Evaluating the Recent 2+26 Regional Strategy for Air Quality Improvement During Two Orange Air Pollution Alerts in Beijing: variations of PM<sub>2.5</sub> concentrations, source apportionment, and the relative contribution of local emission and regional transport

Abstract

<p><strong>Abstract.</strong> To comprehensively evaluate the effects of the recent <q>2+26</q> regional strategy for air quality improvement, we compared the variations in PM<sub>2.5</sub> concentrations in Beijing during four pollution episodes with different emission-reduction strategies. The <q>2+26</q> strategy implemented in March 2018 led to a mean PM<sub>2.5</sub> concentrations of 16.43 % lower than that during the pollution episode in March 2013, when no specific emission-reduction measures were in place. The same <q>2+26</q> strategy implemented in November 2017 led to a mean PM<sub>2.5</sub> concentrations of 32.70 % lower than that during the pollution episode in November 2016, when local emission-reduction measures were implemented. The results suggested that the effects of the <q>2+26</q> regional emission-reduction measures on PM<sub>2.5</sub> reductions were influenced by a diversity of factors and could differ significantly during specific pollution episodes. Furthermore, we found the proportions of sulfate ions decreased significantly and nitrate ions were the dominant PM<sub>2.5</sub> components during the two <q>2+26</q> orange alert periods. Meanwhile, the relative contributions of coal combustion to PM<sub>2.5</sub> concentrations in Beijing during the pollution episodes in March 2013, November 2016, November 2017 and March 2018 was 40 %, 34 %, 28 % and 11 % respectively, indicating that the recent <q>Coal to Gas</q> project and the contingent <q>2+26</q> strategy led to a dramatic decrease in coal combustion in the Beijing-Tianjin-Hebei Region. On the other hand, the relative contribution of vehicle exhaust during the <q>2+26</q> orange alert periods in November 2017 and March 2018 reached 40 % and 54 % respectively. The relative contribution of local emission to PM<sub>2.5</sub> concentrations in Beijing also varied significantly and ranged from 49.46 % to 89.35 % during the four pollution episodes. These results suggested that the <q>2+26</q> regional emission-reduction strategy should be implemented with red air pollution alerts during heavy pollution episodes to intendedly reduce the dominant contribution of vehicle exhausts to PM<sub>2.5</sub> concentrations in Beijing, while specific emission-reduction measures should be implemented accordingly for different cities within the <q>2+26</q> framework.</p>

Highly time-resolved chemical characterization and implications of regional transport for submicron aerosols in the North China Plain

“…In contract, the contributions of sulfate to PM 1 were 12% both in BJ and XL, which were obviously lower than that in nitrate. Recent studies have indicated the increasing role of nitrate in winter haze pollution in BJ (Chen et al, 2018;Li et al, 2019;W. Xu et al, 2019).…”

“…Numerous studies have been performed using AMS, and a variety of views have been proposed Hu et al, 2016;Huang et al, 2018;Li et al, 2018;Sun et al, 2014;Sun et al, 2016). The chemical compositions and sources in different cities of the NCP are quite different (Chen et al, 2018;Ge et al, 2017;Huang et al, 2018;Li et al, 2017;Li et al, 2018). For example, nitrate was the dominant inorganic component in Beijing in recent years (Chen et al, 2018;Ge et al, 2017); however, in industrialized cities southwest of Beijing, sulfate and primary emissions dominated by coal and biomass combustion account for a large proportion of fine particulate matter (Huang et al, 2018;Li et al, 2017).…”

“…The chemical compositions and sources in different cities of the NCP are quite different (Chen et al, 2018;Ge et al, 2017;Huang et al, 2018;Li et al, 2017;Li et al, 2018). For example, nitrate was the dominant inorganic component in Beijing in recent years (Chen et al, 2018;Ge et al, 2017); however, in industrialized cities southwest of Beijing, sulfate and primary emissions dominated by coal and biomass combustion account for a large proportion of fine particulate matter (Huang et al, 2018;Li et al, 2017). The formation mechanisms of secondary aerosols in the NCP have been widely investigated.…”

Temporally-resolved sectoral and regional contributions to air pollution in Beijing: Informing short-term emission controls

“…However, this approach does not capture the interactions between secondary PM precursor species which may be particularly important during episodes with high nitrate levels (Burr and Zhang, 2011). Recently, Chen et al (2019) used the PSAT approach at 12 km resolution to calculate source contributions from districts included in the Chinese government's "2+26" regional emission control strategy, although they did not include the effect of surrounding regions in their analysis, which may be needed to formulate successful emission control policy under less favourable meteorological conditions. Moreover, none of these studies provide information on the temporal contribution of different sources which is important for the design of short-term emergency control measures.…”

“…programme (Chen et al, 2019). While we have focused on the October-November 2014 period associated with the important APEC Summit to explore source sensitivities, we note that emissions are changing rapidly in both Beijing and surrounding regions (Cheng et al, 2019;Zheng et al, 2018) leading to spatial and temporal changes in air pollution (Xiao et al, 2020;Xu and Zhang, 2020).…”