficulties because of the small amount of mass available for analysis, the chemical complexity of the particles, and the nonuniform deposits characteristic of most impactors. Additional problems are posed by the need to measure both a wide range of elements and trace concentrations. Nevertheless, significant progress has been made in the past decade, especially in evaluation of the sources and nature of visibility degradation by fine particles. This chapter is a short summary of the difficulties of obtaining size-specific chemical information and the usefulness of such information once obtained.
    BibTeX:
    @incollection{A.1993,
      author = {Cahill, Thomas A. and Wakabayashi, Paul},
      title = {Compositional Analysis of Size-Segregated Aerosol Samples},
      booktitle = {Advances in Chemistry},
      publisher = {American Chemical Society},
      year = {1993},
      volume = {232},
      pages = {211-228--},
      url = {http://dx.doi.org/10.1021/ba-1993-0232.ch007}
    }
    
    Cahill, T., Kusko, B., Ashbaugh, L., Barone, J., Eldred, R. & Walther, F. Regional and local determinations of particulate matter and visibility in the southwestern United States during June and July, 1979 1981 Atmospheric Environment (1967)
    Vol. 15(10-11)Plumes and Visibility Measurements and Model Components, pp. 2011-2016 
    article URL 
    Abstract: Data on ambient particulate concentrations by size and elemental composition taken in Arizona and Utah are compared to simultaneous telephotometer measurements of standard visual range. Particulate samples were collected during the VISTTA program from 26 June to 11 July 1979, at Zilnez Mesa, Arizona, and compared to similar 24 h measurements made as part of a long term research program at Zion and Canyonlands National Parks in Utah. Samples were collected with rotating drum Multtday impactors which provide three aerodynamic size ranges; 15[mu]m-3.5[mu]m; 3.5[mu]m-0.5[mu]m, and less than 0.5/jm. Elemental composition of samples was measured using the particle induced X-ray emission (PIXE) system at the Crocker Nuclear Laboratory. Measurements of visibility were made at Canyonlands National Park and Zilnez Mesa using both multiwavelength telephotometers and nephelometers. Results indicate that the particulate matter in each size range behaves to a large degree independently of the other size ranges, but that correlations are often observed between sites. On 29 June, an episode of elevated sulfur concentrations, > 1 [mu]m m -3 of S, was observed at all three sites. Decreased visibilities were recorded for the episode period at both Canyonlands and Zilnez Mesa. Sulfur episodes on 22-24 June and 20-21 July measured at Zion and Canyonlands also correlated well with reduced visibility at Canyonlands. Episodes of reduced visibilities also occurred during periods of stable sulfur values. The strongest of these, on 1718 June, as well as a weaker one, 4-7 June, correlated well with fine soils in the 0.5-3.5 [mu]m size range. The conclusion is that reduced visibility is associated with regional episodes of both increased sulfur and increased fine soils, with best correlations occurring in both cases for sizes somewhat greater than 0.5[mu]m dia.
    BibTeX:
    @article{Cahill1981,
      author = {Cahill, T.A. and Kusko, B.H. and Ashbaugh, L.L. and Barone, J.B. and Eldred, R.A. and Walther, F.G.},
      title = {Regional and local determinations of particulate matter and visibility in the southwestern United States during June and July, 1979},
      booktitle = {Plumes and Visibility Measurements and Model Components},
      journal = {Atmospheric Environment (1967)},
      year = {1981},
      volume = {15},
      number = {10-11},
      pages = {2011--2016},
      url = {http://www.sciencedirect.com/science/article/B757C-48CG0RJ-FP/2/ae68d06a1981f949085a2ec062b27fb0}
    }
    
    Cahill, T.M. Size-Resolved Organic Speciation of Wintertime Aerosols in California's Central Valley 2010 Environmental Science & Technology
    Vol. 44(7), pp. 2315-2321 
    article URL 
    Abstract: Size-resolved aerosol samples, including the entire ultrafine fraction, were simultaneously collected along a transect in California’s Central Valley during the winter of 2009. The samples were analyzed for PAHs, alkanes, organic acids, and sugars. The results showed that the organic constituents of aerosols did not follow the same pattern as PM10, thus indicating that simple PM measurements are not good indicators of trace toxic organic chemicals. Levoglucosan, a tracer of wood smoke, was the most abundant organic chemical detected, thus demonstrating the predominance of wood smoke in the valley. The size profile of levoglucosan showed a maximum in the 0.34−0.56 μm size mode, which is larger than published emission profiles. This suggests that wood smoke aerosols increased in size as they aged in the environment. Some chemicals, such as benzo[a]pyrene, had similar aerosol size profiles as levoglucosan and likely arose from the same source. Other chemicals, such as coronene and sugars, had very different size profiles, indicating that they have different sources. One unexpected result was the relatively large fraction of certain chemicals present in the ultrafine fraction, which highlights the importance of collecting the entire ultrafine fraction.
    BibTeX:
    @article{Cahill2010a,
      author = {Cahill, Thomas M.},
      title = {Size-Resolved Organic Speciation of Wintertime Aerosols in California's Central Valley},
      journal = {Environmental Science & Technology},
      publisher = {American Chemical Society},
      year = {2010},
      volume = {44},
      number = {7},
      pages = {2315--2321},
      url = {http://dx.doi.org/10.1021/es902936v}
    }
    
    Chow JC FAU Doraiswamy, P., Doraiswamy P FAU Watson, J.G., Watson JG FAU Chen, L.W.A., Chen LW FAU Ho, S.S.H., Ho SS FAU Sodeman, D.A. & DA, S. Advances in integrated and continuous measurements for particle mass and chemical composition. (1096-2247 (Linking)), pp. -  other  
    Abstract: Recent improvements in integrated and continuous PM2.5 mass and chemical measurements from the Supersite program and related studies in the past decade are summarized. Analytical capabilities of the measurement methods, including accuracy, precision, interferences, minimum detectable levels, comparability, and data completeness are documented. Upstream denuders followed by filter packs in integrated samplers allow an estimation of sampling artifacts. Efforts are needed to: (1) address positive and negative artifacts for organic carbon (OC), and (2) develop carbon standards to better separate organic versus elemental carbon (EC) under different temperature settings and analysis atmospheres. Advances in thermal desorption followed by gas chromatography/ mass spectrometry (GC/MS) provide organic speciation of approximately 130 nonpolar compounds (e.g., n-alkanes, alkenes, hopanes, steranes, and polycyclic aromatic hydrocarbons [PAHs]) using small portions of filters from existing integrated samples. Speciation of water-soluble OC (WSOC) using ion chromatography (IC)-based instruments can replace labor-intensive solvent extraction for many compounds used as source markers. Thermal gas-based continuous nitrate and sulfate measurements underestimate filter ions by 10-50% and require calibration against on-site filter-based measurements. IC-based instruments provide multiple ions and report comparable (+/-10%) results to filter-based measurements. Maintaining a greater than 80% data capture rate in continuous instruments is labor intensive and requires experienced operators. Several instruments quantify black carbon (BC) by optical or photoacoustic methods, or EC by thermal methods. A few instruments provide real-time OC, EC, and organic speciation. BC and EC concentrations from continuous instruments are highly correlated but the concentrations differ by a factor of two or more. Site- and season-specific mass absorption efficiencies are needed to convert light absorption to BC. Particle mass spectrometers, although semiquantitative, provide much information on particle size and composition related to formation, growth, and characteristics over short averaging times. Efforts are made to quantify mass by collocating with other particle sizing instruments. Common parameters should be identified and consistent approaches are needed to establish comparability among measurements.
    BibTeX:
    @other{ChowJCFAUDoraiswamy,
      author = {Chow JC FAU Doraiswamy, Prakash and Doraiswamy P FAU Watson, John G and Watson JG FAU Chen, L W Antony and Chen LW FAU Ho, Steven Sai Hang and Ho SS FAU Sodeman, David A and DA, Sodeman},
      title = {Advances in integrated and continuous measurements for particle mass and chemical composition.},
      number = {1096-2247 (Linking)},
      pages = {--}
    }
    
    Chung, A., Chang, D.P., Kleeman, M.J., Perry, K.D., Cahill, T.A., Dutcher, D., McDougall, E.M. & Stroud, K. Comparison of real-time instruments used to monitor airborne particulate matter. 2001 J Air Waste Manag Assoc
    Vol. 51(1), pp. 109-120 
    article  
    Abstract: Measurements collected using five real-time continuous airborne particle monitors were compared to measurements made using reference filter-based samplers at Bakersfield, CA, between December 2, 1998, and January 31, 1999. The purpose of this analysis was to evaluate the suitability of each instrument for use in a real-time continuous monitoring network designed to measure the mass of airborne particles with an aerodynamic diam less than 2.5 microns (PM2.5) under wintertime conditions in the southern San Joaquin Valley. Measurements of airborne particulate mass made with a beta attenuation monitor (BAM), an integrating nephelometer, and a continuous aerosol mass monitor (CAMM) were found to correlate well with reference measurements made with a filter-based sampler. A Dusttrak aerosol sampler overestimated airborne particle concentrations by a factor of approximately 3 throughout the study. Measurements of airborne particulate matter made with a tapered element oscillating microbalance (TEOM) were found to be lower than the reference filter-based measurements by an amount approximately equal to the concentration of NH4NO3 observed to be present in the airborne particles. The performance of the Dusttrak sampler and the integrating nephelometer was affected by the size distribution of airborne particulate matter. The performance of the BAM, the integrating nephelometer, the CAMM, the Dusttrak sampler, and the TEOM was not strongly affected by temperature, relative humidity, wind speed, or wind direction within the range of conditions encountered in the current study. Based on instrument performance, the BAM, the integrating nephelometer, and the CAMM appear to be suitable candidates for deployment in a real-time continuous PM2.5 monitoring network in central California for the range of winter conditions and aerosol composition encountered during the study.
    BibTeX:
    @article{Chung2001,
      author = {A. Chung and D. P. Chang and M. J. Kleeman and K. D. Perry and T. A. Cahill and D. Dutcher and E. M. McDougall and K. Stroud},
      title = {Comparison of real-time instruments used to monitor airborne particulate matter.},
      journal = {J Air Waste Manag Assoc},
      year = {2001},
      volume = {51},
      number = {1},
      pages = {109--120}
    }
    
    Collins, G. Measurement of variation in output rate from aerosol generators 1975 Journal of Aerosol Science
    Vol. 6(3-4), pp. 169-172 
    article URL 
    Abstract: A method for the measurement of variation in output rate from aerosol generators is described. It may be used with solid particles or liquid droplets and employs a fluorescent tracer sampled on a revolving drum. The drum is then set up under a microscope illuminated with u.v. light and the density of deposit over a period of time is measured by means of a photo-cell connected to a chart recorder. Measurement of areas under the trace for a series of identical time periods enables the coefficient of variation in output rate to be calculated. The method has been used to determine variation in output rate over periods as short as 5 sec.
    BibTeX:
    @article{Collins1975,
      author = {Collins, G.F.},
      title = {Measurement of variation in output rate from aerosol generators},
      journal = {Journal of Aerosol Science},
      year = {1975},
      volume = {6},
      number = {3-4},
      pages = {169--172},
      url = {http://www.sciencedirect.com/science/article/B6V6B-488G5CX-4X/2/5e7173616caf1c5405b77db34b4509e0}
    }
    
