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The Fate and Degradation of Cyanazine in Wetlands

By Y. Fintschenko, E.M. Thurman, F. DeNoyelles, and D.G. Huggins

Abstract

Studies of the water samples from the Mississippi River show that the use of cyanazine, a herbicide from the s-triazine family, is increasing in the midwestern United States. Most of the year the concentration of cyanazine is less than the U.S. Environmental Protection Agency's health advisory level of 1 Îg/L, but during spring runoff, concentrations as large as 20 Îg/L have been measured in surface water. One approach in minimizing these large concentrations is the construction of wetland "buffer strips" where water from crop runoff could collect, degrade, and then be redistributed as "purified" water into the surface or ground water. Before adopting such an approach it is important to determine the degradation pathway of cyanazine in wetlands and the effect of wetland structures on the degradation process.

The objectives of the study described in this proceedings were to determine the effect of wetland structures (1) on the half-life of cyanazine; (2) on the half-lives of the metabolites formed, and (3) on the ratios of the metabolites formed to the parent compound. Additionally, the authors sought to establish whether chemical processes such as hydrolysis and photolysis contribute significantly to the degradation of cyanazine in water. In order to achieve the study objectives two initial wetland structures were chosen--emergent-vegetation and open-water ponds. In both cases, the structures were studied in triplicate, and submergent vegetation was allowed to grow as the summer progressed. Bladex—, the commercial formulation of cyanazine made by DuPont, was applied to each wetland structure to achieve an initial concentration of 5 Îg/L. Potassium bromide (KBr) was applied to achieve an initial concentration of 15 Îg/L as a conservative tracer to correct for volume changes in the ponds. Additionally, three fiberglass tanks with no soil or rooted plants were treated with Bladex and KBr to determine whether photolysis and hydrolysis were significant pathways for degradation. Finally, another three fiberglass tanks treated only with KBr served as controls. Water was sampled in three randomly selected places in each pond and tank. The ponds were approximately 30 meters across and 1.5 meters deep, and the fiberglass tanks were approximately 10 meters across and 1.5 meters deep. Ten sampling events occurred over a period of 140 days. Cyanazine and its metabolites were isolated from the water samples by solid-phase extraction (SPE), and their concentrations were determined by gas chromatography/mass spectrometry (GC/MS) using the selected-ion mode.
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— The use of brand names in this proceedings article is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey.

Additional information about the Organic Geochemistry Research Laboratory can be found at: http://ks.water.usgs.gov/studies/reslab/

Fintschenko, Y., Thurman, E.M., DeNoyelles, Frank, and Huggins, D.G., 1995, The fate and degradation of cyanazine in wetlands, in Preprints of Papers presented at the 209th ACS National Meeting, Anaheim, California, April 2-7, 1995: American Chemical Society, Division of Environmental Chemistry, v. 35, no. 1, p. 274-277.

To request a paper copy of this proceedings article, email: scribner@.usgs.gov

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