Co-occurrence of geogenic uranium and fluoride in a semiarid belt of the Punjab plains, India

Abstract

The inordinate presence of uranium (U) and fluoride (F?) in shallow aquifers of arid/semi-arid regions in northern India has raised a serious health concern; the Muktsar district of Punjab is one such example. In the present study, a total of 38 groundwater samples (17 from <100 ft (very shallow; VSL), 21 from >100 to 180 ft (shallow; SL)) were collected from this district to understand the current health risk associated with U and F? and the major factors/processes influencing these contaminants. Groundwater in the study area is mostly alkaline and oxic in nature. The concentration of U ranged from 18.5 ?g/L to 456 ?g/L exceeding the WHO permissible limit (>30 ?g/L) in 93 and 100% samples from VSL and SL respectively, while F? concentration (ranged from 0.3 to 14.4 mg/L) above the limit (>1.5 mg/L) were found in 75 and 57% samples from VSL and SL respectively. As per the depth-wise distribution of U and F?, there is no significant difference between VSL and SL samples, with a few exceptions. Spearman rank correlation (?) shows a significant positive correlation (p-value < 0.05) between U and F? (? = 0.5), and U with total dissolved solid (TDS) (? = 0.5), salinity (? = 0.6), and bicarbonate (HCO3?) (? = 0.7) and a positive association of F? with TDS (? = 0.3), salinity (? = 0.3), and HCO3? (? = 0.3), indicating these parameters are responsible for the co-occurrence of U and F?. Moreover, this geochemical signature is attributed to their geogenic origin. Uranium speciation data show that UO2(CO3)22? and UO2(CO3)34? are dominant species, while F? predominantly occurs as F? species. The regions with high concentration of U and F? in groundwater primarily have mixed type species (Na�HCO3 and NaCl type). Geochemical modelling revealed that the precipitation of calcite, dolomite, and aragonite is favourable for mobility of F? in groundwater. The hazard quotient (HQ) of F? for adults and children exceeds 1 in 57.8% and 65.7% of samples, respectively, while in case of U, 94.7% and 100% samples exceed 1, respectively, indicating the latter is having greater health impact on local people. The current data indicated an urgent demand to develop low-cost and effective remedial techniques to manage groundwater contamination in this region. � 2023