汽油中烯/芳烃含量对机动车VOCs和PM2.5排放特征谱的影响研究

The fuel quality, as one of the key elements in the pollution prevention and control system of "vehicle-fuel-road", has become a key factor affecting the progress of airborne PM2.5 pollution control in China. The contents of olefin and aromatics in gasoline sold in China are higher than those in Europe and the US, which are key indices for vehicular exhaust and evaporative emission control. But it's not clear yet about their impacts on the profile of VOCs and PM2.5 emissions from vehicles, so it's difficult to clarify the relevance between fuel quality and the formation/transformation of airborne PM2.5. In this study, typical gasoline vehicles from different technical stages are selected for emission tests, using different gasoline samples with specified olefin and aromatics composition. Both tailpipe emissions and evaporative emissions will be measured, and their VOCs and PM2.5 emissions will be sampled for further analysis. Species analysis will be further carried out, including alkane, olefin, alkyne, aromatics and carbonyl groups for VOCs, and carbonaceous fractions, water-soluble ions and elements for PM2.5. Based on the analysis results, data statistics is going to be used to find the key species in the profile of VOCs and PM2.5 emissions those are significantly affected by the olefin and aromatics in gasoline. The outcome of this study will provide basic scientific evidence for further investigation on the effects of fuel quality improvement on the formation of secondary organic aerosol (SOA), so as to support the reasonable and effective decision-making about PM2.5 pollution control in China.

油品质量作为“车-油-路”污染防治体系的要素之一，已成为影响我国大气PM2.5治理进程的一个关键因素。我国汽油中烯烃、芳烃含量相比欧美地区偏高，是影响机动车尾气和蒸发排放的关键指标，但其对VOCs和PM2.5排放特征谱的影响尚不清楚，难以阐明油品质量与大气PM2.5生成转化之间的相关性。本研究针对这一科学问题，选取国内不同技术水平的典型汽油车，使用不同烯烃、芳烃配比的实验油样，分别进行尾气排放和蒸发排放实验，并对其VOCs和PM2.5进行采样；进一步分析VOCs的烷烃、烯烃、炔烃、芳香烃、羰基等组分，和PM2.5的碳质组分、水溶性离子、元素等组分，并通过统计分析，找出VOCs和PM2.5特征谱中受汽油烯烃、芳烃含量影响显著的关键化学组分。研究成果将为进一步探究我国油品质量改善对二次有机气溶胶（SOA）生成转化的影响提供基础科学依据，从而支撑管理部门制定科学有效的大气PM2.5防控对策。

油品质量作为“车-油-路”污染防治体系的要素之一，已成为影响我国大气PM2.5治理进程的一个关键因素。我国汽油中烯/芳烃含量及馏程（T50&T90）等指标相比欧美地区偏高，是影响机动车尾气和蒸发排放的关键指标，但其对VOCs和PM2.5排放特征谱的影响尚不清楚，难以阐明油品质量与大气PM2.5生成转化之间的相关性。针对这一科学问题，本研究从市场上选取PFI和GDI两种技术共10辆典型汽油车，开展不同环境温度下使用不同烯烃含量、芳烃含量、T50和T90共8种试验燃料的尾气排放和蒸发排放试验，在对常规污染物进行检测的同时，对VOCs和PM2.5进行采样，进一步分析VOCs的烷烃、烯烃、炔烃、芳香烃、醛酮等组分，和PM2.5的碳质组分、水溶性离子、元素和多环芳烃组分；最后对油品指标、环境温度等因素与汽车排放VOCs、PM2.5化学组分谱进行关联性研究。结果表明，降低烯/芳烃含量可降低汽车尾气VOCs中烯烃类、芳烃类，尤其是1-丁烯、异戊烷、1-己烯、甲苯及大多数醛酮化合物等组分的排放及其相应臭氧生成潜势，且有降低颗粒物中OC、EC排放的趋势，但对元素、离子和多环芳烃类无影响规律；降低汽油T50&T90会降低尾气VOCs中间二甲苯、乙基苯、甲醛、丁醛、苯甲醛等组分排放，且在降低PM和PN排放的同时，还有降低颗粒物中OC、EC及萘、苊烯、荧蒽和芘等组分趋势；随着环境温度降低，尾气VOCs中一些乙烷、丙烷类小分子以及醛酮类质量占比会有所减少，而带苯环的大分子VOCs组分、颗粒物及颗粒物中部分PAHs会有所增加；另外，本研究也尝试了汽油烯芳烃含量对汽车热浸蒸发和昼间蒸发VOCs排放影响研究。本项目成果可为机动车排放特征谱、大气污染来源解析等研究提供基础数据支撑，为我国车用油品质量的持续改善提供科学决策支撑，从而支撑管理部门制定科学、有效的大气PM2.5防控对策。