Zhang Tao, Li Jian-Hong, Pu Jun-Bing, Wu Fei-Hong, Li Li, Yuan Dao-Xian
School of Geographical Sciences, Southwest University, Chongqing 400715, China.
Key Laboratory of Karst Dynamics, Ministry of Land and Resources/Guangxi; Institute of Karst Geology, Chinese Academy of Geological Sciences; International Research Center on Karst Under the Auspices of UNESCO, Guilin 541004, China.
Huan Jing Ke Xue. 2017 Jul 8;38(7):2773-2783. doi: 10.13227/j.hjkx.201701114.
River is characterized by obvious spatial heterogeneity in catchment, which is exacerbated by special environment features of calcium-rich, alkaline and DIC-rich(dissolved inorganic carbon) in karst river. Thus, it also leads to significant spatial variation in the CO degassing across water-air interface. Main ions, physicochemical parameters, δC value and two common approaches(floating chamber(FC) and thin boundary layer models(TBL) were used to analyze the CO degassing characteristics in Guijiang River, a karst river, China. The results were as follows:1 Hydrochemistry in Guijiang River basin showed a significant spatial change. All of HCO, Ca, specific conductivity, total dissolved solids(TDS), SIc and CO showed similar distribution characteristics in the following order:tributaries in the middle reaches > middle reaches > Downstream > Upstream of Guijiang River. 2 During the monitoring period, CO degassing occurred in all the sampling sites and it was the CO source for the atmosphere. The mean CO evasion was 237 mg·(m·h) in Guijiang River, which located in the range of average CO evasion of global river. However, significant spatial variations also occurred along Guijiang River. The CO degassing flux in tributaries of the middle reaches and middle reaches of the mainstream were obviously larger than those in downstream and upstream of the mainstream. 3 CO degassing was mainly affected by carbonate equilibrium system in tributaries in the middle reaches and middle reaches in the mainstream of the Guijiang River basin, which resulted in obviously larger CO degassing than those in downstream and upstream of mainstream. However, the CO degassing flux in tributaries of the middle reaches was also simultaneously affected by biological photosynthesis, and the minimum CO degassing flux[6.38 mg·(m·h)] appeared in tributaries of the middle reaches. In addition, the CO degassing flux in mainstream upstream was mainly affected by atmospheric environmental factors, while it was synergetically influenced by many factors in mainstream downstream.
河流流域具有明显的空间异质性，而岩溶河流中富含钙、碱性和富溶解无机碳（DIC）的特殊环境特征加剧了这种异质性。因此，这也导致了水-气界面处CO脱气的显著空间变化。采用主要离子、理化参数、δC值以及两种常用方法（浮动箱法（FC）和薄边界层模型（TBL））分析了中国岩溶河流桂江的CO脱气特征。结果如下：1桂江流域水化学呈现出显著的空间变化。HCO、Ca、电导率、总溶解固体（TDS）、SIc和CO的分布特征相似，顺序为：桂江中游支流＞中游＞下游＞上游。2在监测期间，所有采样点均发生了CO脱气，是大气的CO源。桂江的平均CO逸出量为237mg·（m·h），处于全球河流平均CO逸出量范围内。然而，桂江沿线也存在显著的空间变化。中游支流和主流中游的CO脱气通量明显大于主流下游和上游。3桂江流域中游支流和主流中游的CO脱气主要受碳酸盐平衡系统影响，导致其CO脱气明显大于主流下游和上游。然而，中游支流的CO脱气通量同时也受生物光合作用影响，中游支流出现了最小的CO脱气通量[6.38mg·（m·h）]。此外，主流上游的CO脱气通量主要受大气环境因素影响，而主流下游则受多种因素协同影响。
