Polycyclic Aromatic Hydrocarbons and Polychlorinated Biphenyls in Air at an Urban and a Rural Site Near Lake Michigan

Abstract

Air samples were collected at an urban (Chicago, IL) and a rural (University of Wisconsin at Green Bay, UWGB) site during February 1988 to determine concentrations and particle/gas distributions of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). Geometric mean ΣPAHs of molecular weights ≥166 were 195 ng/m 3 in Chicago and 14 ng/m 3 at UWGB. Ratios among PAHs suggested that some labile compounds were depleted during atmospheric transport. Geometric mean ΣPCBs (45 congeners) were 1.3 ng/m 3 in Chicago and 0.13 ng/m 3 at UWGB. PCB profiles of most samples in Chicago and all at UWGB were skewed toward the lower molecular weight congeners, as in mixtures of Aroclors 1242 and 1254. Two Chicago samples showed a heavy PCB profile similar to Aroclor 1260. Apparent particle/gas partition coefficients (K p ) were well correlated with liquid-phase vapor pressures (po L ) within a class of compounds (PAHs or PCBs). PAHs were sorbed to a greater degree than PCBs for compounds of the same volatility. Slopes of log K p vs log p o L plots deviated from the expected value of -1 in Chicago, suggesting nonequilibrium effects. Aerosols at UWGB appeared to be closer to equilibrium with the gas phase, as indicated by slopes close to -1. Measured particulate percentages in the two locations were within a factor of 2 of those predicted by the Junge-Pankow adsorption model.