Perchlorate reconnaissance sampling in streams and groundwater in the Central and Southwestern U.S.

Results

Samples were collected from 171 sites on rivers and streams and 146 sites from groundwater wells during the summer and early fall of 2004. Samples were collected from surface-water sites in 19 States and from groundwater wells in 5 States.

Perchlorate was detected in samples collected in 15 States and was detected in 34 of 182 samples from rivers and streams and in 64 of 148 groundwater samples at concentrations equal to or greater than the 0.4 micrograms per Liter (mg/L) reporting limit. Perchlorate concentrations were 1.0 mg/L or greater in surface-water samples from 7 states and in groundwater samples in 4 states. Only one surface-water and one groundwater sample had concentrations greater than 5.0 mg/L. The perchlorate data have been published in U.S. Geological Survey Data series 495 report and are summarized by State in the following table.

Summary of perchlorate detections and concentrations in selected States

                   
State Number of samples   Number of samples with detectable concentration (0.4 µg/L or greater)   Percent of samples with concentration 1.0 µg/L or greater   Percent of samples with concentration 2.0 µg/L or greater   Percent of samples with concentration 5.0 µg/L or greater Maximum concentration (µg/L)
Surface-water
Arizona 11   1   0   0   0 0.6
Arkansas 3   1   0   0   0 0.68
California 3   2   0   0   0 0.87
Colorado 17   1   0   0   0 0.63
Illinois 17   0   0   0   0 <0.4
Indiana 15   3   13   0   0 1.58
Iowa 30   7   3   0   0 1.12
Michigan 8   1   0   0   0 0.85
Minnesota 14   4   14   7   0 2.53
Missouri 2   0   0   0   0 <0.4
Montana 1   1   0   0   0 0.68
Nebraska 6   1   0   0   0 0.48
Nevada 4   1   25   25   25 6.23
New Mexico 8   3   38   12   0 2.06
Ohio 15   3   20   0   0 1.58
South Dakota 3   0   0   0   0 <0.4
Texas 3   0   0   0   0 <0.4
Wisconsin 18   4   6   0   0 1.41
Wyoming 4   1   0   0   0 0.49
Groundwater
Arkansas 1   1   0   0   0 0.92
California 8   4   13   0   0 1.93
Colorado 21   5   19   9   0 4.19
Iowa 38   9   11   0   0 1.73
Nebraska 80   45   31   6   1 20.9

Maps showing location of sampling sites and perchlorate concentrations.

State   State  
Arkansas and Texas   Arizona and New Mexico  
California and Nevada   Colorado, Wyoming, and South Dakota  
Iowa   Illinois, Indiana, Missouri, and Ohio  
Michigan, Minnesota, and Wisconsin   Nebraska  

Data:

Site information--includes map identification number, USGS station identification number, and site location information

Perchlorate concentrations-- includes map identification number, USGS station identification number, supporting program, date and   time of sample, and perchlorate concentration


In addition to the perchlorate samples for this project, major ion, nutrient, pesticide, and, in some cases, trace element samples were collected concurrently at these sites as part of supporting programs. The additional water quality data are available online from the USGS NWISweb (http://waterdata.usgs.gov/nwis/) and NAWQA data warehouse (http://infotrek.er.usgs.gov/traverse/f?p=NAWQA:HOME).