STUDY OF ARSENIC ENRICHMENT IN GROUND WATER OF GANGA-GHAGRI,PLAIN IN BALLIA-GHAZIPUR REGIONS : A FUTURE CONCERN

This part of the Ganga Plains are the most thickly populated areas of India. The earlier work reported high geogenic arsenic (As) concentration is extensively present in the Holocene alluvial aquifers of the middle Ganga-Ghagra Plain, India. Climatic changes induced weathering processes, surface water interactions, ion exchange, redox processes, and anthropogenic activities are responsible for high concentrations of cations, anions and As in the groundwater. The spatial and temporal variations for As concentrations were greater in the pre-monsoon in comparison to the post-monsoon period. The As enrichment was encountered in the sampling sites that were close to the Ganges River .The depth profile of As revealed that low concentrations of NO₃ ^? are associated with high concentration of As . The As concentration also shows depletion with increasing depth. The poor correlation between As and Fe indicates the As release into the groundwater, depends on weathering, O₂ consumption, and NO₃ ^? reduction and is decoupled from Fe cycling. Statistical analysis were used to identify various factors influencing their enrichment in this Plain. Groundwater is generally supersaturated with respect to calcite and dolomite in post-monsoon period, but not in pre-monsoon period. The saturation index results indicate release of arsenic in redox processes in dry period and dilution of arsenic concentration by recharge during monsoon. Increased concentrations of bicarbonate after monsoon are caused by intense flushing of unsaturated zone, where CO₂ is formed by decomposition of organic matter and reactions with carbonate minerals in solid phase. The study area has vital consideration for the groundwater , which is an exclusive source of drinking water in the region which makes difficulty in managing the situation and needs immediate attention.