ABSTRACT
Chromium is a common groundwater contaminant that has been the focus of regulation and treatment for many years. Because it has several forms that can be present in groundwater, most of the regulations to date have focused on total chromium. Chromium most commonly occurs in two valence states: trivalent (Cr[III]) and hexavalent (Cr[VI]). Cr(III) is the primary form of chromium found in naturally occurring minerals. Cr(VI) is the form of chromium typically introduced as a contaminant from industrial activities and is the form of concern as this element is resurfacing in risk assessment and regulation. Industrial sources of Cr(VI) contamination in groundwater include electroplating, tanning, wood preservation and pulp production, and cooling tower water from industrial operations. Toxicity of chromium is dependent on oxidation state. Both the USEPA and the California EPA have been evaluating Cr(VI) in drinking water supplies and considering establishing a Cr(VI)-specific drinking water standard in recent times.