    Dzepina, K., Arey, J., Marr, L.C., Worsnop, D.R., Salcedo, D., Zhang, Q., Onasch, T.B., Molina, L.T., Molina, M.J. & Jimenez, J.L. Detection of particle-phase polycyclic aromatic hydrocarbons in Mexico City using an aerosol mass spectrometer 2007 International Journal of Mass Spectrometry
    Vol. 263(2-3), pp. 152-170 
    article URL 
    Abstract: We report the quantification of ambient particle-bound polycyclic aromatic hydrocarbons (PAHs) for the first time using a real-time aerosol mass spectrometer. These measurements were carried out during the Mexico City Metropolitan Area field study (MCMA-2003) that took place from March 29 to May 4, 2003. This was the first time that two different fast, real-time methods have been used to quantify PAHs alongside traditional filter-based measurements in an extended field campaign. This paper focuses on the technical aspects of PAH detection in ambient air with the Aerodyne AMS equipped with a quadrupole mass analyzer (Q-AMS), on the comparison of PAHs measured by the Q-AMS to those measured with the other two techniques, and on some features of the ambient results. PAHs are very resistant to fragmentation after ionization. Based on laboratory experiments with eight PAH standards, we show that their molecular ions, which for most particulate PAHs in ambient particles are larger than 200�amu, are often the largest peak in their Q-AMS spectra. Q-AMS spectra of PAH are similar to those in the NIST database, albeit with more fragmentation. We have developed a subtraction method that allows the removal of the contribution from non-PAH organics to the ion signals of the PAHs in ambient data. We report the mass concentrations of all individual groups of PAHs with molecular weights of 202, 216, 226�+�228, 240�+�242, 250�+�252, 264�+�266, 276�+�278, 288�+�290, 300�+�302, 316 and 326�+�328, as well as their sum as the total PAH mass concentration. The time series of the Photoelectric Aerosol Sensor (PAS) and Q-AMS PAH measurements during MCMA-2003 are well correlated, with the smallest difference between measured PAH concentrations observed in the mornings when ambient aerosols loadings are dominated by fresh traffic emissions. The Q-AMS PAH measurements are also compared to those from GC-MS analysis of filter samples. Several groups of PAHs show agreement within the uncertainties, while the Q-AMS measurements are larger than the GC-MS ones for several others. In the ambient Q-AMS measurements the presence of ions tentatively attributed to cyclopenta[cd]pyrene and dicyclopentapyrenes causes signals at m/z 226 and 250, which are significantly stronger than the signals in GC-MS analysis of filter samples. This suggests that very labile, but likely toxic, PAHs were present in the MCMA atmosphere that decayed rapidly due to reaction during filter sampling, and this may explain at least some of the differences between the Q-AMS and GC-MS measurements.
    BibTeX:
    @article{Dzepina2007,
      author = {Dzepina, Katja and Arey, Janet and Marr, Linsey C. and Worsnop, Douglas R. and Salcedo, Dara and Zhang, Qi and Onasch, Timothy B. and Molina, Luisa T. and Molina, Mario J. and Jimenez, Jose L.},
      title = {Detection of particle-phase polycyclic aromatic hydrocarbons in Mexico City using an aerosol mass spectrometer},
      journal = {International Journal of Mass Spectrometry},
      year = {2007},
      volume = {263},
      number = {2-3},
      pages = {152--170},
      url = {http://www.sciencedirect.com/science/article/B6VND-4MWXR1M-2/2/ac65b96ca89aae727a9b2f6bca8289ba}
    }
    
    Emmenegger, C., Kalberer, M., Samburova, V. & Zenobi, R. High Time Resolution and Size-Segregated Analysis of Aerosol-Bound Polycyclic Aromatic Hydrocarbons 2005 Environmental Science & Technology
    Vol. 39(11), pp. 4213-4219 
    article URL 
    Abstract: Polycyclic aromatic hydrocarbons (PAHs) are an ubiquitous class of compounds in the environment, mostly generated by anthropogenic processes. High time resolution measurements are necessary to gain further knowledge on the fate and diurnal pattern of these often carcinogenic and mutagenic compounds in the atmosphere. It is expected to find a strong correlation of the PAH levels with the strength and proximity to sources, as well as with meteorological parameters. To determine the fate of particle-bound PAHs, they were sampled in this study at an urban background site in Zurich, Switzerland, during summer 2002 and winter 2003. Particle-bound PAHs were collected with a rotating drum impactor and subsequently analyzed with two-step laser mass spectrometry. Using this combination of sampling and measurement, size-segregated (10−1.1, 1.1−0.3, and 0.3−0.1 μm) and high time resolution (20 min) data were obtained. The pronounced diurnal cycle (with day/night ratios of 0.1) was only altered during intensive atmospheric mixing periods (resulting in day/night ratios of up to 8) by cleaner air from upper atmospheric layers which was mixed into the boundary layer. During summer, signal intensities due to particle-bound PAHs were about a factor of 2−10 lower than during winter.
    BibTeX:
    @article{Emmenegger2005,
      author = {Emmenegger, Christian and Kalberer, Markus and Samburova, Vera and Zenobi, Renato},
      title = {High Time Resolution and Size-Segregated Analysis of Aerosol-Bound Polycyclic Aromatic Hydrocarbons},
      journal = {Environmental Science & Technology},
      publisher = {American Chemical Society},
      year = {2005},
      volume = {39},
      number = {11},
      pages = {4213--4219},
      url = {http://dx.doi.org/10.1021/es048628n}
    }
    
    Emmenegger, C., Kalberer, M., Samburova, V. & Zenobi, R. Analysis of size-segregated aerosol-bound polycyclic aromatic hydrocarbons with high time resolution using two-step laser mass spectrometry 2004 Analyst
    Vol. 129(5), pp. 416-420 
    article URL 
    Abstract: Polycyclic aromatic hydrocarbons are known for their mutagenic and carcinogenic properties. They are mainly emitted into the atmosphere by anthropogenic, incomplete combustion sources. Their trends over the course of a day are of interest in air quality management. A new combination of methods has been developed for the qualitative monitoring of polycyclic aromatic hydrocarbons in ambient aerosols with high time and size resolution. This has been accomplished by combining sampling with a rotating drum impactor and the analysis two-step laser mass spectrometry (L2MS). A validation for this method was carried out. Essential features of these combined techniques are (i) continuous, automatic sampling and (ii) selective as well as sensitive analysis due to the low detection limits which can be achieved with the L2MS analysis instrument. Analysis of a field sample taken in downtown Zurich, Switzerland, underlines the usefulness of this combined method, for example for following diurnal cycles of polycyclic aromatic hydrocarbons.
    BibTeX:
    @article{Emmenegger2004,
      author = {Emmenegger, Christian and Kalberer, Markus and Samburova, Vera and Zenobi, Renato},
      title = {Analysis of size-segregated aerosol-bound polycyclic aromatic hydrocarbons with high time resolution using two-step laser mass spectrometry},
      journal = {Analyst},
      publisher = {The Royal Society of Chemistry},
      year = {2004},
      volume = {129},
      number = {5},
      pages = {416--420},
      url = {http://dx.doi.org/10.1039/B401201A}
    }
    
    Flocchini, R.G., Cahill, T.A., Ashbaugh, L.L., Eldred, R.A. & Pitchford, M. Seasonal behavior of particulate matter at three rural utah sites 1981 Atmospheric Environment (1967)
    Vol. 15(3), pp. 315-320 
    article URL 
    Abstract: Elemental analysis of size-segregated particulate samples for three rural Utah sites is presented and discussed. Daily samples were collected at each site in three size ranges (15-3.5[mu]m, 3.5-0.5[mu]n, and 0.5-0.1 [mu]m) for a period of one year. Sulfur is shown to be important in the two smaller size ranges. There is no distinctive seasonal pattern in sulfur concentrations. Overall, the mass contribution of the soil related components to ambient particles is greatest. Soil related elements dominate in the two larger size ranges and are significant (amounting to about 50%) in the smallest size range. The soils show a distinctive seasonal variation with winter concentrations, about a factor of three smaller during the summer. Small particle soils may be a significant cause of visibility degradation.
    BibTeX:
    @article{Flocchini1981,
      author = {Flocchini, Robert G. and Cahill, Thomas A. and Ashbaugh, Lowell L. and Eldred, Robert A. and Pitchford, Marc},
      title = {Seasonal behavior of particulate matter at three rural utah sites},
      journal = {Atmospheric Environment (1967)},
      year = {1981},
      volume = {15},
      number = {3},
      pages = {315--320},
      url = {http://www.sciencedirect.com/science/article/B757C-48CG0WV-HD/2/d5743db31be7c3b5d8124e03d9a69e5f}
    }
    
    Flocchini, R.G., Cahill, T.A., Shadoan, D.J., Lange, S.J., Eldred, R.A., Feeney, P.J., Wolfe, G.W., Simmeroth, D.C. & Suder, J.K. Monitoring California's aerosols by size and elemental composition 1976 Environmental Science & Technology
    Vol. 10(1), pp. 76-82 
    article URL 
    Abstract: null
    BibTeX:
    @article{Flocchini1976,
      author = {Flocchini, Robert G. and Cahill, Thomas A. and Shadoan, Danny J. and Lange, Sandra J. and Eldred, Robert A. and Feeney, Patrick J. and Wolfe, Gordon W. and Simmeroth, Dean C. and Suder, Jack K.},
      title = {Monitoring California's aerosols by size and elemental composition},
      journal = {Environmental Science & Technology},
      publisher = {American Chemical Society},
      year = {1976},
      volume = {10},
      number = {1},
      pages = {76--82},
      url = {http://dx.doi.org/10.1021/es60112a008}
    }
    
    Gillette, D.A., Fryrear, D.W., Gill, T.E., Ley, T., Cahill, T.A. & Gearhart, E.A. Relation of vertical flux of particles smaller than 10 um to total aeolian horizontal mass flux at Owens Lake 1997 J. Geophys. Res.
    Vol. 102(D22), pp. 26009-26015 
    article URL 
    Abstract: The vertical flux of particles smaller than 10 &#956;m for a saline playa surface, the particle size composition of which was classified as loam-textured, was estimated for a highly wind-erodible site on the playa of Owens (dry) Lake in California. The ratio of this vertical flux to the horizontal flux of total airborne material through a surface perpendicular to the soil and to the wind, Fa/qtot , is 2.75 � 10&#8722;4 m&#8722;1. This is consistent with that ratio for sand-textured soils and suggests that the binding energy and size of saltating particles for the tested surface material at Owens Lake is of the same order as that for sandier soils. The horizontal mass flux of saltating grains, q, in the reported wind erosion event is 51.3% of the total horizontal mass flux qtot. Therefore the ratio of Fa/q is 5.4 � 10&#8722;4 m&#8722;1.
    BibTeX:
    @article{Gillette1997,
      author = {Gillette, Dale A. and Fryrear, D. W. and Gill, Thomas E. and Ley, Trevor and Cahill, Thomas A. and Gearhart, Elizabeth A.},
      title = {Relation of vertical flux of particles smaller than 10 um to total aeolian horizontal mass flux at Owens Lake},
      journal = {J. Geophys. Res.},
      publisher = {AGU},
      year = {1997},
      volume = {102},
      number = {D22},
      pages = {26009--26015},
      url = {http://dx.doi.org/10.1029/97JD02252}
    }
    
    Grini, A. & Zender, C.S. Roles of saltation, sandblasting, and wind speed variability on mineral dust aerosol size distribution during the Puerto Rican Dust Experiment (PRIDE) 2004 J. Geophys. Res.
    Vol. 109(D7), pp. D07202- 
    article URL 
    Abstract: Recent field observations demonstrate that a significant discrepancy exists between models and measurements of large dust aerosol particles at remote sites. We assess the fraction of this bias explained by assumptions involving four different dust production processes. These include dust source size distribution (constant or dynamically changing according to saltation and sandblasting theory), wind speed distributions (using mean wind or a probability density function (PDF)), parent soil aggregate size distribution, and the discretization (number of bins) in the dust size distribution. The Dust Entrainment and Deposition global model is used to simulate the measurements from the Puerto Rican Dust Experiment (PRIDE) (2000). Using wind speed PDFs from observed National Centers for Environmental Prediction winds results in small changes in downwind size distribution for the production which neglects sandblasting, but it results in significant changes when production includes sandblasting. Saltation-sandblasting generally produces more large dust particles than schemes which neglect sandblasting. Parent soil aggregate size distribution is an important factor when calculating size-distributed dust emissions. Changing from a soil with large grains to a soil with smaller grains increases by 50% the fraction of large aerosols (D &gt;5 &#956;m) modeled at Puerto Rico. Assuming that the coarse medium sand typical of West Africa dominates all source regions produces the best agreement with PRIDE observations.
    BibTeX:
    @article{Grini2004,
      author = {Grini, Alf and Zender, Charles S.},
      title = {Roles of saltation, sandblasting, and wind speed variability on mineral dust aerosol size distribution during the Puerto Rican Dust Experiment (PRIDE)},
      journal = {J. Geophys. Res.},
      publisher = {AGU},
      year = {2004},
      volume = {109},
      number = {D7},
      pages = {D07202--},
      url = {http://dx.doi.org/10.1029/2003JD004233}
    }
    
    Han, J.S., Moon, K.J., Ahn, J.Y., Hong, Y.D., Kim, Y.J., Ryu, S.Y., Cliff, S.S. & Cahill, T.A. Characteristics of Ion Components and Trace Elements of Fine Particles at Gosan, Korea in Spring time from 2001 to 2002 2004 Environmental Monitoring and Assessment
    Vol. 92, pp. 73-93 
    article URL 
    Abstract: Size-segregated measurements of the composition of an aerosol are used to determine the transport of natural and anthropogenic aerosols to the Gosan site in springtime from 2001 to 2002. Although the transport of Asian dust is a well-known phenomenon in springtime, this study shows that not only is soil dust transported into Gosan each spring but so are anthropogenic aerosols, including sulfur, enriched trace metals such as Pb, Zn, Ni, K, S. This study also combines the size- and time-resolved aerosol composition measurements with isentropic, backward air-mass trajectories in order to identify some potential source regions of the anthropogenic aerosols. Finally, four types of transport episodes were identified: (1) anthropogenic pollutants, (2) dust storm mixed with the anthropogenic aerosols, (3) typical dust storms, (4) some sea salt with clean air mass. Overall, in addition to typical soil dust, a large amount of anthropogenic aerosols, whether mixed with the soil dust or not, are transported to Gosan each spring.
    BibTeX:
    @article{springerlink:10.1023/B:EMAS.0000014510.21563.50,
      author = {Han, J. S. and Moon, K. J. and Ahn, J. Y. and Hong, Y. D. and Kim, Y. J. and Ryu, S. Y. and Cliff, S. S. and Cahill, T. A.},
      title = {Characteristics of Ion Components and Trace Elements of Fine Particles at Gosan, Korea in Spring time from 2001 to 2002},
      journal = {Environmental Monitoring and Assessment},
      publisher = {Springer Netherlands},
      year = {2004},
      volume = {92},
      pages = {73-93},
      note = {10.1023/B:EMAS.0000014510.21563.50},
      url = {http://dx.doi.org/10.1023/B:EMAS.0000014510.21563.50}
    }
    
