Tracing the origin of chromium in groundwater: Current and new perspectives

In this review study, the current and new perspectives in tracing the origin of chromium in groundwater are reviewed. Emphasis is given on the role of fertilizers in elevated concentrations of Cr(VI) in groundwater in ultramafic environments and on the isotope approach in evaluating groundwater contamination by Cr(VI). Phosphorous-bearing fertilizers with high Cr content could be a significant anthropogenic source of Cr(III) in soils and, consequently, of Cr(VI), if an oxidizing agent is present. They may also cause anionic Cr(VI) desorption from the iron oxide surfaces by simultaneous PO43− adsorption. Nitrogen-bearing fertilizers are responsible for nitrification, subsequent soil acidification, and increase in dissolution of Cr-bearing minerals. So far, chromium isotopes that are commonly used to distinguish between geogenic and anthropogenic contamination and to monitor the natural attenuation of Cr(VI) indicate the need for a more systematic research study on Cr isotope fractionation in natural and in any anthropogenic Cr-bearing formations. [Display omitted] •Geogenic Cr(VI) up to 120 μg L−1 has been recorded in an ultramafic natural spring•The role of fertilizers in Cr(VI) mobilization is multifold.•δ53Cr helps distinguishing geogenic and anthropogenic Cr(VI) in groundwater.•Shifts of δ53Cr than the accepted zero per mil for the igneous Cr source have been observed.