Monitoring and Laboratory Division, California Air Resources Board, 1900 14th Street, Sacramento, CA 95811, USA.
J Air Waste Manag Assoc. 2013 Aug;63(8):984-96. doi: 10.1080/10962247.2013.795202.
In total, 24 polycyclic aromatic hydrocarbons (PAHs) in both gas and particle phases and 35 nitro-PAHs in particle phase were analyzed in the exhaust from heavy-duty diesel vehicles equipped with after-treatment for particulate matter (PM) and NO(x) control. The test vehicles were carried out using a chassis dynamometer under highway cruise, transient Urban Dynamometer Driving Schedule (UDDS), and idle operation. The after-treatment efficiently abated more than 90% of the total PAHs. Indeed, the particle-bound PAHs were reduced by > 99%, and the gaseous PAHs were removed at various extents depending on the type of after-treatment and the test cycles. The PAHs in gas phase dominated the total PAH (gas + particle phases) emissions for all the test vehicles and for all cycles; that is, 99% of the two-ring and 98% of the three-ring and 97% of the four-ring and 95% of the carcinogenic PAHs were in the gas-phase after a diesel particle filter (DPF) and not bound to the very small amount of particulate matter left after a DPF. Consequently, an evaluation of the toxicity of DPF exhaust must include this volatile fraction and cannot be based on the particle fraction only. The selective catalytic reduction (SCR) did not appear to promote nitration of the PAHs in general, although there might be some selective nitration of phenanthrene. Importantly the after-treatment reduced the equivalent B[a]P (B[a]Peq) emissions by > 95%, suggesting a substantial health benefit.
This study demonstrated that after-treatments, including diesel particulate filters (DPF), diesel oxidation catalysts (DOC), and selective catalytic reduction (SCR), significantly reduce the emissions of PAHs from heavy-duty diesel engines. The gas-phase PAHs dominate the total PAH (gas + particle phases) emissions from heavy-duty diesel vehicles retrofitted with various DPFs and not bound to the very small amount of particulate matter left after a DPF. Consequently, an evaluation of the toxicity of DPF exhaust must also include this volatile fraction and cannot be based on the particle fraction only.
总共分析了配备用于颗粒物（PM）和 NOx 控制的后处理装置的重型柴油车辆尾气中的 24 种气相和颗粒相多环芳烃（PAHs）以及 35 种颗粒相硝基-PAHs。测试车辆在高速公路巡航、瞬态城市动态驾驶计划（UDDS）和怠速运行下使用底盘测功机进行。后处理装置有效地将超过 90%的总 PAHs 消除。事实上，颗粒结合的 PAHs 减少了>99%，而气态 PAHs 的去除程度则取决于后处理类型和测试周期。在所有测试车辆和所有循环中，气相中的 PAHs 都占总 PAH（气相+颗粒相）排放的主导地位；也就是说，经过柴油颗粒过滤器（DPF）后，二苯并[a，h]蒽（B[a]A）和苯并[k]荧蒽（B[k]F）等致癌 PAHs 中有 99%和三环和四环 PAHs 中有 97%以及 95%为气相，而不是 DPF 后残留的极少量颗粒物所结合。因此，DPF 尾气毒性的评估必须包括这一易挥发部分，而不能仅基于颗粒部分。选择性催化还原（SCR）似乎并没有普遍促进 PAHs 的硝化，尽管可能存在一些对菲的选择性硝化。重要的是，后处理装置将等效苯并[a]芘（B[a]Peq）的排放量减少了>95%，这表明对健康有很大的益处。
本研究表明，后处理装置，包括柴油颗粒过滤器（DPF）、柴油氧化催化剂（DOC）和选择性催化还原（SCR），可显著减少重型柴油发动机的 PAHs 排放。配备各种 DPF 的重型柴油车辆的气相 PAHs 占总 PAH（气相+颗粒相）排放的主导地位，且不与 DPF 后残留的极少量颗粒物结合。因此，DPF 尾气毒性的评估也必须包括这一易挥发部分，而不能仅基于颗粒部分。
