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Evaluation of Water Sampling and Storage Procedures Used in Herbicide Dissipation Studies

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Watershed ManWatershed Management to Meet Water Quality Standards and TMDLS (Total Maximum Daily Load) Proceedings of the 10-14 March 2007, San Antonio, Texas  701P0207.(doi:10.13031/2013.22434)
Authors:   Joseph B Fischer, Jerry L Michael, Hilliard L Gibbs
Keywords:   Hexazinone, imazapyr, metsulfuron methyl, sulfometuron methyl, triclopyr, triclopyr ester, herbicide stability, stream water sampling, high-performance liquid chromatography, solid-phase extraction

The recoveries of six herbicides (triclopyr, triclopyr ester, sulfometuron methyl, metsulfuron methyl, imazapyr, and hexazinone) from stream water samples containing two levels of dissolved organic matter were evaluated. Simulated field study conditions were used to evaluate collection, ambient (pre-retrieval) field storage, and freezer storage phases of stream water sampling. Herbicide residue levels were determined by reversed-phase high performance liquid chromatography with ultraviolet absorbance detection. Method detection levels and stability curves were developed for each herbicide in each water matrix. None of the herbicides degraded significantly in either stream water at up to 24 days of dark storage at 22-25C except for sulfometuron methyl, which declined 9-16% after 24 days in both samples. Triclopyr, triclopyr ester, metsulfuron methyl, imazapyr, and hexazinone did not degrade significantly in either stream water after 12 months storage below -15C. Sulfometuron methyl recovery declined 15-20% after 12 months in both stream water samples. None of the herbicides tested appeared to leach from the automatic sampler tubing into subsequently-collected samples. However slight carryover of about 1.0% of the spiking level was observed in the first post-spike blanks collected for all herbicides due to physical adhesion of residual water droplets on the tubing walls. No detectable carryover was observed in the second or third post-spike blanks for any of the herbicide-stream water combinations tested.

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