兰州市典型企业VOCs排放特征及反应活性分析

基于兰州市大气VOCs排放清单，选取石化厂、乙烯厂、涂料厂3个典型企业采集VOCs样品，分析其无组织排放特征，并采用MIR（最大增量反应活性）法和LOH（·OH反应速率）法综合评价其化学反应活性，识别各企业的VOCs活性优势物种，同时探究不同企业特征VOCs比值.结果表明:不同排放源φ（VOCs）差异较大，范围为20.8×10-9~6 520.3×10-9.从VOCs物种构成上来看，涂料厂芳香烃占比最高，而石化厂、乙烯厂均以烷烃物种最为丰富，石化厂不同工艺VOCs物种构成略有差异.从活性上看，涂料厂VOCs活性最高，其LOH和OFP（臭氧生成潜势）分别为2 676.9 s-1和72 519.0×10-9，约为其他行业的18~1 000倍，间/对-二甲苯、乙苯、邻二甲苯等物种活性较大；其次为石化厂，其LOH和OFP分别为273.2 s-1和4 039.1×10-9，正戊烷、异戊烷、乙烯、丙烯等物种活性贡献率高，其中柴油工艺对石化厂VOCs活性贡献率最大；乙烯厂的OFP最低，其LOH和OFP分别为4.6 s-1和69.7×10-9，其VOCs活性主要来自乙烯、丙烯、正丁烯等烯烃物种.各工业源BTEX（苯、甲苯、乙苯及3种二甲苯异构体的合称）分布具有一定的差异，对于指示不同VOCs来源有一定的参考价值，但不同源比值的重叠性也表明并非全部VOCs来源可以通过特征物种比值来区分.研究显示，控制工业源特别是涂料与石化工业VOCs的排放有助于控制兰州市O₃的生成. 

Characteristics and Chemical Reactivity of Fugitive Volatile Organic Compounds from Typical Industries in Lanzhou City

Based on the emission inventory of the VOCs in Lanzhou City, petrochemical plants, coating plants and ethylene plants were selected to analyze the fugitive emission characteristics of VOCs using off-line monitoring instruments. The atmospheric chemical reactivity of VOCs and their OFP (ozone formation potential) were evaluated by using MIR (maximum increment reactivity) and LOH methods (·OH radical reactivity). Also, we studied the diagnostic ratios of the different enterprises. The results showed that the φ(VOCs) varied from 20.8×10-9 to 6, 520.3×10-9 in those VOC sources, among which the coating plants were the highest, the lowest was in ethylene plants. As for the compositions of VOCs, aromatics were the most abundant species in coating factories, while alkanes were in petrochemical plants and ethylene plants. Moreover, the processes of petrochemical plants were also slightly different. The photochemical reactivity of VOCs in the coating plants was higher than that in the other industries of this study, with which LOH and OFP were 2, 676.9 s-1 and 72, 519.0×10-9, respectively. It was about 18 to 1, 000 times that of other industries. Moreover, the aromatic hydrocarbons such as m, p-xylene, ethylbenzene and o-xylene accounted for the highest ratio. The petrochemical industry was followed with the LOH and OFP being 273.2 s-1 and 4, 039.1×10-9, and the major contribution came from diesel. N-pentane, isopentane, ethylene and propylene were dominant species for ozone formation in the petrochemical plants. The contribution of ethylene plants was the lowest in the study, with the LOH and OFP values of 4.6 s-1 and 69.7×10-9. Its photochemical reactivity mainly came from olefin species such as ethylene, propylene and n-butene. BTEX (the combination of benzene, toluene, ethylbenzene and three xylenes) ratios showed that some but not all VOC sources could be distinguished by those diagnostic ratios. The research indicated that the control of the industrial emission sources, especially the coatings and petrochemical plants, would be favorable for controlling ozone formation.