CO2 and CH4 partial press and flux across water-air interface in the downstream of Jinsha River, China

Abstract

This paper takes some typical points at downstream of Jinsha River in China as examples for the overall evaluation of greenhouse gas emissions. In reference of previous literature, this study adopted the combination of headspace balance method and model estimation to obtain the partial pressures of carbon dioxide and methane in surface water and exchange fluxes of CO2 and methane. Additionally, this paper also used field measuring instruments to measure the physical and chemical variables. The Spearman correlation index based on SPSS software are applied to analyse the relationship between between the partial pressures and fluxes of CO2 and methane and environment variables. Experiments’ results showed that mean value for partial pressure of CO2 (p(CO2)) was (1785.87 ± 451.18) µatm, ranked medium in worldwide rivers. In contrast, the average value for p(CH4) was (22.63 ± 11.48) µatm ranked relatively low in worldwide rivers. Among all sampling sites, the p(CH4) for Linjiaba, Shaonvping, Lizhuang located in reservoir area were higher than that for other sites. And the diffusion of CO2 flux was in medium level compared with other major rivers in the world, at (1.71 ± 0.55) mmol/(m2·h), while that of CH4 flux kept in low level at (0.0009 ± 0.0005) mmol/(m2·h), and all benthic flux of CO2 and CH4 were positive indicated the Jinsha River was the source of producing greenhouse gas., the trend of the partial pressure and flux almost remained the same. Moreover, p(CO2) in surface waters showed positive correlations with alkalinity (TA) and dissolved organic carbon(DOC), and p(CH4) showed significant positive correlations with Chl-a and temperature. CO2 flux showed positively correlation with the p(CO2), DOC, alkalinity (TA), and CH4 flux is positively related to p(CH4), wind speed. Other environmental factors showed vague effects on the fluxes.