Ma Jie-Li, Luo Da-Tong, Liu Xin, Wang Lei, Wang Xing, Liu Zhan, Shen Jian, Zhang Jun-Feng, Li Sheng
College of Environment and Resources, Xiangtan University, Xiangtan 411105, China.
Hunan Research Academy of Environmental Sciences, Changsha 410004, China.
Huan Jing Ke Xue. 2023 Nov 8;44(11):5975-5985. doi: 10.13227/j.hjkx.202211170.
Secondary inorganic ions, the main components of atmospheric PM, are a dominant contributor to haze formation. The detailed characteristics and main generation mechanism of secondary inorganic ions in PM are still unclear in the Changsha-Zhuzhou-Xiangtan City Group, which is suffering from severe haze pollution, particularly in the autumn and winter seasons. For our study, we collected PM samples in November 2020 and January 2021 from four urban sites in the Changsha-Zhuzhou-Xiangtan City Group. Secondary inorganic components such as SO, NO, and NH in PM were quantified. The average values(μg·m) of (SO), (NO), and (NH) in autumn and winter were(5.2±2.5) and(7.9±4.8),(4.1±2.2) and(7.2±4.2), and(17.1±10.5) and(7.8±5.2), respectively. During the heavy haze pollution events in winter, the sum of (SO), (NO), and (NH)(SNA) contributed 72.7% to the growth of PM mass concentration, and (NO) accounted for 41.2%. This result suggested that the generation of NO was the key factor leading to the formation of winter haze pollution. In the polluted stage, high aerosol water content(AWC) promoted the rapid secondary generation of SNA, whereas adverse meteorological conditions also led to the accumulation of pollutants. The values of sulfur oxidation rate(SOR) and nitrogen oxidation rate(NOR) were still high in the dissipation stage. It indicated that the PM concentration fell due to the reduction in primary emissions and favorable weather conditions in dissipation, instead of the weakening of secondary generation of SNA. Compared to that in autumn, the higher AWC concentration, pH value, and lower temperature in winter were the main factors for the higher (NO)/(PM) and NOR values in the Changsha-Zhuzhou-Xiangtan City Group. At the same time, the heterogeneous reaction was the main generation pathway of NO, when the AWC concentration was high in winter. Affected by aerosol pH value and generation rate, the liquid-phase oxidation reactions of HO and SO were the main generation pathways of SO in autumn and winter in the Changsha-Zhuzhou-Xiangtan City Group. Compared to that in autumn, the higher AWC was more conducive to forming SO, which led to higher SOR in winter.
二次无机离子作为大气颗粒物（PM）的主要成分，是雾霾形成的主要贡献者。在遭受严重雾霾污染的长株潭城市群，尤其是秋冬季节，PM中二次无机离子的详细特征和主要生成机制仍不明确。在本研究中，我们于2020年11月和2021年1月从长株潭城市群的四个城市站点采集了PM样本。对PM中的SO、NO和NH等二次无机组分进行了定量分析。秋季和冬季（SO）、（NO）和（NH）的平均值（μg·m）分别为（5.2±2.5）和（7.9±4.8）、（4.1±2.2）和（7.2±4.2）、（17.1±10.5）和（7.8±5.2）。在冬季重度雾霾污染事件期间，（SO）、（NO）和（NH）的总和（SNA）对PM质量浓度增长的贡献率为72.7%，其中（NO）占41.2%。这一结果表明，NO的生成是导致冬季雾霾污染形成的关键因素。在污染阶段，高气溶胶含水量（AWC）促进了SNA的快速二次生成，而不利的气象条件也导致了污染物的积累。在消散阶段，硫氧化率（SOR）和氮氧化率（NOR）的值仍然较高。这表明在消散阶段PM浓度下降是由于一次排放减少和有利的天气条件，而非SNA二次生成的减弱。与秋季相比，长株潭城市群冬季较高的AWC浓度、pH值和较低的温度是导致（NO）/（PM）和NOR值较高的主要因素。同时，在冬季AWC浓度较高时，非均相反应是NO的主要生成途径。受气溶胶pH值和生成速率的影响，HO和SO的液相氧化反应是长株潭城市群秋冬季节SO的主要生成途径。与秋季相比，较高的AWC更有利于SO的形成，这导致冬季SOR较高。
