Department of Mechanical Engineering, Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
J Air Waste Manag Assoc. 2010 Oct;60(10):1204-22. doi: 10.3155/1047-3289.60.10.1204.
Atmospheric transformations determine the contribution of emissions from combustion systems to fine particulate matter (PM) mass. For example, combustion systems emit vapors that condense onto existing particles or form new particles as the emissions are cooled and diluted. Upon entering the atmosphere, emissions are exposed to atmospheric oxidants and sunlight, which causes them to evolve chemically and physically, generating secondary PM. This review discusses these transformations, focusing on organic PM. Organic PM emissions are semi-volatile at atmospheric conditions and thus their partitioning varies continuously with changing temperature and concentration. Because organics contribute a large portion of the PM mass emitted by most combustion sources, these emissions cannot be represented using a traditional, static emission factor. Instead, knowledge of the volatility distribution of emissions is required to explicitly account for changes in gas-particle partitioning. This requires updating how PM emissions from combustion systems are measured and simulated from combustion systems. Secondary PM production often greatly exceeds the direct or primary PM emissions; therefore, secondary PM must be included in any assessment of the contribution of combustion systems to ambient PM concentrations. Low-volatility organic vapors emitted by combustion systems appear to be very important secondary PM precursors that are poorly accounted for in inventories and models. The review concludes by discussing the implications that the dynamic nature of these PM emissions have on source testing for emission inventory development and regulatory purposes. This discussion highlights important linkages between primary and secondary PM, which could lead to simplified certification test procedures while capturing the emission components that contribute most to atmospheric PM mass.
大气转化决定了燃烧系统排放对细颗粒物 (PM) 质量的贡献。例如，燃烧系统排放的蒸气会在排放物冷却和稀释时凝结在现有颗粒上或形成新颗粒。进入大气后，排放物会暴露于大气氧化剂和阳光之下，这会导致它们发生化学和物理变化，从而产生二次 PM。本综述讨论了这些转化，重点是有机 PM。有机 PM 排放物在大气条件下具有半挥发性，因此其分配随温度和浓度的变化而连续变化。由于有机物在大多数燃烧源排放的 PM 质量中占很大一部分，因此不能使用传统的静态排放因子来表示这些排放物。相反，需要了解排放物的挥发性分布，以明确说明气体-颗粒分配的变化。这需要更新从燃烧系统测量和模拟 PM 排放的方法。二次 PM 的产生通常大大超过直接或主要 PM 排放；因此，在评估燃烧系统对环境 PM 浓度的贡献时，必须包括二次 PM。燃烧系统排放的低挥发性有机蒸气似乎是二次 PM 的重要前体，但在清单和模型中考虑不足。综述最后讨论了这些 PM 排放的动态性质对排放清单开发和监管目的的源测试的影响。这一讨论强调了一次和二次 PM 之间的重要联系，这可能导致简化认证测试程序，同时捕获对大气 PM 质量贡献最大的排放成分。
