Submitted to: American Chemical Society National Meeting
Publication Type: Abstract only
Publication Acceptance Date: 10/1/2004
Publication Date: 3/17/2005
Citation: Goel, A., Mcconnell, L.L., Torrents, A. 2005. Factors affecting the wet depositional flux of current use pesticides at a rural location on the delmarva peninsula [Abstract]. American Chemical Society National Meeting, March 13-17, 2005, San diego, CA. Agrochemicnals Division, V.68, Abstract No. 14, P. 62. 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. 204 samples of rain water were collected over three years during the 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. A careful examination of three frequently detected chemicals: atrazine, a corn herbicide, chlorothalonil, a fungicide, and endosulfan, and insecticide, reveals different temporal deposition patterns reflecting their usage in the region and their chemical properties. The annual deposition of atrazine, a water soluble chemical used in early spring, was dependent on the number of rain events received in the spring. Chlorothalonil and endosulfan deposition rates were dependent on the total amount of rainfall received regardless of timing.
Technical Abstract: Daily precipitation samples (204 samples from April-September, 2000-2003) were collected at a rural location on the Delmarva Peninsula, to study the effects of local agricultural activity and rainfall patterns on the wet deposition of pesticides used in this region. Of the three target compounds, chlorothalonil was the most frequently detected (in 90% of samples) followed by endosulfan (58%) and atrazine (49%). Concentrations and fluxes were typically high around application time. Endosulfan and chlorothalonil fluxes showed a significant positive correlation with sample volume (r = 0.42-0.46; alpha=0.05), whereas atrazine fluxes correlated with the frequency and timing of precipitation during corn planting. The nearby wetlands, which could be at risk from pesticide wet deposition, are more likely to receive the soluble herbicides in greater amounts during rain events shortly after application. The more persistent insecticides and fungicides are likely to have a more diffuse and continuous deposition throughout the year.