Department of Civil and Environmental Engineering, University of California, Davis, CA 95616, USA.
J Air Waste Manag Assoc. 2010 Oct;60(10):1237-44. doi: 10.3155/1047-3289.60.10.1237.
A state-of-the-science thermodynamic model describing gas-particle absorption processes was used to predict the gas-particle partitioning of mixtures of approximately 60 carbonyl compounds emitted from low-emission gasoline-powered vehicles, three-way catalyst gasoline-powered vehicles, heavy-duty diesel vehicles under the idle-creep condition (HDDV idle), and heavy-duty diesel vehicles under the five-mode test (HDDV 5-mode). Exhaust was diluted by a factor of 120-580 with a residence time of approximately 43 sec. The predicted equilibrium absorption partitioning coefficients differed from the measured partitioning coefficients by several orders of magnitude. Time scales to reach equilibrium in the dilution sampling system were close to the actual residence time during the HDDV 5-mode test and much longer than the actual residence time during the other vehicle tests. It appears that insufficient residence time in the sampling system cannot uniformly explain the failure of the absorption mechanism to explain the measured partitioning. Other gas-particle partitioning mechanisms (e.g., heterogeneous reactions, capillary adsorption) beyond the simple absorption theory are needed to explain the discrepancy between calculated carbonyl partitioning coefficients and observed partitioning. Both of these alternative partitioning mechanisms imply great challenges for the measurement and modeling of semi-volatile primary organic aerosol (POA) species from motor vehicles. Furthermore, as emitted particle concentrations from newer vehicles approach atmospheric background levels, dilution sampling systems must fundamentally change their approach so that they use realistic particle concentrations in the dilution air to approximately represent real-world conditions. Samples collected with particle-free dilution air yielding total particulate matter concentrations below typical ambient concentrations will not provide a realistic picture of partitioning for semi-volatile compounds.
采用一种描述气粒吸收过程的科学热力学模型来预测约 60 种从低排放汽油动力车辆、三效催化剂汽油动力车辆、怠速爬行状态下的重型柴油车辆（HDDV 怠速）和五模式测试下的重型柴油车辆（HDDV 5 模式）排放的羰基化合物混合物的气粒分配。废气通过 120-580 的稀释因子进行稀释，停留时间约为 43 秒。预测的平衡吸收分配系数与实测分配系数相差几个数量级。在稀释采样系统中达到平衡的时间尺度接近 HDDV 5 模式测试中的实际停留时间，比其他车辆测试中的实际停留时间长得多。似乎采样系统中的停留时间不足不能完全解释吸收机制无法解释实测分配的情况。需要超越简单吸收理论的其他气粒分配机制（例如异相反应、毛细吸附）来解释计算的羰基分配系数与观察到的分配之间的差异。这两种替代分配机制都对机动车半挥发性原始有机气溶胶（POA）物种的测量和建模提出了巨大挑战。此外，随着较新车辆排放的颗粒浓度接近大气背景水平，稀释采样系统必须从根本上改变其方法，以便在稀释空气中使用实际的颗粒浓度来大致代表实际情况。用无颗粒稀释空气采集的总颗粒物浓度低于典型环境浓度的样品将无法为半挥发性化合物的分配提供真实情况。
