PROVENANCE, PREVALENCE AND HEALTH PERSPECTIVE OF ARSENIC, FLUORIDE AND URANIUM IN THE GROUNDWATER OF THE LARGEST INHABITED RIVER ISLAND (MAJULI, INDIA), IN THE WORLD

In recent past arsenic (As) and fluoride (F^-) co-contamination has been highlighted from various parts of the world including Argentina, China, India, Mexico and USA. Very recently, the co occurrence of As, F and uranium (U) has also been reported. However, co-contamination perspective needs further investigation for creating database to reach conclusive observation. Thus, in the present study an attempt has been made with the objectives (i) to understand the co-occurrence perspective of As-F^--U (ii) to establish their correlation matrix and (iii) to find out As induced health risk implications. Groundwater(n= 20) and sediment samples (n=5) were collected from the Majuli -the largest island of the Brahmaputra River and analyzed for As, F^- and U along with other physicochemical parameters. The results of groundwater analysis revealed high concentration of As (5-300µgL^-1) and U (0.31-1.15mgL^-1) but low occurrence of F^-(0.02-0.66 mgL^-1).Sediment samples were found to be enriched with As, F and U. The co-occurrence of these three elements was further confirmed by Energy dispersive spectroscopy (EDX) analyses. Multivariate statistical analysis showed poor positive relationship among As-F and As-U. Water type analysis revealed the dominance of Ca²⁺–HCO₃^- and Ca²⁺–Mg²⁺–Cl^- type of water. Arsenic hazard index (HI) values were >1 for both children and adults implying both class of individuals being under threat. The average cancer risk due to consumption of As contaminated water was found to be 5×10^-3 and 21×10^-3 in adults and children respectively. It is concluded that the people are likely to suffer from non-carcinogenic impacts with potential carcinogenic risk. Further, the unsaturated state of water suggests that occurrences of multi-contamination are likely to get aggravated in near future. Findings of the present study, particularly exploration of co-occurrence phenomena can be a vital data source for future extensive research and management practices.

Keywords: Groundwater, Brahmaputra floodplain, arsenic, fluoride, uranium, multielement contamination