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Occurrence and Degradation of Herbicides in Wetlands in Central Nebraska

By Kathy E. Lee
ABSTRACT: The occurrence and degradation of herbicides was studied in 31 wetlands in central Nebraska. Sites were sampled twice, in May and August 1994. Atrazine was detected in 93% of the wetlands in May and in 66% of the wetlands in August. The deethylatrazine (DEA) to atrazine ratio (DAR) was used to compare atrazine degradation in wetlands with previous surface water studies. We expected the DAR in the wetlands would be greater than in other surface waters due to related research indicating more rapid degradation of atrazine in vegetated treatments than in open-water treatments. A subset of 17 wetlands was selected for which valid comparisons could be made (DEA concentrations above the detection level). Approximately 88% of these wetlands showed an increase in the DAR between May and August indicating conversion of atrazine to DEA. The median DAR in the wetlands was 0.17 during May which is similar to the median DAR (0.1) reported for surface waters in the midwestern U.S. during post-planting sampling periods. The median DAR was 0.52 in August which is greater that the median DAR (0.4) found in surface waters during October and November. Herbicide degradation rates in wetlands may be greater than in other surface waters due to biological processes such as plant uptake and increased microbial metabolism.

Lee, K.E., 1995, Occurrence and degradation of herbicides in wetlands in central Nebraska [abs.]: Bulletin of the North American Benthological Society, v. 12, no. 1, p. 160.

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