Enhanced growth rate of atmospheric particles from sulfuric acid
Enhanced growth rate of atmospheric particles from sulfuric acid
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DOI：
10.5194/acp-20-7359-2020
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发表时间：
2020-06-25
影响因子：
6.3
通讯作者：
Winkler, Paul M.
中科院分区：
文献类型：
--
作者：
Stolzenburg, Dominik;Simon, Mario;Winkler, Paul M.
在当今大气中，硫酸是气溶胶粒子形成和初始增长的最重要的蒸汽。然而，从硫酸的纳米颗粒（< 10 nm）的生长速率仍然很难测量。因此，稳定碱的作用，离子的贡献和吸引力对分子碰撞的影响是有争议的。在这里，我们提出了精确的增长率测量不带电的硫酸颗粒从1.8到10纳米，在大气条件下进行的欧洲核子研究中心（欧洲核研究组织）云室。我们的研究结果表明，硫酸颗粒的蒸发超过2纳米是可以忽略不计的，和生长进行动力学，即使在低氨浓度。实验的增长率超过了硬球动力学限制硫酸的冷凝。我们证明，这是由于蒸汽分子和颗粒之间的货车德瓦尔斯力，并解开它从电荷偶极相互作用。增强的幅度取决于假设的颗粒水合和碰撞动力学，但在较小的尺寸越来越重要，导致在所观察到的增长率随尺寸减小而急剧上升。包括在一个全球模型的实验结果，我们发现，硫酸颗粒的增强增长率增加了预测的粒子数浓度在上部自由对流层超过50%。
In the present-day atmosphere, sulfuric acid is the most important vapour for aerosol particle formation and initial growth. However, the growth rates of nanoparticles (< 10 nm) from sulfuric acid remain poorly measured. Therefore, the effect of stabilizing bases, the contribution of ions and the impact of attractive forces on molecular collisions are under debate. Here, we present precise growth rate measurements of uncharged sulfuric acid particles from 1.8 to 10 nm, performed under atmospheric conditions in the CERN (European Organization for Nuclear Research) CLOUD chamber. Our results show that the evaporation of sulfuric acid particles above 2 nm is negligible, and growth proceeds kinetically even at low ammonia concentrations. The experimental growth rates exceed the hard-sphere kinetic limit for the condensation of sulfuric acid. We demonstrate that this results from van derWaals forces between the vapour molecules and particles and disentangle it from charge-dipole interactions. The magnitude of the enhancement depends on the assumed particle hydration and collision kinetics but is increasingly important at smaller sizes, resulting in a steep rise in the observed growth rates with decreasing size. Including the experimental results in a global model, we find that the enhanced growth rate of sulfuric acid particles increases the predicted particle number concentrations in the upper free troposphere by more than 50 %.