Occurrence of pesticides in rain and air in urban and agricultural areas of Mississippi, April-September 1995

In April 1995, the US Geological Survey began a study to determine the occu rrence and temporal distribution of 49 pesticides and pesticide metabolites in air and rain samples from an urban and an agricultural sampling site in Mississippi. The study was a joint effort between the National Water-Quali ty Assessment and the Toxic Substances Programs and was part of a larger st udy examining the occurrence and temporal distribution of pesticides in air and rain in the Mississippi River basin. Concurrent high-volume air and we t-only deposition samples were collected weekly. The air samplers consisted of a glass-fiber filter to collect particles and tandem polyurethane foam plugs to collect gas-phase pesticides. Every rain and air sample collected from the urban and agricultural sites had detectable levels of multiple pes ticides. The magnitude of the total concentration was 5-10 times higher at the agricultural site as compared to the urban site. The pesticide with the highest concentration in rain at both sites was methyl parathion. The pest icide with the highest concentration in the air samples from the agricultur al site was also methyl parathion, but from the urban site the highest conc entration was diazinon followed closely by chlorpyrifos. More than two deca des since p,p'-DDT was banned from use in the United States, p,p'-DDE, a me tabolite of p,p'-DDT, was detected in every air sample collected from the a gricultural site and in more than half of the air samples from the urban si te. (C) 2000 Elsevier Science B.V. All rights reserved.