| |
USGS Develops New Field Method for Detecting Chromium VI in Ground Water
The USGS has developed a new analytical method for detecting toxic chromium VI (Cr(VI)) in ground water in the field. This new method enables scientists and resource managers to distinguish between the toxic and carcinogenic Cr(VI) and the more benign form of chromium–chromium III (Cr(III))–on site. The method overcomes several obstacles that prevented past methods from being able to accurately determinate the concentration of Cr(VI) in water. Past methods were not very accurate, the instability of Cr(VI) was problematic, and expensive laboratory equipment was required for analysis. The advantages of the new method are:
- its detection limit is low–0.1 microgram per liter ( µg/L),
- the small disposable cation-exchange cartridges allow Cr(VI) to be separated and stabilized for later analysis,
- common laboratory analytical equipment can be used, and
- results are available on site so near-real-time decisions can be made, such as the location for collecting additional water samples.
The results of the field method compare well with standard laboratory-based methods.
The new method has been used to characterize chromium-contaminated ground water beneath the Mojave Desert, California, at 29 Palms Marine Corps Air Ground Combat Center, Edwards Air Force Base, and at the Sheep Creek Fan west of Victorville, California. The study found areas with high concentrations of Cr(VI) from natural sources, in addition to Cr(VI) contamination from industrial activities. The natural Cr(VI) is caused by the weathering of dark rocks, such as basalt and amphibolite, in alluvial deposits (sediments deposited by rivers and streams). In addition to distinguishing between the kinds of chromium, knowing the source of Cr(VI) is important to those tasked with cleaning up contamination and protecting drinking water resources. Resource managers can now consider sources of Cr(VI) when determining the responsibility for cleanup, the levels of cleanup required to reach background concentrations, and the regulatory structure for dealing with the contamination.
More Information
References
- Ball, J.W., and Izbicki, J.A., 2004, Occurrence of hexavalent chromium in ground water in the western Mojave Desert , California: Applied Geochemistry, v. 19, p. 1123-1135.
- Ball, J.W., and McCleskey, R.B., 2003, A new cation-exchange method for accurate field speciation of hexavalent chromium: Water-Resources Investigations Report 03-4018, 17 p.
- Ball, J.W., Izbicki, J.A., and Bullen, T.D., 2003, “Stable isotope variations of hexavalent chromium in ground water in the western part of the Mojave Desert, California, USA”: Fifth Conference on Applied Isotope Geochemistry, Heron Island, Australia, May 26-30.
- Ball, J.W., and McCleskey, R.B., 2003, A New Cation-Exchange Method for Accurate Field Speciation of Hexavalent Chromium: Talanta, v. 61, p. 305-313.
Information on Chromium
Back to Headlines Page
|
