加拿大萨斯喀彻温大学Tara F. Kahan团队直接观测了冰表面的蒽团簇。相关研究成果发表在2022年1月4日出版的国际知名学术期刊《美国化学会杂志》。

非均匀过程可以控制大气成分。雪和冰是重要的反应介质，但人们对此知之甚少，它们可以极大地改变极地和温带地区冰层中的空气成分。在冰雪覆盖地区，大气科学家努力将模型预测与现场观测相协调，部分原因是与监测空气-冰界面反应相关的实验挑战，关于反应动力学和机制的争论已经持续了十多年。

该文中，研究人员使用波长分辨荧光显微镜来确定环境相关冻结表面上污染物蒽的分布和化学形态。结果表明，蒽以单体形式吸附到冻结表面，但在横向扩散后，分子最终位于盐水冰面的盐水通道中，而在淡水冰面则位于微米大小的团簇中；发射剖面表明广泛的自关联。

研究人员还测量了蒽在水溶液和由冷冻淡水和盐水溶液制备的人造雪中的光降解动力学。研究结果表明蒽以及其他可能的芳香污染物在淡水冰和海冰表面发生双分子光降解，但在冷冻有机物表面不发生。研究结果将改善对冰层中污染物归宿和暴露风险的预测。所使用的技术可应用于大气科学内外的许多表面。

附：英文原文

Title: Direct Observation of Anthracene Clusters at Ice Surfaces

Author: Subha Chakraborty, Annastacia D. Stubbs, Tara F. Kahan

Issue&Volume: January 4, 2022

Abstract: Heterogeneous processes can control atmospheric composition. Snow and ice present important, but poorly understood, reaction media that can greatly alter the composition of air in the cryosphere in polar and temperate regions. Atmospheric scientists struggle to reconcile model predictions with field observations in snow-covered regions due in part to experimental challenges associated with monitoring reactions at air–ice interfaces, and debate regarding reaction kinetics and mechanisms has persisted for over a decade. In this work, we use wavelength-resolved fluorescence microscopy to determine the distribution and chemical speciation of the pollutant anthracene at environmentally relevant frozen surfaces. Our results indicate that anthracene adsorbs to frozen surfaces in monomeric form, but that following lateral diffusion, molecules ultimately reside within brine channels at saltwater ice surfaces, and in micron-sized clusters at freshwater ice surfaces; emission profiles indicate extensive self-association. We also measure anthracene photodegradation kinetics in aqueous solution and artificial snow prepared from frozen freshwater and saltwater solutions. Our results suggest that anthracene─and likely other aromatic pollutants─undergo bimolecular photodegradation at the surface of freshwater ice and sea ice, but not at the surface of frozen organic matter. These results will improve predictions of pollutant fate and exposure risk in the cryosphere. The techniques used can be applied to numerous surfaces within and beyond the atmospheric sciences.

DOI: 10.1021/jacs.1c09220

Source: https://pubs.acs.org/doi/10.1021/jacs.1c09220