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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Phase transitions of sea-salt/water mixtures at low temperatures: Implications for ozone chemistry in the polar marine boundary layer
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Phase transitions of sea-salt/water mixtures at low temperatures: Implications for ozone chemistry in the polar marine boundary layer

机译：海盐/水混合物在低温下的相变：在极性海洋边界层中对臭氧化学的影响

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We present laboratory experiments employing differential scanning calorimetry as well as how cell microscopy to study the microphysics of aqueous NaCl and sea-salt solutions and droplets at temperatures below 273 K. The freezing and melting points of ice and other precipitates were determined in NaCl and sea-salt bulk samples as well as in emulsion samples. Using flow cell microscopy, we have determined the deliquescence and efflorescence relative humidities of NaCl and sea-salt droplets at temperatures between 249 and 773 K, extending the existing room temperature data to polar conditions. Our measurements suggest that sea-salt aerosols will most likely be liquid most of the time under polar marine boundary conditions. In addition, we show that sea-salt aerosols or seawater spray deposited on the polar ice pack will remain partly liquid down to 230 K, with concentrations of Cl- and Br- increasing by more than an order of magnitude upon cooling when compared to normal seawater concentrations. This is likely to enhance the rate at which heterogeneous bromine activation reactions occur in the sea-salt deposits. Such reaction rate enhancements with decreasing temperatures are currently not implemented in chemical models, and might help explain the fast bromine activation and subsequent ozone destruction observed during ozone depletion events in the polar marine boundary layer in spring. [References: 53]
机译：我们目前使用差示扫描量热法进行的实验室实验，以及如何用细胞显微镜研究温度低于273 K的NaCl和海盐溶液及液滴的微观物理。在NaCl和海中测定了冰和其他沉淀物的凝固点和熔点-盐散装样品以及乳液样品。使用流动池显微镜，我们确定了249至773 K之间的温度下，NaCl和海盐液滴的潮解和风化相对湿度，从而将现有的室温数据扩展到了极地条件。我们的测量结果表明，在极地海洋边界条件下，海盐气溶胶大部分时间都是液态的。此外，我们显示出沉积在极地冰袋上的海盐气溶胶或海水喷雾在低至230 K时仍会部分保持液态，与正常温度相比，冷却后Cl-和Br-的浓度增加超过一个数量级。海水浓度。这可能会提高在海盐沉积物中发生异质溴活化反应的速度。目前，这种化学反应速率随温度降低而提高的方法尚未在化学模型中实现，这可能有助于解释在春季极地海洋边界层中的臭氧消耗事件中观察到的快速溴活化和随后的臭氧破坏。 [参考：53]

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