三峡水库澎溪河流域高阳回水区夏季水体CO2分压日变化特性

水柱中CO2分压(pCO2)的时空分布在一定程度上可反映水中碳的环境地化特征.本研究在夏季分层期间对三峡水库澎溪河(小江)流域高阳回水区段进行了昼夜连续观测发现,恒定的温跃层中pCO2随水深增加而显著增大,表层0.5 m处pCO2均值为152±71μatm,而在水深10.0 m处pCO2均值为4568±1089μatm,同水温、pH及DO存在明显的负相关关系,进一步分析认为水温等将影响微生物、浮游植物的代谢过程及水气界面对流传输,进而对pCO2分布产生影响.对水气界面CO2扩散通量的估算结果表明,夏季分层期间高阳水域总体上表现为CO2的汇,其对大气CO2的吸收量最大值于15:00左右,达到-0.33 mmol/(m2.h);最弱在次日凌晨3:00左右,吸收量仅为-0.17 mmol/(m2.h).

Diurnal variation characteristics of pCO2 in the summer water column of Gaoyang backwater area in Pengxi River, Three Gorges Reservoir

Partial pressure of CO2(pCO2) in water column was an importamt indicator for the geochemical characteristics of carbon.Diel samples for pCO2 and other environmental factors,i.e.pH,DO and water temperature,was taken from Gaoyang backwater area in the Pengxi(Xiaojiang) River,Three Gorges Reservoir in every 6 h.Results showed that in stable metaliminon,vertical pCO2 increased along with the water depth.Mean value of the pCO2 at 0.5 m depth was 152±71 μatm,while that of pCO2 at 10.0 m depth was 4568±1089 μatm.Significant negative correlations between pCO2 and pH,DO,water temperature were detected,indicating metabolism of microbial and planktonic community and penetrative convection were impacted by water temperature that regulated the distribution of pCO2.Estimation of the water-air flux of CO2 indicated that the general characteristic of carbon sink in the Gaoyang backwater area was obvious.A maximum sink flux of-0.33 mmol/(m2·h) was detected in 15:00 while a minimum sink flux of-0.17 mmol/(m2·h) was also detected in 3:00 of the next day.