三峡库区主要河流秋季pCO2及其影响因素

于2015年10月对三峡库区主要河流表层水体中的溶解性碳组成进行了测定,结合水文地质条件和水化学关键指标,对河流表层水体二氧化碳分压(p CO_2)的空间变化及影响因素进行了研究,并利用模型法分析了水-气界面CO_2通量特征.结果表明,三峡库区主要河流秋季pCO_2介于18.75~296.31 Pa之间,均值为(141.06±77.51)Pa;河流CO_2脱气通量平均值为(101.1±78.0)mmol·(m2·d)-1,其中86%的采样点位表现为大气CO_2源的特征.p CO_2与DO和pH显著负相关,与HCO-3显著正相关.由于山区河流流速快和水力停留时间短等特征,河流有机碳原位呼吸是导致p CO_2与DO和pH很强的负相关关系的主要原因.研究结果为准确估算三峡库区河流CO_2逸出量提供了重要的数据支撑.

pCO2 in the Main Rivers of the Three Gorges Reservoir and Its Influencing Factors

An extensive investigation on the main tributaries of the Three Gorges Reservoir (TGR) region was conducted in autumn (Oct. 2015), with focuses on riverine CO₂ partial pressure (pCO₂) and its associated controls. Our results indicated that pCO₂ in the main rivers of the TGR region ranged from 18.75 to 296.31 Pa, with a mean value of (141.06±77.51) Pa in the autumn, which was much higher than the atmospheric CO₂ concentration. Therefore, the studied rivers acted as an atmospheric CO₂ source, and the mean CO₂ emission rate to the atmosphere was estimated at (101.1±78.0) mmol·(m²·d)^-1. The highest and lowest values were (131.9±101.8) and (70.3±54.3) mmol·(m²·d)^-1, respectively. pCO₂ in the main rivers of the TGR area was significantly related to DO, pH, and bicarbonate. Furthermore, the biogeochemical process of within-river respiration of organic carbon rather than photosynthesis resulted in negative relationships between pCO₂ and DO or pH because of the high velocities and short residence time in these mountainous rivers and streams. Our results will help to accurately develop the carbon budget for the rivers of the Three Gorges Region.