China's emission control strategies have suppressed unfavorable influences of climate on wintertime PM<sub>2.5</sub> concentrations in Beijing since 2002

Abstract

Abstract. Severe wintertime PM2.5 pollution in Beijing has been receiving increasing worldwide attention, yet the decadal variations remain relatively unexplored. Combining field measurements and model simulations, we quantified the relative influences of anthropogenic emissions and meteorological conditions on PM2.5 concentrations in Beijing over the winters of 2002–2016. Between the winters of 2011 and 2016, stringent emission control measures resulted in a 21 % decrease in mean mass concentrations of PM2.5 in Beijing, with 7 fewer haze days per winter on average. Given the overestimation of PM2.5 by the model, the effectiveness of stringent emission control measures might have been slightly overstated. With fixed emissions, meteorological conditions over the study period would have led to an increase in haze in Beijing, but the strict emission control measures have suppressed the unfavorable influences of the recent climate. The unfavorable meteorological conditions are attributed to the weakening of the East Asia winter monsoon associated particularly with an increase in pressure associated with the Aleutian Low.

Effect of NO<sub>X</sub>, O<sub>3</sub> and NH<sub>3</sub> on sulfur isotope composition during heterogeneous oxidation of SO<sub>2</sub>: a laboratory investigation

“…Whether the oxidation processes were on the surface of Fe2O3 mineral dust or not, the coexistence of O3 can convert SO2 to sulfate (Gao et al, 2020). The highest sulfate production obtained at a ratio of 1:12 may be attributed to the higher photochemical activities and ozone concentration (Kong et al, 2019).…”

“…Few sulfates were formed via the heterogeneous reaction between NOX and SO2 on the surface of mineral in the dark, whereas the formation of sulfate was enhanced under light, suggesting that UV light could promote the oxidation of SO2. Besides, in the presence of O2, NOX and mineral oxides could act as catalysts to increase the conversion rate of SO2 on the surface of mineral oxides (Gao et al, 2020). In addition, the increase in the amount of NOX was another key factor that led to the acceleration of sulfate formation (Cheng et al, 2016).…”

“…In addition, the pathways of SO2 oxidation in aqueous-phase systems include reactions with O3, H2O2, NO2, and by O2 via catalyst (Hung et al, 2015). The formation of sulfate was demonstrated that it was mainly affected by a synergistic effect between NOX and SO2 (Gao et al, 2020). Sulfate formations measured during autumn were mainly related to excessive O2 with Fe 3+ as catalyst (Guo et al, 2014).…”

Reduced light absorption of black carbon (BC) and its influence on BC-boundary-layer interactions during APEC Blue

“…Over the past several years, the State Council of China has issued a comprehensive Air Pollution Prevention and Control Action Plan (APPCAP), covering major emission sectors (Zhang et al, 2019a). Long-term observations of aerosol chemical composition indicate that both concentrations of BC and other coating components have declined rapidly (Gao et al, 2020b;Ji et al, 2019b;Zhou et al, 2019). Although the changes in BC concentrations in response to emission reduction measures have been documented (Ji et al, 2019b;Gao et al, 2020b), the influence of emission reductions on the aging processes and light absorption of BC has been less explored (Zhang et al, 2019b).…”

Differentiation of the Athens Fine PM Profile during Economic Recession (March of 2008 Versus March of 2013): Impact of Changes in Anthropogenic Emissions and the Associated Health Effect

“…Jiang et al [14] and Zhang et al [15], using a combined field and numerical modeling approach, gave insight on the differentiation of the PM 2.5 mass in connection with its health consequences for a 6 and 4 years' period, respectively. However, the works assessing the effect of the emissions to the obtained chemical PM profile, during several years' period, by combining experimental and emissions data are scarce [16,17]. To the best of our knowledge, information regarding the evolution of the PM 1 fraction over time in conjunction with emission inventories does not exist at all even if this fraction is considered as a better indicator of the anthropogenic sources [2,4,18].…”