Salinity enrichment, sources and its contribution to elevated groundwater arsenic and fluoride levels in Rachna Doab, Punjab Pakistan: Stable isotope (δ2H and δ18O) approach as an evidence.

The present study aimed at exploring the sources of salinity and the link it shares with the enrichment of As (arsenic) and F- (fluoride) in the groundwater of Rachna Doab. Total Dissolved Solids (TDS) were used as the measure of salinity to classify samples into three groups: TDS <1000 mg/L (freshwater), 1000-3000 mg/L (slightly saline) and 3000-10,000 mg/L (moderately saline). The stable isotope analysis (δ2H and δ18O relative to VSMOW) were used to explore the sources of salinity and a conceptual model, based on secondary data was used for comparing the current and past scenarios of groundwater salinization sources. Groundwater ion chemistry and geochemical modeling (PHREEQC) were used to develop a link between the occurrence of salinity and enrichment patterns of As and F- in the groundwater of study area. TDS, As and F- concentrations in groundwater ranged from 234 to 4557 mg/L, below detection limit to 240 µg/L and below detection limit to 3.9 mg/L, respectively. Mineral dissolution, ion exchange processes, and partial input of evaporation were identified as the factors affecting groundwater salinity in the region in accordance with the conceptual model developed based on secondary data. Groundwater salinity accounts as one of the factors that positively influence the enrichment of F- in groundwater, whereas As shows no clear relationship with saline groundwaters.