Longstanding scientific question now resolved, knowledge enables DoD to improve management of chlorinated solvent-contaminated sites. 

 Chlorinated solvents are the most common source of contaminated groundwater on DoD lands. Over the last decade, tremendous progress has been made in understanding the fundamental processes that drive cost-effective remediation at these sites. The cleanup approach used today bears little resemblance to the approaches used 20 year ago. Due to the effort of many SERDP and ESTCP investigators, most DoD sites are cleaned up by either introduced or natural biological processes that break down these contaminants to the point where the harmful chemicals are fully degraded and the site is remediated. These approaches have saved the Department of Defense billions of dollars.

But at a significant number of sites, the process may appear to stall at a point where the solvents have been degraded into the toxic chemicals cis-dichloroethene (DCE) and vinyl chloride (VC). The possible routes and rate for the continued degradation of these chemicals have been a subject of great debate in the scientific literature with significant economic and risk consequences.

Mr. Evan Cox and his colleagues Jim Gossett (Cornell University), Jim Spain (Georgia Institute of Technology), and Elizabeth Edwards and Barbara Sherwood Lollar (the University of Toronto) succeeded in identifying the organisms and elucidating the pathways by which these toxic chemicals may continue to break down at these sites. Through a series of elegant experiments, they determined that micropockets of oxygen, at very low concentration, do in fact exist in groundwater at sites that appear to be anaerobic, promoting aerobic biodegradation of cis-DCE and VC, thus resolving a longstanding scientific question. 

This knowledge will directly reduce DoD costs for cleaning up chlorinated solvent sites and improve management of these sites. Managers will now be able to predict with confidence if a site will continue to remediate itself or if they need to introduce other processes to fully degrade these toxic chemicals.

For this work, Mr. Cox and his team received a Project-of-the-Year award at the annual Partners in Environmental Technology Technical Symposium & Workshop held November 30 – December 2, 2010, in Washington, D.C.

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