Characteristics and source analysis of water-soluble ions in PM_2.5 in Urumqi City

In order to explore the pollution characteristics and sources of water-soluble ions in PM_2.5 during the heating and non-heating periods in Urumqi, PM_2.5 samples were collected in October and December, 2019. Nine water-soluble ions, including K⁺, Na⁺, Ca²⁺, Mg²⁺, NH_4^+,SO_4^2-, NO_3^-, Cl^-, F^-, in PM_2.5 were analyzed and determined by using the ion chromatography and inductively coupled plasma (ICP) emission spectrometer. The principal component analysis (PCA) and positive matrix factorization (PMF) models were used to carry out ion source analysis. The results showed that the average mass concentration of total water-soluble ions at sampling points of Xinjiang Agricultural University, Xiaoximen, Santunbei, and Midong District was (100.8±59.0), (61.1±18.4), (53.1±22.5) and (103.1±67.4) μg/m³, respectively, accounting for 57.9%, 56.7%, 44.0% and 54.1% of PM_2.5, respectively. NH_4^+, SO_4^2- and NO_3^- were the main water-soluble ions in PM_2.5. The average values of SOR and NOR at each sampling point in Urumqi were higher than 0.1, which indicated that there was an obvious secondary transformation process in the atmospheric during the study period. The results of PCA and PMF analysis indicated that the water-soluble ions at each sampling point mainly originated from secondary conversion, dust and combustion activities.