Immersion freezing of birch pollen washing water
Immersion freezing of birch pollen washing water
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DOI：
10.5194/acp-13-10989-2013
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发表时间：
2013-01-01
影响因子：
6.3
通讯作者：
Stratmann, F.
中科院分区：
文献类型：
--
作者：
Augustin, S.;Wex, H.;Stratmann, F.
桦树花粉是一种具有冰核活性的生物颗粒。冰成核活性以前一直被追踪到生物大分子，可以很容易地从水中的花粉粒中提取。在本研究中，我们研究了这些冰核活性（INA）大分子的浸没冻结行为。因此，我们在莱比锡气溶胶云相互作用模拟器（LACIS）中测量了桦树花粉洗涤水产生的颗粒的冷冻分数作为温度的函数。两种不同的桦树花粉样本被认为是，一个来自瑞典，一个来自捷克共和国。对于捷克和瑞典的桦树花粉样本，观察到冷冻分别在-19和-17摄氏度开始。对于两种样品，冷冻液滴的分数增加至-24 ° C。进一步冷却不再增加冷冻部分。相反，在低于1的冷冻级分处形成平台。这一事实可用于确定在这里检查的液滴中的INA大分子的量，这又允许确定单个INA大分子的成核速率。瑞典桦树花粉和捷克桦树花粉的主要差异在-17 ℃到-24 ℃之间的温度范围内是明显的。在这个范围内，可以看到瑞典桦树花粉的第二个高原地区。由于我们假设冰核大分子是冰核形成的原因，我们得出结论，桦树花粉能够产生至少两种不同类型的冰核大分子。我们能够推导出参数化的非均质成核速率为INA大分子类型，使用两种不同的方法：一个简单的指数拟合和足球模型。利用这些参数化方法，我们能够描述来自捷克和瑞典桦树花粉的单个INA大分子的冰核化行为。
Birch pollen grains are known to be ice nucleating active biological particles. The ice nucleating activity has previously been tracked down to biological macromolecules that can be easily extracted from the pollen grains in water. In the present study, we investigated the immersion freezing behavior of these ice nucleating active (INA) macromolecules. Therefore we measured the frozen fractions of particles generated from birch pollen washing water as a function of temperature at the Leipzig Aerosol Cloud Interaction Simulator (LACIS). Two different birch pollen samples were considered, with one originating from Sweden and one from the Czech Republic. For the Czech and Swedish birch pollen samples, freezing was observed to start at -19 and -17 degrees C, respectively. The fraction of frozen droplets increased for both samples down to -24 degrees C. Further cooling did not increase the frozen fractions any more. Instead, a plateau formed at frozen fractions below 1. This fact could be used to determine the amount of INA macromolecules in the droplets examined here, which in turn allowed for the determination of nucleation rates for single INA macromolecules. The main differences between the Swedish birch pollen and the Czech birch pollen were obvious in the temperature range between -17 and -24 degrees C. In this range, a second plateau region could be seen for Swedish birch pollen. As we assume INA macromolecules to be the reason for the ice nucleation, we concluded that birch pollen is able to produce at least two different types of INA macromolecules. We were able to derive parameterizations for the heterogeneous nucleation rates for both INA macromolecule types, using two different methods: a simple exponential fit and the Soccer ball model. With these parameterization methods we were able to describe the ice nucleation behavior of single INA macromolecules from both the Czech and the Swedish birch pollen.