Sources of toxaphene and other organochlorine pesticides in North America as determined by air measurements and potential source contribution function analyses.

A previous study from our laboratory suggested that the Gulf of Mexico might be a potential source of toxaphene to the United States. To investigate this hypothesis, we measured gas-phase toxaphene concentrations at sampling sites ranging from northern Michigan to southern Louisiana; the samples were collected every 12 days during 2002-2003. We also measured other organochlorine pesticides in these samples. We identified major source regions of each pesticide group using the potential source contribution function model with the Clausius-Clapeyron equation defining the criterion levels. These results indicate that southern cotton farms are major sources of both toxaphene and p,p'-DDE to the northern United States. In fact, there is a very strong correlation of toxaphene and DDE atmospheric concentrations at all sites, further indicating a common source. On the other hand, the Gulf of Mexico is not a major source of toxaphene or DDE. DDE's source region is similar to that of toxaphene but somewhat broader, reflecting DDT's historically more diversified use. The level of endosulfan in the atmosphere at all of the sites was similar, and PSCF modeling indicated that its sources were all toward the east of the sampling sites.