| Air concentrations of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) were measured in the urban-industrial complex of Chicago, IL, over southern Lake Michigan, and in a non-urban area as part of the AEOLOS (Atmospheric Exchange Over Lakes and Oceans) Project. Air samples were collected simultaneously in intensive experiments during May and July 1994 and January 1995 in order to determine the increase in the adjacent coastal atmosphere as a result of the urban/industrial complex, gas particle partitioning behavior, source apportionment, and the strength of the urban/industrial source. The urban air emissions increased the average coastal atmospheric concentrations above the continental background signal by factors of 12 and 4 for {dollar}Sigma{dollar}PAHs and {dollar}Sigma{dollar}PCBs, respectively. The PCBs and PAHs were at equilibrium between the gas and particle phases both in Chicago and over southern Lake Michigan despite slopes of log K{dollar}sb{lcub}rm p{rcub}{dollar} vs log p{dollar}sp0sb{lcub}rm L{rcub} > -1.0.{dollar} The dominant absorption mechanism of this equilibrium is absorption into organic matter associated with the atmospheric particulate matter. The major source of PCBs to the atmosphere is volatilization from areas where they had previously been used, stored, spilled, or atmospherically deposited. Incineration of PCB containing material is not a major source. Source apportionment results indicate that coal combustion accounted for 48 {dollar}pm{dollar} 5%, natural gas combustion accounted for 26 {dollar}pm{dollar} 2%, vehicle emissions accounted for 9 {dollar}pm{dollar} 4%, and coke ovens accounted for 14 {dollar}pm{dollar} 3% of the urban and adjacent coastal atmospheric concentration of {dollar}Sigma{dollar}PAHs. The strength of the urban/industrial area source was estimated using the gaussian plume area source equation and the annual flux of contaminants to the adjacent coastal atmosphere was 1700 {dollar}pm{dollar} 600 kg/yr and 275,000 {dollar}pm{dollar} 92,000 kg/yr for {dollar}Sigma{dollar}PCBs and {dollar}Sigma{dollar}PAHs, respectively. |
