[Characteristics and Source Apportionment of Atmospheric Fine Particles in Langfang in Autumn and Winter]

In this study, we report observations of various chemical species in PM_2.5 samples that were collected between November 25, 2019 and March 31, 2020 in the northern, urban, and southern areas of Langfang, among which the concentrations of PM_2.5 followed the order of southern>urban>northern. The abundance and chemical compositions of the particles in this study were temporally and spatially variable, with major contributions from organic matter (25.4%), nitrate (21.5%), sulfate (11.0%), ammonium (13.5%), and crustal matter (13.7%). The contributions of nitrate, sulfate, and ammonium were higher in the urban site compared with that in the southern and northern sites. On the contrary, organic matter and crustal matter exhibited much higher values in the southern and northern sites. In addition, the contributions of organic matter to the particle mass decreased from 27.3% to 23.0%, and the total contributions of sulfate, nitrate, and ammonium ions increased from 38.7% to 51.3% between clean and haze days, respectively. Source apportionment using positive matrix factorization showed five PM_2.5 sources: secondary inorganic aerosol (41.9%), traffic emissions (19.9%), coal combustion (12.7%), industrial pollution (9.1%), and mineral dust (9.3%). The contributions of the first two factors followed the order of urban>northern>southern, whereas the contributions of the last three factors followed the order of southern>northern>urban. Further, the contributions of secondary inorganic aerosol, traffic emissions, and coal combustion were higher on haze days, whereas the contributions of industrial pollution and mineral dust were higher on clean days.