Predicting the formation of ice in the atmosphere presents one of the great challenges in physical sciences with important implications for the chemistry and composition of the Earth’s atmosphere, the hydrological cycle, and climate. Among atmospheric ice formation processes, heterogeneous ice nucleation proceeds on aerosol particles ranging from a few nanometers to micrometers in size, commonly referred to as ice nucleating particles (INPs). Research over the last two decades has demonstrated that organic matter (OM) is ubiquitous in the atmosphere, present as organic aerosol (OA) particles or as coatings on other particle types. The physicochemical properties of OM make predicting how OM can contribute to the INP population challenging. This review focuses on the role of OM in INPs, summarizing and highlighting recent advances in our understanding of the ice nucleation process gained from theoretical, laboratory, and field studies. Examination of ice residuals and INPs with analytical techniques demonstrates that OM participates in atmospheric ice crystal formation. Molecular dynamic simulations provide insight into the microscopic processes that initiate ice nucleation. The amorphous phase state of OM in the supercooled and metastable regime is identified as a key factor in assessing the particles’ nucleation pathways and rates. A theoretical model is advanced, based on particle water activity, to holistically predict amorphous phase changes and ice nucleation rates of particles coated by OM. The goal of this review is to synthesize our current understanding and propose future research directions needed to fully evaluate how OA particles contribute to INPs in the atmosphere.

中文翻译：

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有机气溶胶在大气冰核中的作用

预测大气中冰的形成是物理科学的重大挑战之一，对地球大气的化学和组成，水文循环和气候具有重要意义。在大气冰的形成过程中，异质冰的成核作用是在几纳米到几微米大小的气溶胶颗粒上进行的，通常称为冰成核颗粒（INP）。过去二十年的研究表明，有机物（OM）在大气中无处不在，以有机气溶胶（OA）颗粒或其他颗粒类型的涂层形式存在。OM的理化特性使人们可以预测OM如何对INP人群提出挑战。这篇评论着重于OM在INP中的作用，总结并突出了我们从理论，实验室和现场研究中获得的对冰成核过程理解的最新进展。用分析技术检查冰残留物和INPs表明，OM参与了大气冰晶的形成。分子动力学模拟可洞悉引发冰核化的微观过程。在过冷和亚稳状态下，OM的非晶态被确定为评估颗粒成核途径和速率的关键因素。基于颗粒水活度，建立了一个理论模型，可以从整体上预测OM涂覆的颗粒的非晶相变化和冰成核速率。