[Seasonal Characteristics and Source Analysis of Water-Soluble Ions in PM 2.5 of Anyang City].

We explore the characteristics and sources of water-soluble ions in aerosol fine particulate matter (PM _2.5 ) samples collected from Anyang, China, during typical seasonal months from 2018 to 2019. Nine water-soluble ions (Na ⁺ , NH ₄ ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , F ^- , Cl ^- , NO ₃ ^- , and SO ₄ ^2- ) were analyzed. The analysis of PM _2.5 , water-soluble ion concentration levels, anion-cation balance, nitrogen oxidation rate (NOR), sulfur oxidation rate (SOR), and ion correlation showed that the annual average concentrations of PM _2.5 and water-soluble ions in Anyang were (85.81±45.43) μg·m ^-3 and (48.21±30.04) μg·m ^-3 , respectively. Concentrations of ions were ranked as:NO ₃ ^- > SO ₄ ^2- > NH ₄ ⁺ > Cl ^- > K ⁺ > Ca ²⁺ > Na ⁺ > Mg ²⁺ > F ^- . The annual average concentration of the sum of NH ₄ ⁺ , NO ₃ ^- , and SO ₄ ^2- was (42.72±27.87) μg·m ^-3 , which accounted for 87.14% of total water-soluble ions. Moreover, NH ₄ ⁺ was highly related to SO ₄ ^2- and NO ₃ ^- . The mean values of the nitrogen oxidation rate (NOR) and sulfur oxidation rate (SOR) were 0.25 and 0.37, respectively. These results suggest that these ions were the result of secondary formation. The anion-cation charge equivalent value was 0.75-0.94, which indicates that the sampled aerosols were alkaline. NH ₄ ⁺ mainly existed in the form of (NH ₄ ) ₂ SO ₄ and NH ₄ NO ₃ in spring, summer, and autumn, whereas in winter it mainly existed in the form of NH ₄ Cl. The results of principal component analysis indicated that secondary aerosols, coal combustion, biomass burning, and dust were the main sources of the water-soluble ions in Anyang during the sampled periods.