Characteristics and sources apportionment of air pollution during heating period in Xuzhou

The concentrations of air pollutants in Xuzhou have decreased significantly in recent years. However, the problem of air pollution during the heating periods is still serious. Studying the characteristics and sources of air pollution during the heating periods plays an important role in the early warning and prevention and control of air pollution. A set of approaches, such as ground monitoring, remote sensing satellite monitoring, PM_2.5 composition analysis, potential source contribution factor method (PSCF) and concentration-weighted trajectory analysis (CWT), were comprehensively adopted. The air pollution characteristics of Xuzhou in five heating periods from 2016 to 2020 were analyzed, and the sources of PM_2.5 in the heating periods were analyzed. The results showed that the air quality in Xuzhou had significantly improved in recent years, but the concentrations of most air pollutants during the heating periods were significantly higher than that in the non-heating periods. The heating had a great impact on the concentration of PM_2.5, and during the heating periods, the concentration of PM_2.5 increased by 40%-71% compared with those before and after the heating periods. The concentrations of Cl⁻, NO₃ ⁻, SO₄ ²⁻, and NH₄ ⁺ in the heating periods were significantly higher than those before and after the heating periods, indicating that the concentration of NH₄ ⁺ had a strong correlation with NO₃ ⁻, SO₄ ²⁻ and Cl⁻ during the heating periods. The contribution of coal combustion and industrial emission to PM_2.5 during the heating periods was 9.9% and 13.9%, respectively, higher than that after the heating periods, the SOR and NOR during the heating periods were significantly higher than those in non-heating periods, and the secondary conversion efficiency of SO₂ and NO_x increased significantly. The trajectory analysis indicated that the potential source areas contributed to Xuzhou during the heating periods were mainly distributed in Hebei Province and the areas neighboring Xuzhou, and the main contributing areas with PM_2.5 concentration higher than 75 µg/m³ were from Shandong, Henan, northern Anhui, and southern Hebei.