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Tracing geochemical sources and health risk assessment of uranium in groundwater of arid zone of India

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This study measured uranium in 265 groundwater samples from an arid, carnotite-bearing region of western Rajasthan and northern Gujarat and modeled the geochemistry behind it. Uranium ranged widely, and close to a third of samples were above the WHO provisional guideline the authors cite. Dissolution of the uranium vanadate mineral carnotite, water-rock interaction and evaporation were identified as the main drivers, and modeled ingestion doses and chemical hazard quotients were below the reference values used.

Key numbers

  • Uranium in groundwater: 0.6 to 260 µg/L, mean 24.0 µg/L, n = 265 (abstract, p. 1; p. 3).
  • 69.3% of samples below 30 µg/L, 27.3% between 30 and 60 µg/L, 3% between 60 and 100 µg/L, 0.38% above 100 µg/L (p. 3). The abstract states that 30% surpassed 30 µg/L.
  • Reference values cited by the authors: WHO provisional guideline 30 µg/L; Atomic Energy Regulatory Board radiological limit 60 µg/L; no Bureau of Indian Standards limit (p. 2).
  • Uranium measured by LED fluorimetry, detection range 0.5 to 1000 ppb, detection limit 0.2 ppb (p. 2).
  • Lifetime average daily dose of uranium 0.011 to 5.24 µg/kg body weight per day, mean 0.47, against reference doses of 0.6 (WHO) and 4.4 (AERB) µg/kg per day; hazard quotient mean 0.78, median 0.64 (p. 8; Table 2).
  • Mean annual ingestion dose highest in infants: 49.30 µSv/y (0 to 6 months) and 56.34 µSv/y (7 to 12 months) (p. 8; Table 2).
  • Predominant modeled species in alkaline groundwater: the uranyl tricarbonate anion (p. 10).

Methods (brief)

Grid sampling (8 by 8 km cells) of groundwater filtered at 0.45 µm and acidified; uranium by LED fluorimetry of uranyl complexes, other metals by ICP-AES, major ions by titration, turbidimetry and flame photometry. Speciation and saturation indices were modeled in PHREEQC; principal component analysis identified source processes. Dose and hazard calculations are in supplementary methods.

Evidence fitness

Supports statements about geogenic uranium in arid-zone groundwater used for drinking and about modeled dose and hazard quotients. It does not measure health outcomes in residents and does not cover food.

Limitations

Internal inconsistency between the abstract (30% above 30 µg/L) and the results breakdown; dose and hazard methods are only in supplementary material; single sampling campaign.

Update history

No substantive edit history is available in this build. The full commit record is available in git.

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