Abstract
To estimate dry deposition flux of atmospheric water-soluble nitrogen (N), including ammonium (NH4+), nitrate (NO3−), and water-soluble organic nitrogen (WSON), aerosol samples were collected over the subarctic western North Pacific Ocean in the summer of 2016 aboard the Korean icebreaker IBR/V Araon. During the cruise, concentrations of NH4+, NO3−, and WSON in bulk (fine + coarse) aerosols ranged from 0.768 to 25.3, 0.199 to 5.94, and 0.116 to 14.7 nmol m−3, respectively. Contributions of NH4+, NO3−, and WSON to total water-soluble N represented ~74%, ~17%, and ~9%, respectively. Water-soluble N concentrations showed a strong gradient from the East Asian continent to the subarctic western North Pacific Ocean, indicating that water-soluble N species were mainly derived from anthropogenic or terrestrial sources. During sea fog events, coarse mode NO3− was likely to be scavenged more efficiently by fog droplets than fine mode NO3−; besides, WSON was detected only in fine mode, suggesting that there may have been a significant influence of sea fog on WSON, such as the photochemical conversion of WSON into inorganic N. Mean dry deposition flux for water-soluble total N (6.3 ± 9.4 µmol m−2 d−1) over the subarctic western North Pacific Ocean was estimated to support a minimum carbon uptake of 42 ± 62 µmol C m−2d−1 by using the Redfield C/N ratio of 6.625.
Highlights
Nitrogen (N) is an essential nutrient in terrestrial and marine ecosystems
NO3 − was likely to be scavenged more efficiently by fog droplets than fine mode NO3 − ; besides, water-soluble organic nitrogen (WSON) was detected only in fine mode, suggesting that there may have been a significant influence of sea fog on WSON, such as the photochemical conversion of WSON into inorganic N
Duce et al [5] reported that the flux of atmospheric total reactive N to the ocean surface has increased by 48 TgN/year from preindustrial times to 2000, suggesting that almost all ocean surface areas have been affected by anthropogenic atmospheric reactive N, including oxidized and reduced inorganic
Summary
Nitrogen (N) is an essential nutrient in terrestrial and marine ecosystems. The supply of N to the ocean surface layer is an important factor controlling the ocean ecosystem [1]. Apart from the supply of deep nutrient-rich water by vertical mixing, atmospheric deposition can be a significant source of N to the photic zone of the open ocean where riverine input is negligible [2]. Atmospheric deposition is considered as a dominant pathway for the supply of anthropogenic N to open ocean surface waters [3,4]. Duce et al [5] reported that the flux of atmospheric total reactive N to the ocean surface has increased by 48 TgN/year from preindustrial times to 2000, suggesting that almost all ocean surface areas have been affected by anthropogenic atmospheric reactive N, including oxidized and reduced inorganic
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