The four wells that have been repeatedly analyzed during all the sampling campaigns (namely KD-5, KD-7, KD-10 and KD-8), share a common behavior over time. In fact, when comparing older data with those measured in 2012, it is possible to point out a general trend towards higher concentrations for HCO3− Ca2 + and NO3− which is also accompanied by an increase of TDS. When considering SO42 − and F−, we find that the concentrations increase too, with the only exception of the sampling point KD-5.
In samples collected in 2012 we also analyzed a series of microelements that had not been analyzed during the 2008/9 campaigns, for some of which the maximum concentration in drinking water is regulated in India by BIS (2005). In particular, data, displayed in Table S2 in the online Supplementary material, show that boron and manganese sometimes exceed the recommended limits for drinking water. In addition, uranium, which is not included in the list of contaminants as an inorganic chemical, indirectly exceeds the concentration limit for its quality of alpha emitter. The tolerance limits are also exceeded for As and Mo in stream water, though the latter is not generally used for drinking purposes.