20 Jul 2022
20 Jul 2022

Marine nitrogen fixation as a possible source of atmospheric water-soluble organic nitrogen aerosols in the subtropical North Pacific

Tsukasa Dobashi1,2, Yuzo Miyazaki2, Eri Tachibana2, Kazutaka Takahashi3, Sachiko Horii3,a, Yoko Iwamoto4, Shu-Kuan Wong5,b, and Koji Hamasaki5 Tsukasa Dobashi et al.
  • 1Graduate School of Environmental Science, Hokkaido University, Sapporo, 060-0810, Japan
  • 2Institute of Low Temperature Science, Hokkaido University, Sapporo, 060-0819, Japan
  • 3Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, 113-8657, Japan
  • 4Graduate School of Integrated Sciences for Life, Hiroshima University, Hiroshima, 739-8521, Japan
  • 5Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, 277-8564, Japan
  • anow at: Fisheries Resources Institute, Japan Fisheries Research and Education Agency, Nagasaki, 851-2213, Japan
  • bnow at: National Institute of Polar Research, Tokyo, 190-8518, Japan

Abstract. Water-soluble organic nitrogen (WSON) in marine atmospheric aerosols affect the water-solubility, acidity, and light-absorbing properties of aerosol particles, which are important parameters in assessing both the climate impact and the biogeochemical cycling of bioelements. Size-segregated aerosol and surface seawater (SSW) samples were simultaneously collected over the subtropical North Pacific to investigate the origin of WSON in the marine atmosphere. The fine-mode WSON concentration (7.5±6.6 ngN m−3) at 200–240º E along 23º N defined as the eastern North Pacific (ENP) was significantly higher than that (2.4±1.9 ngN m−3) at 135–200º E, defined as the western North Pacific (WNP). Analysis of the stable carbon isotope ratio of water-soluble organic carbon (WSOC) (δ13CWSOC) together with backward trajectory indicated that most of the observed WSON in the fine particles in the ENP originated from the ocean surface. We found a significant positive correlation between the WSON concentrations and nitrogen fixation rate in SSW. The result indicates that reactive nitrogen (dissolved organic nitrogen and ammonium), produced and exuded by nitrogen-fixing microorganisms in SSW, contributed to the formation of WSON aerosols. This study provides new insights into the role of ocean-derived reactive nitrogen aerosols associated with marine microbial activity.

Tsukasa Dobashi et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-561', Anonymous Referee #1, 08 Sep 2022
  • RC2: 'Comment on egusphere-2022-561', Anonymous Referee #2, 14 Oct 2022

Tsukasa Dobashi et al.

Tsukasa Dobashi et al.


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Short summary
Water-soluble organic nitrogen (WSON) in marine aerosols is important for biogeochemical cycling of bioelements. Our shipboard measurements suggested that reactive nitrogen produced and exuded by nitrogen-fixing microorganisms in surface seawater, likely contributed to the formation of WSON aerosols in the subtropical North Pacific. This study provides new implications for the role of marine microbial activity in the formation of WSON aerosols in the ocean surface.