Groundwater Arsenic Contamination in Semi-Urban Areas of Tando Muhammad Khan District: A Case Study from Deltaic Flood Plain of Sindh, Pakistan

An attempt has been made to assess the arsenic contamination and role of anthropogenic activities on its release in the groundwater of alluvial aquifers occurring on deltaic flood plain of Indus River. Groundwater collected from three semi-urban union councils of Tando Muhammad Khan district revealed that the groundwater has bad quality for drinking which varied in the order of UC-2 UC-1 UC-3. Anoxia is prevalent in the aquifers of study area which is indicated by high HCO3 and low NO3 and Fe contents. However, the natural concentration of sulphate (Mean range: 105-450 mg/L) in the groundwater of study area suggested that anoxia has not reached the stage where sulphate is consumed by SO4 reducing bacteria for organic matter decomposition. On the other hand elevated content of Na and Cl coupled with pathogenic bacteria occurrence indicated that sewage mixing is common in the study area. Elevated arsenic is reported from all there union councils which varied in the order of UC2 UC 1 UC3. Arsenicis mobilized from host sediments (clays/biotite) due to the prevalence of reduced environment caused by organic matter decomposition and triggered by sewage mixing.