Latitudinal Variation of Chemical Composition in Marine Aerosol Over the Central North Pacific in the Summer

Aeolian dust and gaseous and particulate pollutants from the Asian continent are transported eastward over the North Pacific. These natural and anthropogenic materials in the atmosphere can influence regional and global climate by altering the Earth's radiative balance. From the view of biogeochemical cycles, the atmospheric deposition of aerosols containing iron and other essential trace elements may contribute in sustaining primary productivity of phytoplankton, food web structure and chemical properties of marine atmosphere in the central North Pacific region. During the South-North cross-section cruise from 8 August to 21 September 2005, we conducted atmospheric sampling of aerosol and gaseous components on board R/V Hakuho Maru. Results from 10S to 53N along 160E revealed high nitrate concentration in the high latitude zone corresponded with back-air trajectories to subarctic North Pacific from the Asian continent during the summer. The atmospheric supply of nitrogen compounds may affect the primary production of stratified surface layer in the region. Non-sea-salt sulfate concentration was also high over the subarctic region, and downwind of the Hawaii islands. Volcanic and anthropogenic sulfur are suspected to be the sources of nss-sulfate. However, as an indicator of marine biogenic sulfate, methane sulfonic acid (MSA) is also correlated well with the concentration peaks of nss-sulfate both the vicinity of Hawaii islands and subarctic region. We will attempt to separate nss-sulfate into two fractions, marine biogenic and anthropogenic by using the relation between trace metals and sulfate over the source regions.