The Characteristics and Impact Factors of Sulfate and Nitrate in Urban PM[sub.2.5] over Typical Cities of Hangzhou Bay Area, China

• Published in: Atmosphere Vol. 14; no. 12
• Main Authors: Wang, Qiongzhen, Ding, Hao, Yu, Fuwei, Chao, Na, Li, Ying, Jiang, Qiqing, Huang, Yue, Duan, Lian, Ji, Zhengquan, Zhou, Rong, Yang, Zhongping, Zheng, Kaiyun, Miao, Xiaoping
• Format: Journal Article
• Language: English
• Published: MDPI AG 01.12.2023
• Subjects: Air pollution; Composition; Distribution; Environmental aspects; Environmental monitoring; Methods; Nitrates; Particles; Sulfates; China
• ISSN: 2073-4433; 2073-4433
• DOI: 10.3390/atmos14121799

PM[sub.2.5] pollution over Hangzhou Bay area, China has received continuous attention. In this study, PM[sub.2.5] samples were collected simultaneously in six typical cities in Zhejiang Province from 15 October 2019 to 15 January 2020 (autumn and winter) and from 1 June to 31 August 2020 (summer), and major water-soluble ions were analyzed. Average concentrations of NO[sub.3] [sup.−] and SO[sub.4] [sup.2−] in the six cities were 3.93–15.64 μg/m[sup.3] and 4.61–7.58 μg/m[sup.3] in autumn and winter, with mass fractions of NO[sub.3] [sup.−] and SO[sub.4] [sup.2−] in PM[sub.2.5] up to 19.6–34.2% and 13.6–26.3%, respectively, while in summer, they were 1.23–2.64 μg/m[sup.3] and 2.22–4.14 μg/m[sup.3] , with mass fractions of 7.0–15.0% and 14.7~25.1%. Both NO[sub.3] [sup.−] and SO[sub.4] [sup.2−] were mostly from gas-to-particle transformation of precursors. High relative humidity in the six cities was suggested to significantly promote the formation of NO[sub.3] [sup.−] and SO[sub.4] [sup.2−] , particularly in autumn and winter, while enhanced atmospheric oxidation favored the formation of SO[sub.4] [sup.2−] in summer. However, the formation of NO[sub.3] [sup.−] was inhibited under a high temperature of >15 °C. The concentrations of SO[sub.4] [sup.2−] and NO[sub.3] were mostly correlated with each other among the six cities. Potential source contribution function analysis indicated that both SO[sub.4] [sup.2−] and NO[sub.3] [sup.−] were mostly from local pollution of Hangzhou Bay area in Zhejiang Province and also transported from Shanghai and the southern region of Jiangsu Province. This study contributed to the understanding of regional characteristics of SO[sub.4] [sup.2−] and NO[sub.3] [sup.−] in Hangzhou Bay area and suggested that joint prevention and control efforts should be strengthened to reduce regional PM[sub.2.5] pollution.