Department of Chemistry, The Pennsylvania State University, University Park, PA, 16802, USA.
Department of Meteorology and Atmospheric Science, The Pennsylvania State University, University Park, PA, 16802, USA.
Phys Chem Chem Phys. 2023 Apr 26;25(16):11442-11451. doi: 10.1039/d2cp05466c.
Heterogeneous ice nucleation in the atmosphere impacts climate, but the magnitude of the effect of ice clouds on radiative forcing is uncertain. Surfaces that promote ice nucleation are varied. Because O, Si, and Al are the most abundant elements in the Earth's crust, understanding how the Si : Al ratio impacts the ice nucleation activity of aluminosilicates through exploration of synthetic ZSM-5 samples provides a good model system. This paper investigates the immersion freezing of ZSM-5 samples with varying Si : Al ratios. Ice nucleation temperature increases with increasing surface Al content. Additionally, when ammonium, a common cation in aerosol particles, is adsorbed to the zeolite surface, initial freezing temperatures are reduced by up to 6 °C in comparison to proton-terminated zeolite surfaces. This large decrease in ice nucleation activity in the presence of ammonium suggests that the cation can interact with the surface to block or modify active sites. Our results on synthetic samples in which the surface composition is tunable gives insight into the role of surfaces in heterogeneous ice nucleation processes in the atmosphere. We emphasize the importance of examining surface chemical heterogeneities in ice nucleating particles that could result from a variety of aging pathways for a deeper understanding of the freezing mechanism.
大气中的非均相冰核会影响气候，但冰云对辐射强迫的影响程度尚不确定。促进冰核形成的表面多种多样。由于 O、Si 和 Al 是地壳中最丰富的元素，因此通过探索合成 ZSM-5 样品来了解 Si:Al 比对铝硅酸盐冰核活性的影响提供了一个很好的模型系统。本文研究了具有不同 Si:Al 比的 ZSM-5 样品的浸没式冻结。冰核形成温度随表面 Al 含量的增加而升高。此外，当气溶胶颗粒中常见的阳离子铵吸附到沸石表面时，与质子终止的沸石表面相比，初始冻结温度降低了多达 6°C。在存在铵的情况下，冰核活性的这种大幅降低表明阳离子可以与表面相互作用以阻止或修饰活性位点。我们对表面组成可调的合成样品的研究结果深入了解了大气中非均相冰核形成过程中表面的作用。我们强调了研究冰核形成颗粒中表面化学不均匀性的重要性，这可能是由于各种老化途径导致的，以便更深入地了解冻结机制。
