红枫水库水-气界面二氧化碳分压及扩散通量的时空变化

红枫水库是我国西南喀斯特地区典型的人工湖泊,具有特殊的水文地质特征。准确估算其CO_2排放通量,对了解该水库碳循环具有重要意义。因此,于2017年7月至2018年4月采用走航式监测对库区(南湖和北湖)水气界面二氧化碳分压(pCO_2)和水质参数的时空变化进行了调查。结果表明,红枫水库pCO_2的分布具有明显的时空差异。库区秋、冬季表层水体pCO_2均超过大气pCO_2,表现为CO_2的净排放;春、夏季则相反,表现为CO_2的净吸收。从空间分布上来看,春、秋季北湖pCO_2要明显高于南湖,特别是秋季更为明显。另外,基于高频的走航监测数据,计算得到红枫水库全年CO_2的排放均值约为613mmol/(m~2·d)。

Spatiotemporal Variation of CO2 Partial Pressure and Exchange Flux at the Air-water Interface of the Hongfeng Reservoir

The Hongfeng reservoir is a typical artificial lake with special hydrogeological characteristics in the karst area of southwest China. To understand the carbon cycle of this reservoir, the accurate estimation of its CO₂ emission flux is great significant. Therefore, the temporal and spatial variation of pCO₂ and quality parameters in surface waters from different zones, the south lake and the north lake of the reservoir were investigated by the shipboard monitoring from July 2017 to April 2018. The results showed that the spatiotemporal distribution of pCO₂ in the Hongfeng reservoir varied obviously. The pCO₂ near the water surface exceeded the atmospheric pCO₂ during autumn and winter, suggesting that the reservoir is the emission source of CO₂, but it was just opposite in spring and summer. According to the spatial distribution, pCO₂ of the north lake water was significantly higher than that of the south lake in spring and autumn, especially in autumn. Based on the dense data set of the shipboard monitoring, the annual average CO₂ emission of the Hongfeng reservoir was calculated as about 6.13 mmol/(m²·d).