    Han, J.S., Moon, K.J., Lee, S.J., Kim, Y.J., Ryu, S.Y., Cliff, S.S. & Yi, S.M. Size-resolved source apportionment of ambient particles by positive matrix factorization at Gosan background site in East Asia 2006 Atmos. Chem. Phys.
    Vol. 6(1), pp. 211-223 
    article URL 
    BibTeX:
    @article{Han2006,
      author = {Han, J. S. and Moon, K. J. and Lee, S. J. and Kim, Y. J. and Ryu, S. Y. and Cliff, S. S. and Yi, S. M.},
      title = {Size-resolved source apportionment of ambient particles by positive matrix factorization at Gosan background site in East Asia},
      journal = {Atmos. Chem. Phys.},
      publisher = {Copernicus Publications},
      year = {2006},
      volume = {6},
      number = {1},
      pages = {211--223},
      url = {http://www.atmos-chem-phys.net/6/211/2006/}
    }
    
    Hughes, L.S., Cass, G.R., Gone, J., Ames, M. & Olmez, I. Physical and Chemical Characterization of Atmospheric Ultrafine Particles in the Los Angeles Area 1998 Environmental Science & Technology
    Vol. 32(9), pp. 1153-1161 
    article URL 
    Abstract: Atmospheric ultrafine particles (diameter < 0.1 μm) are under study by inhalation toxicologists to determine whether they pose a threat to public health, yet, little is known about the chemical composition of ultrafine particles in the atmosphere of cities. In the present work, the number concentration, size distribution, and chemical composition of atmospheric ultrafine particles is determined under wintertime conditions in Pasadena, CA, near Los Angeles. These experiments are conducted using a scanning dif ferential mobility analyzer, laser optical counter, and two micro-orifice impactors. Samples are analyzed to create a material balance on the chemical composition of the ultrafine particles. The number concentration of ultrafine particles in the size range 0.017 < dp < 0.1 μm, analyzed over 24-h periods, is found to be consistently in the range 1.3 × 104 ± 8.9 × 103 particles cm-3 air. Ultrafine particle mass concentrations are in the range 0.80−1.58 μg m-3. Organic compounds are the largest contributors to the ultrafine particle mass concentration. A small amount of sulfate is present in these particles, at concentrations too low to tell whether it exists as unneutralized sulfuric acid. Iron is the most prominent transition metal found in the ultrafine particles. These data may assist the health effects research community in constructing realistic animal or human exposure studies involving ultrafine particles.
    BibTeX:
    @article{Hughes1998,
      author = {Hughes, Lara S. and Cass, Glen R. and Gone, Jec and Ames, Michael and Olmez, Ilhan},
      title = {Physical and Chemical Characterization of Atmospheric Ultrafine Particles in the Los Angeles Area},
      journal = {Environmental Science & Technology},
      publisher = {American Chemical Society},
      year = {1998},
      volume = {32},
      number = {9},
      pages = {1153--1161},
      url = {http://dx.doi.org/10.1021/es970280r}
    }
    
    Jaffe, D., Anderson, T., Covert, D., Kotchenruther, R., Trost, B., Danielson, J., Simpson, W., Berntsen, T., Karlsdottir, S., Blake, D., Harris, J., Carmichael, G. & Uno, I. Transport of Asian air pollution to North America 1999 Geophys. Res. Lett.
    Vol. 26(6), pp. 711-714 
    article URL 
    Abstract: Using observations from the Cheeka Peak Observatory in northwestern Washington State during March&#8208;April, 1997, we show that Asian anthropogenic emissions significantly impact the concentrations of a large number of atmospheric species in the air arriving to North America during spring. Isentropic back&#8208;trajectories can be used to identify possible times when this impact will be felt, however trajectories alone are not sufficient to indicate the presence of Asian pollutants. Detailed chemical and meteorological data from one of these periods (March 29th, 1997) indicates that the surface emissions were lifted into the free troposphere over Asia and then transported to North America in &#8764;6 days.
    BibTeX:
    @article{Jaffe1999,
      author = {Jaffe, Dan and Anderson, Theodore and Covert, Dave and Kotchenruther, Robert and Trost, Barbara and Danielson, Jen and Simpson, William and Berntsen, Terje and Karlsdottir, Sigrun and Blake, Donald and Harris, Joyce and Carmichael, Greg and Uno, Itsushi},
      title = {Transport of Asian air pollution to North America},
      journal = {Geophys. Res. Lett.},
      publisher = {AGU},
      year = {1999},
      volume = {26},
      number = {6},
      pages = {711--714},
      url = {http://dx.doi.org/10.1029/1999GL900100}
    }
    
    Johnson, K.S., de Foy, B., Zuberi, B., Molina, L.T., Molina, M.J., Xie, Y., Laskin, A. & Shutthanandan, V. Aerosol composition and source apportionment in the Mexico City Metropolitan Area with PIXE/PESA/STIM and multivariate analysis 2006 Atmos. Chem. Phys.
    Vol. 6(12), pp. 4591-4600 
    article URL 
    BibTeX:
    @article{Johnson2006,
      author = {Johnson, K. S. and de Foy, B. and Zuberi, B. and Molina, L. T. and Molina, M. J. and Xie, Y. and Laskin, A. and Shutthanandan, V.},
      title = {Aerosol composition and source apportionment in the Mexico City Metropolitan Area with PIXE/PESA/STIM and multivariate analysis},
      journal = {Atmos. Chem. Phys.},
      publisher = {Copernicus Publications},
      year = {2006},
      volume = {6},
      number = {12},
      pages = {4591--4600},
      url = {http://www.atmos-chem-phys.net/6/4591/2006/}
    }
    
    Johnson, K.S., Laskin, A., Jimenez, J.L., Shutthanandan, V., Molina, L.T., Salcedo, D., Dzepina, K. & Molina, M.J. Comparative Analysis of Urban Atmospheric Aerosol by Particle-Induced X-ray Emission (PIXE), Proton Elastic Scattering Analysis (PESA), and Aerosol Mass Spectrometry (AMS) 2008 Environmental Science & Technology
    Vol. 42(17), pp. 6619-6624 
    article URL 
    Abstract: Quantitative intercomparisons of PIXE/PESA and AMS measurements provide unique information on urban aerosol chemistry and demonstrate the complementary nature of these techniques in field studies.
    BibTeX:
    @article{Johnson2008,
      author = {Johnson, K. S. and Laskin, A. and Jimenez, J. L. and Shutthanandan, V. and Molina, L. T. and Salcedo, D. and Dzepina, K. and Molina, M. J.},
      title = {Comparative Analysis of Urban Atmospheric Aerosol by Particle-Induced X-ray Emission (PIXE), Proton Elastic Scattering Analysis (PESA), and Aerosol Mass Spectrometry (AMS)},
      journal = {Environmental Science & Technology},
      publisher = {American Chemical Society},
      year = {2008},
      volume = {42},
      number = {17},
      pages = {6619--6624},
      url = {http://dx.doi.org/10.1021/es800393e}
    }
    
    Laskin, A., Iedema, M.J. & Cowin, J.P. Time-Resolved Aerosol Collector for CCSEM/EDX Single-Particle Analysis 2003 Aerosol Science and Technology
    Vol. 37(3), pp. 246-260 
    article URL 
    Abstract: An automated Time-Resolved Aerosol Collector (TRAC) has been developed for sequential sampling of field-collected aerosols for laboratory-based Computer Controlled Scanning Electron Microscopy/Energy Dispersed X-ray (CCSEM/EDX) single-particle analysis. The collector is optimized for the use of grid-supported 50 nm carbon films as deposition substrates. The carbon films have low enough X-ray background to permit EDX analysis down to 0.1-0.2 w m particles, including detection of low-Z elements: C, N, and O. The TRAC provides unattended sampling onto a set of 151 individual grids, at sequential time intervals as short as 1 min. After collection, the samples are sealed and refrigerated pending analysis. The utility of the TRAC-CCSEM/EDX approach is exemplified using the aerosol samples collected during the Texas 2000 Air Quality Study (August 15-September 15, 2000). We are able to follow the time evolution in the relative contribution of nonvolatile particles such as ammonium sulfate, mineral dust, sea salt, and carbonaceous in the aerosol makeup. The results show, among other things, the diurnal cycles in appearance of fine carbonaceous and ammonium sulfate particles and substantial mixing/coating of mineral particles with ammonium sulfates.
    BibTeX:
    @article{Laskin2003,
      author = {Laskin, Alexander and Iedema, Martin J. and Cowin, James P.},
      title = {Time-Resolved Aerosol Collector for CCSEM/EDX Single-Particle Analysis},
      journal = {Aerosol Science and Technology},
      publisher = {Taylor & Francis},
      year = {2003},
      volume = {37},
      number = {3},
      pages = {246--260},
      url = {http://www.informaworld.com/10.1080/02786820300945}
    }
    
    Leifer, R.Z., Bench, G.S. & Cahill, T.A. Characterization of the Plumes Passing over Lower Manhattan after the World Trade Center Disaster 2005
    Vol. 919ACS Symposium Series, pp. 135-151- 
    incollection URL 
    Abstract: During the three-month period from October 1, 2001 to December 15, 2001 impactor measurements were carried out on the roof of the Environmental Measurements Laboratory (EML), approximately 45 m above the street level in New York City, to characterize plumes passing over the laboratory. Depending on the wind direction it was hoped to intercept aerosols originating from the disaster of the World Trade Center. More than 25 plumes were detected in our samples. With southwest winds on October 3, an aerosol plume, transported from the WTC, was observed over EML. The total particulates collected on all stages reached a peak mass concentration of 267 ?g/m3 at 08:15 with more than 39% of the mass in the 0.56 to 0.34 ?m stage. The October 3rd sample showed that almost 75% of the total mass at the peak seen at EML was below 1.15 ?m. The observed size distribution was bimodal and showed a strong temporal variation as the modes shifted from a dominant coarse to a fine mode. The detected plume lasted for more than 9 hours. It is this fine particulate mode that is of concern to human health exposure.
    BibTeX:
    @incollection{Z.2005,
      author = {Leifer, Robert Z. and Bench, Graham S. and Cahill, Thomas A.},
      title = {Characterization of the Plumes Passing over Lower Manhattan after the World Trade Center Disaster},
      booktitle = {ACS Symposium Series},
      publisher = {American Chemical Society},
      year = {2005},
      volume = {919},
      pages = {135-151--},
      url = {http://dx.doi.org/10.1021/bk-2006-0919.ch008}
    }
    
    Leifer, R.Z., Jacob, E.M., Marschke, S.F. & Pranitis, D.M. ATMOSPHERIC AEROSOL MEASUREMENTS OF 238U AND 232Th AT FERNALD, OHIO, AND IMPLICATIONS ON INHALATION DOSE CALCULATIONS 2002 Health Physics
    Vol. 83(6), pp. - 
    article URL 
    Abstract: mdash;Measurements of the aerosol size distribution of 238U and 232Th at the U.S. Department of Energy's Fernald Environmental Management Project site were made to improve the inhalation dose calculations to off-site individuals. For approximately 1 y an 8-stage cascade impactor was co-located with a high volume sampler and operated at the Fernald Environmental Management Project site to collect aerosol samples. During most of the year, the site was dominated by giant particles with more than 70% of the mass of 238U above 15 [mu]m. The seasonal average of the activity median aerodynamic diameter, based on the impactor samples, which excluded particles >15 [mu]m, for both uranium and thorium was ~6.5 [mu]m. These numbers reflect the activities at the site and the domination of the resuspension processes. During most sampling periods the size distribution was bimodal. Thorium concentrations were comparable to the uranium concentrations during the late spring and summer period and decreased to ~25% of the 238U concentration in the late summer. Fernald Environmental Management Project is required to calculate the maximum allowable dose from airborne emissions, excluding radon, to meet NESHAP compliance. These calculations assume an AMAD of 1 [mu]m. We found that if you combine size distribution information with the latest ICRP 66 lung model you reduce the estimated dose by a factor of 7. Inclusion of the size distribution of radionuclides at any sampling site would substantially improve the dose estimates to the population. (C)2002Health Physics Society
    BibTeX:
    @article{Leifer2002,
      author = {Leifer, Robert Z. and Jacob, Ethel M. and Marschke, Stephen F. and Pranitis, David M.},
      title = {ATMOSPHERIC AEROSOL MEASUREMENTS OF 238U AND 232Th AT FERNALD, OHIO, AND IMPLICATIONS ON INHALATION DOSE CALCULATIONS},
      journal = {Health Physics},
      year = {2002},
      volume = {83},
      number = {6},
      pages = {--},
      url = {http://journals.lww.com/health-physics/Fulltext/2002/12000/ATMOSPHERIC_AEROSOL_MEASUREMENTS_OF_238U_AND_232Th.17.aspx}
    }
    
