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DRUM Impactors separate particles by size and time

Since 1945, aerosol scientists have used cascade impactors to collect size segregated aerosol samples. A DRUM impactor is a special type of cascade impactor developed by the University of California's DELTA Group. In addition to separating aerosols by size, DRUM impactors using a rotating drum disk impaction surface to record time.

 

What is a cascade impactor?

A cascade impactor is an aerosol monitor that segregates particles into multiple sizes by using the particle's inertial forces. In a cascade impactor, an isokenetic airstream enters the sampler, passing through a specially-sized orifice. The airstream takes a sharp turn away from a perpendicular impaction surface. Larger particles, with greater inertial force impact; smaller particles, dominated by the viscus forces of the airstream, continue to another stage. In subsequent stages, the orifices have lower pressures and higher velocities, allowing smaller particles to impact.

Size

  • Particle size is important for evaluating particle transport. Large particles settle quickly from the atmosphere, whereas nano-particles remain in the atmosphere and travel across continents.
  • Human health effects depend on particle size. Larger particles impact in the nasal cavities. Fine particles, 1 micron in diameter, pass through the larynx and clog the alveoli of the lungs. Nanoparticles may enter into the boodstream and pass the blood/brain barrier.

Time

  • Extreme events may pass quickly, but are often the most damaging to living systems.
  • Temporal cycles are evident, when samples are taken continuously. See pollen emission, day/night cycles, traffic, seasonal changes, etc.
  • Peak concentrations can be traced back to their source using HYSPLIT trajectory models.