Investigating the aerosol mass and chemical components characteristics and feedback effects on the meteorological factors in the Beijing-Tianjin-Hebei region, China.

The measurement of aerosols (PM1.0 and PM2.5) was conducted during 2016 and 2017 in Beijing, Tangshan and Shijiazhuang, investigating the spatial and temporal variations of aerosols and major chemical components. The WRF-Chem model was applied to simulate the impacts of aerosol direct and semi-direct feedbacks on meteorological factors and identify the source of PM2.5. The results showed that the average annual concentrations were 63.3-88.7 μg/m3 for PM1.0 and 81.3-112 μg/m3 for PM2.5 at the three study cities, and the average seasonal concentration ratios of PM1.0/PM2.5 ranged from 64.3% to 86.0%. PM1.0 and PM2.5 showed a good correlation that the squared correlation coefficients were all higher than 0.9, indicating both mainly came from the same emission sources. Water-soluble inorganic ions and carbonaceous components were major chemical species in PM1.0 and PM2.5, accounting for 48.9%-54.1% and 25.6%-27.8% in PM1.0, 48.1%-52.3% and 22.7%-24.7% in PM2.5. Those chemical species showed spatially similar characteristics but pronounced seasonal differences, with higher concentrations in autumn and winter, lower in spring and summer. Aerosol feedbacks had different effects on various meteorological factors. Three study cities monthly-mean incoming solar radiation decreased by 40.6 W/m2, 82.2 W/m2, 38.4 W/m2, and 49.9 W/m2; planetary boundary layer height reduced by 54.0 m, 109 m, 32.2 m and 85.2 m; temperature at 2 m decreased by 0.5 °C, 0.8 °C, 0.5 °C and 1.3 °C; relative humidity increased by 1.5%, 2.6%, 1.3% and 4.7% in April, July, October and January, respectively, while wind speed changes were relatively smaller than above factors. Additionally, the major sources of PM2.5 in January were identified as transportation in Beijing, while industrial and domestic sources in Tangshan and Shijiazhuang. The obtained results will provide more in-depth and comprehensive understanding of aerosol pollution and management strategies.