    Lundgren, D.A. Determination of particulate composition, concentration and size distribution changes with time 1971 Atmospheric Environment (1967)
    Vol. 5(8), pp. 645-651 
    article URL 
    Abstract: A sampling method which enables determination of paniculate composition and concentration from a single aerosol sample, both as a function of particle size and of time, is described. Analysis of the size-classified, time fractioned particulate samples can be accomplished by normal chemical or physical means. To illustrate this method's applicability several samples were analyzed, and results are presented for total weight distribution and particulate sulfate, nitrate, lead and iron concentration.
    BibTeX:
    @article{Lundgren1971,
      author = {Lundgren, Dale A.},
      title = {Determination of particulate composition, concentration and size distribution changes with time},
      journal = {Atmospheric Environment (1967)},
      year = {1971},
      volume = {5},
      number = {8},
      pages = {645--651},
      url = {http://www.sciencedirect.com/science/article/B757C-48CFYVR-1M/2/81e319398e834ba4c91b195d33ad384f}
    }
    
    Macias, E.S., Zwicker, J.O., Ouimette, J.R., Hering, S.V., Friedlander, S.K., Cahill, T.A., Kuhlmey, G.A. & Richards, L. Regional haze case studies in the southwestern U.S--I. Aerosol chemical composition 1981 Atmospheric Environment (1967)
    Vol. 15(10-11)Plumes and Visibility Measurements and Model Components, pp. 1971-1986 
    article URL 
    Abstract: Aerosol chemical composition as a function of particle size was determined in the southwestern U.S.A. during four weeks of sampling in June, July and December, 1979 as a part of project VISITA. Samples were collected at two ground stations about 80 km apart near Page (AZ) and in two aircraft flying throughout the region. Several different size separating aerosol samplers and chemical analysis procedures were intercompared and were used in determining the size distribution and elemental composition of the aerosol. Sulfur was shown to be in the form of water soluable sulfate, highly correlated with ammonium ion, and with an average [NH+4]/[SO2-4] molar ratio of 1.65. During the summer sampling period, three distinct regimes were observed, each with a different aerosol composition. The first, 24 h sampling ending 30 June, was characterized by a higher than average value of light scattering due to particles (bsp) of 24 � 10 -6m-1 and a fine particulate mass (Mf) of 8.5 [mu]g m-1. The fine particle aerosol was dominated by sulfate and carbon. Aircraft measurements showed the aerosol was homogeneous throughout the region at that time. The second regime, 5 July, had the highest average bsp of 51 � 10-6m-1 during the sampling period with Mf of 3.2 [mu]gm -3. The fine particle aerosol had nearly equal concentrations of carbon and ammonium sulfate. For all three regimes, enrichment factor analysis indicated fine and coarse particle Cu, Zn, Cl, Br, and Pb and fine particle K were enriched above crustal concentrations relative to Fe, indicating that these elements were present in the aerosol from sources other than wind blown dust. Particle extinction budgets calculated for the three regimes indicated that fine particles contributed most significantly, with carbon and (NH4)2SO4 making the largest contributions. Fine particle crustal elements including Si did not contribute significantly to the extinction budget during this study. The December sampling was characterized by very light fine particle loading with two regimes identified. One regime had higher fine mass and sulfate concentrations while the other had low values for all species measured.
    BibTeX:
    @article{Macias1981,
      author = {Macias, Edward S. and Zwicker, Judith O. and Ouimette, James R. and Hering, Susanne V. and Friedlander, Sheldon K. and Cahill, Thomas A. and Kuhlmey, Gregory A. and Richards, L.Willard},
      title = {Regional haze case studies in the southwestern U.S--I. Aerosol chemical composition},
      booktitle = {Plumes and Visibility Measurements and Model Components},
      journal = {Atmospheric Environment (1967)},
      year = {1981},
      volume = {15},
      number = {10-11},
      pages = {1971--1986},
      url = {http://www.sciencedirect.com/science/article/B757C-48CG0RJ-FK/2/b8bdd72a54a0df2bd7a49691b7e3cd3d}
    }
    
    Malm, W.C. & Day, D.E. Estimates of aerosol species scattering characteristics as a function of relative humidity 2001 Atmospheric Environment
    Vol. 35(16), pp. 2845-2860 
    article URL 
    Abstract: The absorption of water by ambient aerosols can significantly increase the light scattering coefficient and thereby affect issues such as visibility and climate forcing. Although water absorption by inorganic compounds and mixtures of inorganic compounds can often be modeled with adequate certainty for most applications, modeling water uptake by organic aerosols at present is speculative. In this paper, we present data in the form of f(RH)=bscat(RH)/bscat,dry , where bscat(RH) is the scattering coefficient measured at some relative humidity (RH)>20% and bscat,dry is the scattering coefficient measured at RH <20%. The f(RH) has been measured at Great Smoky Mountains National Park in Tennessee and at Grand Canyon National Park in Arizona. The f(RH) curves obtained from these two sites, which show distinctly different aerosol composition and average RH values, are compared. We also present comparisons between the measured water uptake by ambient aerosol with modeled water uptake by inorganic compounds to estimate the water uptake by organic aerosol.
    BibTeX:
    @article{Malm2001,
      author = {Malm, William C. and Day, Derek E.},
      title = {Estimates of aerosol species scattering characteristics as a function of relative humidity},
      journal = {Atmospheric Environment},
      year = {2001},
      volume = {35},
      number = {16},
      pages = {2845--2860},
      url = {http://www.sciencedirect.com/science/article/B6VH3-42YF8W4-6/2/8d7484f882164464b0d6a44f763c59f3}
    }
    
    Malm, W.C. & Pitchford, M.L. Comparison of calculated sulfate scattering efficiencies as estimated from size-resolved particle measurements at three national locations 1997 Atmospheric Environment
    Vol. 31(9), pp. 1315-1325 
    article URL 
    Abstract: Size distributions and resulting optical properties of sulfur aerosols were investigated at three national parks by a Davis Rotating-drum Universal-size-cut Monitoring (DRUM) impactor. Sulfur size distribution measurements for 88, 177, and 315 consecutive time periods were made at Grand Canyon National Park during January and February 1988, Meadview, AZ during July, August, and September 1992, and at Shenandoah National Park during summer, 1990, respectively. The DRUM impactor is designed to collect aerosols with an aerodynamic diameter between 0.07 and 15.0 [mu]m in eight size ranges. Focused beam particle-induced X-ray emission (PIXE) analysis of the aerosol deposits produces a time history of size-resolved elemental composition of varied temporal resolution. As part of the quality assurance protocol, an interagency monitoring of protected visual environments (IMPROVE) channel A sampler collecting 0-2.5 [mu]m diameter particles was operated simultaneously alongside the DRUM sampler. During these sampling periods, the average sulfur mass, interpreted as ammonium sulfate, is 0.49, 2.30, and 10.36 [mu]g m-3 at Grand Canyon, Meadview, and Shenandoah, respectively. The five drum stages were "inverted" using the Twomey (1975) scheme to give 486 size distributions, each made up of 72 discreet pairs of dC/dlog(D) and diameter (D). From these distributions mass mean diameters (Dg), geometric standard deviations ([sigma]g), and mass scattering efficiencies (em)) were calculated. The geometric mass mean diameters in ascending order were 0.21 [mu]m at Meadview, 0.32 [mu]m at Grand Canyon, and 0.42 [mu]m at Shenandoah corresponding [sigma]g were 2.1, 2.3, and 1.9. Mie theory mass scattering efficiencies calculated from dC/dlog(D) distributions for the three locations were 2.05, 2.59, and 3.81 m2 g-1, respectively. At Shenandoah, mass scattering efficiencies approached five but only when the mass median diameters were approximately 0.4 [mu]m and [sigma]g were about 1.5. [sigma]g near 1.5 were frequently measured at Shenandoah, rarely at Grand Canyon, and never during the summer at Meadview.
    BibTeX:
    @article{Malm1997,
      author = {Malm, William C. and Pitchford, Marc L.},
      title = {Comparison of calculated sulfate scattering efficiencies as estimated from size-resolved particle measurements at three national locations},
      journal = {Atmospheric Environment},
      year = {1997},
      volume = {31},
      number = {9},
      pages = {1315--1325},
      url = {http://www.sciencedirect.com/science/article/B6VH3-3SVR6GN-6/2/3a6968276d427a547962b2b41f66a976}
    }
    
    Malm, W.C., Sisler, J.F., Huffman, D., Eldred, R.A. & Cahill, T.A. Spatial and seasonal trends in particle concentration and optical extinction in the United States 1994 J. Geophys. Res.
    Vol. 99(D1), pp. 1347-1370 
    article URL 
    Abstract: In the spring of 1988 an interagency consortium of Federal Land Managers and the Environmental Protection Agency initiated a national visibility and aerosol monitoring network to track spatial and temporal trends of visibility and visibility-reducing particles. The monitoring network consists of 36 stations located mostly in the western United States. The major visibility-reducing aerosol species, sulfates, nitrates, organics, light-absorbing carbon, and wind-blown dust are monitored as well as light scattering and extinction. Sulfates and organics are responsible for most of the extinction at most locations throughout the United States, while at sites in southern California nitrates are dominant. In the eastern United States, sulfates contribute to about two thirds of the extinction. In almost all cases, extinction and the major aerosol types are highest in the summer and lowest during the winter months.
    BibTeX:
    @article{Malm1994,
      author = {Malm, William C. and Sisler, James F. and Huffman, Dale and Eldred, Robert A. and Cahill, Thomas A.},
      title = {Spatial and seasonal trends in particle concentration and optical extinction in the United States},
      journal = {J. Geophys. Res.},
      publisher = {AGU},
      year = {1994},
      volume = {99},
      number = {D1},
      pages = {1347--1370},
      url = {http://dx.doi.org/10.1029/93JD02916}
    }
    
    MARK, D., VINCENT, J.H., GIBSON, H., AITKEN, R.J. & LYNCH, G. THE DEVELOPMENT OF AN INHALABLE DUST SPECTROMETER 1984 Annals of Occupational Hygiene
    Vol. 28(1), pp. 125-143 
    article URL 
    BibTeX:
    @article{MARK1984,
      author = {MARK, D. and VINCENT, J. H. and GIBSON, H. and AITKEN, R. J. and LYNCH, G.},
      title = {THE DEVELOPMENT OF AN INHALABLE DUST SPECTROMETER},
      journal = {Annals of Occupational Hygiene},
      year = {1984},
      volume = {28},
      number = {1},
      pages = {125--143},
      url = {http://annhyg.oxfordjournals.org/content/28/1/125.abstract N2 - This paper describes the development of a prototype of a new dust spectrometer for sampling inhalable dust and providing the mass distribution of this as a function of particle aerodynamic diameter. From such information it is possible to obtain the aerodynamic size distribution and the airborne mass concentration of any health-related deposition sub-fraction which can be described quantitatively. Therefore, such an instrument has a wide range of potential applications in epidemiological research into dust-related health effects. A review of the literature suggested that a cascade impactor system would be the most suitable general form of spectrometer for the task in question.The new dust spectrometer is a portable static sampler consisting of an inhalable dust entry, a four-stage cascade impactor of the rectangular jet/rotating drum type (similar to that first proposed by LUNDGREN (1967), but with improved inter-stage geometry to minimize wall losses) and a pumping system. Auxiliary instrumentation includes a β-attenuation scanning system for assessing the masses of dust collected at each of the impactor stages.The instrument was tested and comprehensively calibrated in the laboratory and then employed in trials underground at a number of British coal mines. Its potential for carrying out the required functions under arduous practical conditions was clearly established. One particularly useful feature which emerged is its ability to provide information about the airborne dust as a function of time during a complete sampling run.}
    }
    
    Marple, V.A. & Willeke, K. Impactor design 1976 Atmospheric Environment (1967)
    Vol. 10(10), pp. 891-896 
    article URL 
    Abstract: The performance of an impactor can be accurately predicted, if design criteria which were numerically developed and experimentally proven, are adhered to. Based on these criteria, charts have been developed to aid in the design of round or rectangular impaction stages. In the case of round impactors, the desired cutoff size is related to the number and size of nozzles and to the total volumetric flow rate through the stage. In the case of rectangular impactors, the volumetric flow rate is expressed per unit length of the slot.
    BibTeX:
    @article{Marple1976,
      author = {Marple, Virgil A. and Willeke, Klaus},
      title = {Impactor design},
      journal = {Atmospheric Environment (1967)},
      year = {1976},
      volume = {10},
      number = {10},
      pages = {891--896},
      url = {http://www.sciencedirect.com/science/article/B757C-48CNKKM-121/2/bad057cc2da12004757583a31e9625f8}
    }
    
