Abstract: Rivers are important sources of greenhouse gas emissions in inland waters of terrestrial ecosystems. In recent years, the emission of greenhouse gases has increased the seriousness of environmental problems. This paper focuses on the Sichuan section of the Jialing River as the research subject to explore the spatial distribution characteristics of dissolved CH₄ and CO₂ concentrations and emission fluxes, and the response of the water physical and chemical properties and land use types to greenhouse gas emissions. Surface water samples were collected from the Jialing River in October 2021, and a modified headspace method was used to capture dissolved CH₄ and CO₂ in the water. Results indicate that human activities dominate the changes in water quality in the Sichuan section of the Jialing River, with urban and agricultural activities being the primary reasons for the accumulation of nitrogen and phosphorus along the river. The concentrations of CH₄ and CO₂ in the surface water were (16.87±15.55) nmol·L^-1 and (836.11±132.68) μmol·L^-1, respectively. The emission fluxes of CH₄ and CO₂ were (68.39±81.26) nmol·m^-2·d^-1 and (1 596.08±1 291.61) μmol·m^-2·d^-1, respectively. The concentration and emission fluxes of CH₄ and CO₂ exhibited significant spatial heterogeneity. Among the different land use types, the river reach dominated by cultivated land received significant amounts of non-point source pollution and terrigenous carbon. The input of these pollutants changed the physical and chemical properties of water bodies, the growth of aquatic plants and phytoplankton, and the microbial activities in the river, and further influenced the production and release of CH₄ and CO₂. TN, PO₄^3--P, and area proportion of cultivated land are the key factors contributing to greenhouse gas emissions in the Sichuan section of the Jialing River, which indicating that Greenhouse gas emissions are not only influenced by the ecological environment of the river but also by human activities under different land use types.

Key words: Jialing River, greenhouse gas, CH₄, CO₂, flux, spatial distribution