Chromium speciation in natural waters draining contaminated land, Glasgow, UK

Historically, solid waste from chromite ore processing has been disposed of at a number of sites in Glasgow, Scotland. Leachate from these sites has been implicated as a source of chromium (Cr) contamination to both groundwaters and stream waters in the south east area of the city. In this study, chromium speciation has been determined in ground-, stream-, river- and pore waters, to assess the extent of contamination and the associated risk. The speciation of chromium is important, as the trivalent species of chromium (Cr(III)) is an essential form of the element, while hexavalent chromium (Cr(VI)) is a known carcinogen to humans via inhalation. Concentrations of total chromium have also been determined in sediments from the River Clyde, to assess the significance of local concentrations relative to those elsewhere in the catchment.

High concentrations of Cr(VI) were found in groundwaters and streamwaters in the area immediately surrounding the contaminated sites, and high concentrations of chromium were also found in River Clyde sediments downstream of these sites. However, these concentrations rapidly decrease away from the chromium-contaminated south eastern side of the city. Data from porewaters suggest that some reduction of Cr(VI) occurs naturally in the sediments, indicating that the risk posed by high concentrations of Cr(VI) should be decreased over the longer term.