MEASUREMENT OF THE PARTICLE-SIZE DISTRIBUTIONS OF SEMIVOLATILE ORGANIC CONTAMINANTS IN THE ATMOSPHERE

A method using a Berner five-stage, low-pressure cascade impactor was developed to measure the particle-size distributions of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere. Possible sampling artifacts that may occur when sampling semivolatile organic chemicals with this low-pressure particles impactor (e.g., absorption of vapors onto sampler surfaces or volatilization of analytes from collected particles under reduced pressures within the impactor) were quantified for a variety of PAHs in the laboratory. At 20 degrees C, these artifacts were insignificant for the collection of PAHs with vapor pressures less than 10(-8) atm. Several samples collected at a rural site (Egbert, Ontario) and an urban location (Chicago, IL) demonstrate the utility of the Berner impactor to collect PAHs under a variety of field conditions. At both the rural and urban locations, sufficient quantities of particles were collected in the five aerodynamic equivalent diameter size ranges (0.04-0.14, 0.14-0.49, 0.49-1.7, 1.7-6, and 6-21 mu m) during 12 h to provide detectable levels of PAHs. PAHs were most often associated with particles less than (-)1.7 mu m in both the rural and urban areas based on a limited number of observations (N = 5).