典型喀斯特河流水-气界面二氧化碳交换特性及其营养调控因素

Water-air Carbon Dioxide Exchange and Nutritional Controls in a Typical Karst River

为探索喀斯特河流水-气界面二氧化碳(CO_(2))交换特性及其营养控制因素,以我国典型喀斯特河流——芙蓉江为研究对象,探索了区域气象水文参数、碳酸盐平衡参数、营养元素及总有机碳(TOC)的空间变化特征,同时分析了CO_(2)分压(pCO_(2))的空间变化调控因素,pCO_(2)与总氮(TN)、总磷(TP)和TOC及其化学计量比的耦合关系,对比了该研究河流与世界河流的CO_(2)排放情况.结果表明,芙蓉江水-气界面CO_(2)交换速率(k)在2.71~13.0 m·d^(-1)范围内,pCO_(2)在78.5~21 491.2 Pa范围内,且支流高于干流;河流表层水体TOC、TN和TP分别为(302.8±50.1)、(128.9±67.9)和(0.65±0.98)μmol·L^(-1),整体表现为磷限制营养状态;河流pCO_(2)与磷及其相关的化学计量比显著耦合,说明微生物新陈代谢是河流CO_(2)饱和的主要原因;芙蓉江水-气界面CO_(2)排放通量(F)为(534.5±801.4) mmol·(m^(2)·d)^(-1),高于一些世界河流,具有巨大的CO_(2)排放潜力.

To explore water-air carbon dioxide(CO_(2)) exchange and its nutritional controls in karst rivers,water sampling and analyses were conducted in the Furong River as a representative karst river system. Regional hydrometeorological characteristics,carbonate system parameters,total organic carbon(TOC),nutrients and their stoichiometric ratios,and the riverine pressure of aqueous CO_(2)(pCO_(2)) and its couplings to trophic status were analyzed. The results showed that gas transfer velocity of CO_(2)(k) varied between 2. 71 and 13. 0 m·d^(-1). Riverine pCO_(2) varied from 78. 5 Pa to 21 491. 2 Pa and was significantly higher in the tributaries than the main stem.Riverine TOC,total nitrogen(TN),and total phosphorus(TP) concentrations were(302. 8 ± 50. 1),(128. 9 ± 67. 9),and(0. 65 ±0. 98) μmol·L^(-1),respectively,demonstrating the trophic status of P-limitation. Riverine pCO_(2) was tightly linked to P-related parameters,suggesting that in-situ metabolism triggered aquatic CO_(2) supersaturation. Water-air CO_(2) flux(F) averaged(534. 5 ±801. 4) mmol·(m^(2)·d)^(-1) in the Furong River,which is higher than most of the world’s rivers,and thus indicates high potential CO_(2) emissions.