Submitted to: Society of Environmental Toxicology and Chemistry Abstracts
Publication Type: Abstract only
Publication Acceptance Date: 11/11/2001
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: The Choptank River Watershed, located on the Delmarva Peninsula of the Chesapeake Bay, is dominated by agricultural land use, which makes it highly vulnerable to both runoff and atmospheric deposition of pesticides. Very little is known with respect to the magnitude of pesticide atmospheric loadings in this area. Determination of currently used pesticide residues in precipitation presents significant challenges due to their tendency to degrade quickly and their polar properties. Efficient collection requires extraction methods different than those for nonpolar toxic chemicals, e.g. polychlorinated biphenyls. A new event based, automated, rain sample collection and in-line extraction method was developed using a commercially available sampler equipped with a 0.2 m2 stainless steel funnel with the results of average pesticide collection efficiencies of 68-104% with a standard deviation 3-21.5% up to a sample volume of 10 L or the equivalent of 5 cm of precipitation. Event-based rain samples and weekly air samples were collected from April to November 2000 at Horn Point Environmental Laboratory, Cambridge, Maryland. The results of wet deposition showed that chlorothalonil had the highest maximum wet deposition flux (13.4 ug/m2-d) followed by atrazine (8.3 ug/m2-d), metolachlor (5.7 ug/m2-d), alachlor (2.9 ug/m2-d) and simazine (2.1 ug/m2-d). The estimated total wet deposition loading was 150, 61, 51, 20 and 18, 5.5, 2.7, 2.4 kg/yr, respectively, for chlorothalonil, metolachlor, atrazine, simazine, alachlor, 2-chloro-4-isopropylamino-6-amino-s-triazine, beta-endosulfan, and acetochlor.