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溶解无机碳昼夜动态变化对河流水体碳通量的估算有重要影响。本文选择由地下水补给且富含水生植物的典型河流,开展高分辨率水文地球化学监测和高频率水样取样工作,分析了水化学的昼夜动态变化特征,钙与无机碳昼夜循环产生的生物地球化学控制机理,估算了钙与无机碳昼夜通量。结果表明,白天pH、SIC上升,产生钙沉降和水体无机碳(主要为HCO-3)含量的下降,夜间得到地下水的补给,Ca2+和HCO-3浓度回升。监测期间,官村地下河出口地表河流钙与溶解有机碳的流失或沉降量分别为69.04kg/d和168.68kg/d,即51.14g/(m·d)和124.95g/(m·d),分别占输入量的6.2%和4.7%。受水生植物光合作用和钙化作用控制,沿流程发生无机碳向有机碳转化,是真正意义上的自然碳汇。
Diurnal dynamics of dissolved inorganic carbon have a significant impact on estimating carbon flux in river water. In this paper, a typical river recharged by groundwater and rich in aquatic plants was selected to carry out high-resolution hydrogeochemical monitoring and high-frequency sampling of water samples. The diurnal dynamics of water chemistry were analyzed. Chemical control mechanism to estimate diurnal flux of calcium and inorganic carbon. The results showed that pH and SIC increased during the day, resulting in calcium deposition and a decrease in the content of inorganic carbon (mainly HCO-3) in the water. Groundwater was recharged at night and Ca2 + and HCO-3 concentrations recovered. During the monitoring period, the loss or sedimentation of calcium and dissolved organic carbon in the surface rivers at the Guantun underground river outlet were 69.04kg / d and 168.68kg / d, ie 51.14g / (m · d) and 124.95g / (m · d) , Accounting for 6.2% and 4.7% of the input respectively. Under the control of photosynthesis and calcification of aquatic plants, conversion of inorganic carbon to organic carbon occurs along the process and is a true natural carbon sink.