Physical/Chemical Characterization of Trans-Atlantic Airborne Saharan Dust during the Aerosol and Ocean Science Expeditions (AEROSE)

The NOAA centre for Atmospheric Sciences in Howard University has been involved in studying the impact of aerosols on climate, heterogeneous chemistry, and microphysics. One of the objectives was to provide a set of critical measurements to characterize the impacts and microphysical evolution of Saharan dust aerosols transported across the Atlantic Ocean. The AERosol and Oceanic Science Expedition (AEROSE) field campaigns were designed to accomplish this objective on the remote tropical Atlantic environment, as well as provide valuable in-situ marine boundary observations. Conducted aboard the Ronald H. Brown (RHB) research vessel annually between 2004 and 2010, the AEROSE cruise collected aerosol samples at 6-48hr intervals in various portions of the plume using a Quartz Crystal Microbalance Cascade Impactor (QCM) and filter samplers during Saharan dust storms that occurred over the tropical Atlantic Ocean. The Quartz Crystal Microbalance served as a mass distribution monitoring device within the air masses transected, and provided a sampling stage for morphological analysis on a Scanning Electron Microscope (SEM). The elemental composition details will be determined using an Energy Dispersive X-ray (EDX) microanalysis system coupled to the SEM. In addition, Auger electron spectroscopy, and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) will be utilized as confirmatory analytical tools to provide information on the surface chemistry and oxidative state of elements present in the AEROSE samples. The extensive suite of aerosol measurement and size segregation data will be used to characterize aerosol mass distribution, evolution processes, carbon content, chemical and mineral compositions, as a function of season and source region. Morphological changes and evolution of the elements on size as a dependent factor during long distance transported from source region across the Atlantic Ocean will be presented. However, preliminary elemental analysis has identified elements such as C, S, and O, on dust particles as a function of size. This is critical information for unraveling the surface chemistry of these particles and their nucleation potential.