三峡水库典型支流库湾沉积物CH4产生和氧化规律

以三峡水库香溪河库湾为研究对象,采用原位加密采样(2021年5月)和室内培养方法,结合沉积物特性与水环境因子分析,探讨了香溪河库湾沉积物甲烷(CH₄)释放潜力、沉积物-水界面CH₄产生和氧化通量空间分布规律及其影响因素。结果表明:三峡水库泄水期间,香溪河库湾沉积物CH₄释放潜力的变化范围是6.35-2029.37 mg/(kg·d),沉积物-水界面CH₄产生通量和氧化通量的变化范围分别为0.04～0.73、0.03～0.62 mmol/(m²·d);空间上,沉积物CH₄释放潜力、沉积物-水界面CH₄产生及氧化通量在香溪河库湾和各典型横切面(XX02、XX05和XX06)间表现出空间差异性,主要受水深、TOC和温度的影响。垂向上,CH₄产生速率随沉积物深度的增加而减小,表层20 cm沉积物CH₄释放潜力占整柱沉积物的70%,可以用于估算库湾沉积物CH₄释放潜力。此外,沉积...

CH4 production and oxidation of sediments in the typical tributary of Three Gorges Reservoir

In order to study the extent of CH₄ release at the sediment-water interface (SWI) of the tributary bay of the Three Gorges Reservoir (TGR), CH₄ production and oxidation at the SWI and its regulators in the Xiangxi Bay were investigated by combining in situ sampling and indoor incubation with sediment characteristics and environmental factors. The results showed that: (1) During the discharge period of the TGR, the potential sediment CH₄ production rate (MPs) (6.35-2029.37 mg/(kg·d)), CH₄ production fluxes (MP, 0.04-0.73 mmol/(m²·d)) and oxidation fluxes (MO, 0.03-0.62 mmol/(m²·d)) at the SWI showed spatial variations among several transections and increased from downstream (XX00) to upstream (XX07). (2) Vertically, the CH₄ production rate decreased with increasing sediment depth, and MPs from the top 20 cm of sediment can be used to estimate sediment MPs in the bay, which accounted for 70% (55%-82%) of the total CH₄ production from the intact sediment core (between 20 cm and 36 cm in length). (3) MP at the SWI was positively and linearly related to sediment total organic carbon, but negatively related to water depth. MP and MO showed a very significant positive correlation with increasing temperature, resulting in higher CH₄ emission corresponding to a linear decrease in methane oxidation rate (MR). Accordingly, the sediment MR in Xiangxi Bay reached 96.62% during the discharge period of the TGR, indicating low CH₄ emission from sediments.