大兴安岭多年冻土区两种水体温室气体浓度动态与冬季储存特征

北方内陆水体是温室气体排放的热点，对量化区域碳收支起重要作用，但其排放的季节变化尚不清楚。观测了大兴安岭多年冻土区府库奇河及其改道形成的牛轭湖(演替晚期)冻结期冰层中储存的二氧化碳(CO₂)和甲烷(CH₄)浓度，并比较了两种水体中CO₂和CH₄浓度在三个不同时期(冻结期、非冻结期、春季融化)的差异。结果表明：两种水体CO₂和CH₄浓度季节变化存在差异。牛轭湖在冻结期水体中CO₂和CH₄浓度最高，有明显的冰下积累现象，其中CH₄浓度平均值为(2.21±0.54)μmo/L,分别是非冻结期和春季融化期水体CH₄浓度的5倍和14倍。河流水体中CO₂和CH₄浓度最高出现在春季融化期，显著高于非冻结期和冻结期(P<0.05)。水中CO₂和CH₄浓度受多种环境因子的影响，与可溶性有机碳(D...

Greenhouse gas concentration dynamics and winter storage characteristics of two water bodies in the permafrost zone of the Great Hing''an Mountains

Boreal inland waters are hotspots for greenhouse gas emissions, and they play an important role in quantifying the regional carbon budget, but seasonal variations in their emissions are not well understood. In this study, we observed the concentration of carbon dioxide (CO₂) and methane (CH₄) trapped in the ice during the ice cover period of the Fukuchi River and its diverted oxbow lakes (late successional stage) in the permafrost zone of the Great Hing''an Mountains. Differences in dissolved CO₂ and CH₄ concentrations in the two water bodies during three periods (ice cover period, open water period, and spring thaw period) were also compared. The results showed that there were differences in the seasonal variation patterns of dissolved CO₂ and CH₄ concentrations in the two water bodies. Concentrations of dissolved CO₂ and CH₄ were highest in the water column of oxbow lakes during the ice cover period. There was a significant accumulation of CO₂ and CH₄ under the ice layer. The mean dissolved CH₄ concentration in the water column was (2.21±0.54) μmo/L, which was 5 and 14 times higher than the CH₄ concentration during the open water and spring thaw periods, respectively. River had the highest dissolved CO₂ and CH₄ concentrations in the water column during the spring thaw period, which were significantly higher than during the open water period and ice cover period (P<0.05). Dissolved CO₂ and CH₄ in water were influenced by various environmental factors and were positively correlated with dissolved organic carbon (DOC) (P<0.05) and negatively correlated with dissolved oxygen (DO) and water temperature (P<0.05). CO₂ and CH₄ were also trapped within the ice as bubbles when the ice formed during the ice cover period. CO₂ was the main component in bubbles, with concentrations of about 90% or more within the bubbles. As CO₂ and CH₄ concentrations in bubbles are about 1%-30% of those in the water column under the ice, ignoring the greenhouse gases stored in the ice would increase the uncertainty of carbon emissions from boreal inland waters. This study clarified the seasonal characteristics of dissolved CO₂ and CH₄ and the winter storage capacity of two water bodies in the Great Hing''an Mountains permafrost region. The results provide important data to understand carbon cycling processes in the water bodies of this region.