Abstract
Abstract. We measured total dissolved reactive nitrogen in precipitation samples collected at Uljin, a Korean coastal site upwind of the southern East Sea/Sea of Japan (EJS), selected as a representative study site of atmospheric deposition over the northwestern Pacific margin. NO3- was found to be the most abundant nitrogen species, followed by NH4+ and dissolved organic nitrogen (DON). Air-mass back-trajectory (AMBT) analysis revealed that a significant fraction of the inorganic nitrogen (NO3- and NH4+) originated from mainland Asia, whereas the DON was primarily derived from Korea. Using varimax-rotated factor analysis in combination with major ions as tracers, agricultural activities in Korea were identified as the primary sources of DON in these samples. In addition, a positive correlation was found at Uljin between the size of organic fraction in total reactive nitrogen and nitrogen to carbon atomic ratio in organic matter. This correlation has also been observed at other locations worldwide, implying the utilization potential of atmospheric organic nitrogen might increase with its proportion in total nitrogen. Combining wet deposition measurements in this study with literature values for dry deposition observed at a remote island in the EJS, the total atmospheric depositional flux of reactive nitrogen was estimated to be 115 mmol N m−2 yr−1 over the southern EJS. Our study sheds new light on the potentially significant contribution to primary productivity of the northwestern Pacific Ocean by atmospheric deposition of nitrogen, especially the organic fraction.
Highlights
The availability of reactive nitrogen, including all nitrogen species except N2, is often a determinant controlling the primary production in terrestrial and marine ecosystems (Vitousek and Howarth, 1991)
The results presented here might be subject to large uncertainties, such as those associated with spatial variations of depositional fluxes across the EJS, the proportions of organic nitrogen in dry deposition, and the bioavailability of organic nitrogen in the atmosphere
Inorganic nitrogen was found to be mostly derived from the Asian continent through long-range atmospheric transport, whereas the primary sources of dissolved organic nitrogen (DON) are distributed within Korea
Summary
The availability of reactive nitrogen (or fixed nitrogen), including all nitrogen species except N2, is often a determinant controlling the primary production in terrestrial and marine ecosystems (Vitousek and Howarth, 1991). The East Sea/Sea of Japan (EJS) is a semi-closed marginal sea (covering an area of 1.01 × 106 km2) surrounded by Russia, Korea, and Japan, which has been suggested to be an ideal site to investigate the impacts of atmospheric nutrient deposition on the northwestern Pacific Ocean (Kim and Kim, 2013). It is a highly productive region where nitrogen is severely limited (Talley et al, 2004; Jenkins, 2008; Kim and Kim, 2013).
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