Passive air samplers can be used to measure the air concentration of various semivolatile organic compounds (SOCs) with reasonable reliability. To use passive air samplers to measure atmospheric concentrations of pollutants, calibration data are required. Calibration data include parameters such as sampling rates, sampler/air partition coefficients and loss rate constants. These parameters are usually determined in the laboratory, at a reference site or in situ. When using passive sampler data to estimate the air concentration of SOCs, investigators commonly assume that sampling follows first-order exchange kinetics. Thus, during the first stage of sampler uptake, chemicals are accumulated linearly relative to time. The accumulation of many pollutants in passive air samplers is influenced by factors such as changes in wind speed and temperature. The use of performance reference compounds (PRCs) holds considerable promise for assessing the effects of wind speed and temperature on passive sampler performance. The use of PRCs in semipermeable membrane devices (SPMDs) has also shown that photolysis of accumulated polyaromatic hydrocarbons (PAHs) occurs without adequate shading.
