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This article in JEQ

  1. Vol. 38 No. 6, p. 2344-2356
     
    Received: Dec 4, 2008
    Published: Nov, 2009


    * Corresponding author(s): Timothy.Gates@colostate.edu
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doi:10.2134/jeq2008.0499

Assessing Selenium Contamination in the Irrigated Stream–Aquifer System of the Arkansas River, Colorado

  1. Timothy K. Gates *a,
  2. Brent M. Codya,
  3. Joseph P. Donnellyb,
  4. Alexander W. Hertingc,
  5. Ryan T. Baileya and
  6. Jennifer Mueller Pricea
  1. a Civil and Environ. Engineering Dep., Colorado State Univ., Fort Collins, CO 80523
    b URS Corporation, 8181 E. Tufts Ave., Denver, CO 80237
    c Kimley-Horn and Assoc., 7878 N. 16th Street, Suite 300, Phoenix, AZ 85020

Abstract

Prudent interventions for reducing selenium (Se) in groundwater and streams within an irrigated river valley must be guided by a sound understanding of current field conditions. An emerging picture of the nature of Se contamination within the Lower Arkansas River Valley in Colorado is provided by data from a large number of groundwater and surface water sampling locations within two study regions along the river. Measurements show that dissolved Se concentrations in the river are about double the current Colorado Department of Public Health and Environment (CDPHE) chronic standard of 4.6 μg L−1 for aquatic habitat in the upstream region and exceed the standard by a factor of 2 to 4 in the downstream region. Groundwater concentrations average about 57.7 μg L−1 upstream and 33.0 μg L−1 downstream, indicating a large subsurface source for irrigation-induced dissolution and mobilization of Se loads to the river and its tributaries. Inverse correlation was found between Se concentration and the distance to the closest identified shale in the direction upstream along the principal groundwater flow gradient. The data also exhibited, among other relationships, a moderate to strong correlation between dissolved Se and total dissolved solids in groundwater and surface water, a strong correlation with uranium in groundwater, and power relationships with nitrate in groundwater. The relationship to nitrate, derived primarily from N fertilizers, reveals the degree to which dissolved Se depends on oxidation and inhibited reduction due to denitrification and suggests that there are prospects for reducing dissolved Se through nitrate control. Current and future results from these ongoing studies will help provide a foundation for modeling and for the discovery of best management practices (BMPs) in irrigated agriculture that can diminish Se contamination.

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Copyright © 2009. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyAmerican Society of Agronomy, Crop Science Society of America, and Soil Science Society of America