Riverine CO2 emissions in the Wuding River catchment on the Loess Plateau: Environmental controls and dam impoundment impact
Riverine CO2 emissions in the Wuding River catchment on the Loess Plateau: Environmental controls and dam impoundment impact
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DOI：
10.1002/2016jg003713
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发表时间：
2017-06
期刊：
影响因子：
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通讯作者：
L. Ran;Lingyu Li;M. Tian;Xiankun Yang;R. Yu;Ji Zhao;Lixin Wang;Xixi Lu
中科院分区：
文献类型：
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作者：
L. Ran;Lingyu Li;M. Tian;Xiankun Yang;R. Yu;Ji Zhao;Lixin Wang;Xixi Lu
河流生态系统对二氧化碳排放的贡献很大。然而，由于缺乏全面的、空间上可分辨的二氧化碳排放测量，对全球河流二氧化碳排放量的估计仍然存在很大不确定性。在利用浮箱进行密集野外观测的基础上，对黄土高原无定河流域的河流CO2逃逸进行了研究。来自土壤呼吸和化学风化的侧向碳在控制河流二氧化碳分压(PCO2)的变化中起着核心作用。此外，异地有机碳的流中处理也是二氧化碳过剩的一个重要来源，调节了横向碳输入的影响。所有调查的河流都是二氧化碳的净来源，表现出明显的空间和季节变化。春季、夏季和秋季的平均二氧化碳释放量分别为172、116和218mmolm−2d−1。无定河流域的CO2排放不同于一般观测到的源头最强的CO2排放，而是以流序递增的形式，反映了其独特的控制CO2排放的地貌景观。而在水库中，PCO2更多地受到初级生产力的控制，水生同化作用将其限制在较低的水平。从水库中逃逸二氧化碳的幅度和方向都发生了很大的变化。与大量二氧化碳排放的溪流相比，水库是小碳源，甚至是碳汇，主要是因为湍流大大减少和光合作用增强。鉴于黄土高原上有大量的水库，评估由此产生的二氧化碳排放变化及其对区域碳收支的影响值得进一步研究。
River ecosystems contribute significantly to CO2 emissions. However, estimates of global riverine CO2 emissions remain greatly uncertain owing to the absence of a comprehensive and spatially resolved CO2 emission measurement. Based on intensive field measurements using floating chambers, riverine CO2 evasion in the Wuding River catchment on the Loess Plateau was investigated. Lateral carbon derived from soil respiration and chemical weathering played a central role in controlling the variability of riverine CO2 partial pressure (pCO2). In addition, in‐stream processing of allochthonous organic carbon was an also important source of CO2 excess, modulating the influence of lateral carbon inputs. All the surveyed streams were net CO2 sources, exhibiting pronounced spatial and seasonal variabilities. The mean CO2 efflux was 172, 116, and 218 mmol m−2 d−1 in spring, summer, and autumn, respectively. Unlike the commonly observed strongest CO2 emissions in headwater streams, the increasing CO2 efflux with stream order in the Wuding River catchment reflects its unique geomorphologic landscape in controlling CO2 emissions. While in reservoirs, the pCO2 was more controlled by primary production with aquatic photosynthetic assimilation constraining it to a lower level. Both the magnitude and direction of CO2 evasion from reservoirs have been greatly altered. Contrast to streams with large CO2 effluxes, reservoirs were small carbon sources and even carbon sinks, due primarily to greatly reduced turbulence and enhanced photosynthesis. In view of the large number of reservoirs on the Loess Plateau, assessing the resulting changes to CO2 emissions and their implications for regional carbon budgets warrants further research.