Significant Changes in Chemistry of Fine Particles in Wintertime Beijing from 2007 to 2017: Impact of Clean Air Actions

Abstract

The Beijing government implemented a number of clean air action plans to improve air quality in the last 10 years, which contributed to changes in the concentration of fine particles and their compositions. However, quantifying the impacts of these interventions is challenging as meteorology masks the real changes in observed concentrations. Here, we applied a machine learning technique to decouple the effect of meteorology and evaluate the changes in the chemistry of nonrefractory PM 1 (particulate matter less than 1 μm) in winter 2007, 2016, and 2017 as a result of the clean air actions. The observed mass concentrations of PM 1 were 74.6, 90.2, and 36.1 μg m −3 in the three winters, while the deweathered concentrations were 74.2, 78.7, and 46.3 μg m −3 , respectively. The deweathered concentrations of PM 1 , organics, sulfate, ammonium, chloride, SO 2 , NO 2 , and CO decreased by −38, −46, −59, −24, −51, −89, −16, and −52% in 2017 in comparison to 2007. On the contrary, the deweathered concentration of nitrates increased by 4%. Our results indicate that the clean air actions implemented in 2017 were highly effective in reducing ambient concentrations of SO 2 , CO, and PM 1 organics, sulfate, ammonium, and chloride, but the control of nitrate and PM 1 organics remains a major challenge.

Effects of atmospheric circulations on the interannual variation in PM<sub>2.5</sub> concentrations over the Beijing-Tianjin-Hebei region in 2013–2018

“…elements. The studies have been carried out to evaluate the relative effects of emission reduction and meteorological conditions on the recent decrease in PM2.5 concentrations (Ding et al, 2019;Guo et al, 2019;He et al, 2018;Zhang et al, 2019c;Zhao et al, 2019a). Based on a multiple linear regression model, 12% of the decreased PM2.5 over China is due to favorable meteorological conditions between 2013 and 2018 (Zhai et al, 2019).…”

Increased Aerosol Extinction Efficiency Hinders Visibility Improvement in Eastern China

“…With the emission reduction efforts to mitigate haze pollution in past years, PM 2.5 chemical composition in eastern China has been found to experience an obvious transition, especially secondary inorganic aerosol (SNA) during wintertime (Ding et al, 2019; Li, Cheng, et al, 2019; Wang, Wang, et al, 2019; Zhang, Vu, et al, 2019). Nevertheless, the impact of such a transition on haze pollution and atmospheric visibility has not been fully investigated yet.…”

Trends in Air Pollutant Concentrations and the Impact of Meteorology in Shandong Province, Coastal China, during 2013-2019

“…For example, severe air pollution events occurred in North China during January 2020, with the daily average concentration of PM2.5 exceeding 200 μg/m 3 , although the pollutant emissions decreased due to the Spring Festival holiday and coronavirus disease outbreak (Wang et al, 2020d;Zhang et al, 2020a). Several studies have explored the contribution of inter-annual meteorological changes to air pollutant concentration reductions (Hong et al, 2019;Vu et al, 2019;Xue et al, 2020;Zhang et al, 2020b). The decrease in the PM2.5 concentration due to emissions reduction increased annually from 2013-2017 in key regions of China, especially in…”

“…The decrease in the PM2.5/PM10 ratios (⁓7%) of Shandong Province was higher than that in other key regions (such as Beijing-Tianjin-Hebei and the Pearl River Delta), with a reduction of 2%-3% (Wang et al, 2019b), indicating that the stringent measures implemented for reducing particle emissions in Shandong Province are significant and effective. More measures should be implemented to reduce the emissions of particles and their gaseous precursors to mitigate particle pollution in Shandong Province, as particles can consist of various primary and secondary components (such as organic carbon, elemental carbon, sulphate, nitrate, and ammonium) (Wang et al, 2017a;Zhang et al, 2020b).…”