Com-Part: Combustion Particles in the Atmosphere: Properties, Transformations, Fate & Impacts

Com-Part：大气中的燃烧粒子：属性、转变、命运

• 批准号: NE/K014269/1
• 负责人: Roy Harrison
• 金额: $ 11.47万
• 依托单位: University of Birmingham
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2014
• 资助国家: 英国
• 起止时间: 2014 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FK014269%2F1
• 关键词: Com; Part; Combustion; Particles; Atmosphere

Combustion particles have major impacts on air quality and climate. As well as primary particles emitted directly, secondary particles are formed through the atmospheric oxidation of vapour phase organic compounds that are also present in the exhaust. Traditionally, primary and secondary particles have been quantified in terms of the total mass of particulate, however the human health and climate impacts are increasingly recognised to be highly dependent on the exact size and mixing state of particles. Engine exhaust emissions, the dominant particle source in urban environments, are complicated by the fact that primary particles comprise a mixture of pure organic and mixed organic and elemental carbon particles, with the organic fraction near equilibrium with the vapour phase. The exact mixture is dependent on the engine speed, load and temperature. The complexity of the exhaust emission dependence on combustion conditions heavily influences the composition and properties of the primary particles and determines the magnitude and manner of secondary particle production.Com-Part will use new developments in aerosol instrumentation to comprehensively characterise the complex exhaust emitted from a diesel engine under various operating conditions, representative of real-world usage, and subsequently subjected to dilution and photochemical processing using an aerosol reaction chamber. Particular attention will be paid to the mixing state of the refractory black carbon with respect to the primary and secondary organic matter and the fractional contributions of these to the particle mass. In addition to the diesel exhaust, emissions from small appliance engines (including 2-stroke) will be investigated, as these are currently under-characterised from a secondary organic aerosols perspective.In addition to the composition measurements, the wavelength-dependent optical absorption, optical extinction and cloud condensation nuclei (CCN) will be studied, as these are the parameters key to determining the climate impacts of the aerosol. Various model treatments can be used to predict the optical properties based on knowledge of the particulate composition and various assumptions concerning particle morphology. The performance of these models relevant to engine emissions will be critically evaluated and parameterisations will be derived that are suitable for inclusion in radiative transfer models. Similarly, parameterisations of the CCN behaviour of the particles (using simplified single parameter effective "kappa" approaches or similar) will also be derived.To place the measurements in an ambient context, the profiles obtained over a range of operating conditions will be scaled according to typical urban driving conditions, using the standard EURO emissions testing cycles as a basis. This will then be used to generate a typical urban emission and associated SOA formation profile, which can be in turn compared with ambient measurements. These ambient measurements will be made using the same instrumentation as used in the laboratory studies and can also be compared to archived data from intensive measurement campaigns such as ClearfLo and CalNex. Timescales for transformation of the primary particles and of the secondary material that is formed will be derived, based on the "photochemical age" through the chamber experiments. This will be derived by direct measurement of the decay rate of volatile organic compounds of known reactivity towards the major atmospheric oxidant, the OH radical.

燃烧颗粒对空气质量和气候有重大影响。除了直接排放的初级颗粒外，二次颗粒也是通过废气中也存在的气相有机化合物的大气氧化而形成的。传统上，初级颗粒和次级颗粒是根据颗粒的总质量来量化的，然而，人们越来越认识到人类健康和气候的影响高度依赖于颗粒的确切尺寸和混合状态。发动机废气排放是城市环境中的主要颗粒源，由于初级颗粒包含纯有机颗粒以及混合有机和元素碳颗粒的混合物，且有机部分与气相接近平衡，因此问题变得复杂。确切的混合物取决于发动机转速、负载和温度。废气排放对燃烧条件的复杂性极大地影响了一次颗粒的组成和性质，并决定了二次颗粒产生的程度和方式。Com-Part 将利用气溶胶仪器的新发展来全面表征从燃烧室排放的复杂废气。柴油发动机在各种操作条件下（代表实际使用情况），随后使用气溶胶反应室进行稀释和光化学处理。将特别关注耐火炭黑相对于初级和次级有机物的混合状态以及它们对颗粒质量的贡献分数。除了柴油废气外，还将研究小型家电发动机（包括二冲程）的排放，因为目前从二次有机气溶胶的角度尚未充分表征这些排放。除了成分测量外，还研究了与波长相关的光学吸收、将研究消光和云凝核（CCN），因为这些是确定气溶胶气候影响的关键参数。基于颗粒成分的知识和有关颗粒形态的各种假设，可以使用各种模型处理来预测光学特性。这些与发动机排放相关的模型的性能将受到严格评估，并将得出适合包含在辐射传输模型中的参数化。类似地，也将导出颗粒的 CCN 行为的参数化（使用简化的单参数有效“kappa”方法或类似方法）。为了将测量置于环境环境中，在一系列操作条件下获得的轮廓将根据以典型的城市驾驶条件为基础，使用标准的欧元排放测试周期作为基础。然后，这将用于生成典型的城市排放和相关的 SOA 形成剖面，进而可以与环境测量值进行比较。这些环境测量将使用与实验室研究中使用的相同仪器进行，并且还可以与 ClearfLo 和 CalNex 等密集测量活动的存档数据进行比较。初级粒子和所形成的次级材料的转变的时间尺度将基于通过室实验的“光化学年龄”而得出。这将通过直接测量已知对主要大气氧化剂 OH 自由基具有反应性的挥发性有机化合物的衰变率来得出。

项目成果

Technical note: Use of an atmospheric simulation chamber to investigate the effect of different engine conditions on unregulated VOC-IVOC diesel exhaust emissions

技术说明：使用大气模拟室研究不同发动机条件对不受管制的 VOC-IVOC 柴油机废气排放的影响

• DOI: http://dx.10.5194/acp-18-11073-2018
• 发表时间: 2018
• 期刊: Atmospheric Chemistry and Physics
• 影响因子: 6.3
• 作者: Pereira K