不同地质背景水库区夏季水-气界面温室气体交换通量研究

Summer Greenhouse Gases Exchange Flux Across Water-air Interface in Three Water Reservoirs Located in Different Geologic Setting in Guangxi,China

岩溶水库水化学特征受碳酸盐岩溶蚀风化产物所控制,形成"富钙偏碱高溶解无机碳"的特殊环境,其水-气界面温室气体交换特征、过程及影响因素与其他非岩溶水库存在较大差异.为揭示不同地质背景控制下典型水库水-气界面温室气体交换的特征及控制机制,选取广西三座不同地质背景的水库[大龙洞水库(岩溶水库)、五里峡水库(半岩溶水库)、思安江水库(非岩溶水库)],同时运用静态箱法(FC)和模型计算法(TBL)对其水-气界面温室气体(CO2、CH4)交换通量进行比较研究.结果表明:1两种方法获得的结果均显示,大龙洞水库库区和出库水体均为大气CO2、CH4的源;五里峡水库库区总体上为大气CO2的汇、大气CH4的源,其出库水体均为大气CO2、CH4的源;思安江水库库区均为大气CO2的汇、大气CH4的源.2无论是岩溶水库还是非岩溶水库,其出库水体温室气体排放量远大于库区,如何控制水库出库水体的CO2、CH4释放问题值得关注.3在没有大量淹没土壤有机质和植物的情况下,由岩溶地下水补给的水库水-气界面CH4交换通量与其他半岩溶水库和非岩溶水库差别较小,但由于富含DIC水体的输入及受水库热分层的影响,其CO2交换通量要明显高于其他非岩溶水补给的水库.

Due to special hydrogeochemical characteristics of calcium-rich,alkaline and DIC-rich( dissolved inorganic carbon)environment controlled by the weathering products from carbonate rock,the exchange characteristics,processes and controlling factors of greenhouse gas( CO2 and CH4) across water-air interface in karst water reservoir show obvious differences from those of non-karst water reservoir. Three water reservoirs( Dalongdong reservoir—karst reservoir,Wulixia reservoir—semi karst reservoir,Si'anjiang reservoir—non-karst reservoir) located in different geologic setting in Guangxi Zhuang Autonomous Region,China were chosen to reveal characteristics and controlling factors of greenhouse gas exchange flux across water-air interface. Two common approaches,floating chamber( FC) and thin boundary layer models( TBL),were employed to research and contrast greenhouse gas exchange flux across water-air interface from three reservoirs. The results showed that: 1surface-layer water in reservoir area and discharging water under dam in Dalongdong water reservoir were the source of atmospheric CO2 and CH4. Surface-layer water in reservoir area in Wulixia water reservoir was the sink of atmospheric CO2 and the source of atmospheric CH4,while discharging water under dam was the source of atmospheric CO2 and CH4. Surface-layer water in Si'anjiang water reservoir was the sink of atmospheric CO2 and source of atmospheric CH4. 2 CO2 and CH4effluxes in discharging water under dam were much more than those in surface-layer water in reservoir area regardless of karst reservoir or non karst reservoir. Accordingly,more attention should be paid to the CO2 and CH4emission from discharging water under dam. 3 In the absence of submerged soil organic matters and plants,the difference of CH4 effluxes between karst groundwater-fed reservoir( Dalongdong water reservoir) and non-karst area( Wulixia water reservoir and Si'anjiang water reservoir) was less. However,CO2 efflux in karst groundwater-fed reservoir was much higher than that of reservoir in non-karst area due to groundwater of DIC-rich input from karst aquifer and thermal stratification.