Sediment and Submarine Groundwater Discharge Mediated Arsenic Flux into the Bay of Bengal, India: an Appraisal

The Ganga-Brahmaputra delta is among the largest river systems in terms of sediment discharge and the amount of arsenic present in the groundwater. Any slim possibility of arsenic intrusion in the coastal estuaries on account of active submarine groundwater discharge (SGD) can prove fatal to the biotic population at large. In the present study, a working hypothesis for the probable intrusion of arsenic through SGD has been postulated by re-analyzing the data of river discharge, sediment load, and arsenic concentration in the Bengal delta. Our study puts forward a strong argument for the coastal vulnerabilities of Bay of Bengal as the arsenic flux has reached at 1275 × 10³ kg/year and 865.8 × 10³ kg/year in the suspended and the dissolved form respectively. The enriched arsenic adsorbed on the surface of the Cenozoic sediments (dissolved and suspended) is contributing to the majority of arsenic flux to the Bay of Bengal. Furthermore, the flux resulting due to SGD contributes roughly 1% of the total flux, which if unregulated can prove catastrophic to the primary autotrophs. More so, the existence of flood-like conditions, as well as the region susceptibility to the fast-changing climatic trends, significantly increases the risk for the region in the near future. Therefore, ignoring the contributions of SGD in aiding the arsenic carcinogenicity in the coastal region of Bengal cannot continue for long and the time has come when a strong framework for SGD monitoring should be put in place, especially for regions falling under the purview of arsenic hazard zones.