Chemistry and Ionic Sources of Precipitation in the Changsha Area
This study investigates the ionic concentration characteristics and sources of atmospheric precipitation in Changsha, China, based on samples collected from December 2019 to November 2021. The total dissolved solids (TDS) in precipitation ranged from 51.71 to 813.40 μeq·L−1, with a volume-weighted mean (VWM) concentration of 245.58 μeq·L−1. The VWM ionic concentrations followed the order: Ca2+ > SO4^2− > NO3^− > HCO3^− > K+ > Na+ > Cl− > Mg2+. Ca2+ and SO4^2− together accounted for 55.76% of the total ionic mass. Seasonal variation of total ionic concentration was highest in winter and lowest in spring, following the order winter > autumn > summer > spring. Correlation analysis revealed strong positive correlations between SO4^2− and NO3^− (r = 0.78) and between Ca2+ and Mg2+ (r = 0.70), suggesting common sources. Principal component analysis and enrichment factor (EF) analysis indicated that SO4^2− and NO3^− predominantly originated from anthropogenic activities, with contribution rates of 99.5% and 95.4%, respectively, likely from coal combustion and industrial emissions. Ca2+ and K+ were mainly terrestrial, with contribution rates of 99.2% and 98.3%, respectively, from soil and biomass burning. Mg2+ had dual sources: 68.8% terrestrial and 31.2% marine. Cl− exhibited an EFmarine of 0.74 and EFsoil of 50.20, indicating a dominant marine source contributing 98% of its input. These findings provide a scientific basis for understanding regional atmospheric pollution and supporting environmental management strategies.