Methane flux and its relationship with carbon dioxide emission in urban residential areas in Seoul, Korea.

Methane (CH₄) is the second most important greenhouse gas. However, the measurement of urban CH₄ flux is exceptionally scarce. Here we present the observational results based on the eddy-covariance method at the high-rise and high-population residential area in Seoul, Korea. The magnitude and temporal variation of CH₄ flux show a significant strong relationship with carbon dioxide emission rate. The observed emission rate of CH₄ over the residential area is 21.8 nmol m^-2 s^-1 on average, and this is corresponding to 11 gC m^-2 yr^-1 which is comparable with boreal, taiga, and temperate wetlands. The carbon-isotope compositions (δ¹³C) of CH₄ (about -46‰) and CO₂ (about -28‰) point to the same source for both gases suggesting vehicular traffic as a dominant source for CH₄ in this study. 

This study is supported by “National Adaptation Plan for Climate Change” (2022-001-01), conducted by the Korea Environment Institute (KEI) upon the request of the Korea Ministry of Environment, and the Korea Meteorological Administration Research and Development Program (grant no. KMI2021-01610).