Source identification and health risk assessment of uranium in Tahlab aquifer, Taftan geothermal area-SE Iran

Geochemical composition and uranium occurrences in Tahlab aquifer, southeastern Iran, were studied in order to understand the source of U and geochemical processes controlling chemistry of Tahlab aquifer. Also the contamination and health risk assessment of uranium for drinking purposes in 16 sampling wells were investigated. Sulfate, Cl, K and EC for all water samples reveal higher concentrations than the drinking water standard values. Piper diagram of major ions indicated that the water is mostly Na-SO4-Cl type with sulfate and sodium as the dominant anion and cation respectively. The hydrogochemical signature of the investigated groundwater samples suggests that they are mostly affected by a hydrothermal source related to deep circulation waters from Taftan volcano. The results of saturation index (SI) show that the Tahlab aquifer groundwater samples are oversaturated with respect to quartz, chalcedony, hematite, uraninite (68.75% of samples), caffinite (43.75) and U4O9 (31.25%). Principal component analysis (PCA) results and high positive factor loading of U, V, HCO3 and Si revealed that the geogenic activities were major source of uranium in Tahlab aquifer and suggests that the U concentration is controlled by Si-bearing minerals. The results of hazard quotient (HQ) for adults were higher than one in the 81.25% of the groundwater samples, indicating that groundwater of this area may not be safe for drinking purposes. Health risk assessment shows that the consumption of uranium contaminated groundwater poses an emerging health threat to the populations in the study area, and hence needs regular monitoring and management measures.