Clay-plug sediment as the locus of arsenic pollution in Holocene alluvial-plain aquifers

Workflow of the multidisciplinary approach towards geogenic arsenic quantification in clay plug sediments. • Holocene fluvial geomorphology and permeability anisotropy control As-occurrence. Sediment bulk volume abandoned meandering-river bends ( plugs ) is calculated. Remote sensing, side-scan sonar sediment core analyses yielded total As-load. Microbial metabolism effectively controls As Fe fluxes a high-TOC setting. Shallow aquifers many alluvial basins around world have last three decades been identified as pollution hotspots, which spatial variation natural (or: concentration conditioned by lithofacies distribution. Despite large amount publications on specifics pollution, still uncertainties remain to provenance processes that lead enrichment aquifers. In this paper, sediment-filled clay-plugs highlighted primary source aquifer pollution. The combination high organic-carbon deposition rates presence chemically-bound specific geomorphological setting creates potential for microbially-steered reductive dissolution an anoxic environment, subsequent migration desorbed to, stratigraphic entrapment in, adjacent sandy point-bar To assess magnitude clay-plug, calculations were made twenty Middle Ganges Plain Bihar (India), combining clay-plug surface area analysis Sentinel-2 satellite data, depth profiling oxbow lakes River, sedimentological data from five cored shallow wells. ICP-MS based elemental 36 sub-samples, complemented with published similar West Bengal, India, average content 28.75 mg/kg 12-m-thick plugs, amounts 0.07 – 3.13 . 10 6 kg per plug. A scenario presented release microbial metabolism, followed bordering sands.