Variation Characteristics of CO₂ and CH₄ Concentrations in Waliguan Area in 2019 and Potential Source Analysis

Based on the on-line greenhouse gas observation data of Waliguan Station in 2019, the seasonal and daily variation characteristics of CO₂ and CH₄ at the station are analyzed, and the possible potential source areas of CO₂ and CH₄ are discussed.The results show that the concentrations of CO₂ and CH₄ in Waliguan area in 2019 are 412.07±4.78 ppm and 1935.17±21.13 ppb respectively, both of which are slightly higher than the global mean values. The seasonal variation of atmospheric CO₂ is low in summer and autumn, and high in winter and spring. The variation of CH₄ concentration is just the opposite to that of CO₂. It is high in summer and autumn, and low in winter and spring. The seasonal variations may be related to the increased summerautumn grazing activities in Waliguan and the transport of the dominating air flow from Lanzhou-Xining urban group. The average daily variation of CO₂ and CH₄ concentrations is evident, characterized by the interaction between changes in source-sink intensity and atmospheric diffusion intensity. The backward trajectory clustering shows that the air mass from Lanzhou-Xining urban group in Central Gansu and northeast Qinghai contributes the most to the CO₂ and CH₄ in Waliguan. PSCF analysis also shows that Lanzhou-Xining urban group is the main potential source of CO₂ and CH₄ in Waliguan.