Identifying the external N and Hg inputs to the estuary ecosystem based on the triple isotopic information (δ15NNO3, Δ17ONO3 and δ18ONO3)

• Published in: Marine pollution bulletin 2024-03, Vol.200, p.116035-116035, Article 116035
• Main Authors: Kim, Haryun, Kim, Hye Seon, Kim, Jihee, Yang, Dongwoo, Lee, Kitack, Kim, Kitae, Ock, Giyoung, Park, Hyung-Geun, Robinson, Rebecca S., Kim, Min-Seob, Park, Geun-Ha, Kim, Ju-Hyoung, Kim, Young-Il, Lee, Myoung Hoon, Park, Chae-Un, Lim, Dhongil, Han, Seunghee, Kim, Tae-Wook
• Format: Article
• Language: English
• Subjects: Ecosystem; Environmental Monitoring - methods; Estuaries; Estuary; Mercury; Nitrates - analysis; Nitrogen; Nitrogen Isotopes - analysis; Rivers; Triple nitrogen isotope; Water Pollutants, Chemical - analysis
• ISSN: 0025-326X; 1879-3363
• DOI: 10.1016/j.marpolbul.2024.116035

The supply and sources of N and Hg in the Geum estuary of the western coast of Korea were evaluated. Triple isotope proxies (δ15NNO3, Δ17ONO3 and δ18ONO3) of NO3− combined with conservative mixing between river and ocean waters were used to improve isotope finger-printing methods. The N pool in the Geum estuary was primarily influenced by the Yellow Sea water, followed by riverine discharge (821 × 106 mol yr−1) and atmospheric deposition (51 × 106 mol yr−1). The influence of the river was found to be greater for Hg than that of the atmosphere. The triple isotope proxies revealed that the riverine and atmospheric inputs of N have been affected by septic wastes and fossil fuel burning, respectively. From the inner estuary towards offshore region, the influence of the river diminishes, thus increasing the relative impact of the atmosphere. Moreover, the isotope proxies showed a significant influence of N assimilation in February and nitrification in May. Graphic abstract [Display omitted] •Riverine inputs of N and Hg were significant in the estuary ecosystem.•Atmospheric N and Hg inputs were an important contributing factor in the open ocean.•Septic waste and manure waste represented the riverine pollutant sources of estuaries.•Nitrification and assimilation related to N cycling occurred in the estuary ecosystem.•Triple isotopic values of NO3− provided the information on N pollutant sources and biological N processes in estuaries.