Chemistry and Ionic Sources of Precipitation in the Changsha Area

• • The volume-weighted mean total dissolved solids (TDS) in Changsha precipitation was 245.58 μeq·L−1, with a range of 51.71–813.40 μeq·L−1, indicating significant variability in atmospheric solute loading that must be considered in regional deposition models. • • Ca2+ and SO4^2− together constituted 55.76% of the total ionic concentration, with SO4^2− and NO3^− accounting for 48.24% and 29.13% of anions, respectively, highlighting the dominance of acidic precursors from anthropogenic sources. • • Correlation analysis revealed strong positive correlations between SO4^2− and NO3^− (r = 0.78) and between Ca2+ and Mg2+ (r = 0.70), indicating common sources and guiding targeted emission reduction strategies. • • Enrichment factor analysis quantified that anthropogenic contributions accounted for 99.5% of SO4^2− and 95.4% of NO3^−, while Cl− was 98% marine-derived, providing precise source apportionment for policy interventions.