New Cr(VI) Extraction Method for Soils and Geologic Materials

Example chromium data

Elevated chromium (Cr) in the environment, including groundwater and drinking water is a human health concern in many regions of the United States. Chromium can be liberated into the environment by mining and smelting processes, lifecycles of mineral resources, abandoned mine lands, natural weathering of soils and rocks, and wildfires, resulting in downstream chromium contamination. In order to investigate both geogenic and anthropogenic sources of Cr(VI) to groundwater and drinking water, a reliable method for extracting Cr(VI) from a wide range of soils, geologic materials, and mine processing wastes is needed. While methods do exist, they are not consistently effective at quantitatively extracting Cr(VI) from solid materials. Malherbe and others (2011) showed that the Cr(VI) extraction method promulgated by the U.S. EPA (SW-846 Method 3060A) extracted only 32% of the Cr(VI) present in a newly developed soil-based Standard Reference Material (SRM) (NIST 2701). Preliminary studies show that extraction efficiency relies upon mineralogy and particle size distribution. The objective of this study is to develop and test a new extraction method to accurately and reproducibly extract Cr(VI) from a wide variety of natural geologic materials and contaminated soils. The ability to accurately extract Cr(VI) from soil and geologic materials will aid regulatory agencies in establishing reasonable limits for Cr(VI) in groundwaters, particularly in California, where natural weathering of ultramafic rocks (serpentines) may lead to naturally occurring Cr(VI).

Reference Cited

Malherbe, Julien, Isaure, Marie-Pierre, Séby §, Fabienne, Watson, R.P., Rodriguez-Gonzalez, Pablo, Stutzman, P.E.., Davis, C.W., Maurizio, Chiara, Unceta, Nora, Sieber, J.R., Long, S.E., and Donard, O.F.X., 2011, Evaluation of Hexavalent Chromium Extraction Method EPA Method 3060A for Soils Using XANES Spectroscopy: Environmental Science and Technology, 45 (24), p. 10492–10500, doi: 10.1021/es201002g.