Laboratory-generated mixtures of mineral dust particles with biological substances: characterization of the particle mixing state and immersion freezing behavior
Laboratory-generated mixtures of mineral dust particles with biological substances: characterization of the particle mixing state and immersion freezing behavior
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DOI：
10.5194/acp-16-5531-2016
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发表时间：
2016-01-01
影响因子：
6.3
通讯作者：
Stratmann, Frank
中科院分区：
文献类型：
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作者：
Augustin-Bauditz, Stefanie;Wex, Heike;Stratmann, Frank
已知生物颗粒如细菌、真菌孢子或花粉是有效的冰成核颗粒。它们使冰成核的能力是由于冰成核活性大分子（INMs）。有人建议，这些INM保持其成核能力，即使当它们从它们的原始载体分离。这就有可能使这种INMs在土壤中积累，导致矿物粉尘和INMs的内部混合物。如果来自含有生物INM的此类土壤的颗粒随后由于风蚀或农业过程而分散到大气中，则它们可能在生物物质的典型温度下诱导冰成核，即，我们在INUIT（Ice Nucleation research UnIT）研究单位内进行了一项研究，在那里我们调查了与INM内部混合的矿物尘埃颗粒的冰成核行为。具体而言，我们混合了纯矿物粉尘样品（伊利石-NX）与冰活性生物材料（桦树花粉洗涤水），并利用莱比锡气溶胶云相互作用模拟器（LACIS）量化所得颗粒的浸没冷冻行为。一个非常重要的主题，有关的调查，以及在大气中的应用是气溶胶粒子的混合状态的特性。在本研究中，我们使用了不同的方法，如单颗粒气溶胶质谱，扫描电子显微镜（SEM），能量色散X射线分析（EDX），和挥发性吸湿性串联差分迁移率分析仪（VH-TDMA），以调查我们产生的气溶胶的混合状态。并非所有应用的方法在检测矿物粉尘颗粒上的少量生物材料方面都表现得同样好。用VH-TDMA测量混合颗粒的吸湿性/挥发性是最灵敏的方法。我们发现，内部混合颗粒，含有冰活性生物材料，遵循观察到的纯生物颗粒的冰成核行为。我们验证了这一点，通过模拟与足球模型（SBM）的混合颗粒的冻结行为。可以得出结论，位于矿物尘埃颗粒上的单个INM决定了该颗粒的冻结行为，结果是在纯矿物尘埃颗粒尚未具有冰活性的温度下发生冻结。
Biological particles such as bacteria, fungal spores or pollen are known to be efficient ice nucleating particles. Their ability to nucleate ice is due to ice nucleation active macromolecules (INMs). It has been suggested that these INMs maintain their nucleating ability even when they are separated from their original carriers. This opens the possibility of an accumulation of such INMs in soils, resulting in an internal mixture of mineral dust and INMs. If particles from such soils which contain biological INMs are then dispersed into the atmosphere due to wind erosion or agricultural processes, they could induce ice nucleation at temperatures typical for biological substances, i.e., above -20 up to almost 0aEuro-A degrees C, while they might be characterized as mineral dust particles due to a possibly low content of biological material.We conducted a study within the research unit INUIT (Ice Nucleation research UnIT), where we investigated the ice nucleation behavior of mineral dust particles internally mixed with INM. Specifically, we mixed a pure mineral dust sample (illite-NX) with ice active biological material (birch pollen washing water) and quantified the immersion freezing behavior of the resulting particles utilizing the Leipzig Aerosol Cloud Interaction Simulator (LACIS). A very important topic concerning the investigations presented here as well as for atmospheric application is the characterization of the mixing state of aerosol particles. In the present study we used different methods like single-particle aerosol mass spectrometry, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray analysis (EDX), and a Volatility-Hygroscopicity Tandem Differential Mobility Analyser (VH-TDMA) to investigate the mixing state of our generated aerosol. Not all applied methods performed similarly well in detecting small amounts of biological material on the mineral dust particles. Measuring the hygroscopicity/volatility of the mixed particles with the VH-TDMA was the most sensitive method. We found that internally mixed particles, containing ice active biological material, follow the ice nucleation behavior observed for the pure biological particles. We verified this by modeling the freezing behavior of the mixed particles with the Soccerball model (SBM). It can be concluded that a single INM located on a mineral dust particle determines the freezing behavior of that particle with the result that freezing occurs at temperatures at which pure mineral dust particles are not yet ice active.