Groundwater Geochemistry of Hexavalent Chromium Contamination

Hexavalent chromium (Cr(VI)) is a highly soluble and mobile form of chromium that poses significant risks to human health and ecosystems when present in groundwater. Its occurrence reflects a balance of natural processes—such as mineral weathering, redox reactions and pH-controlled desorption—and anthropogenic inputs from industrial discharge, agricultural return flows and historical waste sites. In oxic, alkaline environments Cr(III) minerals may oxidise to Cr(VI), while in reducing settings Cr(VI) can be transformed back to the less toxic Cr(III). The speciation and transport of Cr(VI) depend critically on redox potential, competing anions, organic ligands and physical aquifer properties. Alluvial and carbonate aquifers frequently exhibit elevated concentrations where source rocks or perched groundwater favour chromium release. Coastal aquifers are further influenced by seawater intrusion, which can buffer pH and inhibit Cr(VI) reduction. The global distribution of Cr(VI) in groundwater has led to stringent regulatory limits and a focus on monitoring strategies. Remediation approaches exploit natural attenuation and engineered barriers that promote reductive precipitation or sorptive retention. Advances in reactive transport modelling, isotope tracing and nanomaterial amendments are improving the prediction of contaminant fate and the design of cost-effective mitigation measures. Understanding the interplay of geochemical controls, hydrogeological context and land-use dynamics is essential for safeguarding water supplies and protecting public health.

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Groundwater Geochemistry of Hexavalent Chromium Contamination publication trend

The graph below shows the total number of articles in groundwater geochemistry of hexavalent chromium contamination across all publications each year (not limited to Nature Index journals).

Technical terms

Speciation: The distribution of an element among different chemical forms, affecting its mobility and toxicity.

Redox potential (Eh): A measure of the tendency of groundwater to gain or lose electrons, controlling oxidation–reduction reactions.

Alluvial aquifer: A water-bearing deposit of unconsolidated sediments, often derived from rivers, where groundwater flow is rapid.

Seawater intrusion: The movement of saline water into coastal freshwater aquifers, altering ionic composition and geochemical equilibria.

Oxyanion: A negatively charged ion containing oxygen, such as chromate (CrO42–), which influences sorption and transport processes.

References

1. Cr(VI) occurrence and geochemistry in water from public-supply wells in California. Applied Geochemistry (2015).
2. Natural occurrence of hexavalent chromium in a sedimentary aquifer in Urânia, State of São Paulo, Brazil. Anais da Academia Brasileira de Ciências (2009).
3. The Cr(VI) Stability in Contaminated Coastal Groundwater: Salinity as a Driving Force. Minerals (2021).