    May, K.R. Fog-droplet sampling using a modified impactor technique 1961 Quarterly Journal of the Royal Meteorological Society
    Vol. 87(374), pp. 535-548 
    article DOI URL 
    Abstract: Abstract Possible errors in sampling fog droplets with the cascade impactor are discussed and data are presented which were obtained from 25 fogs by the use of a specially modified impactor in a small portable wind-tunnel. A very wide range of drop diameter (< 1 to > 100 μ) was found, with great numbers of very small drops and great variability in size-distribution. Agreement between the visual range as calculated from the drop measurements and the actual visual range was usually closer than a factor of two, though in some cases there was no such agreement.
    BibTeX:
    @article{QJ:QJ49708737408,
      author = {May, K. R.},
      title = {Fog-droplet sampling using a modified impactor technique},
      journal = {Quarterly Journal of the Royal Meteorological Society},
      publisher = {John Wiley & Sons, Ltd},
      year = {1961},
      volume = {87},
      number = {374},
      pages = {535--548},
      url = {http://dx.doi.org/10.1002/qj.49708737408},
      doi = {http://dx.doi.org/10.1002/qj.49708737408}
    }
    
    May, K.R. The Cascade Impactor: An Instrument for Sampling Coarse Aerosols 1945 Journal of Scientific Instruments
    Vol. 22(10), pp. 187- 
    other URL 
    Abstract: A new instrument is described which will sample windborne and stationary aerosols such as natural fogs and clouds, fine sprays, insecticidal mists, coarse dusts, pollen and spores, etc. By means of four progressively finer jets impinging on glass slides in series the sample is split up into size-graded fractions in a form suitable for microscopic analysis. The greatest efficiency of sampling is achieved for particles in the range 50 μ-1.5μ diameter. The size-grading greatly facilitates the detailed microscopic examination of heterogeneous samples and in some cases enables approximate size-distributions to be obtained by bulk estimations of the samples without the need for microscopic sizing. Experimental results for the efficiency of jets in impacting particles are correlated by dimensional analysis, and a parameter of general applicability for estimating impaction efficiencies of jets is derived. Descriptions are given of new methods of dealing with volatile droplets and of analysing the samples.
    BibTeX:
    @other{May1945,
      author = {May, K R},
      title = {The Cascade Impactor: An Instrument for Sampling Coarse Aerosols},
      journal = {Journal of Scientific Instruments},
      year = {1945},
      volume = {22},
      number = {10},
      pages = {187--},
      url = {http://stacks.iop.org/0950-7671/22/i=10/a=303}
    }
    
    Mazzei, F., Lucarelli, F., Nava, S., Prati, P., Valli, G. & Vecchi, R. A new methodological approach: The combined use of two-stage streaker samplers and optical particle counters for the characterization of airborne particulate matter 2007 Atmospheric Environment
    Vol. 41(26), pp. 5525-5535 
    article URL 
    Abstract: We describe a new experimental methodology based on the contemporary use of two-stage continuous streaker samplers and optical particle counters. This is a complementary approach to size-segregated particulate matter (PM) sampling, and it is able to give information on the elemental size distribution and to assess the contribution of major PM source to size bins. PM samples in the fine and coarse fraction of PM10 have been collected by a two-stage streaker sampler and analyzed by particle-induced X-ray emission (PIXE) to obtain elemental concentration time series with hourly resolution. PM sources and profiles were singled out by positive matrix factorization (PMF). A multi-linear regression of size-segregated number of particles versus the sources, resolved by PMF, made possible the apportionment of size-segregated particles number in a fast and direct way. Results obtained in three sampling sites, located in different urban districts are discussed.
    BibTeX:
    @article{Mazzei2007,
      author = {Mazzei, Federico and Lucarelli, Franco and Nava, Silvia and Prati, Paolo and Valli, Gianluigi and Vecchi, Roberta},
      title = {A new methodological approach: The combined use of two-stage streaker samplers and optical particle counters for the characterization of airborne particulate matter},
      journal = {Atmospheric Environment},
      year = {2007},
      volume = {41},
      number = {26},
      pages = {5525--5535},
      url = {http://www.sciencedirect.com/science/article/B6VH3-4NHM5B1-2/2/6765ac96603dac3714e18f4eb77692fa}
    }
    
    Moffet, R.C., Desyaterik, Y., Hopkins, R.J., Tivanski, A.V., Gilles, M.K., Wang, Y., Shutthanandan, V., Molina, L.T., Abraham, R.G., Johnson, K.S., Mugica, V., Molina, M.J., Laskin, A. & Prather, K.A. Characterization of Aerosols Containing Zn, Pb, and Cl from an Industrial Region of Mexico City 2008 Environmental Science & Technology
    Vol. 42(19), pp. 7091-7097 
    article URL 
    Abstract: High time and size resolution coupled with single particle chemistry are used to help identify the sources of metal-containing industrial particles in Mexico City.
    BibTeX:
    @article{Moffet2008,
      author = {Moffet, Ryan C. and Desyaterik, Yury and Hopkins, Rebecca J. and Tivanski, Alexei V. and Gilles, Mary K. and Wang, Y. and Shutthanandan, V. and Molina, Luisa T. and Abraham, Rodrigo Gonzalez and Johnson, Kirsten S. and Mugica, Violeta and Molina, Mario J. and Laskin, Alexander and Prather, Kimberly A.},
      title = {Characterization of Aerosols Containing Zn, Pb, and Cl from an Industrial Region of Mexico City},
      journal = {Environmental Science & Technology},
      publisher = {American Chemical Society},
      year = {2008},
      volume = {42},
      number = {19},
      pages = {7091--7097},
      url = {http://dx.doi.org/10.1021/es7030483}
    }
    
    Moffet, R.C., Henn, T.R., Tivanski, A.V., Hopkins, R.J., Desyaterik, Y., Kilcoyne, A.L.D., Tyliszczak, T., Fast, J., Barnard, J., Shutthanandan, V., Cliff, S.S., Perry, K.D., Laskin, A. & Gilles, M.K. Microscopic characterization of carbonaceous aerosol particle aging in the outflow from Mexico City 2009 Atmos. Chem. Phys. Discuss.
    Vol. 9(4), pp. 16993-17033 
    other URL 
    BibTeX:
    @other{Moffet2009,
      author = {Moffet, R. C. and Henn, T. R. and Tivanski, A. V. and Hopkins, R. J. and Desyaterik, Y. and Kilcoyne, A. L. D. and Tyliszczak, T. and Fast, J. and Barnard, J. and Shutthanandan, V. and Cliff, S. S. and Perry, K. D. and Laskin, A. and Gilles, M. K.},
      title = {Microscopic characterization of carbonaceous aerosol particle aging in the outflow from Mexico City},
      journal = {Atmos. Chem. Phys. Discuss.},
      publisher = {Copernicus Publications},
      year = {2009},
      volume = {9},
      number = {4},
      pages = {16993--17033},
      url = {http://www.atmos-chem-phys-discuss.net/9/16993/2009/}
    }
    
    Nizkorodov, S.A., Laskin, J. & Laskin, A. Molecular chemistry of organic aerosols through the application of high resolution mass spectrometry 2011 Phys. Chem. Chem. Phys.
    Vol. 13(9), pp. 3612-3629 
    article URL 
    Abstract: Understanding the molecular composition and fundamental chemical transformations of organic aerosols (OA) during their formation and aging is both a major challenge and the area of great uncertainty in atmospheric research. Particularly, little is known about fundamental relationship between the chemical composition and physicochemical properties of OA, their atmospheric history, evolution, and the impact on the environment. Ambient soft-ionization methods combined with high-resolution mass spectrometry (HR-MS) analysis provide detailed information on the molecular content of OA that is pivotal for improving the understanding of their complex composition, multi-phase aging chemistry, direct (light absorption and scattering) and indirect (aerosol-cloud interactions) effects on atmospheric radiation and climate, health effects. The HR-MS methods can detect thousands of individual OA constituents at once, provide their elemental formulae from accurate mass measurements and structural information based on tandem mass spectrometry. Integration with additional analytical tools, such as chromatography and UV/Vis absorption spectroscopy, makes it possible to further separate OA compounds by their polarity and ability to absorb solar radiation. The goal of this perspective is to describe contemporary HR-MS methods, review recent applications in field and laboratory studies of OA, and explain how the information obtained from HR-MS methods can be translated into an improved understanding of OA chemistry.
    BibTeX:
    @article{Nizkorodov2011,
      author = {Nizkorodov, Sergey A. and Laskin, Julia and Laskin, Alexander},
      title = {Molecular chemistry of organic aerosols through the application of high resolution mass spectrometry},
      journal = {Phys. Chem. Chem. Phys.},
      publisher = {The Royal Society of Chemistry},
      year = {2011},
      volume = {13},
      number = {9},
      pages = {3612--3629},
      url = {http://dx.doi.org/10.1039/C0CP02032J}
    }
    
    O'Shaughnessy, P.T. & Raabe, O.G. A Comparison of Cascade Impactor Data Reduction Methods 2003 Aerosol Science and Technology
    Vol. 37(2), pp. 187-200 
    article URL 
    Abstract: The mass median aerodynamic diameter, d g , and geometric standard deviation, † g , of an aerosol is typically determined from a reduction of data obtained with a cascade impactor under the simplifying assumption that each stage of the impactor has an ideal collection efficiency. Two such reduction techniques are described and compared to an "inversion" method that incorporates the actual collection efficiencies of an impactor. Theoretical comparisons were made to demonstrate the difference in the estimate of d g and † g between the 2 ideal reduction methods and the inversion technique. Results indicated that, in general, both d g and † g are overestimated when the collection efficiencies are assumed to be ideal. A spreadsheet application of the inversion method is described.
    BibTeX:
    @article{O'Shaughnessy2003,
      author = {O'Shaughnessy, Patrick T. and Raabe, Otto G.},
      title = {A Comparison of Cascade Impactor Data Reduction Methods},
      journal = {Aerosol Science and Technology},
      publisher = {Taylor & Francis},
      year = {2003},
      volume = {37},
      number = {2},
      pages = {187--200},
      url = {http://www.informaworld.com/10.1080/02786820300956}
    }
    
    Ondov, J., Buckley, T., Hopke, P., Ogulei, D., Parlange, M., Rogge, W., Squibb, K., Johnston, M. & Wexler, A. Baltimore Supersite: Highly time- and size-resolved concentrations of urban PM2.5 and its constituents for resolution of sources and immune responses 2006 Atmospheric Environment
    Vol. 40(Supplement 2)Particulate Matter Supersites Program and Related Studies, Particulate Matter Supersites Program and Related Studies, pp. 224-237 
    article URL 
    Abstract: Protection of public health from the effects of air particulate matter (PM) requires measurements and methods that assess the PM chemical constituents, physical properties, and their sources. Sampling was conducted at three sites in the Baltimore area: a source-oriented (industrial) area in south Baltimore (FMC site), and two receptor area sites (Clifton Park and Ponca Street). FMC measurements were made for the initial 1-month of the project; Clifton measurements lasted for about 2 months, while measurements at Ponca Street lasted for about 9.5 months. Pollutant samples were collected at intervals ranging from 5�min to 1�h using semi-continuous monitors for PM2.5 mass, sulfate, nitrate, elemental and organic carbon, particle number size distributions (10-20,000�nm), CO, NOx, O3, 11 metals, and mass spectra of individual particles, throughout the project. In addition to standard meteorological measurements, a 3D-sonic anemometer and a LIDAR system were operated during selected periods as were a rotating drum impactor with 3- to 6-h resolution and a filter/PUF sampler for 3-h measurements of organic compounds. Standard speciation and FRM mass measurements were also made. This report describes the types of measurements that were made at the various sites of the Baltimore Supersite program as well as presents the summary statistics for some of the PM measurements that have been made. The measurements of aerosol mass, major components, and size distribution data for the three sites are compared. Results show comparable PM concentrations at Ponca Street and Clifton Park. Increased variability was observed at Ponca Street.
    BibTeX:
    @article{Ondov2006,
      author = {Ondov, J.M. and Buckley, T.J. and Hopke, P.K. and Ogulei, D. and Parlange, M.B. and Rogge, W.F. and Squibb, K.S. and Johnston, M.V. and Wexler, A.S.},
      title = {Baltimore Supersite: Highly time- and size-resolved concentrations of urban PM2.5 and its constituents for resolution of sources and immune responses},
      booktitle = {Particulate Matter Supersites Program and Related Studies, Particulate Matter Supersites Program and Related Studies},
      journal = {Atmospheric Environment},
      year = {2006},
      volume = {40},
      number = {Supplement 2},
      pages = {224--237},
      url = {http://www.sciencedirect.com/science/article/B6VH3-4KGG65S-3/2/ba25ea807ce559ec3fa13911ff2ae6b6}
    }
    
