Submitted to: Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2002
Publication Date: 5/2/2003
Citation: SHIPITALO, M.J., OWENS, L.B. ATRAZINE, DEETHYLATRAZINE, AND DEISOPROPYLATRAZINE IN SURFACE RUNOFF FROM CONSERVATION TILLED WATERSHEDS. ENVIRONMENTAL SCIENCE & TECHNOLOGY. 2003. v. 37(5). p. 944-950. Interpretive Summary: The herbicide atrazine is used extensively for weed control in corn and is commonly found in streams and well water, particularly in the Corn Belt region of the US. After atrazine has been sprayed on the crop it begins to breakdown into a number of simpler compounds called metabolites. Two of these metabolites, deethylatrazine and deisopropylatrazine, are similar in toxicity to atrazine, yet there are no federal drinking water standards fo these compounds. In this field study, concentrations of atrazine and these two metabolites were monitored for 6 years in runoff from 7 small fields under a variety of tillage practices. About 100 days after application the concentrations of the metabolites frequently exceeded those of atrazine in runoff. Thus, failure to monitor their presence may result in underestimation of the impact of atrazine usage on the environment. Additionally, some research suggests that the ratio of deethylatrazine to atrazine can be used to separate point from non-point sources of pollution Our results indicate that this ratio can be affected by tillage treatment and weather year and should be used with caution. This research will benefit the regulatory community by providing information on the potential impact of atrazine usage on the environment and by indicating the limitations of using metabolite ratios to identify and track the source of atrazine contamination in streams and wells.
Technical Abstract: Atrazine and two of its metabolites, deethylatrazine (DEA) and deisopropylatrazine (DIA), are frequently detected in surface and ground water. Although their environmental effects may be similar to that of atrazine and ratios of their concentrations are useful in delineating sources of contamination and travel times, few long-term studies of the management and climatic factors affecting DEA and DIA losses in runoff hav been conducted. Therefore, losses of atrazine, DEA, and DIA were monitored for 6 years in surface runoff from 7 small (0.45-0.79 ha) watersheds under 3 different tillage practices. DEA was the most frequently detected metabolite with an average concentration for all watersheds, in the year of atrazine application, of 2.5 ug/L compared to 0.7 ug/L for DIA. Adding the concentrations of DEA and DIA to atrazine increased the length of time the 3 ug/L federal lifetime drinking water Maximum Contaminant Level (MCL) for atrazine was exceeded. Additionally, the molar concentration ratio of DEA to atrazine (DAR) was affected by tillage treatment and weather year. These factors may need to be taken into account when using DAR to distinguish point from non-point sources of contamination and as an index of atrazine movement.