Nearly half of US water bodies and waterways are deemed impaired by Clean Water Act criteria with nonpoint source pollution from croplands a major contributor. Innovative monitoring and modeling strategies are needed to account for pollutant-matrix interactions, climatic conditions, and landscape complexity, especially for nitrate-N. MESA {2-[(2-ethyl-6-methylphenyl) (2-methoxy-1-methylethyl)amino]-2-oxoethanesulfonic acid}, a metabolite of the extensively used herbicide metolachlor, is an ideal nitrate-N tracer because MESA is highly stable and soluble, has a low Koc value, and is formed in the unsaturated zone where nitrate-N is transported to groundwater. Here, we use MESA to track nitrate-N concentrations within the watershed of the Choptank River, a Chesapeake Bay tributary, and to identify critical nitrate-N source areas. Exploiting this fortuitous MESA-nitrate-N correlation in this and other intensive agricultural areas will allow policy makers and land managers greater ability in identifying areas where conservation and mitigation practices will be most effective at curbing agricultural nitrate-N pollution.

Exploring the association of the metolachlor metabolite MESA and agricultural nitrate-N fate and transport in the Choptank River Watershed

244th National Meeting (2012)

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