    Perry, K.D., Cahill, T.A., Eldred, R.A., Dutcher, D.D. & Gill, T.E. Long-range transport of North African dust to the eastern United States 1997 J. Geophys. Res.
    Vol. 102(D10), pp. 11225-11238 
    article URL 
    Abstract: The long-range transport of North African dust to the Middle East, Europe, South America, and the Caribbean has been well documented during the past 25 years. With the advent of routine collection and analysis of fine aerosols at national parks, monuments, and wilderness areas in the continental United States, these North African dust incursions can now be tracked, characterized, and quantified across much of the eastern half of the United States. Identification of the North African source of these dust episodes is confirmed by mass distribution measurements, a characteristic Al/Ca ratio, isentropic backward air mass trajectories, and sequential plots of the spatial distribution of the dust plumes. North African dust incursions into the continental United States persist for &#8764;10 days and occurred, on average, 3 times per year from 1992 to 1995. Fine soil mass usually exceeds 10 &#956;g m&#8722;3 during these dust episodes and dominates local fine soil dust by an order of magnitude or more, even in the so-called &#8220;dust bowl&#8221; states of the central United States. Size-resolved measurements of elemental composition taken during July 1995 indicate that the mass mean diameter of the transported North African dust is &lt; 1 &#956;m. The high mass scattering efficiency and abundant particle surface area associated with these submicron soil aerosols could have important consequences for both the radiative balance of the region and the chemistry of the local aerosols during summer when the long-range transport of North African dust to the United States is most common.
    BibTeX:
    @article{Perry1997,
      author = {Perry, Kevin D. and Cahill, Thomas A. and Eldred, Robert A. and Dutcher, Dabrina D. and Gill, Thomas E.},
      title = {Long-range transport of North African dust to the eastern United States},
      journal = {J. Geophys. Res.},
      publisher = {AGU},
      year = {1997},
      volume = {102},
      number = {D10},
      pages = {11225--11238},
      url = {http://dx.doi.org/10.1029/97JD00260}
    }
    
    Perry, K.D., Cliff, S.S. & Jimenez-Cruz, M.P. Evidence for hygroscopic mineral dust particles from the Intercontinental Transport and Chemical Transformation Experiment 2004 J. Geophys. Res.
    Vol. 109(D23), pp. D23S28- 
    article URL 
    Abstract: Two collocated, eight-stage rotating drum impactors were deployed at Trinidad Head (California) during the spring of 2002 as part of the Intercontinental Transport and Chemical Transformation 2002 (ITCT 2K2) experiment. One of the samplers operated at ambient relative humidity while the other was operated at a relative humidity of 55%. The impaction substrates from these samplers were analyzed using synchrotron X-ray fluorescence (SXRF) to provide continuous measurements of the size-resolved aerosol elemental composition with 3-hour time resolution. The aerosol elemental composition data identified three significant mineral dust episodes near the beginning of the time series. The backward air mass trajectory calculations from the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model and the PM10 to PM2.5 elemental mass ratios are consistent with the long-range transport of mineral dust from Asian sources. The data from the paired ambient relative humidity and low-relative-humidity samplers show that the aluminum, silicon, and iron elemental mass distributions are a function of relative humidity. In each case, the elemental mass distributions shifted toward smaller sizes as the relative humidity was reduced. This behavior indicates that the mineral dust transported from Asia to the west coast of the United States is somewhat hygroscopic upon its arrival. The hygroscopic nature of the aged mineral dust should increase its ability to nucleate cloud droplets (i.e., act as cloud condensation nuclei). Measurements of transported Asian mineral dust made at a high-elevation mountain site in Oregon (i.e., Crater Lake National Park) during the spring of 2002 show a strong correlation between the silicon and sulfur elemental mass concentrations. The ratio of calcium to sulfur makes it unlikely that this coarse sulfur is derived from gypsum (i.e., CaSO4). Instead, it indicates that the coarse mineral dust most likely accumulates sulfate coatings either near the source region or during transport across the Pacific Ocean.
    BibTeX:
    @article{Perry2004,
      author = {Perry, Kevin D. and Cliff, Steven S. and Jimenez-Cruz, Michael P.},
      title = {Evidence for hygroscopic mineral dust particles from the Intercontinental Transport and Chemical Transformation Experiment},
      journal = {J. Geophys. Res.},
      publisher = {AGU},
      year = {2004},
      volume = {109},
      number = {D23},
      pages = {D23S28--},
      url = {http://dx.doi.org/10.1029/2004JD004979}
    }
    
    Per�-Trepat, E., Kim, E., Paatero, P. & Hopke, P.K. Source apportionment of time and size resolved ambient particulate matter measured with a rotating DRUM impactor 2007 Atmospheric Environment
    Vol. 41(28), pp. 5921-5933 
    article URL 
    Abstract: Ambient particulate chemical composition data acquired from samples collected using a three-stage Davis Rotating-drum Universal-size-cut Monitoring (DRUM) impactor in Detroit, MI, between February and April 2002 were analyzed through the application of a three-way factor analysis model. PM2.5 (particulate matter [less-than-or-equals, slant]2.5�[mu]m in aerodynamic diameter) was collected by a DRUM impactor with 3-h time resolution and three size modes (2.5�[mu]m>Dp>1.15�[mu]m, 1.15�[mu]m>Dp>0.34�[mu]m and 0.34�[mu]m>Dp>0.1�[mu]m). A novel three-way factor analysis model was applied to these data where the source profiles are a three-way array of size, composition and source while the contributions are a matrix of sample by source. Nine factors were identified: road salt, industrial (Fe+Zn), cloud processed sulfate, two types of metal works, road dust, local sulfate source, sulfur with dust, and homogeneously formed sulfate. Road salt had high concentrations of Na and Cl. Mixed industrial emissions are characterized by Fe and Zn. The cloud processed sulfate had a high concentration of S in the intermediate size mode. The first metal works represented by Fe in all three size modes and by Zn, Ti, Cu, and Mn. The second included a high concentration of small size particle sulfur with intermediate size Fe, Zn, Al, Si, and Ca. Road dust contained Na, Al, Si, S, K, and Fe in the large size mode. The local and homogeneous sulfate factors show high concentrations of S in the smallest size mode, but different time series behavior in their contributions. Sulfur with dust is characterized by S and a mix of Na, Mg, Al, Si, K, Ca, Ti, and Fe from the medium and large size modes. This study shows that the utilization of time and size resolved DRUM data can assist in the identification of sources and atmospheric processes leading to the observed ambient concentrations.
    BibTeX:
    @article{Pere-Trepat2007,
      author = {Per�-Trepat, Emma and Kim, Eugene and Paatero, Pentti and Hopke, Philip K.},
      title = {Source apportionment of time and size resolved ambient particulate matter measured with a rotating DRUM impactor},
      journal = {Atmospheric Environment},
      year = {2007},
      volume = {41},
      number = {28},
      pages = {5921--5933},
      url = {http://www.sciencedirect.com/science/article/B6VH3-4NB99N7-1/2/414e0521a5b1a500a01e5aa21973c727}
    }
    
    Raabe, O.G., Braaten, D.A., Axelbaum, R.L., Teague, S.V. & Cahill, T.A. Calibration studies of the drum impactor 1988 Journal of Aerosol Science
    Vol. 19(2), pp. 183-195 
    article URL 
    Abstract: Calibration studies were performed on the Davis Rotating-drum Universal-size-cut Monitoring (DRUM) sampler utilizing fluorescent monodisperse aerosols of polystyrene latex. The DRUM sampler is an eight-stage Lundgren-type rotating drum cascade impactor utilizing a series of single round jets for each stage including low-pressure stages. The DRUM sampler operates continuously for up to 2 weeks with particle collection on slowly rotating, greased substrate-coated cylindrical drums. The resulting narrow linear deposit for each stage can be evaluated with time resolution as short as 4 h utilizing Particle Induced X-ray Emission (PIXE) spectroscopy and other analytical methods. The DRUM sampler is particularly useful for evaluating environmental aerosols for size-related chemical properties. Aerosols of monodisperse fluorescent polystyrene latex spheres were generated by nebulization from dilute aqueous suspensions, dried with a diffusion drier, and reduced in electrostatic charge with a krypton-85 discharger. The aerosols were characterized by electron microscopy and with a Climet-208 light scattering particle counter; they were quantified utilizing the fluorescent label. DRUM samples were collected at selected flow rates up to the critical 18.3 cm3 s-1, and the square root of the non-dimensionalized Stokes' number was plotted vs collection efficiency for the impactor stages. The results were in reasonable agreement with the expected effective cut-off aerodynamic diameters based on the non-dimensionalized theory of Marple and with the data of Mercer. All the stages demonstrated dynamic similarity when the Stokes' numbers were calculated at the reduced pressure and temperature at orifice outlets with orifice areas corrected for contraction at sonic and near sonic speeds. The measured cut-off values for another low pressure impactor were verified with these results. A wall loss study was conducted using polydisperse respirable aerosols of ammonium fluorescein generated by nebulization with a Lovelace nebulizer, dried with a diffusion drier, and reduced to Boltzmann equilibrium with a krypton-85 discharger. The results show wall losses to be about 10.7% of the sample.
    BibTeX:
    @article{Raabe1988,
      author = {Raabe, Otto G and Braaten, David A and Axelbaum, Richard L and Teague, Stephen V and Cahill, Thomas A},
      title = {Calibration studies of the drum impactor},
      journal = {Journal of Aerosol Science},
      year = {1988},
      volume = {19},
      number = {2},
      pages = {183--195},
      url = {http://www.sciencedirect.com/science/article/B6V6B-4893VN7-N/2/b067d4c1c1d32a2218e262325053f09b}
    }
    
    Rao, A. & Whitby, K. Non-ideal collection characteristics of inertial impactors--II. Cascade impactors 1978 Journal of Aerosol Science
    Vol. 9(2), pp. 87-100 
    article URL 
    Abstract: Calibration of the four-stage Lundgren impactor and the six-stage Andersen sampler with oil particles, and particle bounce in the Andersen sampler with solid particles are described. Collection characteristics of oil-coated steel plates, uncoated steel plates, glass fiber filters and Whatman filters in the Andersen sampler were determined using monodisperse polystyrene latex and methylene blue aerosols. For the Lundgren impactor, whose design and operation satisfy the assumptions of impactor theory, the calibration curves are in good agreement with the theoretical curves. However, the calibration curves of the Andersen sampler are less steep and are shifted towards higher aerodynamic dia. With oil-coated steel plates, the collection efficiency curves rise monotonically from zero to 100% efficiency. However, with uncoated steel plates, the efficiency curves rise up to 20 or 50% and then drop. The peak efficiency of stages is very sensitive to jet velocity and to some extent to particle size. The use of glass fiber filters as collection surface minimizes bounce, but modifies the collection characteristics. Some Whatman filter papers are unsatisfactory as collection surfaces.
    BibTeX:
    @article{Rao1978,
      author = {Rao, A.K. and Whitby, K.T.},
      title = {Non-ideal collection characteristics of inertial impactors--II. Cascade impactors},
      journal = {Journal of Aerosol Science},
      year = {1978},
      volume = {9},
      number = {2},
      pages = {87--100},
      url = {http://www.sciencedirect.com/science/article/B6V6B-48BC8JC-5X/2/d0af428346d03682d7fb605db6b0b818}
    }
    
    Reid, E.A., Reid, J.S., Meier, M.M., Dunlap, M.R., Cliff, S.S., Broumas, A., Perry, K. & Maring, H. Characterization of African dust transported to Puerto Rico by individual particle and size segregated bulk analysis 2003 J. Geophys. Res.
    Vol. 108(D19), pp. 8591- 
    article URL 
    Abstract: As part of the Puerto Rico Dust Experiment (PRIDE), airborne and surface dust particle samples from Africa were collected and subjected to bulk elemental and single-particle analysis. Airborne samples were collected on polycarbonate filters at various altitudes and underwent single-particle scanning electron microscopy with energy dispersive analysis with X-rays (EDAX) to derive elemental ratios of key soil elements. Particle chemistry was related to size and morphological characteristics. At the principle surface site, particles were collected on a Davis Rotating Drum (DRUM) cascade impactor strips in eight stages from 0.1 to 12 &#956;m at 4 hour time resolution. These samples were subjected to X-ray florescence (XRF) to determine bulk elemental composition from Al through Zn. The elemental data showed good correlation between the DRUM and the aircraft samples. Cluster analysis of single-particle data resulted in 63 statistically significant clusters. Several clusters can be easily related to their parent mineralogical species. However, as dust particles are to a large extent aggregates, most clusters are based on a continuum of varied mineralogical species and cannot be easily categorized. With 60,500 total particles counted from the airborne filters, a statistically significant number of large particles could be analyzed. Estimated mean surface area modal diameter is &#8764;5 &#956;m, with an average aspect ratio of 1.9. An apparent change in source region is seen in the morphological data and non alumino-silicate minerals but is not seen in the aluminum to silicon ratio. We suspect homogenization during long-range transport.
    BibTeX:
    @article{Reid2003a,
      author = {Reid, Elizabeth A. and Reid, Jeffrey S. and Meier, Michael M. and Dunlap, Michael R. and Cliff, Steven S. and Broumas, Aaron and Perry, Kevin and Maring, Hal},
      title = {Characterization of African dust transported to Puerto Rico by individual particle and size segregated bulk analysis},
      journal = {J. Geophys. Res.},
      publisher = {AGU},
      year = {2003},
      volume = {108},
      number = {D19},
      pages = {8591--},
      url = {http://dx.doi.org/10.1029/2002JD002935}
    }
    
