三峡水库两条支流水-气界面CO_2、CH_4通量比较初探

Comparative Study on Water-air CO_2,CH_4 Flux in Two Tributaries in the Three Gorges Reservoir,China

三峡水库是亚热带气候背景下的超大型水库,其水生生态系统碳循环过程存在显著的时空异质性.本研究于2010年6月～2011年5月对三峡水库两条支流(龙溪河、澎溪河)水-气界面CO2、CH4通量特征进行了1 a的定位跟踪观测与比较分析.研究发现,位于三峡水库库尾变动回水区的龙溪河CO2、CH4通量年均值分别为(7.30±1.89)mmol·(m2.h)-1、(0.11±0.095)mmol·(m2.h)-1.而位于三峡水库库中常年回水区的澎溪河CO2、CH4通量年均值分别为(0.71±0.46)mmol·(m2.h)-1、(0.007 4±0.001 7)mmol·(m2.h)-1.龙溪河的温室气体通量水平显著高于澎溪河,季节性变化剧烈,幅度也显著大于澎溪河.相比澎溪河,龙溪河回水区极不稳定的水力、生境条件让浮游植物难以稳定生长,其水体固碳能力显著受限;加之龙溪河受淹区域土壤有机质、全氮含量以及单位流域面积内污染负荷程度均显著高于澎溪河,共同导致了龙溪河温室气体通量水平普遍高于澎溪河流域.两条支流CH4通量的主要影响因素仍需进一步研究.

The Three Gorges Reservoir （TGR） is a huge reservoir under the subtropical climate condition. It shows great spatio- temporal heterogeneity on biogeochemical cycling of carbon in the TGR＇s aquatic ecosystem. 1 a field monitoring on water-air CO2 and CH4 fluxes was conducted from June, 2010 to May, 2011 in Longxi River and Pengxi River, the 2 typical tributaries in the Three Gorges Reservoir. Comparative study showed that annual CO2 diffusive fluxes in the Longxi River and Pengxi River were （7.30 ±1.89） mmol.（m2.h）-l and （0.71 ±0.46） mmol＇（m2·h）-1, respectively, and the CH4 diffusive fluxes were （0. 11 ±0.095） mmol. （m2.h） -1 and （0. 007 4 ± 0. 001 7） mmol. （m2.h） -1. Higher intensities and seasonal variance of CO2 and CH4 fluxes were observed in Longxi River compared to those in Pengxi River. Through a comparative analysis of the environmental and watershed parameters in both rivers, it was found that the unstahle hydraulic conditions and habitat of Longxi River prohibited the growth of phytoplankton, reducing its capability of carbon assimilation. The higher pollution load in the basin and the higher organic matters and total nitrogen in the impounding soil of Longxi River also resulted in the higher level of greenhouse gas fluxes compared to those in the Pengxi River. More studies shall be conducted to elucidate the variance of CH4 flux and its controlling factors in both rivers.