Publications by authors named "Thomas S Varner"
Previous studies along the banks of the tidal Meghna River of the Ganges-Brahmaputra-Meghna Delta demonstrated the active sequestration of dissolved arsenic (As) on newly formed iron oxide minerals (Fe(III)-oxides) within riverbank sands. The sand with high solid-phase As (>500 mg/kg) was located within the intertidal zone where robust mixing occurs with oxygen-rich river water. Here we present new evidence that upwelling groundwater through a buried silt layer generates the dissolved products of reductive dissolution of Fe(III)-oxides, including As, while mobilization of DOC by upwelling groundwater prevents their reconstitution in the intertidal zone by lowering the redox state.
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- The high levels of dissolved arsenic in Bangladesh's shallow aquifers are mainly due to bacteria breaking down arsenic-bearing iron compounds in organic-rich, low-oxygen environments.
- The interaction between the Meghna River and groundwater forms a natural barrier that helps trap arsenic, which researchers studied by analyzing sediments from both the riverbank and the aquifer.
- The study found that while both sediment types contained similar elemental compositions, the amounts of iron and arsenic extracted differed significantly, with aquifer sediments releasing much higher concentrations due to variations in the type of organic matter present.