The United States spends around $2 billion a year on remediation at hazardous waste sites, with a large portion of this used for ground water monitoring. Yet according to Rolf Halden, a researcher at Arizona State University's Biodesign Institute, the information gathered often is of limited value.

Under a new three-year, $1.15 million grant from the U.S. Department of Defense (DoD), Halden, assistant director at the Institute's Swette Center for Environmental Biotechnology, is pursuing a novel method to conduct these vital tests. His team's efforts are part of a quest to provide more accurate results at lower cost, and produce fewer harmful byproducts during the monitoring process.

When considering techniques suitable for ground water monitoring, three components are key – the quality of data provided, the cost of the procedure and the environmental impact. Conventional monitoring typically accounts for at least 20 percent of the total cleanup costs incurred during site remediation. From a project management standpoint, however, the analyses and acquired data often can be misleading and unsatisfactory, as well as environmentally damaging.

Normally, ground water is extracted from the earth for testing and then sent to a lab for detailed analysis. The method is financially and environmentally costly, because the water must be transported, and the process can generate significant amounts of hazardous waste at the surface.

Halden's technique involves monitoring ground water while it still is in place in the subsurface, using a device known as the in-situ sampler or IS2, which may be custom-fit into ground water monitoring wells. The IS2 is deployed downhole, where its integrated pumps draw up ambient ground water at milliliter per day rates. Analytes of interest are concentrated onto solid adsorption media for analysis. One of the advantages of this in-situ approach is that effluent from the device remains in the subsurface. Only the device itself with the extracted analytes is removed from the well. In this way, monitoring can be conducted without the use of purge water or the liberation of wastewater at the surface.

Once the device has completed its work and is removed from the well, the contaminant-charged media are shipped to the laboratory, where they undergo automated analysis assisted by robotics, as well as standard methods including mass spectrometry and ion chromatography. The new technology boasts extremely low detection limits – in the ng/L to pg/L range. Further, it produces no wastewater, and may be carried out at a low cost per sample, thanks to the use of automation.

The IS2 sentinel will be applied on a pilot basis at DoD sites and used in multiple deployments to examine a range of ground water contaminants, including volatile organic compounds like tetrachloroethene, trichloroethene and vinyl chloride; water-soluble fuel components (benzene and toluene); explosives (RDX and TNT); semi-volatile compounds (phenol); polycyclic aromatic hydrocarbons (naphthalene and phenanthrene); inorganic water contaminants (perchlorate); and heavy metals (arsenic and lead). Each of these analytes will be captured in-situ, using a pair of customized IS2 devices. Results will be compared to those obtained with conventional water-monitoring approaches.

The project seeks to demonstrate improved detection limits, 10 times to 100 times lower than those achieved through current Environmental Protection Agency (EPA) methods.