Ambient fine particulate matter and ozone pollution in China: synergy in anthropogenic emissions and atmospheric processes

Abstract

Since 2013, China has taken a series of actions to relieve serious PM2.5 pollution. As a result, the annual PM2.5 concentration decreased by more than 50% from 2013 to 2021. However, ozone pollution has become more pronounced, especially in the North China Plain. Here, we review the impacts of anthropogenic emissions, meteorology, and atmospheric processes on ambient PM2.5 loading and components and O3 pollution in China. The reported influence of interannual meteorological changes on PM2.5 and O3 pollution during 2013-2019 ranged from 10%-20% and 20%-40%, respectively. During the same period, the anthropogenic emissions of NOx, SO2, primary PM2.5, NMVOC and NH3 are estimated to decrease by 38%, 51%, 35%, 11% and 17%, respectively. Such emission reduction is the main cause for the decrease in PM2.5 concentration across China. However, the imbalanced reductions in various precursors also result in the variation in nitrate gas-particle partitioning and hence an increase in the nitrate fraction in PM2.5. The increase of ozone concentration and the enhancement of atmospheric oxidation capacity can also have substantial impact on the secondary components of PM2.5, which partly explained the growth of organic aerosols during haze events and the COVID-19 shutdown period. The uneven reduction in NOx and NMVOC is suggested to be the most important reason for the rapid O3 increase after 2013. In addition, the decrease in PM2.5 may also have affected O3 formation via radiation effects and heterogeneous reactions. Moreover, climate change is expected to influence both anthropogenic emissions and atmospheric processes. However, the extent and pathways of the PM2.5-O3 interplay and how it will be impacted by the changing emission and atmospheric conditions making the synergetic control of PM2.5 and O3 difficult. Further research on the interaction of PM2.5 and O3 is needed to provide basis for a scientifically-grounded and effective co-control strategy.

Sources of Organic Aerosol in China from 2005 to 2019: A Modeling Analysis

“…The NO x emission affects the OA concentration by changing the HO x (OH + HO 2 ) and ozone concentration, which determines the conversion rates of OA precursors. Most of the urban cities are in VOC-limited and transitional regimes, 46,47 and the reduction of NO x would elevate the oxidation capacity and worsen the OA pollution. From 2005 to 2014, the NO x emission increased markedly and lowered the HO x level, hence resulting in lower SOA concentration (−0.2 μg/m 3 ), which is quite the opposite case from the period of 2014−2019, when Figure 6 and Table S6 show the influence of NO x concentration on OH, HO 2 , O 3 , and SOA concentrations in three metropolitans, i.e., Beijing, Shanghai, and Guangzhou.…”

NH3 Weakens the Enhancing Effect of SO2 on Biogenic Secondary Organic Aerosol Formation

“…Recently, stringent laws have been established to regulate atmospheric pollution, which has caused a considerable shift in the emission patterns of anthropogenic pollutants. For example, emissions of SO 2 and NO x in China have been considerably reduced, whereas NH 3 emissions have remained stable and O 3 concentrations have increased . Although SO 2 considerably enhanced aerosol particle formation at low NH 3 levels and some studies have shown that an increase in NH 3 concentration may increase SOA formation through the formation of ammonium nitrate, , this study found that an increase in NH 3 concentration may weaken the enhancement effect of SO 2 on biogenic SOA formation.…”

“…For example, emissions of SO 2 and NO x in China have been considerably reduced, whereas NH 3 emissions have remained stable and O 3 concentrations have increased. 52 Although SO 2 considerably enhanced aerosol particle formation at low NH 3 levels and some studies have shown that an increase in NH 3 concentration may increase SOA formation through the formation of ammonium nitrate, 53,54 this study found that an increase in NH 3 concentration may weaken the enhancement effect of SO 2 on biogenic SOA formation. Thus, while analyzing the impacts of NO x , SO 2 , and NH 3 on the production of SOA, their concentration levels should be carefully considered.…”

Extreme Emission Reduction Requirements for China to Achieve World Health Organization Global Air Quality Guidelines

“…Liu et al found that meteorological conditions change in 2050 under RCP8.5 would increase PM 2.5 concentration in most regions in eastern China when anthropogenic emissions are held constant as in 2015, but decrease PM 2.5 concentrations when anthropogenic emissions are reduced largely. Even if large uncertainties in studies on climate change due to different model configurations and scenario settings, − large emission reduction is expected to release additional challenges by climate change. Furthermore, we need to point out that climate change and meteorological conditions have an impact on nature emissions and pollution transport patterns. , Thus, the response of China to transboundary pollution and background concentration would change in the future.…”