HR: 1340h
AN: A53A-0173    [Abstracts]
TI: Mixing State Effects That Influence Aerosol Optical Properties: Black Carbon Aggregation With Dust in Outflow From East Asia
AU: * Anderson, J
EM: janderson@asu.edu
AF: Arizona State University, Dept. of Mechanical and Aerospace Engineering, Tempe, AZ 85287-6106 United States
AU: Hua, X
EM: huaxin@asu.edu
AF: Arizona State University, Dept. of Mechanical and Aerospace Engineering, Tempe, AZ 85287-6106 United States
AB: East Asian dust aerosols dominated by silicate minerals are commonly modified during their passage over industrial areas by mixing with anthropogenic pollution, in particular the various forms of black carbon. Extensive dust/BC aggregation was observed in East Asia outflow during the ACE-Asia Experiment, but is also a common feature of dust in other regions including the US Southwest. Because particle morphology and the nature of particle aggregation (the "state of mixing") affect light scattering and absorption, this mixing changes the climate forcing effects of dust aerosols. It is important to assess typical examples of this mixing if the climate forcing effects of major dust storms are to be properly understood. A large number of East Asian dust samples have been studied to date in which on average 20 percent or more of the mineral particle surface is covered by smaller black carbon particles. Additional complexity is added if sulfate is also aggregated on the mineral particle surfaces, but sulfate is not always present whereas black carbon is almost always present to some extent. Even without the addition of primary and secondary pollutant aerosols to dust storm air masses, a significant fraction of dust aerosols are complexly shaped aggregates of multiple minerals, some of which may be optically absorbing and some of which may not. The degree of aggregation of dust and black carbon has been determined using a field emission SEM with thin-window EDS for chemical composition. Resultant high-resolution images were manually annotated to separate dust and black carbon and then image analysis was applied to determine the cross-sectional area of mineral particles, black carbon particles, and the extent of aggregation of the two.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0365 Troposphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005