Vegetated agricultural drainage ditches for the mitigation of pyrethroid-associated runoff

Authors

  • Erin R. Bennett,

    1. U.S. Department of Agriculture, Agricultural Research Service National Sedimentation Laboratory, Oxford, Mississippi 38655
    2. Zoological Institute, Technical University, Fasanenstrasse 3, D-38092 Braunschweig, Germany
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  • Matthew T. Moore,

    Corresponding author
    1. U.S. Department of Agriculture, Agricultural Research Service National Sedimentation Laboratory, Oxford, Mississippi 38655
    • U.S. Department of Agriculture, Agricultural Research Service National Sedimentation Laboratory, Oxford, Mississippi 38655
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  • Charles M. Cooper,

    1. U.S. Department of Agriculture, Agricultural Research Service National Sedimentation Laboratory, Oxford, Mississippi 38655
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  • Sammie Smith Jr.,

    1. U.S. Department of Agriculture, Agricultural Research Service National Sedimentation Laboratory, Oxford, Mississippi 38655
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  • F. Douglas Shields Jr.,

    1. U.S. Department of Agriculture, Agricultural Research Service National Sedimentation Laboratory, Oxford, Mississippi 38655
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  • Ken G. Drouillard,

    1. Great Lakes Research Institute, University of Windsor, Windsor, Ontario N9B 3P4, Canada
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  • Ralf Schulz

    1. Zoological Institute, Technical University, Fasanenstrasse 3, D-38092 Braunschweig, Germany
    2. Institute for Environmental Sciences, University Koblenz-Landau, Fortstrasse 7, D-76829 Landau, Germany
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Abstract

Drainage ditches are indispensable components of the agricultural production landscape. A benefit of these ditches is contaminant mitigation of agricultural storm runoff. This study determined bifenthrin and lambda-cyhalothrin (two pyrethroid insecticides) partitioning and retention in ditch water, sediment, and plant material as well as estimated necessary ditch length required for effective mitigation. A controlled-release runoff simulation was conducted on a 650-m vegetated drainage ditch in the Mississippi Delta, USA. Bifenthrin and lambda-cyhalothrin were released into the ditch in a water-sediment slurry. Samples of water, sediment, and plants were collected and analyzed for pyrethroid concentrations. Three hours following runoff initiation, inlet bifenthrin and lambda-cyhalothrin water concentrations ranged from 666 and 374 μg/L, respectively, to 7.24 and 5.23 μg/L at 200 m downstream. No chemical residues were detected at the 400-m sampling site. A similar trend was observed throughout the first 7 d of the study where water concentrations were elevated at the front end of the ditch (0–25 m) and greatly reduced by the 400-m sampling site. Regression formulas predicted that bifenthrin and lambda-cyhalothrin concentrations in ditch water were reduced to 0.1% of the initial value within 280 m. Mass balance calculations determined that ditch plants were the major sink and/or sorption site responsible for the rapid aqueous pyrethroid dissipation. By incorporating vegetated drainage ditches into a watershed management program, agriculture can continue to decrease potential non-point source threats to downstream aquatic receiving systems. Overall results of this study illustrate that aquatic macrophytes play an important role in the retention and distribution of pyrethroids in vegetated agricultural drainage ditches.

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