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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >From molecular clusters to nanoparticles: Role of ambient ionization in tropospheric aerosol formation
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From molecular clusters to nanoparticles: Role of ambient ionization in tropospheric aerosol formation

机译：从分子簇到纳米颗粒：环境电离在对流层气溶胶形成中的作用

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We investigate the role of background ionization, associated mainly with galactic cosmic radiation, in the generation and evolution of ultrafine particles in the marine boundary layer. We follow the entire course of aerosol evolution, from the initial buildup of molecular clusters (charged and uncharged) through their growth into stable nanoparticles. The model used for this purpose is based on a unified collisional (kinetic) mechanism that treats the interactions between vapors, neutral and charged clusters, and particles at all sizes. We show that air ions are likely to play a central role in the formation of new ultrafine particles. The nucleation of aerosols under atmospheric conditions involves a series of competing processes, including molecular aggregation, evaporation, and scavenging by preexisting particles. In this highly sensitive nonlinear system, electrically charged embryos have a competitive advantage over similar neutral embryos. The charged clusters experience enhanced growth and stability as a consequence of electrostatic interactions. Simulations of a major nucleation event observed during the Pacific Exploratory Mission (PEM) Tropics-A can explain most of the observed features in the ultrafine particle behavior. The key parameters controlling this behavior are the concentrations of precursor vapors and the surface area of preexisting particles, as well as the background ionization rate. We find that systematic variations in ionization levels due to the modulation of galactic cosmic radiation by the solar cycle are sufficient to cause a notable variation in aerosol production. This effect is greatest when the ambient nucleation rate is limited principally by the availability of ions. Hence we conclude that the greatest influence of such ionization is likely to occur in and above the marine boundary layer. While a systematic change in the ultrafine particle production rate is likely to affect the population of cloud condensation nuclei and hence cloud optical properties, the magnitude of the effect cannot be directly inferred from the present analysis, and requires additional analysis based on specific aerosol-cloud interactions. [References: 85]
机译：我们调查背景电离的作用，主要与银河宇宙辐射有关，在海洋边界层中超细颗粒的产生和演化中。从分子团簇（带电荷和不带电荷）的最初建立到其生长成稳定的纳米颗粒，我们将遵循整个气溶胶演化过程。用于此目的的模型基于统一的碰撞（动力学）机制，该机制处理蒸气，中性团簇和带电团簇以及各种尺寸的粒子之间的相互作用。我们表明，空气离子可能在新的超细颗粒的形成中发挥核心作用。大气条件下气溶胶的成核过程涉及一系列竞争过程，包括分子聚集，蒸发和通过预先存在的颗粒清除。在这种高度敏感的非线性系统中，带电的胚胎比类似的中性胚胎具有竞争优势。带电簇由于静电相互作用而经历了增强的生长和稳定性。对太平洋探索任务（PEM）Tropics-A期间观察到的主要成核事件的模拟可以解释超细颗粒行为中大多数观察到的特征。控制此行为的关键参数是前体蒸气的浓度和预先存在的颗粒的表面积，以及背景电离速率。我们发现由于太阳周期对银河宇宙辐射的调制而导致的电离能级的系统变化足以引起气溶胶产量的显着变化。当环境成核速率主要受离子可用性限制时，此效果最大。因此，我们得出结论，这种电离的最大影响很可能发生在海洋边界层之内和之上。尽管超细颗粒产生速率的系统变化可能会影响云凝结核的数量，进而影响云的光学性质，但无法从当前分析中直接推断出影响的程度，并且需要基于特定的气溶胶-云进行其他分析互动。 [参考：85]

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