汽车维修行业挥发性有机物排放特征及大气化学反应活性

汽车维修行业挥发性有机物排放是臭氧前体物VOCs的重要来源，但目前汽车维修行业的VOCs减排政策主要基于VOCs的排放量，而没有考虑其化学反应活性，这将影响VOCs减排对改善空气质量的效果.通过分析汽车维修企业不同工段VOCs的产排污节点，结合各工段油漆用量及其VOCs质量分数，采用物料衡算法获得不同工段VOCs产生量及其组分，系统分析末端尾气VOCs的排放特征，并通过计算其臭氧生成潜势评估VOCs各组分的大气反应活性.结果表明，汽车维修行业油漆中产生的VOCs组分主要为苯系物，其中乙酸丁酯和二甲苯的质量分数最高.清漆由于其本身VOCs质量分数较高且用量较大，为汽车维修行业最大的VOCs排放源（92%）.企业采用油性面漆VOCs产生量（22%）比水性面漆（3%）有较大程度增大，采用水性漆对汽修企业减少VOCs排放有显著效果.排气筒尾气中共检测出49种VOCs组分，前10种VOCs组分排放量占总排放量的97.9%，种类相对集中.主要污染物类别为芳香烃类（10种，30.90%~69.30%），主要组分有间/对-二甲苯（2.89%~45.00%）；其次为OVOC （12种）和卤代烃（22种），贡献率分别为8.82%~43.71%和2.40%~25.00%，其他组分相对含量较少.芳香烃是汽车维修企业VOCs排放的最大组分，但是在不同研究中主要VOCs种类差异较大.汽车维修企业排放VOCs的OFP平均值为194.04 mg·m^-3，SR平均值为3.37 g·g^-1.间/对-二甲苯对汽车维修行业OFP贡献率最大（70.24%），为优先控制污染物.芳香烃对OFP的贡献率达到99.29%，是化学反应活性最强的组分.酯类在汽车维修行业VOCs组分中占比较大，但对OFP的贡献率相对较低，因此汽车维修行业应重点控制芳香烃类物质的排放.

Emission Characteristics and Atmospheric Chemical Reactivity of Volatile Organic Compounds(VOCs) in Automobile Repair Industry

Volatile organic compounds (VOCs) emitted by the automobile repair industry are an important source of ozone precursors. However, the current reduction policy generally focuses on the emissions of VOCs, without considering their chemical reactivity. Based on an investigation of the development status of China''s automobile repair industry, this study analyzes VOCs emission nodes in different sections of automobile repair enterprises. The amount and VOCs content of paint in each section was determined, and a material balance algorithm was used for sections with different VOCs quantities and compositions to analyze the emission characteristics of exhaust VOCs. The atmospheric reactivity of VOCs components was evaluated by calculating ozone generation potential (OFP). The results show that VOCs components produced by automobile repair paint are mainly benzene homologues, with butyl acetate and xylene the highest. Varnish is the largest contributor to VOCs emissions in automobile repair industries (92%), due to its high VOCs content and high dosage. The VOCs content of solvent-based coatings (22%) is higher than that of water-based coatings (3%). The application of water-based coatings leads to a remarkable reduction in VOCs emissions in automobile repair industries. A total of 49 VOCs components have been detected in gas from exhaust cylinders, with the top 10 VOCs components accounting for 97.9% of the total emissions. The main pollutants are aromatic hydrocarbons (10 types, 30.90%-69.30%), and OVOC (12 types) and halogenated hydrocarbons (22 types) were the second-highest contributors, with contribution rates of 8.82%-43.71% and 2.40%-25.00%, respectively. Aromatic hydrocarbon is the largest VOCs component emitted by automobile repair industries, but the main types of VOCs vary greatly in different studies. VOCs discharged by automobile repair industries have an average OFP value of 194.04 mg ·m^-3 and an average SR value of 3.37 g ·g^-1. The m/p-xylene component contributes the most to OFP (70.24%) and is the preferred pollutant in automobile repair industry. Aromatic hydrocarbons contribute a maximum of 99.29% to the OFP value and are also the most chemically reactive component. Although esters account for a large proportion of VOCs, their contribution to OFP is relatively low. Therefore, the automobile repair industry should focus on controlling the emission of aromatic hydrocarbons.