Substantial short- and long-term health effect due to PM2.5 and the constituents even under future emission reductions in China.

Heavy pollution events of fine particulate matter (PM2.5) frequently occur in China, seriously affecting the human health. However, how meteorological factors and anthropogenic emissions affect PM2.5 and the major constituents, as well as the subsequent health effect, remains unclear. Here, based on regional climate and air quality models Weather Research and Forecasting (WRF) and Community Multiscale Air Quality (CMAQ), the PM2.5 and major constituents in China at present and mid-century under the carbon neutral scenario Shared Socioeconomic Pathways (SSP)1-2.6 are simulated. Due to anthropogenic emission reduction, concentrations of PM2.5 and the constituents decrease substantially in SSP1-2.6. The long-term exposure premature deaths at present are 2.23 million per year in mainland China, which is projected to increase by 76 % under SSP1-2.6 despite emission reduction, primarily attributable to aging which strikingly offsets the effect of air quality improvement. The number of annual premature deaths resulting from short-term exposure is 228,104 in mainland China at present, which is projected to decrease in the future. Using North China Plain as an example, we identify that among the major constituents of PM2.5, organic carbon leads to the most short-term exposure deaths considering the largest exposure-response coefficient. Regarding the abnormally meteorological conditions, we find, relative to low relative humidity (RH) and non-stagnation, the compound events, defined as concurrence of high RH and atmospheric stagnation, exhibit an amplified role inducing larger premature deaths compared to the additive effect of the individual event of high RH and atmospheric stagnation. This nonlinear effect occurs at both present and future, but diminished in future due to emission reductions. Our study highlights the importance of considering both the long- and short-term premature deaths associated with PM2.5 and the constituents, as well as the critical effect of extreme weather events.

Unveiling the spatial and sectoral characteristics of a high-resolution emission inventory of CO2 and air pollutants in China.

Under the target of carbon neutrality as well as stringent air quality guideline, understanding the spatial characteristics of both greenhouse gases and air pollutants emissions, in particular of their mutual sources, is crucial for assessing the feasibility of achieving their concomitant emission control, which, nevertheless, remains to be unclear yet. To this end, we construct a high-resolution (10 km × 10 km) emission inventory including both CO2 and air pollutants in China, which fosters us an opportunity to examine their spatial and sectoral characteristics. The primary sources for both CO2 and air pollutant emissions are power and industry. Among different subsectors in industry, detailed information indicates cement, iron and steel are the major subsectors for both CO2 and majority of air pollutants. Analysis of the high-resolution spatial distribution indicates that for CO2, 5 % of the grids account for 90 % of the total CO2 emissions, indicative of the existence of spatial heterogeneity. These grids are the major locations with air pollutant emissions as well, i.e., 73 % for SO2 emissions, and more than 50 % for volatile organic compounds (VOCs), CO, NOx, PM10 and PM2.5, stressing the spatial consistency between greenhouse gases and air pollutant emissions. A large portion of emissions concentrate in a relatively small number of grids further implies the possibility to achieve the mutual control of both greenhouse gas emissions and air pollutant emissions, which is useful for future policy in particular of achieving the carbon neutrality and air quality improvement.

The Impact of Meteorology and Emissions on Surface Ozone in Shandong Province, China, during 2014-2019.

China has been experiencing severe ozone pollution problems in recent years. While a number of studies have focused on the ozone-pollution-prone regions such as the North China Plain, Yangtze River Delta, and Pearl River Delta regions, few studies have investigated the mechanisms modulating the interannual variability of ozone concentrations in Shandong Province, where a large population is located and is often subject to ozone pollution. By utilizing both the reanalysis dataset and regional numerical model (WRF-CMAQ), we delve into the potential governing mechanisms of ozone pollution in Shandong Province-especially over the major port city of Qingdao-during summer 2014-2019. During this period, ozone pollution in Qingdao exceeded the tier II standard of the Chinese National Ambient Air Quality (GB 3095-2012) for 75 days. From the perspective of meteorology, the high-pressure ridge over Baikal Lake and to its northeast, which leads to a relatively low humidity and sufficient sunlight, is the most critical weather system inducing high-ozone events in Qingdao. In terms of emissions, biogenic emissions contribute to ozone enhancement close to 10 ppb in the west and north of Shandong Province. Numerical experiments show that the local impact of biogenic emissions on ozone production in Shandong Province is relatively small, whereas biogenic emissions on the southern flank of Shandong Province enhance ozone production and further transport northeastward, resulting in an increase in ozone concentrations over Shandong Province. For the port city of Qingdao, ship emissions increase ozone concentrations when sea breezes (easterlies) prevail over Qingdao, with the 95th percentile reaching 8.7 ppb. The findings in this study have important implications for future ozone pollution in Shandong Province, as well as the northern and coastal areas in China.