Fate, Transport and Toxicity of Nanoscale Zero-Valent Iron (nZVI) Used During Superfund Remediation

Abstract

As a result of the Superfund Amendments and Reauthorization Act (SARA) of 1986, the United States Environmental Protection Agency (EPA) has increased consideration and implementation of newer and more efficient innovative technologies to treat wastes rather than the traditional “dig-and-haul” and “pump-and-treat” methods for removing contaminated soils and groundwater from the site (U.S. EPA 2008b). One such emerging field that holds potential for cleaning up Superfund sites in a more cost effective and efficient manner is nanotechnology.

The impacts of nanotechnology are increasingly evident in all areas of science and technology, including the field of environmental studies and treatment. Experts anticipate the development and implementation of environmentally beneficial nanotechnologies in the categories of sensing and detecting, pollution prevention, and treatment and remediation. Of the three, the category of treatment and remediation has experienced the most growth in recent years. In terms of site remediation, the development and deployment of nanotechnology for contaminant destruction has already taken place.

Nanoscale zero-valent iron (nZVI) particles and the subsequent derivatives (bimetallic iron particles and emulsified iron) represent a viable, commercially available nanotechnology for in situ remediation at Superfund and other contaminated sites. Responsible use of nZVI in environmental applications and careful management of the associated risks requires a fundamental understanding of their mobility, potential bioavailability/bioaccumulation and impacts on a wide variety of organisms. Currently this fundamental understanding of the environmental fate of nZVI and its oxidation products is not well understood for the variety of environmental conditions that may occur.

In general, the high tendency of bare nZVI to agglomerate indicates that migration in the groundwater should not be an issue for groundwater drinking wells, streams and other bodies of water. This agglomeration will also limit the risk of human and environmental exposure to nZVI used for remediation. Issues, however, may exist for organisms in the environment that are directly exposed to the nZVI before much oxidation of the particles takes place. Concerns may also exist with incomplete conversion of certain contaminants and the offsite mobilization of contaminants that bind to the nZVI. Understanding the fate, transport and toxicity of nZVI in its early phases of use is essential before the technology can be used on a large scale.