Can chemically modified potassium feldspars nucleate ice?
Abstract
Ice clouds play an important role in the Earth's radiative budget and hence climate. Heterogeneous ice nucleation (IN), a major pathway for ice formation in cirrus and mixed-phase clouds, is inducedby active sites present on atmospheric aerosol particles termed as ice-nucleating particles. Despite the importance of mineral dusts for ice nucleation, the role of atmospheric aging (e.g. processing due to chemical species) on their IN efficiency is largely unknown. This is primarily due to the lack of obtaining microscopic level insight into nucleation from laboratory/field-based experiments due to the inability to experimentally access small spatial and temporal scale at which nucleation process occurs - a problem that can be potentially tackled with computer simulations. We utilize Direct Molecular Dynamics (MD) simulations (GROMACS 5.1.4) to investigate the effects of solutes on different surfaces of potassium feldspar mineral in the microcline phase (one the most effective ice nucleator) and interfacial water structure at a microscopic scale. The interaction of water/solutions with mineral surfaces can influence the IN ability of mineral surfaces. This ongoing work investigates the interactions of monovalent cations (H3O+, Li+, Na+, K+, Cs+, NH4+) with (001), (010) and (100) surfaces of microcline, and its subsequent effects on the near-surface water structure at 300 K. In addition, we examine the structure of supercooled water (230 K) in contact with the aforementioned surfaces after being equilibrated with the ions at 300 K. Feldspar is modeled with the widely used CLAYFF force field, and the TIP4P/Ice model is employed for water. Preliminary results show that NH4+ has the strongest affinity for the surfaces - either via ion exchange (with native K+) or adsorption. The extent of exchange/adsorption is a function of hydrated cation size, cation charge distribution, time of exposure and the thickness of mineral layer investigated. The modified microcline surfaces (after interacting with ions) are likely to affect the structure of supercooled water (230 K). Hence, the current work will provide us an improved understanding of the processes modifying the mineral surfaces in water and aqueous solutions and its subsequent impacts on ice formation.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMA011.0013K
- Keywords:
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- 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSES;
- 3337 Global climate models;
- ATMOSPHERIC PROCESSES;
- 3359 Radiative processes;
- ATMOSPHERIC PROCESSES;
- 3360 Remote sensing;
- ATMOSPHERIC PROCESSES