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This article in JEQ

  1. Vol. 29 No. 6, p. 1856-1862
    Received: Dec 31, 1999

    * Corresponding author(s): ShadN@gnv.ifas.ufl.edu
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Stability and Mobility of Napropamide Complexed with Dissolved Organic Matter in Soil Columns

  1. S. D. Nelson *,
  2. W. J. Farmer,
  3. J. Letey and
  4. C. F. Williams
  1. Department of Soil and Environmental Sciences, Univ. of California, Riverside, CA 92521-0424.



The herbicide napropamide [N,N-diethyl-2-(1-naphthyloxy)propanamide] has been shown to complex with various sources of dissolved organic matter (DOM), potentially increasing the risk of ground water contamination by facilitating napropamide transport through soil. Two factors that may reduce the threat of facilitated transport of chemicals through soils are soil profile depth and soil horizon variability. Movement through the soil profile may cause herbicide complexed with DOM to break apart and readsorb to the soil. Differences in soil horizon organic matter content throughout the soil profile may also alter the potential for facilitated transport of herbicides. Napropamide was used in column studies to determine if organic matter differences in horizons and soil profile depth would reduce the risk of facilitated transport. A silt loam soil was used with and without sewage sludge amendment (SS and NoSS) to represent differences in organic matter content. Results showed that <6% of the applied mass of napropamide moved as DOM complexes through soil. The majority of complexed napropamide was very stable and relatively nonadsorbing in solution such that doubling of soil depth only reduced facilitated transport by 20% or less. We present evidence to show that napropamide-DOM complexes are relatively nonadsorbing in solution and exhibit transport characteristics similar to those of a inert compounds in soil solution.

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