Davis Ryan D, Tolbert Margaret A
Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Boulder, CO 80309, USA.
Department of Chemistry and Biochemistry, University of Colorado, Boulder, Boulder, CO 80309, USA.
Sci Adv. 2017 Jul 19;3(7):e1700425. doi: 10.1126/sciadv.1700425. eCollection 2017 Jul.
Particle collisions are a common occurrence in the atmosphere, but no empirical observations exist to fully predict the potential effects of these collisions on air quality and climate projections. The current consensus of heterogeneous crystal nucleation pathways relevant to the atmosphere dictates that collisions with amorphous particles have no effect on the crystallization relative humidity (RH) of aqueous inorganic aerosols because there is no stabilizing ion-surface interaction to facilitate the formation of crystal nuclei. In contrast to this view of heterogeneous nucleation, we report laboratory observations demonstrating that collisions with hydrophobic amorphous organic aerosols induced crystallization of aqueous inorganic microdroplets at high RH, the effect of which was correlated with destabilizing water-mediated ion-specific surface interactions. These same organic aerosols did not induce crystallization once internally mixed in the droplet, pointing toward a previously unconsidered transient ion-specific crystal nucleation pathway that can promote aerosol crystallization via particle collisions.
粒子碰撞在大气中很常见，但目前尚无实证观测结果能完全预测这些碰撞对空气质量和气候预测的潜在影响。当前关于与大气相关的异质晶核形成途径的共识表明，与无定形颗粒的碰撞对无机水气溶胶的结晶相对湿度（RH）没有影响，因为不存在稳定的离子-表面相互作用来促进晶核的形成。与这种异质成核观点不同，我们报告了实验室观察结果，表明与疏水性无定形有机气溶胶的碰撞在高相对湿度下会诱导无机微滴结晶，其效果与破坏水介导的离子特异性表面相互作用相关。一旦这些相同的有机气溶胶在液滴中内部混合，就不会诱导结晶，这指向了一种以前未被考虑的瞬态离子特异性晶核形成途径，该途径可通过粒子碰撞促进气溶胶结晶。
