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Fate and Distribution of Current-Use Pesticides in the Albemarle-Pamlico Estuarine System of North Carolina

Estuaries are complex ecosystems that are composed of a number of sensitive and inter-dependent environments. An abundance of nutrients combine with the dynamic conditions to create some of the most productive environments on the planet. Almost 85% of the commercially harvested fish in the United States depend on estuaries and the surrounding coastal waters at some stage in their life history. Many estuarine drainage basins contain large quantities of agricultural acreage. Over 29 million pounds of active ingredient of pesticides are applied in coastal drainage basins in the United States each year. Studies have shown that the overall condition of the nation's estuaries is fair, while benthic condition is poor. Seventy five percent of estuarine sediments are contaminated with pesticides. Concentrations of pesticides in 30% of the estuaries exceed the levels that are known to result in ecological effects at least 10% of the time. There have been few comprehensive pesticide studies in estuaries to date. The Albemarle-Pamlico (A-P) Drainage Basin of North Carolina forms the second largest estuarine system in the United States and supports heavy agricultural production with high pesticide use. I evaluated measurement and modeling strategies to assess exposure in the A-P drainage basin. Atrazine and metolachlor were the most frequently detected pesticides in water samples that were collected in the A-P drainage basin in 2000 and 2001. Concentrations of these compounds exceeded both human health and aquatic life criteria in 2000. No toxicity thresholds were exceeded in samples collected in 2001. Due to the expense associated with field sampling and pesticide analysis alternative methods for estimating pesticide exposure have been developed, including fate models. The Exposure Analysis Modeling System (EXAMS) was modified to model the fate of pesticides, specifically atrazine and metolachlor, in a small tidal estuary of the larger A-P estuarine system. Based on the estimate that 10% of the total amount of atrazine and metolachlor applied in the Bath Creek drainge basin would enter the estuary the EXAMS steady state model predicts concentrations of both atrazine and metolachlor that fall between the mean and maximum values that were measured in Bath Creek in 2002. Concentrations of pesticides in the A-P drainage basin, both measured and modeled, are significantly less than acute toxicity thresholds for even the most sensitive aquatic species. Due to the short lived nature of these compounds it is unlikely that organisms in the region would experience adverse health effects due to exposure to the existing concentrations.
Date19 December 2002
CreatorsMcCarthy, Annette
ContributorsDave Eggleston, Rich McLaughlin, Ross Leidy, Damian Shea, Greg Cope
Source SetsNorth Carolina State University
Detected LanguageEnglish
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