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

The current method for monitoring hexavalent chromium in groundwater at environmental legacy sites is labor intensive, costly and does not allow for continuous in situ monitoring. The research project is developing an affordable, sensitive, durable and low-maintenance in situ sensor capable of real-time, long-term measurement of hexavalent chromium in groundwater wells at contaminated sites. The chromate ion, which is the dominant form of hexavalent chromium in groundwater, can be measured at low concentrations using near- ultraviolet absorption spectrophotometry. Interference caused by suspended particulate matter (turbidity) can be accurately compensated by measuring the amount of ultraviolet light scattered by the turbidity. As a result of the Phase I investigation, submersible prototypes capable of measuring hexavalent chromium concentration, with simultaneous correction for turbidity, have been produced and are ready for initial field trials. Refinement of the current prototype in Phase II will include the development of a more sensitive optical configuration and a more compact design of the sensor housing to allow for installation in smaller diameter monitoring wells. Special emphasis will be on long-term stability; automated instrument control, diagnostics, and data processing; and multi-well pilot- scale field testing and data integration. Commercial Application and Other Benefits: This sensor system will be a valuable tool in the determination of environmental fate and transport of hexavalent chromium and can be used to assess the effectiveness of remediation techniques. This approach provides a cost-reducing option for long-term contaminant monitoring at U.S Department of Energy Superfund sites and private sector sites such as chrome plating facilities.