Ebullition fluxes of CO<sub>2</sub> and CH<sub>4</sub> in Pengxi River, Three Gorges Reservoir

Abstract

气泡释放是天然水体中水-气交换的重要途径之一.采用改进的倒置漏斗型气泡通量监测装置于2012年3 8月期间对三峡支流澎溪河高阳平湖库湾水域进行气泡释放通量的监测研究.研究期间,研究水域CH₄气泡释放通量变化范围为0.01~23288.64μmol/(m²·d);CO₂气泡释放通量变化范围为0~799.89μmol/(m²·d).不同常规采样点CH₄、CO₂气泡释放通量均呈现出高度的时空异质性特征.但CH₄气泡释放通量显著高于CO₂气泡释放通量,且二者释放过程具有同步性.同国外已有水库监测结果相比,澎溪河回水区高阳平湖库湾水域CH₄、CO₂气泡释放通量位于中等水平.CH₄气泡释放通量约为同期CH₄扩散通量的0~1893.90%,超量释放下CH₄气泡释放通量可达同水域CH₄扩散通量的6270.5%±390.0%.CO₂气泡释放通量仅占同期扩散通量绝对值的0~21.74‰,超量释放下,CO₂气泡释放通量亦仅为同期扩散通量绝对值的40.33‰±0.93‰.CH₄气泡释放通量在支流库湾水域对总通量的贡献不可忽视.;Ebullitions of CH₄ and CO₂ from sediments to water surface are one of the critical pathways of greenhouse gas emission in natural water bodies. Modified gas collecting funnels were applied to collect CH₄ and CO₂ ebullition and estimate their emission fluxes at an embayment in Lake Gaoyang, Pengxi River, in the Three Gorges Reservoir. From March to August, 2012, ebullition emission fluxes of CH₄ were 0.01-23288.64 μmol/(m²·d), while that of CO₂ were 0-799.89 μmol/(m²·d). Significant spatial-temporal heterogeneities were detected. Generally, ebullition emission fluxes of CH₄ were much higher than that of CO₂. Correlation analysis indicated that ebullition emissions of both CH₄ and CO₂ were simultaneously. Comparing with the global datasets, CH₄ and CO₂ ebullition emission fluxes in this area were in the middle level. Comparing with the air-water diffusive fluxes monitored simultaneously, CH₄ ebullition fluxes were about 0-1893.90% of those of diffusive fluxes. In excess ebullition situation, this ratio could go up to 6270.5% ± 390.0%; CO₂ ebullition fluxes about 0-21.74‰ and up to 40.33‰ ± 0.93‰. It can be concluded that CH₄ ebullition fluxes should not be neglected in evaluation of the total emission fluxes in this area.