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.
CITATION:
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.