Some researchers mentioned that high pH resulted in elevated fluoride concentration in groundwater.
It is found true; it is also seen that in the same area at some other locations though the pH is high but fluoride concentration is low. What's the explanation?
Yes it is true in my PhD studies also. the alkaline nature of pH promotes leaching of F in groundwater.
Dr. Pandith Madhnure - I have also mentioned that it is true.
My question - Why it is not the case in other places of the same area - pH is high but F is low?
There may the other reasons like, how much leachable fluoride is availabel, what is the source rock, other reasons like high Ca etc.
Yes, there must be some scientific reasons - probably related to the composition of host rocks. The detailed work on this aspect - I have not yet read. Thanks
Dear Dr. Bhojraj Nandlal - The pH has a significant role in F− solubility; at a pH range of 5 - 6.5, F− solubility is low and the F− is adsorbed on the surface of the clay . The higher pH values (>7) of groundwaters are found to be greater than the point of zero charge (PZC) of most minerals (>7–8); in such system, the surface charge of the solids is neutral or slightly negative, which depresses the adsorption of negatively charged F─ . Conversely, as OH− and F− ions have similar ionic radius (0.136 nm), the OH− in groundwater can replace the exchangeable F− of clay minerals (biotite/muscovite, illite, chlorite, and amphiboles) resulting in increase of F− concentration in groundwater.
Thanks for your query.
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