Characteristics and Sources of Water-Soluble Inorganic Ions in PM2.5 in Urban Nanjing, China

In this study, the water-soluble inorganic ions (WSIIs) composition of fine particulate matter (PM2.5) was measured in northern Nanjing city from 2015 to 2021. NH4+, NO3− and SO42− concentrations dominated total WSIIs (Na+, K+, Mg2+, Ca2+, Cl−, SO42−), accounting for 87.8%. The nitrate with highest average concentration among all 11.0 μg·m−3. Total were higher winter lower summer, levels December (45.6 μg·m−3) lowest August (15.1 μg·m−3). NO3−/SO42− than 1, indicating important contribution mobile sources. aerosols exhibited a weak acidic by molar ratio anions cations. Positive matrix factorization (PMF) analysis results showed that secondary sulfate major pollution sources 2016 2020. 2020 increased 47.6% compared 2016, while decreased 42.4%. potential source demonstrated aerosol concentrations, regional transport north Anhui increased, local emissions decreased. study could contribute better prevention control air future.