Real-Time, In Situ Measurement of Hexavalent Chromium in Groundwater

The U.S Department of Energy is seeking a sensitive and robust sensor that can perform real-time, in situ monitoring of hexavalent chromium in groundwater wells at environmental legacy sites, and that is capable of operating for extended periods without maintenance. Recent laboratory tests have shown that chromate ion, which is the dominant form of hexavalent chromium at the near-neutral pH of natural groundwater, can be measured at low concentrations (a few parts per billion) using near- ultraviolet absorption spectrophotometry, and that interference caused by turbidity (suspended particulate matter) can be accurately compensated by measuring the amount of UV light scattered by the turbidity. The overall objective of the proposed research is a cable-deployed, submersible, stable, and cost-effective instrument that performs the in situ measurements on demand or on a set schedule, and which yields a signal suitable for telemetry or storage in a data logger, as well as for on-site real-time investigations. Commercial Applications and Other Benefits: Significant reduction of costs associated with groundwater sampling and analysis for monitoring hexavalent chromium at DOE and industrial sites (e.g., Hanford Site, tanneries, chrome plating operations) would in itself be a national benefit. Depth-discrete profiling of hexavalent chromium concentrations in wells, important for understanding contaminant distribution and optimizing groundwater remedial methods, will be greatly simplified. The technology developed will be immediately adaptable for controlling and monitoring remedial methods such as pump & amp; treat, which will increase its commercial appeal