158-2 Distribution and geochemical processes of oxidatively enriched components in groundwater

Session: Redox-Driven Nutrient and Contaminant Dynamics in Terrestrial Systems

Presenting Author:

Authors:

Abstract:

Groundwater Cr(VI) may be of geological origin in many parts of the world, which poses severe impacts on human health (1). Many studies reported that high Cr groundwater normally occurred in ultramafic rocks-related aquifers (2, 3). However, recently we observed the wide occurrence of high Cr(VI) groundwater in sandstone-related aquifers (4). Less is known about the sources and enrichment mechanisms of dissolved Cr(VI) in those aquifers. This study showed that high Cr(VI) groundwater existed in relatively oxic environment. Chromium isotopes indicated the oxidation of Cr(III) in the aquifers, especially for those hosting high Cr(VI) groundwater. Silicate weathering was the dominant rock-water interactions in the aquifer, which enhanced the release of the unweathered silicate-bound Cr into groundwater. Relatively high pH and ionic strength led to desorption of Cr(VI). There were significant differences in the compositions and structures of microbial communities between low Cr(VI) groundwaters and high Cr(VI) ones. Functional “specialists” related to Cr biotransformation, including Cr(VI) reducing bacteria (CRB) and Mn-oxidizing bacteria (MnOB) were positively correlated to total Cr and Cr(VI) concentrations in groundwater, illustrating the contribution of MnOB mediated Cr(III) oxidation to Cr(VI) enrichment. This study highlights the geological origin of high dissolved Cr(VI) in sandstone aquifers and the significant roles of microbial ecological functional “specialists” MnOB and CRB in Cr(VI) enrichment in groundwater.

Acknowledgement

The study was financially supported by the National Natural Science Foundation of China (grant No. 42130509), 111 project (No. B20010).

References

(1) Nriagu, J. O.; Nieboer, A. John Wiley & Sons: New York, 1988, pp 399−442.

(2) Morrison, J. M.; Goldhaber, M. B.; Mills, C. T.; et al. Appl. Geochem. 2015, 61, 72−86.

(3) Vengosh, A.; Coyte, R.; Karr, J.; et al. Environ. Sci. Technol. Lett. 2016, 3, 409−414.

(4) Guo, H., Chen, Y., Hu, H., et al. Environ. Sci. Technol. 2020, 54(16), 10068–10077.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-5748

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