徐州市不同类型颗粒物重污染过程特征及组分差异性分析

经过多年的大气污染防治,我国空气质量有了大幅改善,但重污染过程仍有发生。对2018—2021年徐州市3种不同类型颗粒物重污染过程的污染特征、演变趋势、PM_2.5组分特征和相关性及污染成因分析结果表明:在不同类型的重污染过程中,二次无机离子NO₃^-、SO₄^2-、NH₄⁺在PM_2.5中的占比均是最高。在累积型重污染期间,NO₃^-、SO₄^2-、NH₄⁺分别增长144%、142%、183%,二次无机离子对PM_2.5的增长贡献较大。结合相关性分析及SOR、NOR值发现,硝酸盐和硫酸盐的二次生成作用显著。在沙尘型重污染期间,结合雷达监测结果及后向轨迹图可以看出,沙尘沉降至高空与近地面污染物叠加造成颗粒物高值。化学组分中Ca²⁺、Mg²⁺浓度对PM_2.5浓度的影响最大,二次生成和转化对其影响较小。在烟花燃放型重污染期间,和烟花爆竹有关的K⁺、Mg²⁺、Cl^-离子较污染前分别上升1 112%、2 058%、和239%,对污染过程影响显著。

Characteristic and Component Differences of Heavy Pollution Process of Different Types of Particulate in Xuzhou City

After years of air pollution prevention and control,China''s air quality had been greatly improved,but heavy pollution process still occurs. The process of heavy pollution of three different types of particulate matter in Xuzhou from 2018 to 2021 was analyzed from pollution characteristics,evolution trend,characteristics and correlation of PM_2.5 components and pollution causes. The results showed that,in the process of different types of heavy pollution,the proportion of secondary inorganic ions NO₃^-,SO₄^2-, NH₄⁺ in PM_2.5 was still the highest. During the cumulative heavy pollution period,NO₃^-,SO₄^2-,NH₄⁺ increased by 144%,142% and 183% respectively,and secondary inorganic ions contributed greatly to the growth of PM_2.5. Combining correlation analysis and SOR and NOR values,it was found that the secondary generation of nitrate and sulfate was significant. During the period of heavy dust pollution,based on the radar monitoring results and the backward trajectory map,it could be seen that the sedimentation of sand and dust at high altitude and the superposition of pollutants near the ground caused high values of particulate matte. The concentration of Ca²⁺ and Mg²⁺ in chemical components had the greatest impact on the concentration of PM_2.5,and the secondary generation and transformation had little impact on it. During the heavy pollution period of fireworks discharge,the K⁺,Mg²⁺ and Cl^- ions which have a greater relationship with fireworks increased by 1 112%,2 058% and 239% respectively compared with those before the pollution,which had a significant increase in the influence on the pollution process.