Organic Carbon transport model of abandoned river channels - A motif for floodplain geomorphology influencing biogeochemical swaying of arsenic

Meandering-river geomorphology, forming abandoned channels/lakes with organic carbon-burial and microbial reductive dissolution, plays a crucial role in controlling arsenic fluxes in sinks such as contaminated aquifers of alluvial plains across the world. Suhiya oxbow-lake in the middle alluvial plain of the Ganga River, was selected as the natural laboratory. A top-down multidisciplinary approach was chosen employing satellite imagery to analyse the annual oxbow-lake surface vegetation dynamics (Eichhornia and Hydrilla). Side-scan sonar profiles across two oxbow-lakes along with Ganga River core data and vintage topographical maps, estimated the lake-sedimentation rate of 9.6 cm/yr. Organic carbon (amino acids, aromatics, lingophenols and lipids hydrocarbons) infiltration, based on hydrophobicity and molecular-mass, was detected at different depths along the water and sedimentary-column. Elemental analysis showed that the As concentration varied between lake surface to groundwater (0.37 to 185 µg/l) . A microbial diversity based study showed that large-sized photoautotrophs Nostoc, Anabaena are replaced by small-sized Fe-oxido-reducing As-metabolizing (Acidovorax, Dechloromonas etc.) and enteric bacteria (Enterobacter, Salmonella) from anthropogenic inputs at the bottom of water-column. Based on all these inferences, a conceptual organic carbon transport model was constructed to understand the preferential preservation and microbial uptake and diagenesis resulting in mobilization of As and other geogenic elements.

Publication year:2021

BOF-keylabel:yes

IOF-keylabel:yes

BOF-publication weight:6

CSS-citation score:2

Authors:International

Authors from:Higher Education

Accessibility:Open