RESUMO
To explore the characteristics and sources of PM2.5 pollution in winter of Handan City in the past five years, PM2.5 samples were collected in winter of 2016 to 2020, and eight types of water-soluble inorganic ions were analyzed. The principal component analysis(PCA) model was used to analyze the types of pollution sources, and the backward trajectory and potential source contribution factor(PSCF) were used to simulate the transport trajectory and pollution sources. The results showed that the PM2.5 concentration in winter of 2018 was the highest, increasing by 60.44%, 25.46%, 91.43%, and 21.53% compared with that in 2016, 2017, 2019, and 2020, respectively. In the winter of 2020, the concentration of water-soluble inorganic ions(WSIIs) decreased by 18.86% compared with that in 2016, and WSIIs/PM2.5 decreased to 26.69%. The PM2.5 concentration(110.20-209.65 µg·m-3) at night was higher than that in the daytime(95.21-193.00 µg·m-3). The concentration of NO3- and NH4+ increased more at night. On the contrary, the concentration and proportion of Cl-decreased annually. In the winter of 2020, the daytime concentrations of K+, Ca2+, Na+, and Mg2+ decreased by 69.72%, 97.10%, 90.91%, and 74.51% compared with that of 2018, and the night concentrations decreased by 66.67%, 95.38%, 91.67%, and 77.78%, respectively. In 2020, the concentrations of NO3-, SO42-, and NH4+ on polluted days were 4.90, 5.80, and 5.20 times those on non-polluted days, with the largest increase in five years. PCA results showed that the main sources of pollution were secondary sources, coal sources, biomass combustion sources, and road and building dust. The backward trajectory and PSCF analysis results showed that pollution transport continued to exist between south-central Mongolia and central Inner Mongolia in winter and was influenced by the transport between northern Henan and Handan and central Hebei and Handan in winter of 2016 and 2017, whereas the latter had a greater impact in winter of 2018-2020.
RESUMO
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 PM2.5 samples were collected and analyzed from November 23 to December 12, 2020. During the observation period, the daily average ρ(PM1)and ρ(PM2.5) were 114.53 µg·m-3 and 124.25 µg·m-3, respectively, and the ratio of PM1/PM2.5 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 (SO42-, NO3-, and NH4+) in PM1 increased by 14.5% during heavy pollution, and SNA in PM2.5 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 PM2.5 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 PM2.5 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 SO42-, NO3-, EC, OC, and inorganic elements were mainly from the north and southwest directions of the observation area.