Herbicides Mississippi River Basin

The overall objective of the precipitation study was to (1) determine the occurrence and temporal distribution of herbicides and their degradation products in precipitation, (2) estimate the amounts of atrazine deposited by precipitation annually in individual states and over a large part of the United States, (3) relate annual deposition of atrazine to amounts applied annually, and (4) compare annual herbicide deposition by precipitation within the Mississippi River Basin to the estimated annual amount transported out of the basin in streamflow. 

Some recent surveys in the Mississippi River basin pointed out the importance of chloroacetanilide metabolites in surface water. Thus, sulfonic acid and oxanilic acid (OXA) averaged 70% of the total herbicide concentration in samples from the upper Mississippi River, whereas this proportion was much less in the Missouri and Ohio Rivers, 24% and 41%, respectively. ... 

Rebich, R. A., Coupe, R. H., and Thurman, E. M., Herbicide concentrations in the Mississippi River Basin—the importance of chloroacetanilide herbicide degradates. Set Total Environ., 321, 189-199,... 

In a study that included comprehensive spatial and temporal sampling, 70% of the total herbicide concentration in water from the Mississippi River Basin was from transformation products [39]. Other studies in the United States have documented similar results. For example, in 1993, the annual load of alachlor ethanesulfonic acid was almost 500 metric t whereas, the annual load of alachlor was less than 50 metric t [40]. 

Clark GM, Goolsby DA, Battaglin WA (1999) Seasonal and annnal load of herbicides from the Mississippi River Basin to the Gulf of Mexico. Environ Sci Technol 33 981-986 Schnoebelen DJ, Kalkhoff SJ, Becher KD, Thurman EM (2003) Water-quality assessment of the Eastern Iowa Basins Selected pesticides and pesticide degradates in streams, 1996-98. US. Geological Survey Water-Resources Investigations Report 03-4075... 

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