HR: 0800h
AN: A31C-0081    [Abstracts]
TI: The Trace Metals in Atmospheric Aerosols and Their Deposition Over the East China Sea During the Asian Dust Period
AU: * Endo, M
EM: makiendo@ori.u-tokyo.ac.jp
AF: Ocean Research Institute, The University of Tokyo, 1-15-1 Minamidai, Nakano-ku , Tokyo, 164-8639 Japan
AU: Nakamura, T
EM: toku@ori.u-tokyo.ac.jp
AF: Ocean Research Institute, The University of Tokyo, 1-15-1 Minamidai, Nakano-ku , Tokyo, 164-8639 Japan
AU: Narita, Y
EM: narita@ori.u-tokyo.ac.jp
AF: Ocean Research Institute, The University of Tokyo, 1-15-1 Minamidai, Nakano-ku , Tokyo, 164-8639 Japan
AU: Uematsu, M
EM: uematsu@ori.u-tokyo.ac.jp
AF: Ocean Research Institute, The University of Tokyo, 1-15-1 Minamidai, Nakano-ku , Tokyo, 164-8639 Japan
AB: The East China Sea is strongly affected by anthropogenic and mineral dust aerosols from Asian continent. Especially, in springtime, dust storms are frequent over Asia and the dust is transported over long distances. Although the deposition of dust from atmosphere to ocean plays an important role in the oceanic biogeochemical cycles, there is a dearth of simultaneous dust particle measurements in the atmosphere and the surface ocean. We continuously measured trace metals in aerosols, rain and the surface seawater over the western North Pacific and the East China Sea from 4 to 20 March 2004. High concentrations of mineral dust and anthropogenic substances were observed in the north of the East China Sea. The mean concentration of Al during the dust period was 4.5 $\mu$g m$^{-3}$, which was about 14 times higher than that in non-dust period. The concentration of Al in the suspended particles in surface seawater during the dust period was 0.88 $\mu$g l$^{-1}$, which was about 2.3 times higher than that in the non-dust period. The concentrations of Al and Fe showed similar variations between aerosols and seawater compared to other trace metals, indicating most of Al and Fe are supplied from atmosphere and these trace metals have lower solubility. During the non-dust and the dust periods, the means of (excess-Zn/Al) $_{suspended particles}$ / (Zn/Al) $_{aerosols}$ were about 0.74 and 1.2, respectively. During non-dust period, the solubility of Zn in the surface seawater is estimated to be 20-40% and is higher than that of Al (0.6-10% ;Duce et al.,1991). The atmospheric deposition of highly soluble trace metals to seawater might affect biogeochemical cycles in this region. During dust period, the deposition rate of giant particles ($>$10$\mu$m) of Al increased compared to that of Zn, therefore the settling velocity of Al in seawater seemed to be higher than that of Zn. The trace metals associated with large size particles play an important role in the underlying sediments though their role in dissolved state in the surface seawater may be limited.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0312 Air/sea constituent fluxes (3339, 4504)
DE: 0330 Geochemical cycles
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting