The ice-nucleating ability of quartz immersed in water and its atmospheric importance compared to K-feldspar
The ice-nucleating ability of quartz immersed in water and its atmospheric importance compared to K-feldspar
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DOI：
10.5194/acp-19-11343-2019
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发表时间：
2019-09-09
影响因子：
6.3
通讯作者：
Murray, Benjamin J.
中科院分区：
文献类型：
--
作者：
Harrison, Alexander D.;Lever, Katherine;Murray, Benjamin J.
矿物尘埃粒子被认为是地球仪周围混合相云体系中一种重要的冰核粒子。虽然富钾长石（K-长石）已被确定为是一个特别重要的成分，矿物粉尘的冰成核，它已被证明，石英也是相对的冰成核活性。考虑到石英通常构成大气沙漠尘埃的很大一部分，它可能对云冰川作用很重要。在这里，我们调查了10个α-石英样品（最常见的石英多晶型物）浸入微升过冷水滴时的冰成核能力。尽管所有的样品都是α-石英，但对于恒定的活性位点密度，它们诱导冻结的温度变化约12摄氏度。我们发现，一些石英样品是非常敏感的水悬浮液和空气中的老化，导致冰成核活性的损失，而其他样品是不敏感的暴露于空气和水在许多个月。例如，一个石英样品的冰成核温度在1小时内下降了2摄氏度，在水中16个月后下降了12摄氏度。对水和空气的敏感性可能是令人惊讶的，因为石英被认为是一种耐化学腐蚀的矿物，但这一观察表明，负责成核的活性部位不如矿物的主体稳定。我们发现，石英类矿物的活性通常比钾长石低约7摄氏度，尽管最活跃的石英样品具有与某些K-石英晶石相似的活性，活性部位密度n（s）（T）在-9 ℃时为1 cm（-2）。我们还发现，新鲜研磨的石英样品通常比斜长石组矿物更活跃约5摄氏度，钠长石端元具有中间活性。使用新的和文献数据，活性位点密度参数化已被提出为新鲜研磨石英，钾长石，斜长石和钠长石。结合这些参数化与典型的大气中每种矿物的丰度支持以前的工作，这表明钾长石是最重要的冰成核矿物在空气中的矿物尘埃。
Mineral dust particles are thought to be an important type of ice-nucleating particle (INP) in the mixed-phase cloud regime around the globe. While K-rich feldspar (K-feldspar) has been identified as being a particularly important component of mineral dust for ice nucleation, it has been shown that quartz is also relatively ice-nucleation active. Given quartz typically makes up a substantial proportion of atmospheric desert dust, it could potentially be important for cloud glaciation. Here, we survey the ice-nucleating ability of 10 alpha-quartz samples (the most common quartz polymorph) when immersed in microlitre supercooled water droplets. Despite all samples being alpha-quartz, the temperature at which they induce freezing varies by around 12 degrees C for a constant active site density. We find that some quartz samples are very sensitive to ageing in both aqueous suspension and air, resulting in a loss of ice-nucleating activity, while other samples are insensitive to exposure to air and water over many months. For example, the ice-nucleation temperatures for one quartz sample shift down by similar to 2 degrees C in 1 h and 12 degrees C after 16 months in water. The sensitivity to water and air is perhaps surprising, as quartz is thought of as a chemically resistant mineral, but this observation suggests that the active sites responsible for nucleation are less stable than the bulk of the mineral. We find that the quartz group of minerals is generally less active than K-feldspars by roughly 7 degrees C, although the most active quartz samples are of a similar activity to some K-feldspars with an active site density, n(s)(T), of 1 cm(-2) at -9 degrees C. We also find that the freshly milled quartz samples are generally more active by roughly 5 degrees C than the plagioclase feldspar group of minerals and the albite end member has an intermediate activity. Using both the new and literature data, active site density parameterizations have been proposed for freshly milled quartz, K-feldspar, plagioclase and albite. Combining these parameterizations with the typical atmospheric abundance of each mineral supports previous work that suggests that K-feldspar is the most important ice-nucleating mineral in airborne mineral dust.