    Reid, J.S., Cahill, T.A., Wakabayashi, P.H. & Dunlap, M.R. Geometric/aerodynamic equivalent diameter ratios of ash aggregate aerosols collected in burning Kuwaiti well fields 1994 Atmospheric Environment
    Vol. 28(13), pp. 2227-2234 
    article URL 
    Abstract: The ratio of aerodynamic equivalent diameter to geometric diameter was found for aerosols collected at ground-level from burning oil fields in Kuwait. Ash and soil aerosols collected using an eight-stage DRUM impactor were geometrically sized by scanning electron microscopy. Ash aggregates are shown to have a geometric diameter over an order of magnitude larger than their aerodynamic value. Additionally, ash aggregates showed changes in both particle and aggregate morphology with aerodynamic size.
    BibTeX:
    @article{Reid1994,
      author = {Reid, Jeffrey S. and Cahill, Thomas A. and Wakabayashi, Paul H. and Dunlap, Michael R.},
      title = {Geometric/aerodynamic equivalent diameter ratios of ash aggregate aerosols collected in burning Kuwaiti well fields},
      journal = {Atmospheric Environment},
      year = {1994},
      volume = {28},
      number = {13},
      pages = {2227--2234},
      url = {http://www.sciencedirect.com/science/article/B6VH3-4BSFJJ5-W/2/e6ef88dca7c87bcb3c7878de9bc419f9}
    }
    
    Reid, J.S., Flocchini, R.G., Cahill, T.A., Ruth, R.S. & Salgado, D.P. Local meteorological, transport, and source aerosol characteristics of late autumn Owens Lake (dry) dust storms 1994 Atmospheric Environment
    Vol. 28(9), pp. 1699-1706 
    article URL 
    Abstract: The time evolution of aerosol generation in the saltation dominated fine particle production from Owens (dry) Lake, California, was measured by size and elemental composition for four dust events in November-December 1991. Time resolved aerosol size distributions were measured during all storm periods from genesis to cessation at the township of Keeler, less than 1 km from the border of one of the dust-producing regions. The size distributions of aerosols showed a much greater concentration of soil elements in very fine modes than is usual in typical soils, with a PM10 mass median diameter in the 2.5-5 [mu]m size range. Four meteorological stations on and around the lake, time lapse photography of the northern lake bed, and nephelometers located 100 km to the south allowed for the continuous monitoring of local meteorology as well as transport patterns during storm periods. Local meteorological and transport patterns observed are discussed.
    BibTeX:
    @article{Reid1994a,
      author = {Reid, Jeffrey S. and Flocchini, Robert G. and Cahill, Thomas A. and Ruth, Robert S. and Salgado, Daniel P.},
      title = {Local meteorological, transport, and source aerosol characteristics of late autumn Owens Lake (dry) dust storms},
      journal = {Atmospheric Environment},
      year = {1994},
      volume = {28},
      number = {9},
      pages = {1699--1706},
      url = {http://www.sciencedirect.com/science/article/B6VH3-4BSMHWM-28/2/ace6259bb17d30e0551dbefe8de7b353}
    }
    
    Reid, J.S., Jonsson, H.H., Maring, H.B., Smirnov, A., Savoie, D.L., Cliff, S.S., Reid, E.A., Livingston, J.M., Meier, M.M., Dubovik, O. & Tsay, S.-C. Comparison of size and morphological measurements of coarse mode dust particles from Africa 2003 J. Geophys. Res.
    Vol. 108(D19), pp. 8593- 
    article URL 
    Abstract: A multitude of sensitivity studies in the literature point to the importance of proper chemical and morphological characterization of particles when the radiative impacts of airborne dusts are modeled. However, the community data set is based on heterogeneous measurement methods relying on varying aerodynamic, chemical, morphological, and optical means. During the Puerto Rico Dust Experiment, size distributions of dust particles from Africa were measured using a variety of aerodynamic, optical, and geometric means. Consistent with the literature, comparisons of these size distributions showed quite dissimilar results. &#8220;Measured&#8221; volume median diameters varied from 2.5 to 9 &#956;m for various geometric, aerodynamic, optical, and optical inversion methods. Aerodynamic systems showed mixed performance. Column integrated size distributions inverted from AERONET Sun/sky radiance data produced somewhat reasonable results in the coarse mode when given proper constraints and taken in the proper context. The largest systematic errors were found in optical particle counters due to insensitivities to particle size in the 4&#8211;10 &#956;m region with further complications due to dust particle morphology and index of refraction issues. As these methods can produce quite dissimilar size distributions, considerable errors in calculated radiative properties can occur if incorrectly modeled into dust parameters. None of the methods compared in this study can adequately reproduce the measured mass extinction or mass scattering efficiency of the dust using spherical geometry methods. Given all of the uncertainties in the sizing methods, we promote the use of fundamental and quantifiable descriptors of particles such as mass as a function of aerodynamic diameter.
    BibTeX:
    @article{Reid2003,
      author = {Reid, Jeffrey S. and Jonsson, Halflidi H. and Maring, Hal B. and Smirnov, Alexander and Savoie, Dennis L. and Cliff, Steven S. and Reid, Elizabeth A. and Livingston, John M. and Meier, Mike M. and Dubovik, Oleg and Tsay, Si-Chee},
      title = {Comparison of size and morphological measurements of coarse mode dust particles from Africa},
      journal = {J. Geophys. Res.},
      publisher = {AGU},
      year = {2003},
      volume = {108},
      number = {D19},
      pages = {8593--},
      url = {http://dx.doi.org/10.1029/2002JD002485}
    }
    
    Reid, J.S., Reid, E.A., Walker, A., Piketh, S., Cliff, S., Al Mandoos, A., Tsay, S.-C. & Eck, T.F. Dynamics of southwest Asian dust particle size characteristics with implications for global dust research 2008 J. Geophys. Res.
    Vol. 113(D14), pp. D14212- 
    article URL 
    Abstract: As part of the United Arab Emirates Unified Aerosol Experiment (UAE2), the size distribution and chemistry of dust particles were measured for the months of August and September 2004 at an Arabian Gulf coastal site impacted by dust from several sources within southwest Asia. The characteristics of common mode dust (0.8 &lt; dp &lt; 10 &#956;m) were examined using an aerodynamic particle sizer (APS), a DRUM cascade impactor, and AERONET Sun/sky retrievals. While size properties from these distinct methods do correlate, accurate dust measurement is still an outstanding challenge. But when instruments are applied consistently in the correct context, the dynamics of dust particle size can be accurately studied. Here, observations are used to study the stability of dust size and chemistry characteristics. We found that dust particle size, chemistry, and morphology appear to be fairly static from individual sources, confirming preliminary hypotheses based on large-scale observations of Saharan dust. Thus, our data provide experimental evidence that on regional scales, common mode dust is not functionally impacted by production wind speed, but rather influenced by soil properties such as geomorphology or roughness length. Similarly, we found transport processes from the mesoscale to near synoptic scale do not significantly impact common mode dust size either. When combined with other APS observations around the world, the dust coarse mode is found to be fairly robust with a volume median diameter on the order of &#8764;3.5 &#956;m � 30%. Finally, evidence for a strong submicron dust mode, suggested in previous studies, was inconclusive.
    BibTeX:
    @article{Reid2008,
      author = {Reid, Jeffrey S. and Reid, Elizabeth A. and Walker, Annette and Piketh, Stuart and Cliff, Steve and Al Mandoos, Abdulla and Tsay, Si-Chee and Eck, Thomas F.},
      title = {Dynamics of southwest Asian dust particle size characteristics with implications for global dust research},
      journal = {J. Geophys. Res.},
      publisher = {AGU},
      year = {2008},
      volume = {113},
      number = {D14},
      pages = {D14212--},
      url = {http://dx.doi.org/10.1029/2007JD009752}
    }
    
    Richard, A., Bukowiecki, N., Lienemann, P., Furger, M., Weideli, B., Fierz, M., Minguillón, M.C., Figi, R., Flechsig, U., Appel, K., Prévôt, A.S.H. & Baltensperger, U. Quantitative sampling and analysis of trace elements in ambient air: impactor characterization and Synchrotron-XRF mass calibration 2010 Atmos. Meas. Tech. Discuss.
    Vol. 3(3), pp. 2477-2513 
    article URL 
    BibTeX:
    @article{Richard2010,
      author = {Richard, A. and Bukowiecki, N. and Lienemann, P. and Furger, M. and Weideli, B. and Fierz, M. and Minguillón, M. C. and Figi, R. and Flechsig, U. and Appel, K. and Prévôt, A. S. H. and Baltensperger, U.},
      title = {Quantitative sampling and analysis of trace elements in ambient air: impactor characterization and Synchrotron-XRF mass calibration},
      journal = {Atmos. Meas. Tech. Discuss.},
      publisher = {Copernicus Publications},
      year = {2010},
      volume = {3},
      number = {3},
      pages = {2477--2513},
      url = {http://www.atmos-meas-tech-discuss.net/3/2477/2010/}
    }
    
    Salcedo, D., Onasch, T.B., Dzepina, K., Canagaratna, M.R., Zhang, Q., Huffman, J.A., DeCarlo, P.F., Jayne, J.T., Mortimer, P., Worsnop, D.R., Kolb, C.E., Johnson, K.S., Zuberi, B., Marr, L.C., Volkamer, R., Molina, L.T., Molina, M.J., Cardenas, B., Bernabé, R.M., Márquez, C., Gaffney, J.S., Marley, N.A., Laskin, A., Shutthanandan, V., Xie, Y., Brune, W., Lesher, R., Shirley, T. & Jimenez, J.L. Characterization of ambient aerosols in Mexico City during the MCMA-2003 campaign with Aerosol Mass Spectrometry: results from the CENICA Supersite 2006 Atmos. Chem. Phys.
    Vol. 6(4), pp. 925-946 
    article URL 
    BibTeX:
    @article{Salcedo2006,
      author = {Salcedo, D. and Onasch, T. B. and Dzepina, K. and Canagaratna, M. R. and Zhang, Q. and Huffman, J. A. and DeCarlo, P. F. and Jayne, J. T. and Mortimer, P. and Worsnop, D. R. and Kolb, C. E. and Johnson, K. S. and Zuberi, B. and Marr, L. C. and Volkamer, R. and Molina, L. T. and Molina, M. J. and Cardenas, B. and Bernabé, R. M. and Márquez, C. and Gaffney, J. S. and Marley, N. A. and Laskin, A. and Shutthanandan, V. and Xie, Y. and Brune, W. and Lesher, R. and Shirley, T. and Jimenez, J. L.},
      title = {Characterization of ambient aerosols in Mexico City during the MCMA-2003 campaign with Aerosol Mass Spectrometry: results from the CENICA Supersite},
      journal = {Atmos. Chem. Phys.},
      publisher = {Copernicus Publications},
      year = {2006},
      volume = {6},
      number = {4},
      pages = {925--946},
      url = {http://www.atmos-chem-phys.net/6/925/2006/}
    }
    
    Seinfeld, J.H., Carmichael, G.R., Arimoto, R., Conant, W.C., Brechtel, F.J., Bates, T.S., Cahill, T.A., Clarke, A.D., Doherty, S.J., Flatau, P.J., Huebert, B.J., Kim, J., Markowicz, K.M., Quinn, P.K., Russell, L.M., Russell, P.B., Shimizu, A., Shinozuka, Y., Song, C.H., Tang, Y., Uno, I., Vogelmann, A.M., Weber, R.J., Woo, J.-H. & Zhang, X.Y. ACE-ASIA: Regional Climatic and Atmospheric Chemical Effects of Asian Dust and Pollution 2004 Bulletin of the American Meteorological Society
    Vol. 85(3), pp. 367-380 
    article DOI URL 
    BibTeX:
    @article{doi:10.1175/BAMS-85-3-367,
      author = {Seinfeld, John H. and Carmichael, Gregory R. and Arimoto, Richard and Conant, William C. and Brechtel, Frederick J. and Bates, Timothy S. and Cahill, Thomas A. and Clarke, Antony D. and Doherty, Sarah J. and Flatau, Piotr J. and Huebert, Barry J. and Kim, Jiyoung and Markowicz, Krzysztof M. and Quinn, Patricia K. and Russell, Lynn M. and Russell, Philip B. and Shimizu, Atsushi and Shinozuka, Yohei and Song, Chul H. and Tang, Youhua and Uno, Itsushi and Vogelmann, Andrew M. and Weber, Rodney J. and Woo, Jung-Hun and Zhang, Xiao Y.},
      title = {ACE-ASIA: Regional Climatic and Atmospheric Chemical Effects of Asian Dust and Pollution},
      journal = {Bulletin of the American Meteorological Society},
      year = {2004},
      volume = {85},
      number = {3},
      pages = {367-380},
      url = {http://journals.ametsoc.org/doi/abs/10.1175/BAMS-85-3-367},
      doi = {http://dx.doi.org/10.1175/BAMS-85-3-367}
    }
    
