In Situ Remediation of Arsenic in Contaminated Soils

Owing to its toxic nature and relative abundance, arsenic is a common contaminant of concern in environmental cleanup. Arsenic is identified as a constituent of concern at 728 National Priorities List (NPL) sites as of fiscal year 1998, and arsenic in soil is specifically identified at 32 percent of these sites (Fiedler, 2001). Exposure to arsenic has been linked to a variety of cancers, cardiovascular disease, diabetes, and anemia, as well as having reproductive, developmental, immunological, and neurological effects (U.S. Environmental Protection Agency [US EPA], 2003). In October 2001, the U.S. Environmental Protection Agency (US EPA) revised the arsenic standard for drinking water from 50 μg/L to 10 μg/L (effective as of 2006)—sparking substantial research into cost-effective methods to reduce arsenic concentrations in drinking water and increasing attention to remediation of arsenic in both water and soil systems. Soil cleanup levels are often established not only based on direct exposure risks to human and ecological receptors, but also on the potential for the contaminant to be leached from the soil matrix and transported to groundwater and surfacewater resources. As a result, the revised arsenic drinking water standard will result in more stringent cleanup levels for arsenic in soils, to be protective of these resources. Traditionally, remediation of arsenic-contaminated soils is achieved by excavation and ex situ treatment (most typically solidification/stabilization) and/or disposal. However, the high cost of such practices has fueled the development of in situ alternatives for remediation of contaminated soils that are less disruptive and, often, less costly than conventional treatment. Available treatment technologies for in situ remediation of