HR: 0800h
AN: A31C-0086    [Abstracts]
TI: Nitrate and sulfate in the marine boundary layer around Japan: Implications to chloride depletion
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: * Narita, Y
EM: narita@ori.u-tokyo.ac.jp
AF: Japan Science and Technology Cooperation, 4-1-8, Honmachi, Kawaguchi, 332-0012 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
AU: Uematsu, M
EM: uematsu@ori.u-tokyo.ac.jp
AF: Japan Science and Technology Cooperation, 4-1-8, Honmachi, Kawaguchi, 332-0012 Japan
AB: Gases and aerosols react with sea salt in the marine boundary layer. Atmospheric nitrate and sulfate are known to result in the chloride depletion by altering the nature of sea salt or mineral dust aerosol and ultimately may influence the marine ecosystem processes. Thus, it is important to understand these process and depositions of nitrate and sulfate to the sea. Significant quantities of anthropogenic gases and aerosol from the Asian Continent are transported over the North Pacific Ocean. A self-cruising observation boat (Self Cruising Ocean Observation Platform; SCOOP) was fabricated to monitor aerosol and gaseous compounds in the marine atmosphere as a part of VMAP project. The atmospheric samples were collected during SCOOP cruises (No. 0102; 26-31 August 2001and No. 0103; 3-8 December 2001) to the south of Honshu, Japan and near Hachijo Island, respectively. Ambient aerosols segregated into two size fractions (d$<$2.5 $\mu$m: fine mode; d$>$2.5 $\mu$m: coarse mode) were colleted at 4 hours intervals on a PTFE fiber filter by a dichotomous virtual impactor. Cl$^{-}$, NO$_{3}$$^{-}$, SO$_{4}$$^{2-}$, Na$^{+}$, K$^{+}$, NH$_{4}$$^{+}$, Mg$^{2+}$, and Ca$^{2+}$ in two size ranges were extracted into ultra pure water and analyzed by IC. During both the cruises air masses originated mainly from the northern and the central China. Mean concentrations of NO$_{3}$$^{-}$, nss-SO$_{4}$$^{2-}$, NH$_{4}$$^{+}$ and chloride depletion and in the fine particles were 4.5 $\pm$ 4.8, 36.7$\pm$30.5, 51.8$\pm$46.6, 12.7$\pm$9.9 nmol m$^{-3}$, respectively, in the SCOOP-0102 cruise and 4.6$\pm$3.6, 29.3$\pm$16.9, 41.7$\pm$27.7, 15.7$\pm$9.6 nmol m$^{-3}$, respectively, in the SCOOP-0103 cruise. Sulfate in fine particles was almost neutralized with ammonium ion and seems to be a predominant reactant causing chloride depletion. Although nitrate role appears to be limited, it was an initiator of the depletion reaction when sulfate was almost neutralized by ammonium ion. Our results suggest that chloride depletion reaction in fine mode can be controlled by the difference in concentrations of sulfate and ammonium ions and that nitrate can denature the mineral dust more than sulfate.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0335 Ion chemistry of the atmosphere (2419, 2427)
DE: 0345 Pollution--urban and regional (0305)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting