[Chemical Characteristics and Sources of Atmospheric Aerosols in the Surrounding District of a Heavily Polluted City in the Southern Part of North China]

Abstract

In order to explore the chemical composition and source profiles of atmospheric particulate matter in winter in the northern area of Handan, a heavily polluted city in the southern part of North China, PM₁ and PM_2.5 samples were collected and analyzed from November 23 to December 12, 2020. During the observation period, the daily average ρ(PM₁)and ρ(PM_2.5) were 114.53 μg·m^-3 and 124.25 μg·m^-3, respectively, and the ratio of PM₁/PM_2.5 was 83.3%-95.3%, which was significantly higher than those of other cities in the Beijing-Tianjin-Hebei region, indicating that air pollution of fine particulate matter, especially sub-micron particulate matter, was more serious in Handan. Compared with that during clean days, SNA (SO₄^2-, NO₃^-, and NH₄⁺) in PM₁ increased by 14.5% during heavy pollution, and SNA in PM_2.5 increased by 15.2%; the nitrogen oxidation rate (NOR) in particular increased by three times on heavy pollution days. With the deepening of pollution, the proportion of secondary organic carbon (SOC) in PM₁ and PM_2.5 increased by 22.0% and 12.5%, respectively. SOC tended to accumulate in small particles, whereas the proportion of primary organic carbon (POC) and elemental carbon (EC) in PM₁ decreased by 15.4% and 6.6%, and the POC and EC in PM_2.5 decreased by 8.2% and 4.3%, respectively. The above results indicated that secondary formation played an important role in the heavy pollution of particulate matter. With the aggravation of air pollution, the liquid water content of the particles increased, and both the sulfur oxidation ratio (SOR) and nitrogen oxidation ratio (NOR) increased, indicating that the aqueous phase chemical reaction made an important contribution to the formation of secondary inorganics. With the deepening of pollution, inorganic elements were on the rise; Se, As, Pb, and Zn were highly enriched in inorganic elements. The results of principal component analysis (PCA) showed that secondary formation, industrial emissions, vehicle exhaust, and biomass burning emissions were the main sources of particulate pollutants. The results of potential source contribution factor analysis (PSCF) showed that the high value areas of SO₄^2-, NO₃^-, EC, OC, and inorganic elements were mainly from the north and southwest directions of the observation area.

Keywords: PM1; PM2.5; backward trajectory; heavy air pollution; potential source; source apportionment.