2019年7月石家庄市O_(3)生成敏感性及控制策略解析

Ozone Sensitivity Analysis and Control Strategy in Shijiazhuang City in July 2019

基于石家庄市2019年7月近地面污染物和气象观测数据,分析夏季O_(3)污染状况及其影响因素;结合WRF-CMAQ模式和O_(3)浓度等值线(EKMA曲线),探究不同区域O_(3)-VOCs-NO_(x)的非线性响应关系,旨在探究最佳的前体物减排方案.结果表明,观测期间,石家庄市市区MDA8 O_(3)超标率高达70.9%.污染天期间,伴随着高温、低湿、小风,且以南风和东南风为主.石家庄市市区属于VOCs控制区,郊县为NO_(x)和VOCs协同控制区.在臭氧污染时段,市区在仅削减NO_(x)排放,且削减比例超过50%时,持续减排NO_(x)使得O_(3)浓度呈逐渐下降趋势.在非臭氧日时段,市区在VOCs和NO_(x)的削减比例大于1倍时,O_(3)浓度才不会出现反弹.对于市区应考虑以仅削减VOCs为先;对于郊县区域而言,不同的NO_(x)和VOCs削减比例下,O_(3)浓度均会下降,建议减排比例(VOCs∶NO_(x))为1∶2.

The pollution characteristics of surface ozone and its response to meteorological factors were studied based on monitoring in July 2019 in Shijiazhuang City,China.Furthermore,the WRF-CMAQ model coupled with O_(3) isopleths(EKMA curves)were applied to explore the non-linear response relationship of O_(3) to precursors VOCs and NO_(x),aiming to identify a suitable precursor control strategy.The results showed that the days with the maximum daily 8-hour average ozone concentration(MDA8 O_(3))exceeded the standard by 70.9%.The nonattainment days were usually accompanied by higher temperature,lower relative humidity,and low winds,and the south and southeast winds occurred frequently.The O_(3) formation was in the strong VOC-limited regime in the urban area of Shijiazhuang,whereas it was in the NO_(x) and VOCs transition regime in suburban areas.As for the urban area,under the condition of single NO_(x) emission reduction,O_(3) pollution improved when continuous NO_(x) emission reduction was higher than 50%during the nonattainment days.By contrast,during the non-polluted days,O_(3) concentrations would not rebound when the reduction ratio of NO_(x) and VOCs was higher than 1.In conclusion,VOCs reduction should be the priority for emission reduction plans in urban areas,whereas all different NO_(x) and VOCs ratios led to a decline in O_(3) concentration in the suburban areas,and a VOCs∶NO_(x) of 1∶2 was recommended.