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Sulfate reduction accelerates groundwater arsenic contamination even in aquifers with abundant iron oxides.


ABSTRACT: Groundwater contamination by geogenic arsenic is a global problem affecting nearly 200 million people. In South and Southeast Asia, a cost-effective mitigation strategy is to use oxidized low-arsenic aquifers rather than reduced high-arsenic aquifers. Aquifers with abundant oxidized iron minerals are presumably safeguarded against immediate arsenic contamination, due to strong sorption of arsenic onto iron minerals. However, preferential pumping of low-arsenic aquifers can destabilize the boundaries between these aquifers, pulling high-arsenic water into low-arsenic aquifers. We investigate this scenario in a hybrid field-column experiment in Bangladesh where naturally high-arsenic groundwater is pumped through sediment cores from a low-arsenic aquifer, and detailed aqueous and solid-phase measurements are used to constrain reactive transport modelling. Here we show that elevated groundwater arsenic concentrations are induced by sulfate reduction and the predicted formation of highly mobile, poorly sorbing thioarsenic species. This process suggests that contamination of currently pristine aquifers with arsenic can occur up to over 1.5 times faster than previously thought, leading to a deterioration of urgently needed water resources.

SUBMITTER: Nghiem AA 

PROVIDER: S-EPMC10074394 | biostudies-literature | 2023 Feb

REPOSITORIES: biostudies-literature

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Sulfate reduction accelerates groundwater arsenic contamination even in aquifers with abundant iron oxides.

Nghiem Athena A AA   Prommer Henning H   Mozumder M Rajib H MRH   Siade Adam A   Jamieson James J   Ahmed Kazi Matin KM   van Geen Alexander A   Bostick Benjamin C BC  

Nature water 20230216 2


Groundwater contamination by geogenic arsenic is a global problem affecting nearly 200 million people. In South and Southeast Asia, a cost-effective mitigation strategy is to use oxidized low-arsenic aquifers rather than reduced high-arsenic aquifers. Aquifers with abundant oxidized iron minerals are presumably safeguarded against immediate arsenic contamination, due to strong sorption of arsenic onto iron minerals. However, preferential pumping of low-arsenic aquifers can destabilize the bounda  ...[more]

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