Seasonal Distribution of Atmospheric Coarse and Fine Particulate Matter in a Medium-Sized City of Northern China

Atmospheric particulate matter (PM) was measured continuously at an urban site in Baoji city in northern China in 2018 to investigate the seasonal distribution characteristics. Coarse PM (PM2.5-10) was more prevalent in spring, substantially due to the regional transport of dust. High loadings of coarse PM were found at night compared to daytime, which could result from high production and unfavorable dispersion conditions. Fine PM (PM2.5) constituted, on average, 54% of the total PM mass concentration, whereas it contributed more than 97% of the total PM number concentration. The number and mass concentrations of fine PM increased substantially in the winter, which was possibly due to the enhanced production of atmospheric secondary processes and coal combustion. Precursor gaseous pollutants and meteorology greatly influenced the PM distributions. Fine PM was associated more strongly with gas pollutants than coarse PM, which suggested that it largely originated from secondary production and combustion sources. High relative humidity appeared to promote the production of fine PM, whereas it facilitated the removal of coarse PM. This study highlights that different air-pollution control strategies should be used for coarse and fine PM according to the distribution characteristics and influencing factors in similar medium-sized urban areas.

Automated summary

This study continuously measured atmospheric particulate matter (PM) in an urban area in Baoji city, northern China, in 2018 to investigate its seasonal distribution characteristics. The findings revealed that coarse PM (PM2.5-10) was more prevalent in spring due to regional dust transport. Winter saw a substantial increase in the number and mass concentrations of fine PM (PM2.5), possibly due to enhanced secondary production processes and coal combustion. The study highlighted the influence of precursor gaseous pollutants and meteorology on PM distributions, with fine PM being more strongly associated with gas pollutants than coarse PM.