Which mechanism causes increased groundwater arsenic concentration in alluvial aquifers after prolonged flooding?

💡 Explanation

When alluvium is flooded, reducing conditions develop, and microbial activity enhances the dissolution of iron oxides, causing arsenic adsorbed to those oxides to be released into the groundwater via enhanced pyrite oxidation. Therefore arsenic concentration increases, rather than from agricultural, industrial activities, or atmospheric deposition that are independent of flooding duration within the alluvium.

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