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United States Department of Agriculture

Agricultural Research Service

Title: Occurence of Metolachlor Esa and Atrazine Metabolites in a Riparian Ecosystem

Authors
item Rice, Clifford
item Bialek Kalinski, Krystyna
item McCarty, Gregory
item Angier, Jonathan

Submitted to: American Society of Agronomy
Publication Type: Abstract Only
Publication Acceptance Date: October 25, 2001
Publication Date: N/A

Technical Abstract: Metolachlor is known to readily degrade to the sulphonated metabolite, metolachlor ethane sulfonic acid (MESA), in soil systems. Methods for analysis for MESA were developed based on LC/MS-MS techniques. A standard of MESA was synthesized and compared to an industry standard. Recovery using different solid phase methods (ENV+ and C-18) were carried out. The eC-18 method proved best for MESA and metolachlor oxanilic acid. Measurement of this compound along with its parent, metolachlor, the other major metabolite of metolachlor, oxanilic acid, and atrazine plus the atrazine degradates (hydroxy atrazine, desethyl atrazine, desisopropyl atrazine and the hydroxy forms of these two) were carried out in water samples collected from a riparian area. This riparian area neighbored a cornfield where metolachlor and atrazine are applied annually for weed control. Comparing the varying levels of the parent herbicides and their degradates in the various samples (groundwater, in-flow runoff, and stream flow) indicated that each of the degradates may arise through different processes. For example, higher levels of MESA were maintained over the course of the year than were observed for the degradates of atrazine.

Last Modified: 11/1/2014