典型工业城市夏季VOCs污染特征及反应活性

Characteristics and Reactivity of VOCs in a Typical Industrial City in Summer

为研究典型工业城市夏季挥发性有机物(VOCs)污染对环境的影响及成因,利用2020年7月在淄博市城区的VOCs在线监测数据,分析了污染日和清洁日VOCs的污染特征、化学反应活性和臭氧(O_(3))污染成因.结果表明,污染日总挥发性有机物(TVOC)小时浓度均值较清洁日高32.5%,分别为(50.6±28.3)μg·m^(-3)和(38.2±24.9)μg·m^(-3),污染日和清洁日各组分贡献率均为:烷烃>芳香烃>烯烃>炔烃,TVOC和O_(3)浓度日变化均呈现相反的变化趋势.污染日臭氧生成潜势(OFP)、·OH消耗速率(L_(·OH))和二次有机气溶胶生成潜势(SOA_(p))均高于清洁日,烯烃对OFP和L_(·OH)贡献最大,芳香烃对SOA_(p)贡献最大;OFP和SOA_(p)日变化趋势和TVOC基本一致;化学反应活性优势物种以烯烃和芳香烃类物质居多.VOCs/NO_(x)法判断污染日和清洁日O_(3)敏感区属性均处于VOCs控制区和过渡区,而烟雾产量模型法(SPM)诊断污染日O_(3)敏感区属性在08:00~16:00期间处于VOCs控制区和过渡区交替状态,清洁日各时段均处于VOCs控制区.为减轻该市夏季O_(3)污染,应加强对VOCs(烯烃和芳香烃)和氮氧化物(NO_(x))的协同控制.

To investigate the ambient pollution caused by volatile organic compounds(VOCs) in a typical industrial city in summer,the characteristics and chemical reactivity from VOCs and the causes of ozone(O_(3)) pollution were analyzed using online VOCs measurements during polluted and non-polluted periods in Zibo city in July 2020.The results showed that the average hourly concentration of total volatile organic compounds(TVOC) during the polluted period [(50.6±28.3)] μg·m^(-3) was 32.5% higher than that during the non-polluted period [(38.2±24.9) μg·m^(-3)].The contribution of all VOCs categories were as follows:alkanes>aromatics>alkenes>alkynes,and the diurnal averages of TVOC and O_(3) concentrations were opposite during the polluted and non-polluted period.Ozone formation potential(OFP),·OH radical loss rate(L_(·OH)),and secondary organic aerosol formation potential(SOA_(p)) during the polluted period were higher than those during the non-polluted period.Alkenes contributed most to OFP and L_(·OH),whereas aromatics contributed most to SOA_(p).The tendency of the diurnal average of OFP and SOA_(p) was overall consistent with that of TVOC.The priority species of OFP,L_(·OH,) and SOA_(p) were alkenes and aromatics.The VOCs/NO_(x) method was applied to identify the O_(3)-VOC-NO_(x) sensitivity during the polluted and non-polluted periods,and the results showed that the photochemical regimes were VOCs-limited and transition regions.In addition,the smog production model(SPM) was employed to identify the O_(3) formation regime,and the results showed that those during the polluted period were identified as VOCs-limited and transition regions from 08:00 to 16:00,whereas the non-polluted period was mainly considered to be VOCs-limited.To mitigate the O_(3) pollution in summertime,the synergistic control of VOCs(especially alkenes and aromatics) and NO_(x) emissions should be enforced.