Characteristics of Water-Soluble Inorganic Ions in PM 2.5 in Typical Urban Areas of Beijing, China

• Published in: ACS omega Vol. 7; no. 40; pp. 35575 - 35585
• Main Authors: Hong, Xiuping, Yang, Kang, Liang, Handong, Shi, Yunyun
• Format: Journal Article
• Language: English
• Published: United States 11-10-2022
• ISSN: 2470-1343; 2470-1343
• DOI: 10.1021/acsomega.2c02919

Following the implementation of "coal-to-gas conversion" policy in the Haidian District of Beijing during summer, the present comparative study was performed employing 41 PM
samples as precursors to analyze the characteristics of water-soluble inorganic ions. The concentrations of water-soluble inorganic ions in PM
were analyzed by ion chromatography, and the occurrence form of ions was characterized via time-of-flight secondary ion mass spectrometry (TOF-SIMS). Results revealed that the daily average mass concentration of PM
in Beijing during the sampling period was 94.28 ± 52.49 μg/m
. As compared to the winter of 2016, the average daily PM
concentration in Beijing decreased by 29 μg/m
in 2017 (28.2% decrease), with a remarkable decline in the number of days with pollution. During the pollution period, the concentrations of NO
, SO
, and NH
were significantly higher in PM
as compared to the cleaning period. The ratio of the concentrations of [NO
]/[SO
] was greater than 1, and the contribution from mobile sources was relatively large, indicating that the implementation of the "coal-to-gas conversion" policy in Beijing has led to the reduction of SO
emissions from fixed sources, such as coal. Furthermore, TOF-SIMS analysis results showed that NH
tended to exist in the form of molecular ammonium sulfate or ammonium hydrogen sulfate during the period of pollution.