Subsoil Contaminant Cr Fate and Transport

Hexavalent chromium [Cr⁶+] is a groundwater contaminant at numerous sites of the U.S. Department of Energy (DOE) or other sites across the United States. Globally, Cr⁶+ contamination is a major concern, and remediation of the Cr-contaminated sites remains one of the most challenging environmental issues. The Hanford site in the State of Washington (USA) was the location of the government’s primary plutonium production during the World War II Manhattan Project and the Cold War. Because of its corrosion-resistant properties, Cr was used extensively at the site as sodium dichromate, which led to its release into the environment. As a result, chromate ( https://www.w3.org/1998/Math/MathML"> CrO 4 2 − https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315372952/55acbd01-4a7c-4b6c-99dc-d931a043bf8c/content/inline-math_57_B.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> ) was, and in some areas still is, one of the major contaminants of concern near the Columbia River in the 100 Area at the Hanford Site (2010 Groundwater Annual Report: DOE/RL-2010-11). Oxidized aqueous Cr⁶⁺, which has higher toxicity than reduced Cr³⁺, is highly mobile under neutral and slightly alkaline conditions that are commonly present in contaminated sites and strict regulations are in place to mitigate risks. For this contaminant, which is considered highly toxic to both plants and animals (Abbasi and Soni, 1984; Paschin et al., 1983) and a human carcinogen (Ono, 1988), the aquatic water quality criterion of 11 μ L⁻¹ is lower than drinking water standards (0.1 mg L⁻¹) (Dresel et al., 2008).