Abstract：
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 CO2 degassing across water-air interface. Main ions, physicochemical parameters, δ13CDIC value and two common approaches(floating chamber(FC) and thin boundary layer models(TBL) were used to analyze the CO2 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 HCO3-, Ca2+, specific conductivity, total dissolved solids(TDS), SIc and pCO2 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, CO2 degassing occurred in all the sampling sites and it was the CO2 source for the atmosphere. The mean CO2 evasion was 237 mg·(m2·h)-1 in Guijiang River, which located in the range of average CO2 evasion of global river. However, significant spatial variations also occurred along Guijiang River. The CO2 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 CO2 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 CO2 degassing than those in downstream and upstream of mainstream. However, the CO2 degassing flux in tributaries of the middle reaches was also simultaneously affected by biological photosynthesis, and the minimum CO2 degassing flux[6.38 mg·(m2·h)-1] appeared in tributaries of the middle reaches. In addition, the CO2 degassing flux in mainstream upstream was mainly affected by atmospheric environmental factors, while it was synergetically influenced by many factors in mainstream downstream.
摘要：
河流流域具有明显的空间异质性，富含钙的特殊环境特征加剧了这种情况，岩溶河中富含碱性和DIC(溶解无机碳)。因此，它还导致水-空气界面上CO2脱气的显着空间变化。主要离子,物理化学参数，采用δ13CDIC值和两种常用方法（浮室（FC）和薄边界层模型（TBL）分析了贵江的CO2脱气特性，一条喀斯特河,中国。研究结果如下：1贵江流域水化学呈现显著的空间变化。所有的HCO3-，Ca2+,比电导率，总溶解固体（TDS），SIc和pCO2按以下顺序表现出相似的分布特征：中游支流>中游>下游>贵江上游。2监测期间,CO2脱气发生在所有采样位置，它是大气的CO2来源。桂江平均CO2逃逸量为237mg·(m2·h)-1，位于全球河流平均二氧化碳逃逸范围内。然而,桂江沿线也发生了显著的空间变化。中游支流和中游支流的CO2脱气通量明显大于下游和上游。3CO2脱气主要受贵江流域中游支流和中游支流碳酸盐平衡系统的影响，这导致CO2脱气明显大于主流下游和上游。然而,中游支流的CO2脱气通量也同时受到生物光合作用的影响，中游支流出现最小CO2脱气通量[6.38mg·（m2·h）-1]。此外,上游干流CO2脱气通量主要受大气环境因素影响,而它在主流下游受到许多因素的协同影响。
