Remediating Subsurface ARSENIC Contamination with Monitored Natural Attenuation

摘要

In January 2001, the U.S. EPA established a new standard of 10 μg/L for arsenic in drinking water. Even before this revision, arsenic was at the top of the Comprehensive Environmental Response, Compensation, and Liability Act (Su-perfund) Priority List of Hazardous Substances. Prepared by EPA and the Agency for Toxic Substances and Disease Registry, this list prioritizes substances that occur most commonly at Superfund sites and that, on the basis of their toxicity and potential for human exposure, pose the most significant risk to human health. Because the revision of the arsenic standard was driven by health concerns―specifically the risks of bladder and lung cancer―closer scrutiny will most likely be directed toward the potential threats at contaminated sites. At some sites, however, arsenic contamination poses no immediate hazard to human or ecosystem health. In such cases, the potential risks associated with arsenic migration and exposure may be mitigated by natural attenuation, which is defined as "physical, chemical, or biological processes that, under favorable conditions, act without human intervention to reduce the mass, toxicity, volume, or concentration of contaminants in soil or groundwa-ter". Here, we examine the processes that could affect the natural attenuation of arsenic and the feasibility of these natural processes as a remediation strategy for arsenic-contaminated sites.