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Aerosol Chemistry Research at ASRC

Researchers:  Jim Schwab

Atmospheric aerosol particles have a proven influence on climate and play an important role in toxicological issues. To learn more about the chemical composition of these particles and about their impact on climate and human health, very sophisticated analytical technologies have to be applied. The assessment of new aerosol analysis technology is the main focus of aerosol physics researchers at ASRC.

In the PM Lab aerosols of a variety of chemical compounds are produced under well-known environmental conditions using a TSI Atomizer and DMA and the aerosol tube, developed at ASRC, which allows adjusting relative humidity and aerosol concentration. Aerosol characterization is done with a Scanning Mobility Particle Sizer (SMPS, TSI), Condensation Particle Counters (CPC, TSI), an Aerodynamic Particle Sizer (APS, TSI), on-line mass concentration measurement (TEOM, R&P) and filter samples (Partisol, R&P).

Beyond calibration and characterization of these particle instruments, a couple of recently developed aerosol analysis techniques are assessed in the Particle Lab: on-line Nitrate Monitors, on-line Sulfate Monitors and an on-line Aerosol Mass Spectrometer (AMS, Aerodyne, Inc.).

The AMS provides size resolved information on different selected particle components as well as aerosol bulk concentration of species with sufficient volatility. Ambient air is sampled into the AMS via a 100 mm pinhole at a flow of 0.1 l/min. The air passes an aerodynamic lens, which produces a fine particle beam from the aerosol particles in the sample, and expands into the vacuum chamber. Particles are accelerated in this supersonic expansion according to their aerodynamic size. After passing a chopper, the particle beam crosses a flight chamber and impacts on a resistively heated surface where volatile and semivolatile particle compounds evaporate. This vapor is ionized by electron impact and analyzed with a quadrupole mass spectrometer. Particle sizing is performed by flight time measurement.