典型喀斯特河流/溪流系统水-气界面CO2释放研究: 以猫跳河上游为例

The traditional global carbon cycle model was confined to the land, ocean and atmosphere. Inland water system have been considered as passive pipes in global and regional carbon balance computations, delivering significant amounts of terrestrially carbon from land to ocean. Recent studies indicate that inland water system behave as not only the carbon transportation vector, but also an important participator in carbon cycle, especially for the carbon emissions from the rivers and streams, which is considered as the “hotspot” of carbon released from river system. However, due to the significant regional variation in aquatic carbon flux, it’s challenging to conduct accurate quantitative data with either global or regional carbon cycle equilibrium model. Karst district is a huge carbon pool, as well as the active regions of carbon emission, carbon sequestration and carbon transport. Here, we take the upper reach of Maotiaohe River, a typical karst basin located in Guizhou province, as the research area to study the CO2 emissions across stream and river surfaces. High frequency sampling and field experiments for k will be conducted in the rivers and streams to obtain the spatial and temporal distribution of CO2 emissions. Meanwhile, the carbon emission mechanism and driving factors of the subtropical steams will be discussed, combining with land cover, land use, hydraulics, water chemistry and carbon isotope. This may provide foundation data for modeling the regional and global carbon cycle.

传统的碳循环模型只包含陆地、海洋的和大气三个系统，河流则被认为只是连接陆地和海洋的通道。而近些年的研究表明内陆水体不仅仅是碳输送的媒介，也是碳循环的一个重要组成部分，河流系统碳排放的“热点”。然而，由于不同背景条件的小流域CO2释放研究还很少，在全球或区域碳循环平衡模型中都很难进行合理的定量统计。喀斯特地区拥有巨大的碳库，是碳释放、碳吸收、碳输送的活跃地区。本研究以贵州省典型喀斯特河流猫跳河上游河流/溪流系统为研究对象，通过高频率的现场监测和采样分析，现场实验获得CO2交换速率系数，估算不同级别河流的CO2释放通量，分析喀斯特河流CO2释放的时空变化；同时结合土地利用、地貌条件、水力学参数、水化学参数、碳同位素数据，探讨喀斯特小流域的碳排放机制和驱动因素，为我国西南喀斯特地区碳循环模和碳收支平衡提供科学依据。

传统的碳循环模型只包含陆地、海洋的和大气三个系统，河流则被认为只是连接陆地和海洋的通道。而近些年的研究表明内陆水体中的溪流不仅仅是碳输送的媒介，也是碳循环的一个重要组成部分，是河流系统碳排放的“热点”。然而，目前不同背景条件的小流域CO2释放研究还很少。本研究以贵州省贵阳市阿哈湖小流域为研究对象，通过连续一年的现场监测和采样分析，现场实验获得CO2交换速率系数，估算不同级别河流的CO2释放通量，分析了喀斯特河流CO2释放的时空变化。研究结果表明，阿哈湖小流域不同河段交换系数（kTC）差异巨大，变化范围在3.6~48.9/cm·h-1之间，水-气界面CO2交换速率差异巨大，小流域CO2释放通量计算还存在很大的挑战，需要更深入的研究。在分析CO2交换影响因素时，发现人为活动会对相同地质背景喀斯特小流域风化碳汇和水气界面CO2释放造成显著的影响，（1）人类活动会导致流域风化碳汇量被高估，受矿山和农业活动影响的阿哈湖游鱼河小流域风化对大气CO2的消耗量被高估3.5倍。受城市排污影响明显的小阿哈湖湖金钟河小流域风化碳汇量被高估0.53倍。（2）人类活动会显著加速河流二氧化碳释放速率，受到矿山和城市排污影响的两条小流域二氧化碳释放速率比未受明显影响的河流高3-4倍。