[Greenhouse Gas Emissions Characteristics and Driving Factors Analysis in the Eutrophic Saline Lake Daihai Lake].

Abstract

To investigate the greenhouse gas emission characteristics and driving factors of eutrophic saline lakes in northern China, considering Daihai Lake in Inner Mongolia as an example, 10 monitoring sites were selected based on hydrological distribution characteristics in April, July, and October 2023. Using headspace gas chromatography and modeling methods, dissolved concentrations and exchange fluxes of carbon dioxide （CO₂）, methane （CH₄）, and nitrous oxide （N₂O） were determined in the nearshore zone, open lake area, and lake center surface water. During the study period, Daihai Lake exhibited significant seasonal variations in greenhouse gas concentration and flux. The average concentrations of CO₂, CH₄, and N₂O in surface water were （26.52 ± 17.58） μmol·L^-1, （282.30 ± 172.30） nmol·L^-1, and （9.09 ± 1.64） nmol·L^-1, respectively. The average fluxes were （5.29 ± 11.98） mmol·（m²·d）^-1, （178.24 ± 63.34） μmol·（m²·d）^-1, and （-0.74 ± 1.28） μmol·（m²·d）^-1, with cumulative emissions of 50 770.77, 543.52, -4.21 kg·km^-2 and a global warming potential （expressed in CO₂-equivalent） of 50 770.77, 15 218.49, -1 254.48 kg·km^-2. Daihai Lake acted as a source of atmospheric CO₂ and CH₄ but a sink for N₂O during the study period. Correlation and stepwise regression analyses revealed that pH and total dissolved solids （TDS） influenced CO₂ concentration and flux, while the factors affecting CH₄ were water temperature （WT）, water depth （WD）, wind speed （WS）, oxidation-reduction potential （ORP）, and total nitrogen （TN）. For N₂O, the influencing factors were WT, WS, and TN. Additionally, Daihai Lake's eutrophication and salinity characteristics influenced the generation and emission of greenhouse gases. This study provides insights into the greenhouse gas dynamics and environmental factors in eutrophic saline lakes like Daihai Lake.