Survey of uranium in drinking water sources in India: interim observations

A nationwide survey is being conducted for mapping uranium content in drinking water sources across India, in association with local educational and research institutions. For this, an optimum grid size of 6 × 6 sq. km was selected based on the international practices for geochemical mapping. About 55,554 surface as well as groundwater samples, used for drinking purpose, were collected covering approximately 1.2 × 106 sq. km. Light emitting diode-based fluorimeter having wide dynamic range and 0.2 μg l–1 lower detection limit was used for direct measurement of uranium content in the water samples. Uranium was detected in 83.6% of all the collected water samples. The geometric mean of uranium concentration in surface and groundwater samples was found to be 0.8 μg l^–1 (range: ≤0.2–22 μg l^–1) and 2.1 μg l^–1 (range: ≤0.2–4918 μg l^–1) respectively. Out of 12 water quality parameters measured to understand the geochemical processes governing uranium content in water sources, eight were found to exceed the acceptable limits set by the Bureau of Indian Standards for drinking water. The parameters sulphate, chloride, nitrate, fluoride, total dissolved solids, alkalinity and hardness exceeded their limits by 4.2%, 12.9%, 14%, 20.5%, 34.3%, 45% and 51.6% respectively. Uranium content in 98% of groundwater samples was found to be less than the national limit set by the Atomic Energy Regulatory Board for radiological safety. Dissolved uranium content in groundwater samples showed an upward trend with total dissolved solids and depth of water sources. No surface water samples exceeded the prescribed regulatory limit.