Herich Hanna, Tritscher Torsten, Wiacek Aldona, Gysel Martin, Weingartner Ernest, Lohmann Ulrike, Baltensperger Urs, Cziczo Daniel J
Institute for Atmospheric and Climate Science, ETH Zurich, CH-8092, Zurich, Switzerland.
Phys Chem Chem Phys. 2009 Sep 28;11(36):7804-9. doi: 10.1039/b901585j. Epub 2009 Apr 1.
Airborne mineral dust particles serve as cloud condensation nuclei (CCN), thereby influencing the formation and properties of warm clouds. It is therefore of atmospheric interest how dust aerosols with different mineralogy behave when exposed to high relative humidity (RH) or supersaturation (SS) with respect to liquid water. In this study the subsaturated hygroscopic growth and the supersaturated cloud condensation nucleus activity of pure clays and real desert dust aerosols were determined using a hygroscopicity tandem differential mobility analyzer (HTDMA) and a cloud condensation nuclei counter (CCNC), respectively. Five different illite, montmorillonite and kaolinite clay samples as well as three desert dust samples (Saharan dust (SD), Chinese dust (CD) and Arizona test dust (ATD)) were investigated. Aerosols were generated both with a wet and a dry disperser. The water uptake was parameterized via the hygroscopicity parameter kappa. The hygroscopicity of dry generated dust aerosols was found to be negligible when compared to processed atmospheric aerosols, with CCNC derived kappa values between 0.00 and 0.02 (the latter corresponds to a particle consisting of 96.7% by volume insoluble material and approximately 3.3% ammonium sulfate). Pure clay aerosols were generally found to be less hygroscopic than natural desert dust particles. The illite and montmorillonite samples had kappa approximately 0.003. The kaolinite samples were less hygroscopic and had kappa=0.001. SD (kappa=0.023) was found to be the most hygroscopic dry-generated desert dust followed by CD (kappa=0.007) and ATD (kappa=0.003). Wet-generated dust showed an increased water uptake when compared to dry-generated samples. This is considered to be an artifact introduced by redistribution of soluble material between the particles. Thus, the generation method is critically important when presenting such data. These results indicate any atmospheric processing of a fresh mineral dust particle which leads to the addition of more than approximately 3% soluble material will significantly enhance its hygroscopicity and CCN activity.
空气中的矿物尘埃颗粒充当云凝结核（CCN），从而影响暖云的形成和特性。因此，对于不同矿物学组成的尘埃气溶胶在暴露于相对于液态水的高相对湿度（RH）或过饱和度（SS）时的行为，大气科学界很感兴趣。在本研究中，分别使用吸湿性串联差分迁移率分析仪（HTDMA）和云凝结核计数器（CCNC）测定了纯粘土和真实沙漠尘埃气溶胶的亚饱和吸湿增长和过饱和云凝结核活性。研究了五种不同的伊利石、蒙脱石和高岭土粘土样品以及三种沙漠尘埃样品（撒哈拉尘埃（SD）、中国尘埃（CD）和亚利桑那试验尘（ATD））。气溶胶通过湿式和干式分散器产生。通过吸湿性参数κ对吸水量进行参数化。与经过处理的大气气溶胶相比，发现干式产生的尘埃气溶胶的吸湿性可忽略不计，CCNC得出的κ值在0.00至0.02之间（后者对应于一个由96.7%（体积）不溶性物质和大约3.3%硫酸铵组成的颗粒）。一般发现纯粘土气溶胶的吸湿性低于天然沙漠尘埃颗粒。伊利石和蒙脱石样品的κ约为0.003。高岭土样品的吸湿性较低，κ=0.001。发现SD（κ=0.023）是吸湿性最强的干式产生的沙漠尘埃，其次是CD（κ=0.007）和ATD（κ=0.003）。与干式产生的样品相比，湿式产生的尘埃显示出吸水量增加。这被认为是颗粒间可溶性物质重新分布引入的假象。因此，在呈现此类数据时，产生方法至关重要。这些结果表明，新鲜矿物尘埃颗粒的任何大气处理过程，只要导致添加超过约3%的可溶性物质，都会显著增强其吸湿性和CCN活性。
