Determination of single particle mass spectral signatures from light-duty vehicle emissions.
Determination of single particle mass spectral signatures from light-duty vehicle emissions.
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DOI：
10.1021/es0489947
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发表时间：
2005-05
影响因子：
11.4
通讯作者：
D. Sodeman;Stephen M. Toner;K. Prather
中科院分区：
文献类型：
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作者：
D. Sodeman;Stephen M. Toner;K. Prather
在这项研究中，28辆轻型汽油车（LDV）在位于加利福尼亚州埃尔蒙特的加州空气资源委员会哈根斯米特设施的底盘测功机上运行。使用气溶胶飞行时间质谱法（ATOFMS）测量了这些飞行器排放的单个颗粒的质谱。本研究的主要目标是确定具有代表性的粒径分辨单颗粒质谱特征，可用于未来的环境颗粒物源解析研究。不同的循环被用来模拟城市驾驶条件，包括联邦测试程序（FTP），统一循环（UC），和校正循环（CC）。这些车辆的选择涵盖了一系列催化转化器（三元，氧化和无催化剂）和发动机技术（1953年至2003年的车型）。排气颗粒直接从稀释和停留室系统中取样，使用颗粒尺寸测量仪器和配备有空气动力学透镜的ATOFMS（UF-ATOFMS）分析50和300 nm之间的颗粒。根据化学成分，10种独特的化学类型描述了大多数具有不同大小和时间特征的颗粒。在超细尺寸范围内（50和100纳米之间），三种元素碳（EC）颗粒类型占主导地位，所有显示出不同的EC签名结合钙，磷酸盐，硫酸盐，和较低丰度的有机碳（OC）。EC颗粒类型的相对分数随着颗粒尺寸的增加而降低，其中OC颗粒在100 nm以上变得更加普遍。根据车辆和循环，几种不同的OC颗粒类型产生不同的离子模式，包括取代的芳香族化合物和多环芳烃（PAH），以及其他化学物质，包括铵，EC，硝酸盐，硫酸盐，磷酸盐，V和Ca。颗粒中Ca和磷酸盐的最可能来源是润滑油。观察到不同汽车类别内以及同一辆汽车在不同驾驶条件下运行时所排放的颗粒物的化学组成存在很大差异。两分钟的时间分辨率测量提供了关于FTP周期中化学类别演变的信息。冷启动的前两分钟产生的颗粒数量是循环的任何其他部分的5倍以上，其中一类超细颗粒（EC与Ca、OC和磷酸盐结合）优先产生。从数量上看，三种含钙的EC（也含有OC、磷酸盐和硫酸盐）是不吸烟车辆产生的最丰富的类别。吸烟者类别产生的颗粒数量最多，主要类别是由取代的单芳族化合物和多环芳烃组成的OC，加上钙和磷酸盐，因此表明使用过的润滑油与许多这些颗粒有关。这些研究表明，从数量上看，EC颗粒在超细尺寸范围内占主导地位，特别是对于排放量最低的新型车辆，这表明EC签名不能单独用作柴油的独特示踪剂。这是第一次报告的高时间和尺寸分辨的化学成分数据显示的混合状态的颗粒，如EC的车辆排放在测功机源测试的非耐火元素。
In this study, 28 light-duty gasoline vehicles (LDV) were operated on a chassis dynamometer at the California Air Resources Board Haagen-Smit Facility in El Monte, CA. The mass spectra of individual particles emitted from these vehicles were measured using aerosol time-of-flight mass spectrometry (ATOFMS). A primary goal of this study involves determining representative size-resolved single particle mass spectral signatures that can be used in future ambient particulate matter source apportionment studies. Different cycles were used to simulate urban driving conditions including the federal testing procedure (FTP), unified cycle (UC), and the correction cycle (CC). The vehicles were selected to span a range of catalytic converter (three-way, oxidation, and no catalysts) and engine technologies (vehicles models from 1953 to 2003). Exhaust particles were sampled directly from a dilution and residence chamber system using particle sizing instruments and an ATOFMS equipped with an aerodynamic lens (UF-ATOFMS) analyzing particles between 50 and 300 nm. On the basis of chemical composition, 10 unique chemical types describe the majority of the particles with distinct size and temporal characteristics. In the ultrafine size range (between 50 and 100 nm), three elemental carbon (EC) particle types dominated, all showing distinct EC signatures combined with Ca, phosphate, sulfate, and a lower abundance of organic carbon (OC). The relative fraction of EC particle types decreased as particle size increased with OC particles becoming more prevalent above 100 nm. Depending on the vehicle and cycle, several distinct OC particle types produced distinct ion patterns, including substituted aromatic compounds and polycyclic aromatic hydrocarbons (PAH), coupled with other chemical species including ammonium, EC, nitrate, sulfate, phosphate, V, and Ca. The most likely source of the Ca and phosphate in the particles is attributed to the lubricating oil. Significant variability was observed in the chemical composition of particles emitted within the different car categories as well as for the same car operating under different driving conditions. Two-minute temporal resolution measurements provide information on the chemical classes as they evolved during the FTP cycle. The first two minutes of the cold start produced more than 5 times the number of particles than any other portion of the cycle, with one class of ultrafine particles (EC coupled with Ca, OC, and phosphate) preferentially produced. By number, the three EC with Ca classes (which also contained OC, phosphate, and sulfate) were the most abundant classes produced by the nonsmoking vehicles. The smoker category produced the highest number of particles, with the dominant classes being OC comprised of substituted monoaromatic compounds and PAHs, coupled with Ca and phosphate, thus suggesting used lubricating oil was associated with many of these particles. These studies show, by number, EC particles dominate gasoline emissions in the ultrafine size range particularlyforthe lowest emitting newer vehicles, suggesting the EC signature alone cannot be used as a unique tracer for diesels. This represents the first report of high time- and size-resolved chemical composition data showing the mixing state of nonrefractory elements in particles such as EC for vehicle emissions during dynamometer source testing.