机动车尾气排放VOCs源成分谱及其大气反应活性

选取轻型汽油车、重型柴油车和摩托车等城市典型机动车种分别采用底盘测功机及实际道路实验,结合SUMMA罐采样的方法,获得了小轿车、出租车、公交车、卡车、摩托车和LPG助动车的尾气VOCs样品,利用气相色谱-质谱分析了各车型机动车尾气VOCs的浓度及其物种组成.结果表明,轻型汽油车尾气VOCs以甲苯、二甲苯等芳香烃为主,占43.38%～44.45%;重型柴油车以丙烷、n-十二烷及n-十一烷等烷烃组分为主,占46.86%～48.57%,还有13.28%～15.01%的丙酮等含氧特征组分;摩托车与LPG助动车的主要成分为乙炔,分别占39.75%和76.67%左右.各车型中,摩托车和轻型汽油车尾气VOCs的化学活性显著高于重型柴油车辆,以上海市为例,其大气化学活性贡献分别占55%和44%左右,是影响城市和区域大气氧化能力的关键污染源,其中以甲苯、二甲苯、丙烯、苯乙烯等关键活性物种的贡献最大.

Source Profile and Chemical Reactivity of Volatile Organic Compounds from Vehicle Exhaust

Light-duty gasoline taxis (LDGT) and passenger cars(LDGV), heavy-duty diesel buses (HDDB) and trucks (HDDT), gasoline motorcycles (MC) and LPG scooters (LPGS), were selected for tailpipe volatile organic compounds (VOCs) samplings by using transient dynamometer and on road test combined with SUMMA canisters technology. The samples were tested by GC-MS to analyze the concentration and species composition of VOCs. The results indicate that light-duty gasoline automobiles have higher fractions of aromatic hydrocarbons, which account for 43.38%-44.45% of the total VOCs, the main aromatic hydrocarbons are toluene and xylenes. Heavy-duty diesel vehicles have higher fractions of alkanes, which constitute 46.86%-48.57% of the total VOCs, the main alkanes are propane, n-dodecane and n-undecane. In addition, oxy-organics account for 13.28%-15.01% of the VOCs, the main oxy-organics is acetone. The major compound from MC and LPGS exhaust is acetylene, it accounts for 39.75% and 76.67% of the total VOCs, respectively. VOCs exhaust from gasoline motorcycles and light-duty gasoline automobiles has a significantly higher chemical reactivity than those from heavy-duty diesel vehicles, which contribute 55% and 44% to the atmospheric chemical reactivity in Shanghai. The gasoline motorcycles and light-duty gasoline automobiles are the key pollution sources affecting city and region ambient oxidation, and the key active species of toluene,xylenes,propylene, and styrene make the greatest contribution.