Not all feldspars are equal: a survey of ice nucleating properties across the feldspar group of minerals
Not all feldspars are equal: a survey of ice nucleating properties across the feldspar group of minerals
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DOI：
10.5194/acp-16-10927-2016
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发表时间：
2016-09-05
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.;Whale, Thomas F.;Murray, Benjamin J.
来自风吹土壤的矿物粉尘颗粒在大气中被认为是有效的冰核颗粒，并且被认为在混合相云的冰川作用中起重要作用。最近的研究表明，长石是大气矿物粉尘中常见的矿物最有效的成核剂。然而，长石矿物群是复杂的，包括一系列的化学成分和晶体结构。为了进一步研究长石群的冰核性质，我们测量了15个具有特征的长石样品的冰核活性。我们发现碱长石，特别是钾长石，通常比斜长石系列中含有大量钙的长石更有效地成核冰。我们还发现，在这些群体中，冰的成核能力是不同的。六种富钾长石中有五种具有相似的冰成核能力，一种富钾长石样品和一种富钠长石样品的冰成核活性明显更高。高活性钠长石在水中悬浮时间越长，活性越弱，16个月内平均冻结温度降低约16℃；高活性钾长石的平均冻结温度在16个月内下降了2℃，而“标准”钾长石在实验的不确定度内没有改变活性。这些结果，结合对现有文献数据的回顾，与先前的发现一致，钾长石是干旱或肥沃土壤尘埃冰核的重要组成部分。然而，我们也表明，一些碱长石可能具有增强的冰成核能力，这可能对大气中冰成核颗粒浓度的预测有影响。
Mineral dust particles from wind-blown soils are known to act as effective ice nucleating particles in the atmosphere and are thought to play an important role in the glaciation of mixed phase clouds. Recent work suggests that feldspars are the most efficient nucleators of the minerals commonly present in atmospheric mineral dust. However, the feldspar group of minerals is complex, encompassing a range of chemical compositions and crystal structures. To further investigate the ice-nucleating properties of the feldspar group we measured the ice nucleation activities of 15 characterized feldspar samples. We show that alkali feldspars, in particular the potassium feldspars, generally nucleate ice more efficiently than feldspars in the plagioclase series which contain significant amounts of calcium. We also find that there is variability in ice nucleating ability within these groups. While five out of six potassium-rich feldspars have a similar ice nucleating ability, one potassium rich feldspar sample and one sodium-rich feldspar sample were significantly more active. The hyper-active Na-feldspar was found to lose activity with time suspended in water with a decrease in mean freezing temperature of about 16 degrees C over 16 months; the mean freezing temperature of the hyper-active K-feldspar decreased by 2 degrees C over 16 months, whereas the "standard" K-feldspar did not change activity within the uncertainty of the experiment. These results, in combination with a review of the available literature data, are consistent with the previous findings that potassium feldspars are important components of arid or fertile soil dusts for ice nucleation. However, we also show that there is the possibility that some alkali feldspars may have enhanced ice nucleating abilities, which could have implications for prediction of ice nucleating particle concentrations in the atmosphere.