| Abstract
| - Air−water exchange of persistent organic pollutants(POPs) such as polychlorinated biphenyls (PCBs) is animport process for the delivery of contaminants to waterbodies, as well as for their removal, and is thus a pivotalparameter in the construction of mass balances inaquatic systems. Simultaneous measurements of PCBconcentrations in the gas and dissolved phases conductedin Green Bay in 1989 and in southern Lake Michigan in 1994−1995 were used to estimate air−water exchange fluxes.In this work, improved Henry's law constants for PCBs andnew mass-transfer rates across the air−water interfacewere used to update the previous calculations. The newmodel calculations suggest that the net volatilization flux ofPCBs out of Green Bay ranges from +170 to +5300 ngm-2 day-1, which is 2−20 times larger than previous estimates.The flux of PCBs in southern Lake Michigan exhibits netvolatilization of +0.5 to +230 ng m-2 day-1 throughout thestudy period (May and July 1994, January 1995), whereasprevious estimates reported that the net flux wasseasonally absorptive. Thus, water-to-air fluxes are moreimportant for the removal of PCBs from both Green Bay andLake Michigan than previously recognized.
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