Department of Mechanical Engineering, Colorado State University, Fort Collins, CO, USA.
Environ Sci Process Impacts. 2019 May 22;21(5):819-830. doi: 10.1039/c8em00571k.
Exposure to diesel exhaust particles (DEP) has been linked to adverse human health outcomes. DEPs are reactive and can directly or indirectly lead to oxidative stress, which promotes inflammation in the body. The oxidative potential (OP) of DEPs is not well understood, particularly for combustion with alternative fuels, under different engine loads, and in combination with modern emissions control devices. In this study, we measured the OP of DEPs using a dithiothreitol assay (OP-DTT) from a modern-day non-road diesel engine for two different fuels (conventional diesel and soy-based biodiesel), two different engine loads (idle and 50% load), and with and without an emissions control system. The OP-DTT of DEPs was sensitive to the fuel used and the presence of an emissions control system but not to the engine load. On average, the use of biodiesel resulted in factor of ∼6 reduction in OP-DTT normalized to the DEP mass and a factor of ∼12 reduction in OP-DTT normalized to the fuel consumed. The use of the emissions control, on average, resulted in a factor of ∼6 reduction in OP-DTT normalized to the DEP mass and a three order of magnitude decrease in OP-DTT normalized to the fuel consumed. When studied in conjunction with the DEP composition, the OP-DTT seemed to correlate most strongly with elemental carbon (EC), followed by semi-volatile organic vapors. Assays performed on DEPs where EC was deliberately filtered out suggested that the species responsible for the OP-DTT might be correlated with EC but would need to be water soluble (e.g., quinones). The semi-volatile organic vapors accounted for more than a quarter of the OP-DTT of DEPs collected on the quartz filters. Finally, sensitivity studies performed with a different filter membrane (i.e., Teflon®) and solvent (i.e., dichloromethane) tended to increase the OP-DTT value. OP-DTT is emerging as an important metric for studying the adverse effects of DEPs and PM2.5 on human health; results of this work help define the sources and components of diesel PM2.5 that contribute to OP-DTT.
柴油机排放颗粒（DEP）的暴露与不良的人类健康结果有关。DEP 具有反应性，可直接或间接导致氧化应激，从而促进体内炎症。DEP 的氧化潜力（OP）尚未得到很好的理解，特别是对于使用替代燃料、在不同发动机负荷下以及与现代排放控制装置结合使用的情况。在这项研究中，我们使用二硫苏糖醇测定法（OP-DTT）测量了一种现代非道路柴油机排放颗粒的 OP，该柴油机使用了两种不同的燃料（传统柴油和基于大豆的生物柴油）、两种不同的发动机负荷（怠速和 50%负荷）以及有和没有排放控制系统。DEP 排放颗粒的 OP-DTT 对所用燃料和排放控制系统的存在敏感，但对发动机负荷不敏感。平均而言，与使用传统柴油相比，使用生物柴油导致 OP-DTT 归一化为 DEP 质量的因子减少了约 6 倍，归一化为消耗燃料的因子减少了约 12 倍。平均而言，使用排放控制系统会使 OP-DTT 归一化为 DEP 质量的因子减少约 6 倍，归一化为消耗燃料的因子减少三个数量级。当与 DEP 组成一起研究时，OP-DTT 似乎与元素碳（EC）最密切相关，其次是半挥发性有机蒸气。在对故意过滤出 EC 的 DEP 进行的测定中，研究人员认为负责 OP-DTT 的物质可能与 EC 相关，但需要具有水溶性（例如，醌）。半挥发性有机蒸气占收集在石英滤纸上的 DEP 中 OP-DTT 的四分之一以上。最后，使用不同的滤膜（即聚四氟乙烯（Teflon®））和溶剂（即二氯甲烷）进行的敏感性研究往往会增加 OP-DTT 值。OP-DTT 正成为研究柴油机排放颗粒和 PM2.5 对人类健康的不良影响的重要指标；这项工作的结果有助于确定导致 OP-DTT 的柴油机 PM2.5 的来源和成分。
