Submitted to: American Chemical Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: August 11, 2004
Publication Date: September 2, 2004
Citation: Rice, C., Bialek Kalinski, K.M., Angier, J., Mccarty, G.W. 2004. The persistence of metolachlor breakdown products in a riparian buffer system [abstract]. 228th American Chemical Society Meeting. p. 334.
The effectiveness of a riparian buffer in removing the herbicide metolachlor, as it moves through the system from an adjoining agricultural field, was studied. The riparian system contains a first-order stream that receives groundwater and surface runoff from an active cornfield that is treated yearly with a pre-emergent mix of metolachlor and atrazine. The fate of the parent compound and its degradation products, metolachlor ethane sulfonic acid (MESA), metolachlor oxanilic acid (MEOA), and hydroxy metolachlor (OH-metolachlor) was followed over several years. Of the four products, MESA was detected in the highest concentration within the buffer zone (subsurface and exfiltrated groundwater, and stream water). MESA typically averaged 500 to 1000x higher in concentration than its parent (and most other pesticide products) in the buffer zone. Higher levels of MEOA were also observed, but these levels were generally about 1/10 to 1/5 of the concentration of MESA. Seldom was OH-metolachlor observed in samples from the riparian system. This situation prevailed year round except for a 1-2 week period following spraying when spikes in parent compound were observed in the stream. These spikes coincided with post-spraying rain events. There appears to be a particular persistence of MESA in this riparian ecosystem.