State of mixture of atmospheric submicrometer black carbon particles and its effect on particulate light absorption

The state of mixture of light-absorbing carbonaceous particles was investigated in relation to light absorption properties using electron microscopic examinations, black carbon (BC) analyses of quartz filter by thermal/optical reflectance (TOR) method, measurements with two continuous light-absorbing photometers at a suburban site of Tsukuba, about 60 km northeast of Tokyo. The volume fraction of water-soluble material (E) in individual particles is important for assessing particulate light-absorbing and/or scattering of atmospheric aerosols. The values of F in BC particles were evaluated by electron micrographs before and after dialysis (extraction) of water-soluble material. The mass absorption coefficient (MAC in units of m(2) g(-1)) tended to increase with increasing the average epsilon in BC particles with the radius range of 0.05-0.5 mu m. Thus, our results indicate that coatings of water-soluble material around BC particles can enhance the absorption of solar radiation. Moreover, the single scattering albedo (SSA) will increase because a large amount of coating material will scatter more light. (C) 2008 Elsevier Ltd. All rights reserved.