Nature and sources of ionic species in rainwater during monsoon periods in and around sixteenth-seventeenth century CE monuments in Yamuna River basin, India.

The nature and sources of ionic species were studied in the monsoon rainwater collected from two monuments of the sixteenth-seventeenth century CE in the Yamuna River basin from 2016 to 2018. The results showed the acidic pH of the rainwater with high dissolved SO4-2 and NO3-, and soil-derived components (Ca+2, Mg+2, and K+). The anionic (SO4-2, NO3-, Cl-, F-, and HCO3-) and cationic (Ca+2, Mg+2, K+, NH4+, and Na+) concentrations showed regional differences in yearly contribution mainly from the fossil fuel combustion, soil dust, and farm residue burning. The rainwater analysis showed low dissolved ions at SCTK (Sheikh Chilli's Tomb, Kurukshetra) compared to KBMP (Kabuli Bagh Mosque, Panipat). The mean concentration of SO4-2 was 1.5 times higher than the NO3- apportioning the sulfate as a dominant acidifying constituent in rainwater. Pearson's correlation and principal component analysis (PCA) showed terrestrial and marine origins of dissolved ions in the rainwater. The Na-normalized molar ratios and the analysis of sea salt and non-sea salt fractions indicate the dominance of non-marine contributions in the precipitation. Based on neutralization factors, cations showed neutralization of rainwater acidity as follows: NFCa+2 > NFMg+2 > NFNH4+ > NFK+. The potential index showed the dominance of the neutralization potential (NP) on acidic potential (AP) at both locations.