Comparison of two alluvial aquifers shows the probable role of river sediments on the release of arsenic in the groundwater of district Vehari, Punjab, Pakistan

The study was done to assess the effect of the river Sutlej on arsenic (As) contamination. Sampling was done from the alluvial plain with increasing distance from the river Sutlej in district Vehari and compared with the study done in the proximity of River Sutlej. Sixty (60) groundwater samples mostly from shallow depths were collected and analyzed for As concentrations. Multivariate statistical tools (PCA and CA), saturation index, piper plots and Gibbs diagrams were used to detect evidence about the interrelationship and sources of As and other water quality variables responsible for groundwater contamination. Results revealed that As concentration ranged from below detection limit to 156 A mu g/L indicating that 50% samples exceeding the WHO guidelines (10 A mu g/L) and 17% exceeding the Pakistan National Environmental Quality Standards (NEQS) limits (50 A mu g/L) Sutlej. The piper plot revealed that water chemistry of the study area was Ca-HCO3 (-), Ca-Mg-Cl, type. Correlations between As and HCO3 (-) (r (2) = 0.433) was positive, while negative correlations were observed between As-Mn2+ and As-Fe2+ (r (2) = - 0.102), (r (2) = 0.107) respectively. Geochemical signatures of the groundwater in the study area showed that the As could be released by oxidative dissolution to some extent and elevated evaporation in the arid environment of the study area under the stimulus of alkaline water and high pH (range 7.1-8.4). Although the concentrations are exceeding the WHO limit in 50% of the water samples but, are less than the previous study done in Mailsi near River Sutlej. Further, the concentrations decreased as the distance from the River increased which shows the probable role of sediments deposited by the River Sutlej