Tailwater recovery systems recycle irrigation water using a network of edge-of-field ditches and storage reservoirs. Tailwater recovery has the potential to reduce agricultural groundwater use in Arkansas critical groundwater depletion zones and intercept downstream export of agrochemicals, but residual herbicides in these systems could lead to cross-crop contamination through irrigation water and yield loss in sensitive crops. Further, during the non-growing season, tailwater may serve as source water for artificial groundwater recharge if compliant with environmental and human health standards. Therefore, residual herbicide concentrations in these systems must be assessed. This study monitored concentrations of a suite of herbicides in seven tailwater recovery systems in the Cache Critical Groundwater Area in Northeast Arkansas. Grab samples were collected weekly from ditches and reservoirs during the growing season (April-August) and biweekly thereafter. Samples were processed by filtration through 0.45 µm membrane filters and concentration using solid phase extraction on a Strata-X polymer sorbent. Target herbicides were 2,4-D, clomazone, dicamba, glyphosate metolachlor, propanil, and quinclorac and were selected based on grower application information. All analytes, except glyphosate, were measured using high performance liquid chromatography with diode array detection with a C18 column and an acetonitrile : 0.1% H3PO4 (aq) gradient mobile phase. Glyphosate was measured with enzyme-linked immunosorbent assay. We will report on year one findings and explore preliminary spatial and temporal trends in herbicide concentrations in the tailwater systems.<br/>

Preliminary assessment of residual herbicide concentrations in tailwater recovery systems

256th National Meeting (2018)

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