典型岩溶水系统碳汇通量估算

现代岩溶学研究成果表明,碳酸盐岩在全球碳循环中响应极其迅速,水循环过程中的碳汇效应显著。本研究选取广西桂林寨底地下河系统、广西环江大安地下河系统、重庆北碚青木关地下河系统三个典型岩溶地下水系统,利用各系统地下河的流量和HCO3-浓度的监测资料,采用简单化学平衡模式法估算碳汇通量(CO2)。结果显示,寨底地下河系统的单位面积年碳汇通量为68.82 t/(km2.a),大安地下河系统的单位面积年碳汇通量为81.18 t/(km2.a),青木关地下河系统的单位面积年碳汇通量为100.07 t/(km2.a)。分析认为同一个岩溶水系统的结构特征和环境条件基本上是稳定的;地下河的流量和HCO3-浓度是影响岩溶碳汇强度的关键因素,尤其是地下河流量的变化对碳汇强度的影响显著;不同岩溶水系统的碳汇通量不但受水化学条件和地下水动力条件的控制,同时受土地利用变化的影响。该研究对于改进碳循环模型和评价岩溶地质碳汇有重要意义。

Flux Estimation of Carbon Sink in Typical Karst Water Systems

Select results from modern karstology research show that carbonate rock can be actively involved in the global carbon cycle with a quick response, thus the carbon sink effect from the water cycle in carbonate rock areas is very important. As described in this paper, three representative karst groundwater systems were selected, including Guangxi province Guilin Zhaidi, Guangxi province Huanjiang county Da'an groundwater and Chongqing Qingmuguan groundwater. Carbon sink flux (CO₂) of each underground water system was estimated from the serial monitoring data of discharges and bicarbonate concentrations by using the simple chemical equilibrium method. The fluxes in Zhaidi, Da'an and Qingmuguan were 68.82 t/(km²·a), 81.18 t/(km²·a) and 100.07 t/(km²·a) respectively. The structures and environmental conditions in each karst water system were relatively stable; accordingly, the groundwater discharge and HCO₃^- concentration were two key factors influencing karst carbon sink intensity, especially the flow rate change of underground streams. However, the carbon sink flux could be controlled by water chemistry and hydraulic conditions and was also impacted by land use change for different karst water systems. The results of carbon sink fluxes from three typical underground water systems provided references for the improvement of the carbon cycle model and the estimation of the karst carbon sink.