Analyses and Simulations of PM 2.5 Pollution Characteristics under the Influence of the New Year's Day Effects in China.

Regional haze often occurs after the New Year holiday. To explore the characteristics of PM_2.5 pollutions under the influence of the New Year's Day effect, this study analyzed the spatiotemporal changes relating to PM_2.5 during and around the New Year's Day holiday in China from 2015 to 2022, and used the Weather Research and Forecasting-Community Multiscale Air Quality (WRF-CMAQ) model to study the effects of human activities and meteorological factors on PM_2.5 pollutions, as well as the differences in the contributions of different industries to PM_2.5 pollutions. The results show that for the entire study period (i.e., before, during, and after the New Year's Day holiday) from 2015 to 2022, the average concentrations of PM_2.5 in China decreased by 41.9% overall. In 2019~2022, the New Year's Day effect was significant, meaning that the average concentrations of PM_2.5 increased by 18.9~46.8 μg/m³ from before to after the New Year's Day holiday, with its peak occurring (64.3~74.9 μg/m³) after the holiday. In terms of spatial differences, the average concentrations of PM_2.5 were higher in the Beijing–Tianjin–Hebei region, the Yangtze River Delta, and central China. Moreover, the Beijing–Tianjin–Hebei region and its surrounding areas, the Chengdu–Chongqing region, the Fenwei Plain, and the middle reaches of the Yangtze River region were greatly affected by the New Year's Day effect. Human activities led to higher increases in PM_2.5 in Henan, Hubei, Hebei, and Anhui on 3 and 4 January 2022. If the haze was accompanied by cloudy days or weak precipitation, the accumulation of surface water vapor and atmospheric aerosols further increased the possibility of heavy pollution. It was found that, for the entire study period, PM_2.5 generated by residential sources contributed the vast majority (60~100 μg/m³) of PM_2.5 concentrations, and that the main industry sources that caused changes in time distributions were industrial and transportation sources. [ABSTRACT FROM AUTHOR]