|HOME SCHEDULE AUTHOR INDEX SUBJECT INDEX|
(619) Transport and fate of atrazine and metolachlor in a riparian wetland system.
Rice, Clifford*,1, Bialek, Krystyna1, Angier, Jonathan1, Sadeghi, Ali1, Greg, McCarty1, 1 U.S. Department of Agriculture, Environmental Quality Laboratory, Beltsville, MD, USA
ABSTRACT- Riparian buffer areas are widely touted for their ability to abate pollutants emerging from agricultural fields. We are studying this abatement process for the pesticides atrazine and metolachlor, using a heavily instrumented riparian wetland site located in Beltsville, Maryland. The site was selected because clearly delineated flow pathways intersect a well defined riparian strip that supports a 1st-order stream. An important objective was to compare pesticide transport through this system with the transport of N-nitrate and other nutrients. Initial work involved characterizing the pesticide makeup, parent compounds and their degradates, in groundwater as it moves into the buffer area and also identify the load of pesticides exiting through the 1st order stream draining the system. Early results showed that atrazine, deethyl and deisopropyl atrazine losses follow the same pattern as N-nitrate, even to the point where preferential flow effects were observed. The other pesticides, especially hydroxy atrazine and metolachlor plus degradates, appear to behave quite differently. Some additional pathways for pesticide input into the 1st order stream were investigated. One important pathway appears to be atmospheric, especially as drift (aerosol or particulate) or as gases adsorbing onto surfaces (plants or surface litter). During rain events these sorbed materials or their subsequent degradates then become available for washoff directly into the buffer area. Analyses of rain collected beneath the tree cover in the buffer area demonstrated that much more of certain pesticides and their degradates were deposited in rain that passed through the forest canopy than were found in the rain falling outside the forested area, e.g. metolachlor ethane sulfonic acid, 90% as through-fall and hydroxy atrazine, 85% as stem-flow. Results from direct measurements of these loading pathways and modeling data will be presented in an attempt to characterize pesticide processes taking place in this riparian wetland system.
Key words: riparian buffer, pesticides, runoff, exfiltration
Internet Services provided by|
Allen Press, Inc. | 810 E. 10th St. | Lawrence, Kansas 66044 USA
e-mail email@example.com | Web www.allenpress.com
All content is Copyright © 2002 SETAC