Evaporating brine from frost flowers with electron microscopy and implications for atmospheric chemistry and sea-salt aerosol formation
| Autor: | Jiří Runštuk, Ján Krausko, Vilém Neděla, Dominik Heger, Gabriela Ondrušková, Ľubica Vetráková, Xin Yang |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
Atmospheric Science
Bromine 010504 meteorology & atmospheric sciences Ice crystals Chemistry Mineralogy chemistry.chemical_element 02 engineering and technology 010501 environmental sciences Atmospheric temperature range 021001 nanoscience & nanotechnology 01 natural sciences lcsh:QC1-999 lcsh:Chemistry Brine lcsh:QD1-999 13. Climate action Atmospheric chemistry Ice nucleus 0210 nano-technology Sea salt aerosol Environmental scanning electron microscope lcsh:Physics 0105 earth and related environmental sciences |
| Zdroj: | Atmospheric Chemistry and Physics, Vol 17, Iss 10, Pp 6291-6303 (2017) |
| ISSN: | 1680-7324 1680-7316 |
| Popis: | An environmental scanning electron microscope was used for the first time to obtain well-resolved images, in both temporal and spatial dimensions, of lab-prepared frost flowers (FFs) under evaporation within the chamber temperature range from −5 °C to −18 °C and pressures above 500 Pa. Our scanning shows temperature-dependent NaCl speciation: the brine covering the ice was observed at all conditions, whereas the NaCl crystals were formed at temperatures below −10 °C as the brine oversaturation was achieved. Finger-like ice structures covered by the brine, with a diameter of several micrometres and length of tens to one hundred micrometres, are exposed to the ambient air. The brine-covered fingers are highly flexible and cohesive. The exposure of the liquid brine on the micrometric fingers indicates a significant increase in the brine surface area compared to that of the flat ice surface at high temperatures, whereas the NaCl crystals can become sites of heterogeneous reactivity at lower temperatures. There is no evidence that, without external forces, salty FFs could automatically fall apart to create a number of sub-particles at the scale of micrometres as the exposed brine fingers seem cohesive and hard to break in the middle. The fingers tend to combine together to form large spheres and then join back to the mother body, eventually forming a large chunk of salt after complete dehydration. A present microscopic observation rationalizes several previously unexplained observations, namely, that FFs are not a direct source of sea salt aerosols and that saline ice crystals under evaporation could accelerate the heterogeneous reactions of bromine liberation. |
| Databáze: | OpenAIRE |
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