10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Single-Particle Mixing State and Mineralogy of North African Dust: A Comparison of Ambient Transported Dust with Laboratory Generated Proxies
NICHOLAS MARSDEN, Romy Ullrich, Ottmar Möhler, Paul Williams, Michael Flynn, James Allan, Hugh Coe, University of Manchester
Abstract Number: 835 Working Group: Unraveling the Many Facets of Ice Nucleating Particles and Their Interactions with Clouds
Abstract Mineral dust has been the subject of many laboratory simulations of ice nucleation (IN) due to the potential for these particles to act as ice-nucleating particles (INP). In many studies, the mineralogy of single particles has been found to influence the conditions at which ice is formed and is therefore an important parameter in this type of experiment. Furthermore, the internal mixing state, such as the coating with sulphate and organics, can alter the characteristics of INP and is also an important consideration. Therefore, the characterisation of single-particle mineralogy and mixing state of mineral dust is an important for the modelling of IN at atmospherically relevant conditions.
In this study, we present the online analysis of the fine fraction (<2.5µm) of North African dust using single-particle mass spectrometry (LAAPTOF, AeroMegt GmbH), a technique that has a unique ability to make online measurements of single-particle composition and mixing state at high temporal resolution. Using novel data evaluation methods, we evaluated the number concentrations of felsic, illite and kaolinite clay particles and the internal mixing with organic, inorganic and biological material in commonly used mineral dust proxies including; crushed microcline feldspar, synthetic illite NX, natural soil from the North-West margin of the Sahara, and natural soil from the Sahel region. The materials were sampled from the AIDA chamber, Karlsruhe Institute of Technology, prior to ice formation during the INUIT09 campaign July 2017. The data is compared to the composition of transported dust measured with the same instrument in the marine boundary layer at Praia, Republic of Cabo Verde, during the ICE-D campaign in August 2015.
The similarities and differences of the ambient dust compared to the laboratory generated proxies will be discussed with reference to the implications of dust modification during transport and the atmospheric relevance of commonly used mineral dust proxies.