Submitted to: American Chemical Society National Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 7/15/2003
Publication Date: 9/7/2003
Citation: Goel, A., Kuang, Z., Mcconnell, L.L., Torrents, A., Meritt, D., Tobash, S. 2003. Temporal trends in wet-deposition of pesticides to the choptank river watershed, chesapeake bay [abstract]. ACS National Meeting, September 7-11, 2003, New York, NY, USA, AGRO 65; Abstract #80. Interpretive Summary:
Technical Abstract: Choptank river basin is an area of intense agricultural activity with 59% of the land in the watershed under cultivation. Aerial deposition of pesticides used in the basin (1.1 x 103 metric tons in 1994) may be an important source of these compounds to the Choptank River and ultimately to the Chesapeake Bay. Concentrations of pesticides (insecticides, herbicides and fungicides) in precipitation (April-November, 2000-2002) were monitored on an event basis at one site in the Choptank River basin. Maximum concentrations for chlorothanonil (0.5 - 2.0 ug/L) and atrazine (10.5 - 0.9 ug/L) occurred during the application period (typically April to September, depending on the pesticide). Chlorothalonil was the most abundant (35-46 % of total pesticide wet flux) and the most frequently detected compound (% detections = 80, n= 183). Herbicides were detected mostly during the application period (>90% of the yearly metolachlor flux was during April-June). The timing and amount of rainfall influenced the flux of insecticides to a greater extent than for herbicides. From 2000-2002 the net yearly fluxes of chlorothalonil and atrazine decreased by 32-41 % and 20-25%, respectively (over the previous year's values), while those of trifluralin increased by 40-100%. The total load of pesticides through wet deposition decreased from 176 ug/m2 in 2000 to 113 ug/m2 in 2002. The results indicate that the usage patterns for pesticides in the Choptank river watershed may be changing, and the effects of usage changes can be seen in the precipitation pattern in the region. Pesticide usage in other parts of the Delmarva Peninsula may be affecting deposition flux in the Choptank river basin via atmospheric transport.