Challenges Associated with Generating Reliable Nanogram-per-Liter Measurements of Hexavalent Chromium in Groundwater

The US Environmental Protection Agency (USEPA) and several states are considering regulatory limits for hexavalent chromium (Cr(VI)) <100 ng/L, increasing the importance of obtaining accurate and reliable data. The present study presents the results of 2 studies investigating the effectiveness of chemical preservation on ng/L concentrations of Cr(VI) in groundwater. Chemically preserved and unpreserved aliquots of a groundwater sample were spiked with a known amount of Cr(VI), and then analyzed in tandem with sets of preserved and unpreserved performance test samples over 28 d. The studies showed that although Cr(VI) appears to be relatively stable over 28 d, it may be sensitive to minor matrix changes after collection. The studies also demonstrated significant challenges to measuring Cr(VI) below 100 ng/L, because the results can be subject to positive bias or contamination that may not be readily apparent. We conclude that Cr(VI) measurements using a USEPA published method below 100 ng/L may be categorized as semiquantitative at best. Environ Toxicol Chem 2020;39:1526-1533. © 2020 SETAC.

Selenium bioaccumulation in fish exposed to coal ash at the Tennessee Valley Authority Kingston spill site

In December 2008, 4.1 million cubic meters of coal ash were released into the Emory and Clinch Rivers by the Tennessee Valley Authority Kingston Fossil Plant. Coal ash contains several contaminants, including the bioaccumulative metalloid selenium (Se). Because Se is predominantly accumulated in aquatic organisms through dietary rather than aqueous exposure, tissue-based toxicity thresholds for Se are currently being considered. The proposed threshold concentrations range between 4 μg/g and 9 μg/g Se (dry wt.) in whole body fish, with a proposed fillet threshold of 11.8 μg/g. In the present study, the authors examined the spatial and temporal trends in Se bioaccumulation and examined the relationship between the Se content in fillets and in whole bodies of fish collected around the Kingston spill site to determine whether Se bioaccumulation was a significant concern at the ash spill site. Whereas Se concentrations in fish (whole bodies and fillets) were elevated at sampling locations affected by the Kingston ash spill relative to reference locations, concentrations do not appear to be above risk thresholds and have not been increasing over the 5-yr period since the spill. These findings are not only relevant to guiding the human health and ecological risk assessments at the Kingston ash spill site, but because of current national discussions on appropriate guidelines for Se in fish as well for the disposal of coal combustion wastes, the results are also relevant to the general understanding of Se bioaccumulation in contaminated water bodies.