SizeDependent Mass and Dry Deposition Fluxes of Atmospheric Aerosols along Dust Transport Routes

Using the sizesegregated measurements of atmospheric aerosols collected in Beijing and Qingdao in China and Fukuoka in Japan during the spring of 2002, the size distributions of the mass of atmospheric aerosols with aerodynamic diameter (Dp) ≤ 11 μm (PM11) along dust transport routes are investigated. The size distribution of these aerosols in mass concentration during nondust periods exhibits a bimodal pattern, ie., a fine modes with Dp< 2.1 μm and a coarse mode between 2.1 μm and 11 μm. On the other hand, the size distribution of these aerosols in mass concentration during dust periods attempts to exhibit a unimodal pattern in the coarse particle size range. The coarse mode diameter decreases with the distance from the dust source zone to the west and east coast of the Yellow Sea during the heavy dust periods. It is not case in regular dust periods. The sizedependent dry deposition fluxes of the aerosols over the Yellow Sea in springtime are estimated using an improved Williams' model. The dry deposition fluxes increase with the increasing size in the coarse particle size range during the nondust and dust periods. It appears that no evident variations occurred in the fine mode. The estimated PM11 fluxes over the Yellow Sea during the dust and nondust periods range from 31.70 to 58.59 mg·m-2·d-1 and ranged from 8.33 to 15.94 mg·m-2·d-1, respectively. Although the dry deposition fluxes of the coarse particles increase evidently during dust periods, the relative contributions of the coarse particles to that of PM11 do not change significantly regardless of the occurrence of and absence of dust events. The authors find that coarse particles are the main contributor to the PM11 dry deposition in springtime over the Yellow Sea, the percentage reaches over 94.2%.