The present study is conducted to understand the rainwater chemistry at three different locations in India during the Southwest monsoon season from June to September 2018. The rainwater samples were analyzed for the pH, conductivity, along with the major anions (F−, Cl−, NO2−, NO3−, SO42−), and cations (Ca2+, Mg2+, NH4+, K+, Na+). The mean pH and conductivity shows a significant heterogeneity in rainwater samples with alkaline nature at Jaipur (7.09 and 43.46 µS/cm) and Varanasi (7.31 and 55.42 \(\mu\) µS/cm) whereas acidic nature at Dhanbad (5.10 and 31.98 µS/cm). Moreover, the ionic compositions of rainwater were found to be drastically different at all the three stations, which are also reflected in the neutralization of rainwater. Neutralization factors of Ca2+, NH4+ and Mg2+ ions suggest that Ca2+ was the major neutralizing species in rainwater at Jaipur and Varanasi (but not at Dhanbad), with high neutralization factors of 3.10 and 2.65, respectively. The correlation among the measured ionic species indicates a significantly high correlation between SO42− and NO3−, Ca2+ and Mg2+ and Na+ and Cl− ions at all the three stations. Principal component analysis (PCA) was applied to identify the possible sources of rainwater constituents, explaining the crustal dust, biomass burning, fossil fuel combustion, agricultural emissions, and coal burning as possible sources of observed ions in rainwater. Further, the air mass back-trajectory clusters were also computed to estimate terrestrial influence on rainwater chemistry over these regions. Results suggest that the contribution from both local and regional sources significantly influenced monsoonal rainwater chemistry.
