Chin Jo-Yu, Batterman Stuart A
University of Michigan, School of Public Health, Environmental Health Sciences, 1420 Washington Heights, Ann Arbor, MI 48109-2029, USA.
Chemosphere. 2012 Mar;86(9):951-8. doi: 10.1016/j.chemosphere.2011.11.017. Epub 2011 Dec 10.
The formulation of motor vehicle fuels can alter the magnitude and composition of evaporative and exhaust emissions occurring throughout the fuel cycle. Information regarding the volatile organic compound (VOC) composition of motor fuels other than gasoline is scarce, especially for bioethanol and biodiesel blends. This study examines the liquid and vapor (headspace) composition of four contemporary and commercially available fuels: gasoline (<10% ethanol), E85 (85% ethanol and 15% gasoline), ultra-low sulfur diesel (ULSD), and B20 (20% soy-biodiesel and 80% ULSD). The composition of gasoline and E85 in both neat fuel and headspace vapor was dominated by aromatics and n-heptane. Despite its low gasoline content, E85 vapor contained higher concentrations of several VOCs than those in gasoline vapor, likely due to adjustments in its formulation. Temperature changes produced greater changes in the partial pressures of 17 VOCs in E85 than in gasoline, and large shifts in the VOC composition. B20 and ULSD were dominated by C(9) to C(16)n-alkanes and low levels of the aromatics, and the two fuels had similar headspace vapor composition and concentrations. While the headspace composition predicted using vapor-liquid equilibrium theory was closely correlated to measurements, E85 vapor concentrations were underpredicted. Based on variance decomposition analyses, gasoline and diesel fuels and their vapors VOC were distinct, but B20 and ULSD fuels and vapors were highly collinear. These results can be used to estimate fuel related emissions and exposures, particularly in receptor models that apportion emission sources, and the collinearity analysis suggests that gasoline- and diesel-related emissions can be distinguished.
机动车燃料的配方会改变整个燃料循环过程中蒸发排放物和尾气排放物的数量及成分。关于非汽油类机动车燃料中挥发性有机化合物（VOC）成分的信息很少，尤其是生物乙醇和生物柴油混合物。本研究检测了四种市面上现有的当代燃料的液体和蒸汽（顶空）成分：汽油（乙醇含量<10%）、E85（85%乙醇和15%汽油）、超低硫柴油（ULSD）和B20（20%大豆生物柴油和80% ULSD）。纯燃料和顶空气体中汽油和E85的成分以芳烃和正庚烷为主。尽管E85的汽油含量低，但其蒸汽中几种VOC的浓度高于汽油蒸汽中的浓度，这可能是由于其配方的调整。温度变化导致E85中17种VOC的分压变化比汽油中的更大，且VOC成分发生了很大变化。B20和ULSD以C(9)至C(16)正构烷烃为主，芳烃含量低，这两种燃料的顶空气体成分和浓度相似。虽然用气液平衡理论预测的顶空成分与测量值密切相关，但E85蒸汽浓度预测偏低。基于方差分解分析，汽油和柴油燃料及其蒸汽中的VOC是不同的，但B20和ULSD燃料及其蒸汽是高度共线的。这些结果可用于估算与燃料相关的排放和暴露，特别是在分配排放源的受体模型中，共线性分析表明可以区分与汽油和柴油相关的排放。
