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United States Department of Agriculture

Agricultural Research Service

Title: Wet Deposition of Current Use Pesticides at a Rural Location on the Delmarva Peninsula: Impact of Rainfall Patterns and Agricultural Activity

Authors
item Goel, Anubha - UNIV. OF MARYLAND
item McConnell, Laura
item Torrents, Alba - UNIV. OF MARYALND

Submitted to: Journal of Agriculture and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 1, 2005
Publication Date: September 13, 2005
Repository URL: http://hdl.handle.net/10113/838
Citation: Goel, A., Mcconnell, L.L., Torrents, A. 2005. Wet deposition of current use pesticides at a rural location on the delmarva peninsula: impact of rainfall patterns and agricultural activity. Journal of Agriculture and Food Chemistry. 53:7915-7924.

Interpretive Summary: The atmosphere can act as a source for pesticides to sensitive areas of the Chesapeake Bay Watershed. Some fraction of pesticides applied to crops is lost to the atmosphere through drift or volatilization processes. These residues can be redeposited into nearby waterways and wetlands. The Delmarva Peninsula is a highly agricultural region of the larger Chesapeake Bay Watershed. Limited information is available regarding the distribution and trends in pesticide deposition in rainfall. From 2000-2003, 204 samples of rain water were collected agricultural season (April to September) from a site on the Delmarva Peninsula. These samples were analyzed for a large number of currently-used and historically-used pesticides. Although chlorothalonil is the single biggest contributor to pesticide flux (33-46%), pesticide wet deposition is dominated by herbicides (46-61%) with the greatest fluxes occurring during the time of herbicide application on corn and soybeans. The extent of wet deposition of herbicides depends on the timing of precipitation relative to herbicide application. The insecticide and fungicide flux was greater in years with above average rainfall (2001 and 2003) suggesting that for these pesticides deposition flux is dependent on the total amount of rainfall in the agricultural season. This project provides important information to regulators and producers on potential risk to sensitive wildlife from pesticide exposure from aerial deposition pathways.

Technical Abstract: Event-based precipitation samples were collected during the main agricultural season (April-Sept) over four years (2000-2003) at one site in the Choptank River watershed on the Delmarva Peninsula. The samples were analyzed for 20 agricultural pesticides to determine the contribution of wet deposition as a source of these compounds to the Chesapeake Bay and the factors affecting the temporal trends in deposition. Chlorothalonil was detected most frequently (90% samples) followed by metolachlor (70%) and endosulfans (58%). Although chlorothalonil is the single biggest contributor to pesticide flux (33-46%), pesticide wet deposition is dominated by herbicides (46-61%) with the greatest fluxes occurring during the time of herbicide application on corn and soybeans. The extent of wet deposition of herbicides depends on the timing of precipitation relative to herbicide application. The insecticide and fungicide flux was greater in years with above average rainfall (2001 and 2003) suggesting that for these pesticides deposition flux is dependent on the total amount of rainfall in the agricultural season. Data indicates that the use of chlorpyrifos, an organophosphate insecticide which is on the Toxics of Concern list the Bay, is on the increase. Total pesticide flux ranged from 90 'g/m2 (2001) to 180 'g/m2 (2000). Wet deposition can account for up to 10-20% of the annual loadings of pesticides to the Bay.

Last Modified: 9/23/2014
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