Impact of meteorological conditions and reductions in anthropogenic emissions on PM2.5 concentrations in China from 2016 to 2020

Many efforts have been made to control PM2.5 pollution in China during the National 13th Five-Year Plan and PM2.5 concentrations significantly declined nationwide. Meteorological conditions and pollution emissions play the most important roles in PM2.5 pollution. However, extant quantitative estimations of the contributions of meteorological conditions and anthropogenic emission reductions during the period were mostly based on surface observations data. Using a reanalysis dataset from 2016 to 2020, our results reveal that the annual average PM2.5 concentrations have been reduced yearly in the four key regions: the Beijing-Tianjin-Hebei (BTH) region, Yangtze River Delta (YRD), Pearl River Delta (PRD) and central China. The frequency of stagnation days decreased in 2020 in the YRD and PRD, while it did not show significant fluctuations in the BTH region and central China. Through the sensitivity simulation experiments in 2016 and 2020, the implementation of the emission regulations led to PM2.5 pollution reductions of 6.59 and 5.12 mu g m 3, respectively in the BTH region and central China, of which the worsening meteorological conditions offset 61.46% (4.05 mu g m 3) and 19.53% (1.00 mu g m 3) respectively. However, the impacts of favorable weather conditions and effective anthropogenic restrictions jointly contributed to the improvement in air quality in the YRD and PRD. Anthropogenic controls explained 81.95% (3.75 mu g m 3) of the total 4.58 mu g m 3 reduction in the YRD and 52.10% (1.86 mu g m 3) of the total 3.57 mu g m 3 reduction in the PRD. The findings provide a perspective on the causes of pollution events and would help formulate more effective emission reduction policies in the future.