Perchlorate reconnaissance sampling in streams and groundwater in the Central and Southwestern U.S.
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)|
Maps showing location of sampling sites and perchlorate concentrations.
|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|
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).