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- Bartels-Rausch, T., et al.
(författare)
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A review of air-ice chemical and physical interactions (AICI): Liquids, quasi-liquids, and solids in snow
- 2014
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 14:3, s. 1587-1633
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Tidskriftsartikel (refereegranskat)abstract
- Snow in the environment acts as a host to rich chemistry and provides a matrix for physical exchange of contaminants within the ecosystem. The goal of this review is to summarise the current state of knowledge of physical processes and chemical reactivity in surface snow with relevance to polar regions. It focuses on a description of impurities in distinct compartments present in surface snow, such as snow crystals, grain boundaries, crystal surfaces, and liquid parts. It emphasises the microscopic description of the ice surface and its link with the environment. Distinct differences between the disordered air-ice interface, often termed quasi-liquid layer, and a liquid phase are highlighted. The reactivity in these different compartments of surface snow is discussed using many experimental studies, simulations, and selected snow models from the molecular to the macro-scale. Although new experimental techniques have extended our knowledge of the surface properties of ice and their impact on some single reactions and processes, others occurring on, at or within snow grains remain unquantified. The presence of liquid or liquid-like compartments either due to the formation of brine or disorder at surfaces of snow crystals below the freezing point may strongly modify reaction rates. Therefore, future experiments should include a detailed characterisation of the surface properties of the ice matrices. A further point that remains largely unresolved is the distribution of impurities between the different domains of the condensed phase inside the snowpack, i.e. in the bulk solid, in liquid at the surface or trapped in confined pockets within or between grains, or at the surface. While surface-sensitive laboratory techniques may in the future help to resolve this point for equilibrium conditions, additional uncertainty for the environmental snowpack may be caused by the highly dynamic nature of the snowpack due to the fast metamorphism occurring under certain environmental conditions. Due to these gaps in knowledge the first snow chemistry models have attempted to reproduce certain processes like the long-term incorporation of volatile compounds in snow and firn or the release of reactive species from the snowpack. Although so far none of the models offers a coupled approach of physical and chemical processes or a detailed representation of the different compartments, they have successfully been used to reproduce some field experiments. A fully coupled snow chemistry and physics model remains to be developed. © Author(s) 2014.
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| 2. |
- Kong, Xiangrui, et al.
(författare)
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A surface-promoted redox reaction occurs spontaneously on solvating inorganic aerosol surfaces
- 2021
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 374:6568
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Tidskriftsartikel (refereegranskat)abstract
- A surface-promoted sulfate-reducing ammonium oxidation reaction was discovered to spontaneously take place on common inorganic aerosol surfaces undergoing solvation. Several key intermediate species-including elemental sulfur (S-0), bisulfide (HS-), nitrous acid (HONO), and aqueous ammonia [NH3(aq)]-were identified as reaction components associated with the solvation process. Depth profiles of relative species abundance showed the surface propensity of key species. The species assignments and depth profile features were supported by classical and first-principles molecular dynamics calculations, and a detailed mechanism was proposed to describe the processes that led to unexpected products during salt solvation. This discovery revealed chemistry that is distinctly linked to a solvating surface and has great potential to illuminate current puzzles within heterogeneous chemistry.
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| 3. |
- Kong, Xiangrui, et al.
(författare)
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Adsorbed Water Promotes Chemically Active Environments on the Surface of Sodium Chloride
- 2023
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Ingår i: Journal of Physical Chemistry Letters. - 1948-7185. ; 14:26, s. 6151-6156
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Tidskriftsartikel (refereegranskat)abstract
- Gas-particleinterfaces are chemically active environments.This study investigates the reactivity of SO2 on NaCl surfacesusing advanced experimental and theoretical methods with a NH4Cl substrate also examined for cation effects. Results showthat NaCl surfaces rapidly convert to Na2SO4 with a new chlorine component when exposed to SO2 underlow humidity. In contrast, NH4Cl surfaces have limitedSO(2) uptake and do not change significantly. Depth profilesreveal transformed layers and elemental ratios at the crystal surfaces.The chlorine species detected originates from Cl- expelled from the NaCl crystal structure, as determined by atomisticdensity functional theory calculations. Molecular dynamics simulationshighlight the chemically active NaCl surface environment, driven bya strong interfacial electric field and the presence of sub-monolayerwater coverage. These findings underscore the chemical activity ofsalt surfaces and the unexpected chemistry that arises from theirinteraction with interfacial water, even under very dry conditions.
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