徐州市臭氧污染特征及前体物协同控制策略分析

Analysis of ozone pollution characteristics and precursor cooperative control strategy in Xuzhou City

近年来大气臭氧污染问题凸显,但臭氧前体物及其效应复杂,控制难度大.为探究徐州市臭氧污染特征,掌握臭氧前体物的作用机理,实现多种前体物协同优化控制,本研究基于国控点、省控站点、网格点2018—2021年及2022年4—6月的多要素监测数据进行了全面剖析及减排效应模拟.结果表明:①徐州市复合污染变化特征表现为PM2.5波动下降,臭氧污染整体逐年加重的趋势,臭氧作为首要污染物出现时间提前、时间持续变长,以臭氧为首要污染物的超标天数已超过PM2.5;②根据臭氧小时变化特征,其日变化呈“单峰型”,臭氧2022年6月峰值时间较2018—2021年6月推后1 h,不同臭氧浓度下源排放强度和光化学反应对臭氧的影响显著,高温时臭氧前体物VOCs浓度明显高于平均值;③基于观测的模型(Observation-Based Model,OBM)模拟结果显示,单独减排NOx或VOCs降低臭氧污染难度较大,在徐州地区VOCs与NOx的削减比例不低于1.8∶1才能达到臭氧前体物协同控制的效果;④在当前VOCs来源结构下,削减人为源VOCs比天然源VOCs控制臭氧效果更显著,同样削减10%的VOCs,人为源产生的臭氧生成潜势的下降幅度可达到天然源的17倍.

Atmospheric ozone pollution has emerged as a major environmental issue in recent years,but the ozone precursors and their effects are complex and hard to control.In order to explore the characteristics of ozone pollution in Xuzhou city,to capture the ozone precursor mechanism,and to conduct synergistic and optimal control of multiple precursors,a comprehensive analysis and simulation of emissions reduction effects was conducted based on multi-parameter monitoring data from national monitoring stations,provincial monitoring stations,and grid monitoring sites from April through June 2018 to 2021 and 2022.The results showed that:①The change characteristics of compounds pollution showed that PM2.5 was fluctuating downwards,overall ozone pollution worsened year by year,ozone as a primary pollutant emerged earlier and longer,the number of days with ozone as the primary pollutant exceeded PM2.5;②Based on the hourly ozone characteristics,its daily change was single-peaked,the ozone peak in June 2022 was delayed by 1 hour compared to June 2018 and 2021,source emission intensities and photochemical reactions had important effects on ozone at different ozone concentrations,and the VOCs concentration as ozone precursors during high temperature was significantly higher than average;③Observation-Based Model(OBM)simulation results showed that it was difficult to reduce NOx or VOCs alone in order to reduce ozone pollution,and the reduction ratio of VOCs to NOx in Xuzhou should be no less than 1.8∶1 to achieve the effect of synergistic control of ozone precursors;④The current source structure of VOCs suggests that reducing anthropogenic VOCs is more effective than natural sources of VOCs in controlling ozone.With the same 10%reduction in VOCs,the reduction in ozone generation potential from anthropogenic sources can be as much as 17 times greater than that from natural sources.