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Plume-exit modeling to determine cloud condensation nuclei activity of aerosols from residential biofuel combustion

机译：羽流模型确定居民生物燃料燃烧产生的气溶胶的云凝结核活性

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Residential biofuel combustion is an important source of aerosols and gases in the atmosphere. The change in cloud characteristics due to biofuel burning aerosols is uncertain, in part, due to the uncertainty in the added number of cloud condensation nuclei (CCN) from biofuel burning. We provide estimates of the CCN activity of biofuel burning aerosols by explicitly modeling plume dynamics (coagulation, condensation, chemical reactions, and dilution) in a young biofuel burning plume from emission until plume exit, defined here as the condition when the plume reaches ambient temperature and specific humidity through entrainment. We found that aerosol-scale dynamics affect CCN activity only during the first few seconds of evolution, after which the CCN efficiency reaches a constant value. Homogenizing factors in a plume are co-emission of semi-volatile organic compounds (SVOCs) or emission at small particle sizes; SVOC co-emission can be the main factor determining plume-exit CCN for hydrophobic or small particles. Coagulation limits emission of CCN to about 10sup16/sup per kilogram of fuel. Depending on emission factor, particle size, and composition, some of these particles may not activate at low supersaturation (is/isubsat/sub). Hygroscopic Aitken-mode particles can contribute to CCN through self-coagulation but have a small effect on the CCN activity of accumulation-mode particles, regardless of composition differences. Simple models (monodisperse coagulation and average hygroscopicity) can be used to estimate plume-exit CCN within about 20?% if particles are unimodal and have homogeneous composition, or when particles are emitted in the Aitken mode even if they are not homogeneous. On the other hand, if externally mixed particles are emitted in the accumulation mode without SVOCs, an average hygroscopicity overestimates emitted CCN by up to a factor of 2. This work has identified conditions under which particle populations become more homogeneous during plume processes. This homogenizing effect requires the components to be truly co-emitted, rather than sequentially emitted.
机译：住宅生物燃料燃烧是大气中气溶胶和气体的重要来源。由于生物燃料燃烧的气溶胶引起的云特征变化是不确定的，部分原因是由于生物燃料燃烧产生的云凝结核（CCN）增加数量的不确定性。通过显式模拟从排放到烟羽排出的年轻生物燃料烟羽中的烟羽动力学（凝结，冷凝，化学反应和稀释），我们提供了生物燃料燃烧气溶胶CCN活性的估算值，此处定义为烟羽达到环境温度时的状况和通过夹带的特定湿度。我们发现，气溶胶尺度动力学仅在演变的最初几秒钟内影响CCN活性，此后CCN效率达到恒定值。羽流中的均质化因素是半挥发性有机化合物（SVOC）的共同排放或小颗粒排放。 SVOC共发射可能是决定疏水性或小颗粒羽状CCN的主要因素。凝结将CCN的排放限制为每千克燃料约10 16 。根据排放因子，颗粒大小和组成，其中一些颗粒可能在低过饱和度（ s sat ）下不活化。吸湿性的Aitken模式颗粒可通过自凝作用而贡献于CCN，但对累积模式颗粒的CCN活性影响很小，而与成分差异无关。如果颗粒是单峰的并且具有均一的成分，或者即使颗粒不均匀也以艾特肯模式发射，则可以使用简单的模型（单分散凝聚和平均吸湿性）来估计羽状出口的CCN在20％以内。另一方面，如果外部混合颗粒以无SVOC的累积模式排放，则平均吸湿性会高估排放的CCN高达2倍。这项工作确定了在羽流过程中颗粒总体变得更加均匀的条件。这种均质化效果要求成分被真正地共同发射，而不是顺序发射。

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