Work

Identification of carbon dioxide and methane emission characteristic across Heihe River, China

Year: 2025

Type: article

Abstract: Rivers are major sources of methane (CH 4 ) and carbon dioxide (CO 2 ) emissions into the atmosphere. However, limited research on CH 4 and CO 2 fluxes and production mechanisms in high-altitude and arid-region rivers constrains a comprehensive understanding of riverine carbon cycle . Heihe River is the second- largest inland basin in China, which originates from the Tibetan Plateau and flows through the arid regions of northwestern China. This study focused on CH 4 and CO 2 emissions along the Heihe River using the headspace technique and a gas chromatograph method. A total of 31 sampling sites were selected along the upstream and downstream stretches of the Heihe River, with 18 sites from the upstream and 13 from the downstream. The results indicate that the Heihe River is the sources of both CH 4 and CO 2 emissions, with higher concentrations and fluxes in the downstream arid region. The average diffusion fluxes of CH 4 and CO 2 in the downstream region are 80.1 μmol·m −2 ·d −1 and 63.6 mmol·m −2 ·d −1 , respectively, while they are 35.9 μmol·m −2 ·d −1 and 31.1 mmol·m −2 ·d −1 in the upstream region. CH 4 and CO 2 fluxes in the upstream region were primarily controlled by the physical and chemical parameters (salinity, conductivity, air temperature, pH) and groundwater recharge ( 222 Rn), while downstream emissions were influenced by DIC (Dissolved Inorganic Carbon) concentration and groundwater recharge . CH 4 primarily originates from thermogenic sources (δ 13 C-CH 4 > −50 ‰) in the upstream region, while CO 2 was primarily derived from atmospheric input and CH 4 oxidation (α c < 1.04). In contrast, CH 4 was produced via acetoclastic methanogenesis (1.04 <α c < 1.06) and anthropogenic activities in the downstream region, while CO 2 sources were influenced by both anthropogenic activities and CH 4 oxidation . This study has enhanced our understanding of the carbon cycle in inland rivers of arid regions through the analysis of CH 4 and CO 2 fluxes and production mechanisms along the Heihe River.

Source: The Science of The Total Environment

DOI: 10.1016/j.scitotenv.2025.179175