Characteristics of Concentrations and Water-Soluble Ions in PM2.5 in Xinjiang Province, Northwest China Based on Super Station Observation

Abstract

Atmospheric fine particulate matter (PM_2.5) is one of the most significant air pollutants posing a threat to human health and the environment. Investigating its water-soluble ions is both essential and urgent. From January to December 2022, continuous monitoring of PM_2.5and its components was conducted using the Urumqi Atmospheric Environment Super Station. Nine water-soluble ions in PM_2.5 were analyzed using ion chromatography (IC) and other instruments, and their sources were identified through principal component analysis and the PMF model.The results revealed that the annual average PM_2.5 concentration in 2022 was 60.40 μg m⁻³. During both the heating period and the Spring Festival, PM_2.5 levels exceeded 75 μg/m³, while the non-heating period exhibited relatively lower concentrations, averaging 16.88 μg m⁻³. The primary water-soluble ions in PM_2.5 were SO₄²⁻, NH₄⁺, and NO₃⁻, accounting for 24%–55%, 11%–38%, and 10%–25%, respectively. These three ions constituted 90.5% of the total mass concentration of water-soluble anions and cations. The strongest correlations were observed between NH₄⁺ and SO₄²⁻ (r = 0.948) and NH₄⁺ and NO₃⁻ (r = 0.937).The concentrations of secondary inorganic aerosols (SNAs) during the non-heating and heating periods were (31.31 ± 4.95) μg m⁻³ and (79.31 ± 46.31) μg/m³, representing 68.17% and 80.53% of the total water-soluble ions, respectively. Additionally, the metal elements Sb, As, Cd, Pb, and Ti were found to be highly enriched. In summary, the primary sources of water-soluble ions in PM_2.5 originate from secondary aerosol formation, combustion processes, and fugitive dust emissions. Meanwhile, the concentration of PM2.5 components continues to exceed the national secondary air quality standards, necessitating intensified regional environmental governance measures.