[Analysis of Chemical Composition, Source and Evolution of Submicron Particles in Xianghe, Hebei Province]

Haze formation is closely related to the chemical composition of fine particles. An aerosol chemical speciation monitor (ACSM), aethalometer, etc. were used to investigate the chemical components、 source, and evolution of submicron particles at Xianghe, a suburban site located between the megacities of Beijing and Tianjin from May 31 to June 30, 2013. The results suggest that the air quality in Xianghe has suffered severe deterioration, which is imminent to improve air quality and pollution. On average, PM₁ accounted for ~71% of PM_2.5 and PM₁ distributed in 20-80 μg·m^-3 mainly. Organic aerosols had a high degree of oxidation. Significant straw burning events were observed during June 2013 in Xianghe. During the straw burning period, the mass concentration of PM₁ significantly increased and the mass fraction of organic aerosols in PM₁ rapidly increased to about 47%, on average. The contribution of nitrate was generally greater than that of other inorganic components. Affected by the straw burning events, the aerosol acidity turns from weak alkaline to weak acid. Positive matrix factorization was performed on the ACSM OA mass spectra, which identified two primary OA (POA), i.e., BBOA and HOA, and two secondary OA (SOA), i.e., LV-OOA and SV-OOA, factors. The SOAs dominated the OAs during the observation, contributing ~69% of OAs. However, after the straw burning period was removed, the positive matrix factorization (PMF)results did not reveal biomass combustion organic aerosols.