    Shadoan, D., Barone, J. & Cahill, T. Above ground aerosol characterization utilizing PIXE analysis and airborne samplers 1981 Nuclear Instruments and Methods
    Vol. 181(1-3), pp. 503-508 
    article URL 
    Abstract: A particulate aerosol collection system has been developed and tested. The sampling system, designed for a wide range of aircraft, collects size-segregated particulate samples. Design features enable it to compensate for the constraints normally associated with aircraft sampling. Within UCD's PIXE analysis system, high flux, focused beams have been developed to analyze the particulate samples collected. Evaluation of the system has demonstrated its reliability, accuracy, and utility in many types of airborne sampling. Data from samples collected in California's Central Valley reveal striking differences between ground level and above ground aerosol composition.
    BibTeX:
    @article{Shadoan1981,
      author = {Shadoan, D.J. and Barone, J.B. and Cahill, T.A.},
      title = {Above ground aerosol characterization utilizing PIXE analysis and airborne samplers},
      journal = {Nuclear Instruments and Methods},
      year = {1981},
      volume = {181},
      number = {1-3},
      pages = {503--508},
      url = {http://www.sciencedirect.com/science/article/B73DN-471XD95-N1/2/f6f78309d49357ac97ae4c7827a49754}
    }
    
    Shutthanandan, V., Thevuthasan, S., Disselkamp, R., Stroud, A., Cavanagh, A., Adams, E., Baer, D., Barrie, L., Cliff, S., Jimenez-Cruz, M. & Cahill, T. Development of PIXE, PESA and transmission ion microscopy capability to measure aerosols by size and time 2002 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
    Vol. 189(1-4), pp. 284-288 
    article URL 
    Abstract: We describe a new capability that consists of a combination of proton induced X-ray emission (PIXE), proton elastic scattering analysis (PESA) and transmission ion microscopy (all performed at the same location on the sample) techniques to address some of the research needs associated with time series and size-dependent composition of atmospheric aerosols. Simultaneous measurements of PIXE and PESA can be performed on aerosols collected using 3 stage improved rotating DRUM impactor by size (Stage A: 2.5-1.15 [mu]m; Stage B: 0.34-1.15 [mu]m; Stage C: 0.07-0.34 [mu]m) with time resolution set by the rotation rate from 1 mm every 4 h to 1 mm every 6 min on a 16.8 cm long impaction strips that can be coated with Mylar, stretched Teflon, or aluminum, depending on the analysis method chosen. Preliminary measurements carried out using a 1 mm diameter proton beam were made on industrial test samples, yielding promising results at a time resolution of only 6 min.
    BibTeX:
    @article{Shutthanandan2002,
      author = {Shutthanandan, V. and Thevuthasan, S. and Disselkamp, R. and Stroud, A. and Cavanagh, A. and Adams, E.M. and Baer, D.R. and Barrie, L.A. and Cliff, S.S. and Jimenez-Cruz, M. and Cahill, T.A.},
      title = {Development of PIXE, PESA and transmission ion microscopy capability to measure aerosols by size and time},
      journal = {Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms},
      year = {2002},
      volume = {189},
      number = {1-4},
      pages = {284--288},
      url = {http://www.sciencedirect.com/science/article/B6TJN-44PDGK6-C/2/ede00a8c6d3bd9b4a968d97e96c094a4}
    }
    
    Thompson, N. The estimation of vertical diffusion over medium distances of travel 1966 Q.J.R. Meteorol. Soc.
    Vol. 92(392), pp. 270-276 
    article URL 
    Abstract: Abstract 10.1002/qj.49709239210.abs Experiments have been carried out in which the vertical diffusion of a tracer has been measured after several kilometres travel. Simultaneous measurements of atmospheric turbulence provided an opportunity to use the treatment described by Thompson (1965) to estimate the ratio of the Lagrangian and Eulerian scales of turbulence. The scale ratio was again found to increase with an increase in stability, with a variation in magnitude from near unity in unstable conditions to around 15 in moderate stabilities.
    BibTeX:
    @article{Thompson1966,
      author = {Thompson, N.},
      title = {The estimation of vertical diffusion over medium distances of travel},
      journal = {Q.J.R. Meteorol. Soc.},
      publisher = {John Wiley & Sons, Ltd},
      year = {1966},
      volume = {92},
      number = {392},
      pages = {270--276},
      url = {http://dx.doi.org/10.1002/qj.49709239210}
    }
    
    Uno, I., Satake, S., Carmichael, G.R., Tang, Y., Wang, Z., Takemura, T., Sugimoto, N., Shimizu, A., Murayama, T., Cahill, T.A., Cliff, S., Uematsu, M., Ohta, S., Quinn, P.K. & Bates, T.S. Numerical study of Asian dust transport during the springtime of 2001 simulated with the Chemical Weather Forecasting System (CFORS) model 2004 J. Geophys. Res.
    Vol. 109(D19), pp. D19S24- 
    article URL 
    Abstract: The regional-scale aerosol transport model Chemical Weather Forecasting System (CFORS) is used for analysis of large-scale dust phenomena during the Asian Pacific Regional Characterization Experiment (ACE-Asia) intensive observation. Dust modeling results are examined with the surface weather reports, satellite-derived dust index (Total Ozone Mapping Spectrometer (TOMS) Aerosol Index (AI)), Mie-scattering lidar observation, and surface aerosol observations. The CFORS dust results are shown to accurately reproduce many of the important observed features. Model analysis shows that the simulated dust vertical loading correlates well with TOMS AI and that the dust loading is transported with the meandering of the synoptic-scale temperature field at the 500-hPa level. Quantitative examination of aerosol optical depth shows that model predictions are within 20% difference of the lidar observations for the major dust episodes. The structure of the ACE-Asia Perfect Dust Storm, which occurred in early April, is clarified with the help of the CFORS model analysis. This storm consisted of two boundary layer components and one elevated dust (&gt;6-km height) feature (resulting from the movement of two large low-pressure systems). Time variation of the CFORS dust fields shows the correct onset timing of the elevated dust for each observation site, but the model results tend to overpredict dust concentrations at lower latitude sites. The horizontal transport flux at 130�E longitude is examined, and the overall dust transport flux at 130�E during March&#8211;April is evaluated to be 55 Tg.
    BibTeX:
    @article{Uno2004,
      author = {Uno, Itsushi and Satake, Shinsuke and Carmichael, Gregory R. and Tang, Youhua and Wang, Zifa and Takemura, Toshihiko and Sugimoto, Nobuo and Shimizu, Atsushi and Murayama, Toshiyuki and Cahill, Thomas A. and Cliff, Steven and Uematsu, Mitsuo and Ohta, Sachio and Quinn, Patricia K. and Bates, Timothy S.},
      title = {Numerical study of Asian dust transport during the springtime of 2001 simulated with the Chemical Weather Forecasting System (CFORS) model},
      journal = {J. Geophys. Res.},
      publisher = {AGU},
      year = {2004},
      volume = {109},
      number = {D19},
      pages = {D19S24--},
      url = {http://dx.doi.org/10.1029/2003JD004222}
    }
    
    VanCuren, R.A. & Cahill, T.A. Asian aerosols in North America: Frequency and concentration of fine dust 2002 J. Geophys. Res.
    Vol. 107(D24), pp. 4804- 
    article URL 
    Abstract: Using an elemental signature for Asian dust derived from events in April 1998, we probed a long-term set of routine aerosol samples to develop the first empirical assessment of the frequency and intensity of dust transport from Asia to midlatitude North America. Our data reveal a pattern of consistent, frequent transport that contradicts the episodic characterization derived from short-term studies and anecdotal reports. We find that fine (&lt;2.5 &#956;m) Asian dust is a regular component of the troposphere over the eastern Pacific and western North America and is common, at least in spring, across North America. Typical Asian fine dust concentrations (24-hour average) are between 0.2 and 1 &#956;g/m3 and only very rarely exceed 5 &#956;g/m3. Our data also indicate that Asian dust is concentrated in an altitude zone ranging from about 500 to 3000 m MSL, consistent with isentropic transport processes previously observed in the western Pacific.
    BibTeX:
    @article{VanCuren2002,
      author = {VanCuren, Richard A. and Cahill, Thomas A.},
      title = {Asian aerosols in North America: Frequency and concentration of fine dust},
      journal = {J. Geophys. Res.},
      publisher = {AGU},
      year = {2002},
      volume = {107},
      number = {D24},
      pages = {4804--},
      url = {http://dx.doi.org/10.1029/2002JD002204}
    }
    
    VanCuren, R.A., Cliff, S.S., Perry, K.D. & Jimenez-Cruz, M. Asian continental aerosol persistence above the marine boundary layer over the eastern North Pacific: Continuous aerosol measurements from Intercontinental Transport and Chemical Transformation 2002 (ITCT 2K2) 2005 J. Geophys. Res.
    Vol. 110(D9), pp. D09S90- 
    article URL 
    Abstract: We report analyses of aerosols collected for the 2002 Intercontinental Transport and Chemical Transformation experiment (ITCT-2K2). Sampling was conducted 15 April to 25 May 2002. Data are from three sites: a sea level site at Trinidad Head, California, a coastal mountain site 1 km altitude (Trinity Alps), and an inland mountain site near 2 km altitude (Mount Lassen). Aerosols were continuously collected in eight size bins (0.09 to 10 micrometers aerodynamic diameter) using eight-stage rotating drum impactors. Samples were analyzed in 3-hour time steps by synchrotron x-ray fluorescence. We find the following. (1) Aerosol chemical composition at Trinidad Head was generally dominated by marine aerosols with varying minor contributions from local sources. Despite the presence of Asian continental aerosol above the marine boundary layer, significant concentrations of Asian aerosols were observed at sea level only during a strong frontal passage between 22 and 25 April. (2) At the elevated sites, aerosol elemental composition was predominantly Asian despite wide swings in concentration. Analysis of soil-forming elements shows that Asian continental dust and associated combustion products overwhelmed local-source aerosols through the first half of the sampling period; in the latter half, Asian aerosols present in the free troposphere were regularly delivered to the mountain sampling sites by nocturnal subsidence. (3) Asian aerosols in the lower free troposphere, although highly variable, were very persistent, not arriving only in discrete &#8220;transport events.&#8221; We conclude that throughout the experiment the aerosols in the lower free troposphere over the northeastern Pacific Ocean and western North America were dominated by continental outflow from Asia, with little marine or North American continental influence. Viewed in the context of previously published analyses of the long-term aerosol history for Mount Lassen that showed frequent, strong Asian influence throughout spring, summer, and fall, the Asian impact appears likely to be quasi-continuous for much of the year.
    BibTeX:
    @article{VanCuren2005,
      author = {VanCuren, Richard A. and Cliff, Steven S. and Perry, Kevin D. and Jimenez-Cruz, Michael},
      title = {Asian continental aerosol persistence above the marine boundary layer over the eastern North Pacific: Continuous aerosol measurements from Intercontinental Transport and Chemical Transformation 2002 (ITCT 2K2)},
      journal = {J. Geophys. Res.},
      publisher = {AGU},
      year = {2005},
      volume = {110},
      number = {D9},
      pages = {D09S90--},
      url = {http://dx.doi.org/10.1029/2004JD004973}
    }
    
    Yu, X.-Y., Cowin, J.P., Iedema, M.J. & Ali, H. Fast time-resolved aerosol collector: proof of concept 2010 Atmospheric Measurement Techniques Discussions
    Vol. 3(3), pp. 2515-2534 
    article DOI URL 
    BibTeX:
    @article{amtd-3-2515-2010,
      author = {Yu, X.-Y. and Cowin, J. P. and Iedema, M. J. and Ali, H.},
      title = {Fast time-resolved aerosol collector: proof of concept},
      journal = {Atmospheric Measurement Techniques Discussions},
      year = {2010},
      volume = {3},
      number = {3},
      pages = {2515--2534},
      url = {http://www.atmos-meas-tech-discuss.net/3/2515/2010/},
      doi = {http://dx.doi.org/10.5194/amtd-3-2515-2010}
    }
    

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