Coal fly ash: linking immersion freezing behavior and physicochemical particle properties
Coal fly ash: linking immersion freezing behavior and physicochemical particle properties
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DOI：
10.5194/acp-18-13903-2018
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发表时间：
2018-10
影响因子：
6.3
通讯作者：
Sarah Grawe;S. Augustin-Bauditz;Hans-Christian Clemen;M. Ebert;Stine Eriksen Hammer;Jasmin Lubitz;N. Reicher;Y. Rudich;J. Schneider;R. Staacke;F. Stratmann;A. Welti;H. Wex
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作者：
Sarah Grawe;S. Augustin-Bauditz;Hans-Christian Clemen;M. Ebert;Stine Eriksen Hammer;Jasmin Lubitz;N. Reicher;Y. Rudich;J. Schneider;R. Staacke;F. Stratmann;A. Welti;H. Wex
抽象的。到目前为止，只有几项研究调查了煤飞灰颗粒在云滴中引发异质冰核的可能性。所提供的测量旨在扩展稀疏数据集，并提高对物理化学颗粒特性如何影响浸入水中的飞灰颗粒的冻结行为的过程的理解。首先，利用莱比锡气溶胶云相互作用模拟器(LAIS)和冰核光谱仪(SPIN)这两种单粒子技术进行了浸没冻结实验。根据两种仪器的停留时间不同，采用干法和湿法两种方法，分析了悬浮时间对浸泡在云滴中的飞灰粒子效率的影响。其次，应用了两个冷级装置，一个使用微升大小的液滴(莱比锡冰核阵列)，另一个使用纳升大小的液滴(在微阵列上观察到的魏兹曼过冷液滴)。我们发现，在干燥生成时，煤飞灰颗粒的浸泡冻结行为与矿物粉尘相当。然而，在用Lacis和Spin中的湿生成颗粒进行实验时，观察到浸泡冻结效率显著下降。湿法生成粒子的效率与冷态测量结果一致。为了了解失活的原因，对湿法和干法生成的颗粒进行了一系列的化学成分、形貌和结晶学分析(单颗粒质谱分析、扫描电子显微镜与能量色散X射线显微分析、X射线衍射分析)。从这些研究中，我们得出结论，无水CaSO4和CaO-如果以纯形式研究，表现出与观察到的干法生成的飞灰颗粒相同的定性浸泡冻结行为-有助于触发颗粒-水界面的非均相成冰。观察到的与水接触时的失活与颗粒表面性质的变化有关，这可能是由CaSO4和CaO的水化引起的。因此，飞灰对周围冰核粒子数量的贡献取决于粒子是否浸泡在云滴中以及浸入云滴的时间有多长。
Abstract. To date, only a few studies have investigated the potential of coal fly ash particles to trigger heterogeneous ice nucleation in cloud droplets. The presented measurements aim at expanding the sparse dataset and improving process understanding of how physicochemical particle properties can influence the freezing behavior of coal fly ash particles immersed in water. Firstly, immersion freezing measurements were performed with two single particle techniques, i.e., the Leipzig Aerosol Cloud Interaction Simulator (LACIS) and the SPectrometer for Ice Nuclei (SPIN). The effect of suspension time on the efficiency of the coal fly ash particles when immersed in a cloud droplet is analyzed based on the different residence times of the two instruments and employing both dry and wet particle generation. Secondly, two cold-stage setups, one using microliter sized droplets (Leipzig Ice Nucleation Array) and one using nanoliter sized droplets (WeIzmann Supercooled Droplets Observation on Microarray setup) were applied. We found that coal fly ash particles are comparable to mineral dust in their immersion freezing behavior when being dry generated. However, a significant decrease in immersion freezing efficiency was observed during experiments with wet-generated particles in LACIS and SPIN. The efficiency of wet-generated particles is in agreement with the cold-stage measurements. In order to understand the reason behind the deactivation, a series of chemical composition, morphology, and crystallography analyses (single particle mass spectrometry, scanning electron microscopy coupled with energy dispersive X-ray microanalysis, X-ray diffraction analysis) were performed with dry- and wet-generated particles. From these investigations, we conclude that anhydrous CaSO4 and CaO – which, if investigated in pure form, show the same qualitative immersion freezing behavior as observed for dry-generated coal fly ash particles – contribute to triggering heterogeneous ice nucleation at the particle–water interface. The observed deactivation in contact with water is related to changes in the particle surface properties which are potentially caused by hydration of CaSO4 and CaO. The contribution of coal fly ash to the ambient population of ice-nucleating particles therefore depends on whether and for how long particles are immersed in cloud droplets.