Variabilities of inorganic nitrogen in airborne particulate matter in Busan, South Korea

The atmospheric deposition of anthropogenic nitrogen is an increasingly important new source of nitrogen (N) in the ocean. This study examines the variabilities of the atmospheric inorganic reactive nitrogen species in airborne particulate matter, based on the two-year sample collection of total suspended particles (TSP) in Busan, South Korea adjacent to the Korea Strait (KS) from March 2019 to February 2021. Concentrations of nitrate (NO₃^-), ammonium (NH₄⁺), and non-sea-salt sulfate (nss-SO₄^2-) ions contained in the TSP significantly declined by ~9, ~25, and ~24 %, respectively, between the two years. The seasonally clustered backward trajectories have shown significant decreases in those ionic concentrations from the Asian outflow, primarily owing to the reduced human activities after the COVID-19 pandemic outbreak. The atmospheric deposition of the inorganic N species (i.e. NO₃^- and NH₄⁺) may contribute ~0.78 % and ~2.6 % to the annual mean oceanic net primary production (NPP) and the new production, respectively, in a 2° latitude × 2° longitude domain in the KS. Given the expected wet and organic N deposition, the atmospheric total N deposition could account for ~2.1 % and ~7 % of the annual mean NPP and the new production in the KS, respectively.