Water-soluble organic compounds (WSOCs) readily uptake water and form atmospheric droplets. Understanding the water-uptake ability of these WSOCs can improve our understanding of their radiative effects and thus can improve current climate models. In this study, we measure the subsaturated and supersaturated droplet growth of four WSOCs: levoglucosan, sucrose, raffinose, and trehalose. Specifically, we use three distinct nanoscale droplet growth methods: cavity ring-down spectroscopy (CRDS), hygroscopic tandem differential mobility analysis (H-TDMA), and cloud condensation nuclei (CCN) counting and report optical growth factor (fRH), growth factor (G_f), refractive indices, and critical activation diameters (d_p50) for each aerosol system. Köhler theory (assuming a droplet surface tension equal to that of pure water) is applied to all droplet growth measurements, and the single-parameter hygroscopicity, κ, is reported for the four WSOCs measured on the different platforms. The three experimental methods measure decreased hygroscopicity with an increase in WSOC molecular weight. When assuming the droplets are dilute, κ values from measurements are consistent with known values. The three experimental methods have comparable precision with systematic deviations in the average κ for each method. Few studies have employed fRH data to obtain κ values. The current two methods to estimate κ from fRH data produce similar results, are dry aerosol size-dependent, and agree with κ values that assume dilute solution behavior. Thus, the presented measured data set and analysis contribute to the comparison of subsaturated and supersaturated data from optical and geometric methods for organic aerosol.

中文翻译：

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直接比较水溶性糖的亚微米气溶胶吸湿性

水溶性有机化合物（WSOC）容易吸收水并形成大气液滴。了解这些WSOC的吸水能力可以增进我们对其辐射效应的了解，从而可以改善当前的气候模型。在这项研究中，我们测量了四种WSOC的亚饱和和过饱和液滴生长：左旋葡聚糖，蔗糖，棉子糖和海藻糖。具体来说，我们使用三种不同的纳米级液滴生长方法：腔衰荡光谱（CRDS），吸湿串联微分迁移率分析（H-TDMA）和云凝结核（CCN）计数并报告光学生长因子（f RH），生长系数（G _f），折射率和临界激活直径（d _p50）的每个喷雾系统。将Köhler理论（假设液滴表面张力等于纯水的张力）应用于所有液滴的生长测量，并报告在不同平台上测量的四个WSOC的单参数吸湿率κ。三种实验方法测量的吸湿性随WSOC分子量的增加而降低。当假设液滴被稀释时，来自测量的κ值与已知值一致。三种实验方法具有相当的精度，每种方法的平均κ有系统偏差。很少有研究使用f RH数据获得κ值。当前从f估计κ的两种方法RH数据产生相似的结果，取决于干燥的气溶胶大小，并且与假定稀溶液行为的κ值一致。因此，提出的测量数据集和分析有助于比较来自有机气溶胶光学方法和几何方法的亚饱和和过饱和数据。