Investigation of the concentrations and fluxes of potent greenhouse gases (NO, CH, and CO) in the port and harbor seawaters of Jeju Island, Korea.

Quantifying greenhouse gas (GHG) emissions from coastal environments is essential for understanding their role in climate change. Ports and harbors, which are semi-enclosed coastal systems, often experience nutrient accumulation from human activities, leading to GHG emissions. Jeju Island, with numerous ports and harbors along its coast, provides an ideal location for studying GHG emissions in these environments. This study investigates the spatial distribution, air-sea fluxes, and radiative forcing of NO, CH, and CO in Jeju's port and harbor waters during the summer of 2021. Sampling sites were classified into four categories based on dominant industry: Urban, Aquaculture, Nature tourism, and Agriculture. Greenhouse gas concentrations varied by region, with elevated NO in urban and CH in tourism regions, while pCO was relatively low in both due to biological uptake. Additionally, Jeju's ports and harbors acted as a source of NO, CH, and CO to the atmosphere, with average fluxes of 1.67 ± 1.41 μmol m d 10.30 ± 10.24 μmol m d 0.16 ± 0.78 mmol m d, respectively. Radiative forcing calculations indicated that while dissolved NO levels were still low to exhibit radiative forcing, CH exhibited positive forcing only in the tourism region where concentrations were elevated, and CO concentrations were sufficiently high to exhibit radiative forcing. These findings highlight the importance of port and harbor environments as hotspots of coastal GHG emissions.