气候变化领域集成服务门户(CCPortal): Nitrate-dominated PM2.5 and elevation of particle pH observed in urban Beijing during the winter of 2017

CCPortal

DOI	10.5194/acp-20-5019-2020
	Nitrate-dominated PM2.5 and elevation of particle pH observed in urban Beijing during the winter of 2017
	Xie Y.; Wang G.; Wang X.; Chen J.; Chen Y.; Tang G.; Wang L.; Ge S.; Xue G.; Wang Y.; Gao J.
发表日期	2020
ISSN	16807316
起始页码	5019
结束页码	5033
卷号	20 期号:8
英文摘要	The Chinese government has exerted strict emission controls to mitigate air pollution since 2013, which has resulted in significant decreases in the concentrations of air pollutants such as SO2. Strict pollution control actions also reduced the average PM2:5 concentration to the low level of 39.7 ugm-3 in urban Beijing during the winter of 2017. To investigate the impact of such changes on the physiochemical properties of atmospheric aerosols in China, we conducted a comprehensive observation focusing on PM2:5 in Beijing during the winter of 2017. Compared with the historical record (2014-2017), SO2 decreased to the low level of 3.2 ppbv in the winter of 2017, but the NO2 level was still high (21.4 ppbv in the winter of 2017). Accordingly, the contribution of nitrate (23.0 ugm-3) to PM2:5 far exceeded that of sulfate (13.1 ugm-3) during the pollution episodes, resulting in a significant increase in the nitrate-To-sulfate molar ratio. The thermodynamic model (ISORROPIA II) calculation results showed that during the PM2:5 pollution episodes particle pH increased from 4.4 (moderate acidic) to 5.4 (more neutralized) when the molar ratio of nitrate to sulfate increased from 1 to 5, indicating that aerosols were more neutralized as the nitrate content elevated. Controlled variable tests showed that the pH elevation should be attributed to nitrate fraction increase other than crustal ion and ammonia concentration increases. Based on the results of sensitivity tests, future prediction for the particle acidity change was discussed. We found that nitrate-rich particles in Beijing at low and moderate humid conditions (RH: 20 %-50 %) can absorb twice the amount of water that sulfate-rich particles can, and the nitrate and ammonia with higher levels have synergetic effects, rapidly elevating particle pH to merely neutral (above 5.6). As moderate haze events might occur more frequently under abundant ammonia and nitrate-dominated PM2:5 conditions, the major chemical processes during haze events and the control target should be re-evaluated to obtain the most effective control strategy. © 2020 Copernicus GmbH. All rights reserved.
关键词	ammonia atmospheric pollution emission control haze nitrate particulate matter pH urban atmosphere winter Beijing [Beijing (ADS)]Beijing [China]China
语种	英语
来源机构	Atmospheric Chemistry and Physics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/132072
推荐引用方式 GB/T 7714	Xie Y.,Wang G.,Wang X.,et al. Nitrate-dominated PM2.5 and elevation of particle pH observed in urban Beijing during the winter of 2017[J]. Atmospheric Chemistry and Physics,2020,20(8).
APA	Xie Y..,Wang G..,Wang X..,Chen J..,Chen Y..,...&Gao J..(2020).Nitrate-dominated PM2.5 and elevation of particle pH observed in urban Beijing during the winter of 2017.,20(8).
MLA	Xie Y.,et al."Nitrate-dominated PM2.5 and elevation of particle pH observed in urban Beijing during the winter of 2017".20.8(2020).