Atmospheric Dry Deposition of Water-Soluble Nitrogen to the Subarctic Western North Pacific Ocean during Summer

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.

Upper Ocean Biogeochemistry of the Oligotrophic North Pacific Subtropical Gyre: From Nutrient Sources to Carbon Export

“…In addition to model simulations, observations of enhanced deposition of reactive N due to anthropogenic emissions from northeastern Asia have been made across the North Pacific (Kim et al., 2014). Limited cruise observations found that the total dry deposition of reactive N to the NPSG ranged from 5 to 1,100 μmol N m −2 d −1 , mostly on the order of 10–100 μmol N m −2 d −1 , and was highest in spring (Jung et al., 2011, 2019; L. Luo et al., 2016, 2018; Seok et al., 2021; Shi et al., 2021). Overall, atmospheric N deposition in the western NPSG shows strong seasonal and spatial variability, and some regions are influenced by episodic events.…”

Summertime fluorescence characteristics of atmospheric water-soluble organic carbon in the marine boundary layer of the western Arctic Ocean

“…Aerosol samples were analyzed for major ionic species using the method described by Jung et al (2019Jung et al ( , 2020. Briefly, the collected aerosol samples were divided into four equivalent subsamples.…”

“…3). Previous studies (Jacob et al, 1984;Bergin et al, 1995;Sasakawa et al, 2003;Herckes et al, 2007;Jung et al, 2013Jung et al, , 2019) demonstrated that compared with fine aerosols, coarse aerosols (D > 0.5 μm) predominantly acted as condensation nuclei of sea fog droplets, and that the water vapor condensation on pre-existing particles increases the aerosol size and accelerates their removal from the atmosphere. Similarly, in this study, Na + concentration in the coarse-mode aerosols was not correlated with mean wind speed (r = 0.35, p > 0.2), whereas Na + concentration in the fine-mode aerosols was significantly correlated with the mean wind speed (r = 0.68, p < 0.05).…”