|Blanchard, Paul - UNIV OF MO|
|Thurman, E - US GEOLOGICAL SURVEY|
Submitted to: Journal of Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 23, 1997
Publication Date: N/A
Interpretive Summary: Prevailing agricultural practices have resulted in significant atrazine contamination in Midwestern streams. Atrazine breaks down in soil forming two major groups of breakdown products, or metabolites: chlorinated and hydroxylated. These stable metabolites may be toxic and can also contaminate streams. The objective of this research was to determine the contribution of the hydroxylated atrazine metabolites to the total atrazin load (i.e., atrazine + stable metabolites) in streams. Samples were collected before (pre-plant) and after (post-plant) atrazine application from 141 streams in nine Midwestern states in 1994 and 1995. Results showed that hydroxylated atrazine metabolites did significantly contribute to the total atrazine load in streams. At pre-plant, hydroxylated metabolites were more commonly detected than atrazine and the chlorinated metabolites. One of the hydroxylated metabolites had concentrations similar to atrazine and greater than chlorinated atrazine metabolites at pre-plant. At post-plant, the hydroxylated metabolites were commonly detected, but their levels in stream water were lower than atrazine and the chlorinated metabolites. To fully assess the impact of atrazine contamination on human health and stream ecology, hydroxylated metabolites need to be monitored.
Technical Abstract: The contribution of hydroxylated atrazine degradation products (HADPs) to the total atrazine load (i.e., atrazine plus stable metabolites) in streams needs to be determined to fully assess the impact of atrazine contamination on stream ecosystems and human health. The objectives of this study were: 1) to determine the contribution of HADPs to the total atrazine load in streams of nine Midwestern states; and 2) to discuss the mechanisms controlling the concentrations of HADPs in streams. Stream samples were collected from 95 streams in Northern Missouri at pre-plant and post-plant in 1994 and 1995, and an additional 46 streams were sampled in eight Midwestern states at post-plant in 1995. Samples were analyzed for atrazine, deethylatrazine, deisopropylatrazine, and three HADPs. Overall, frequency of HADP detections ranged from 87-100% for hydroxyatrazine (HA), 0-58% for deethylhydroxyatrazine (DEHA), and 0% for deisopropylhydroxyatrazine (DIHA) with method detection limits of 0.04-0.1 ppb. Atrazine metabolites accounted for nearly 60% of the atrazine load in Northern Missouri streams at pre-plant, with HA the predominant metabolite present. Data presented in this study and a continuous monitoring study support the hypothesis that a combination of desorption from stream sediments and dissolved-phase transport control HADP concentrations in streams.