HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Gates, T. K. Articles by Mueller Price, J. PubMed PubMed Citation Articles by Gates, T. K. Articles by Mueller Price, J. Agricola Articles by Gates, T. K. Articles by Mueller Price, J. Related Collections Surface Water Quality Field-Scale Studies Toxic Trace Metals Ground Water Quality Irrigation

TECHNICAL REPORTS

Surface Water Quality

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

^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

^* Corresponding author (Timothy.Gates{at}colostate.edu).

Received for publication December 4, 2008. 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.

Abbreviations: BMP, best management practices • CDPHE, Colorado Department of Public Health and Environment • DO, dissolved oxygen • LARV, Lower Arkansas River Valley • ORP, oxidation reduction potential • TMDL, total maximum daily load