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Comments on: Large-Scale Uranium Contamination of Groundwater Resources in India D.P.S. Rathore Environ. Sci. Technol. Lett., Just Accepted Manuscript • DOI: 10.1021/acs.estlett.8b00382 • Publication Date (Web): 02 Aug 2018 Downloaded from http://pubs.acs.org on August 2, 2018
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Environmental Science & Technology Letters
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Comments on: Large-Scale Uranium Contamination of Groundwater Resources in India
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D.P.S. Rathore*
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Atomic Minerals Directorate for Exploration & Research, Department of Atomic Energy,
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Jaipur-302030, India.*Email:
[email protected] 5
COMMENTS
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I have read the cited article1 very carefully thoroughly. The title of the manuscript- Large-
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scale uranium contamination of groundwater resources in India is highly misleading and
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created panic among public. Facilities for water sample analysis for uranium determination
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are well established in India, and under no circumstances, water samples should have been
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sent abroad for their chemical analysis. There are contradictory statements1 on mobility of
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uranium with nitrate and bicarbonate complexation in ground water from hot arid regions in
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the northwestern Indian states. The declining ground water situation is a global phenomenon,
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and not just restricted to India. Further situation will not be grave as is made out in the article,
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because of uranium as there are technologies already developed to remove uranium and
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fluoride (defluoridation) including rain–water harvesting on large scale to make the water
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potable. Further, WHO limits on uranium concentration in ground are not for India specific,
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AERB limits already exists2.
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As clearly stated, on page 343 of the manuscript1, beyond doubt, uranyl carbonate
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complexes are important for mobilization of uranium in natural water from hot arid regions in
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the northwestern Indian states. Uranyl carbonate complexes further interacts with excess of
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available calcium to form ternary species3,4. Further statement, on page 344 of the
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manuscript, relating to Controls on the Occurrence of Uranium, it is the carbonate ion
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responsible for complexation and not bicarbonate4. As further stated in the manuscript, 2nd
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Para on page 345 of the manuscript, clearly supports promoting the formation of soluble
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uranyl carbonate complexes. These are contradictory statements as quoted above from the
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manuscript1.
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As far as correlation of uranium with bicarbonate concentration is also misleading and
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is incorrect. From Figure 2B, and also from Table S4, the data are scattered and there is no
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correlation of uranium versus bicarbonate concentration. Say, for uranium concentration of
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30 µg/l in water samples, the bicarbonate concentration varies from 300 to 800(mg/L). In
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fact, measurement of uranium is the best indicator for uranium exploration programme. Laser
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–induced fluorimetry is the best field technique for the direct measurement of uranium in
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natural water systems5.
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The correlation/statement on nitrate pollution on uranium mobilization in hot arid
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regions in the northwestern Indian states is also incorrect. As stated in abstract section, the
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statement is contradictory to the observation stated by authors on page 345, 3rd Para of the
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manuscript, related to correlations between uranium and nitrate were either weak or not
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significant. There is no correlation of nitrate and uranium reported in other publication also6.
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The nitrate ion is known to very weakly complex uranyl7. Therefore, nitrate pollution cannot
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mobilize uranium in ground water, absolutely wrong conclusion.
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As stated in the acknowledgements section, on page 346 of the manuscript1, it appears
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that the water samples were not properly collected and preserved by any of the authors in this
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publication including sample analysis. The reliability of chemical analysis for naturally
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occurring water samples depends on sampling and its preservation. This warrants the need
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and use of Mobile Geochemical Laboratory for quick analysis of water samples8. The time
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interval of sampling and analysis of, say bicarbonate content?( not stated). A large variation
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in the values of pH, conductance, major cations and anions including uranium contents in
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water samples have been observed with respect to the time-interval between sample
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collection and analysis( if not properly preserved)8. This variation in these contents depends 2
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on total dissolved salts (TDS). High TDS in water samples results in larger variation in major
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cations and anions, uranium contents with respect to time-interval between collection and
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analysis.
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The transport and deposition of uranium in significant concentration in natural waters
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is controlled by the organic and inorganic chemistry of the waters involved. The detailed
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composition of sample (major cations and anions, fluoride) are not included in the paper. The
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major cations, anions and trace elements present in ground water play a major role in
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characterizing the strata given below the water table. Fluoride content, above 1.5 ppm has
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been reported in this part of country. Calcium fluoride is very good co-precipitant of uranium
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9-10
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publications related to uranium in water in Punjab, India and requested the authors to further
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documents the reliability of their findings11-13.In my opinion, actual value of uranium
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contents in such water samples (containing fluoride) should not be abnormally very high. The
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presence of fluoride above 1.5 mg/l in water samples effects the variation in the contents of
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uranium in water samples( or if not properly acidified for preservation, pH
