宝鸡市秋冬季大气VOCs浓度特征及其O3和SOA生成潜势

2017年10月、12月在宝鸡市城区开展了共29d的挥发性有机物（VOCs）浓度在线监测，共测出102种VOCs，分别采用最大增量反应活性（MIR）系数法和气溶胶生成系数（FAC）法估算了宝鸡市各VOCs组分的臭氧生成潜势（OFPs）和二次有机气溶胶生成潜势（SOAFPs），筛选出生成O₃与SOA活性最大的VOCs成分.结果表明：宝鸡市秋季和冬季TVOC的浓度分别为（68.62±21.85）×10^-9和（42.44±16.62）×10^-9，总OFPs分别为185.49×10^-9和126.00×10^-9，总SOAFPs分别为3.26，0.65μg/m³.秋季VOCs中含量最多的2种组分为烷烃（21.83×10^-9）和芳香烃（13.37×10^-9），分别占TVOC的31.82%和19.49%，乙烯、反-2-戊烯和甲苯是OFPs最大的3个成分，甲苯、间/对二甲苯和乙苯是SOAFPs最大的3个成分.而在冬季，烷烃（17.34×10^-9）和炔烃（8.81×10^-9）是VOCs中含量最多的2种组分，分别占TVOC的40.85%和20.75%，乙烯、丙烯、乙炔是OFPs最大的3个成分，甲苯、间/对二甲苯、乙苯是SOAFPs最大的3个成分.优先减少烯烃和芳香烃的排放是宝鸡市秋冬季抑制O₃和SOA的形成的有效途径.

Characteristics of VOCs and formation potential of O3 and SOA in autumn and winter in Baoji,China

A total of 102 ambient volatile organic compounds (VOCs) were detected during the 29-day online real-time scrutiny conducted in the urban area of Baoji during October and December, 2017. The ozone formation potential (OFPs) and the secondary organic aerosol formation potential (SOAFPs) of VOCs species were estimated using the maximum incremental reactivity (MIR) coefficient and the fractional aerosol coefficient (FAC), respectively, so as to screen out the VOCs species that had the largest contribution to the formation of O₃ and SOA. The results showed that the concentration of TVOC in Baoji in the autumn and winter were (68.62±21.85)×10^-9 and (42.44±16.62)×10^-9. The total OFPs were 185.49×10^-9 and 126.00×10^-9 in the autumn and winter, respectively; the total SOAFPs were 3.26, 0.65μg/m³ in the two seasons, respectively. In the autumn, alkanes (21.83×10^-9) and aromatics (13.37×10^-9) contributed the highest contents, which accounted for 31.82% and 19.49% of TVOC, respectively. In the autumn, ethylene, trans-2-pentene and toluene were the species having the largest contribution to OFPs, whereas toluene, m, p-xylene and ethylbenzene were the largest contributors to SOA production. In the winter, alkane (17.34×10^-9) and alkyne (8.81×10^-9) were the top two abundant species, which accounted for 40.85% and 20.75% of TVOC, respectively. In the winter, ethylene, propylene and acetylene were the three major components that had the largest contribution to OFPs; whereas toluene, m-p-xylene, and ethylbenzene were the top three VOCs that had the largest contribution to SOA production. To conclude, it is an efficient way to reduce O₃ and SOA pollution in autumn and winter in Baoji through controlling concentrations of alkenes and aromatics in ambient air.