河流-水库体系水体表层pCO_2时空变化特征及其扩散通量——以六冲河、洪家渡水库、红枫湖为例

为了了解筑坝后河流-水库体系CO2的释放特征,本研究于2011年5月至2012年5月调查了乌江流域的六冲河以及处于不同营养水平的洪家渡水库和红枫湖表层水体的基本物理、化学和生物参数及溶解无机碳碳同位素组成(δ13 CDIC),分析计算表层水体pCO2及水气界面的CO2交换通量(CO2flux)。六冲河、洪家渡水库和红枫湖表层水体的pCO2年平均值分别为684±195μatm、884±484μatm和592±596μatm,均大于大气中的pCO2,表现为大气CO2的源。红枫湖表层水体中的pCO2受到藻类等水生生物的作用最强,洪家渡水库次之,六冲河表层水体最弱,导致它们表层水体中的pCO2具有明显不同的时间分布特征,相应的CO2flux的时间分布也明显不同。红枫湖的初级生产力水平最高,在2011年5月至2011年9月时表现为大气CO2的汇,水气界面的交换通量平均为-5.70mmol.m-2.d-1。δ13 CDIC和pCO2同步变化揭示了水体表层pCO2时空变化受藻类等生物活动的影响。本研究表明,高频率的监测对于准确评估河流-水库体系CO2flux非常必要。

Spatiotemporal Characteristics and Diffusion Flux of Partial Pressure of Dissolved Carbon Dioxide (pCO2) in the River-Reservoir System as Exemplified by the Liuchonghe River, Hongjiadu Reservoir and Hongfenghu Lake

In order to understand the diffusion characteristics of CO2 in the river-reservoir system after damming,the Liuchonghe River,Hongjiadu Reservoir and Hongfenghu Lake which are different in trophic levels were investigated during May,2011 to May,2012.The basic physical,chemical and biological factors and the isotopic composition of dissolved carbon dioxide(δ13CDIC) in these surface waters were measured,too.pCO2 and the exchange flux of CO2(CO2 flux) through the water-air interface were calculated.The average pCO2 in the Liuchonghe River,Hongjiadu Reservoir and Hongfenghu Lake were 684±195 μatm,884±484 μatm and 592±596 μatm,respectively,which were the carbon source relative to atmospheric pCO2.The pCO2 was affected differently by algal activity in the Liuchonghe River,Hongjiadu Reservoir and Hongfenghu Lake.The pCO2 had different biweekly changes in the Liuchonghe River,Hongjiadu Reservoir and Hongfenghu Lake,and so did the CO2 flux.The Hongfenghu Lake,of the highest primary productivity,behaved as a carbon sink during May,2011 to September,2011,and the average CO2 flux was-5.70 mmol·m-2·d-1.δ13CDIC and pCO2 changed synchronously,indicating that the biogeochemical process controlled the spatiotemporal change of pCO2 in surface water.The necessity of high monitoring for estimating the CO2 flux in the river-reservoir system was accurately explained.