2005 Salt Lake City Annual Meeting (October 16–19, 2005)
Paper No. 192-1
Presentation Time: 1:30 PM-5:30 PM

PERCHLORATE OCCURRENCE IN SHALLOW GROUND WATER IN THE NORTH CENTRAL UNITED STATES

KALKHOFF, Stephen J., Water Resourses Discipline, U.S. Geological Survey, PO Box 1230, Iowa City, IA 52244, sjkalkho@usgs.gov, STETSON, Sarah J., Colorado School of Mines, 1500 Illinois St, Golden, CO 80401, WANTY, Richard B., U.S. Geological Survey, PO Box 25046, Denver Federal Center, Mailstop 973, Denver, CO 80225, and LINDER, Gregory L., Biological Resources Discipline, U.S. Geological Survey, Heron Works Field Office, 5400 Tacoma Street NE, Brooks, OR 97305

The occurrence of perchlorate in shallow ground water was investigated in agricultural areas in north-central United States during the summer and fall of 2004. Previous studies have documented the presence of perchlorate in potash-bearing minerals from the United States and Canada that are currently being used as fertilizers. The purpose of this project was to determine if perchlorate is leaching to shallow aquifers in north-central United States where land use ranges from intensive row-crop agriculture in Iowa to irrigated row-crop agriculture in Nebraska to dry land farming in Colorado.

Perchlorate samples were collected as part of several ongoing U.S. Geological Survey monitoring programs. More than 150 wells screened in shallow unconsolidated aquifers were sampled from June through September 2004. Use of these monitoring sites provided additional water chemistry, geologic, climatologic and land use data needed to assist in the understanding of perchlorate occurrence.

Samples were analyzed for perchlorate using ion chromatography techniques developed by researchers at Texas Tech University that provided about an order of magnitude lower detection levels than US. Environmental Protection Agency method 314. The method reporting limit using chromatography techniques was 0.4 μg/L.

A substantial number of wells, about 40 percent, contained water with detectable concentrations of perchlorate. Perchlorate detections were found across the study area, however, most wells containing water with perchlorate concentration greater than 1 μg/L were found from western Iowa, through Nebraska, and into Colorado. Although there was a significant positive correlation between perchlorate concentrations and concentrations of two constituents (nitrate and chloride) commonly attributed to agriculture, additional work is needed to fully understand the sources of perchlorate in ground water in north-central United States.

2005 Salt Lake City Annual Meeting (October 16–19, 2005)
General Information for this Meeting
Session No. 192--Booth# 69
Naturally Occurring Perchlorate (and Other Oxyanions) in the Hydrologic Cycle—Origins, Accumulation, Transformations, and Transport (Posters)
Salt Palace Convention Center: Hall C
1:30 PM-5:30 PM, Tuesday, 18 October 2005

Geological Society of America Abstracts with Programs, Vol. 37, No. 7, p. 433

© Copyright 2005 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.