夏季朱衣河二氧化碳分压分布特征及影响因素分析

Distributions of partial pressure of carbon dioxide and its affecting factors in the Zhuyi River in summer

为研究夏季三峡水库支流库湾-朱衣河的水体二氧化碳分压(p(CO_2))分布特征及影响因素,于2016年7月进行两次分层采样。根据水体的碳酸平衡原理和亨利公式计算水体p(CO_2)并利用水体中超额的二氧化碳分压(E_(p(CO_2)))和表观耗氧量(AOU)的比值(E_(p(CO_2))/AOU)表征生物好氧呼吸作用对p(CO_2)影响程度,研究结果为:上游表层水体的p(CO_2)变化范围大概在5.14~53.67 Pa,受使水体中H+减小的浮游植物光合作用影响较大,导致碳酸盐平衡向右移动,水体中CO_2极不饱和;5 m以下分层水体的p(CO_2)随着水深有变大的趋势,变化范围最低是26.04 Pa,最高是117.28 Pa,而?E_(p(CO_2))/?AOU值高达1.04~2.91,远高于评估上限值,其主要受外源碳汇入影响明显;河口的p(CO_2)大概为39.93 Pa,?E_(p(CO_2))/?AOU的值为0.64±0.01,受生物好氧呼吸作用影响显著;整体的p(CO_2)与温度(T)、pH、溶解氧(DO)、叶绿素ɑ(Chl-a)、硝氮(NO_3^-)存在显著的负相关关系,与浊度(TD)有显著的正相关性,与溶解有机碳(DOC)无显著相关性。

In order to analyze the distribution characteristics of partial pressure of carbon dioxide(p(CO2))and its affecting factors in Zhuyi River in summer,which is one tributary bay of the Three Gorges Reservoir,stratified sampling had been carried out twice in July2016.The p(CO2)was calculated by the chemical balance and Henry's Law,and the ratio?è??EpCO2AOU of excess carbon dioxide partial pressure(EpCO2)to pparent oxygen utilization(AOU)was used to measure the effect of biological aerobic respiration on p(CO2).Results are as follows:In upper surface water,the p(CO2)varies from about5.14to53.67Pa,and they are mainly influenced by photosynthesis with the decrease of H+in water,that led to carbonate equilibrium moveing to right and an extremely unsaturated CO2contained in water.In stratified water(>5m),the p(CO2)are mainly influenced by external input carbon,and p(CO2)increases with the water depth.The lowest and the highest values of p(CO2)are26.04Pa and117.28Pa,respectively.The ratios(EpCO2/AOU)reach up to1.04～2.91,which are far higher than the upper limited value.The p(CO2)in estuaryis is influenced by aerobic respiration evidently,and it is about39.93Pa and the ratios?è??EpCO2AOU are0.64±0.01.Furthernore,p(CO2)is negatively correlated with temperature(T),pH,dissolved oxygen(DO),chlorophyll alpha(Chl-a)and nitrate nitrogen(NO-3).Also,p(CO2)has a significant positive correlation with turbidity(TD),but no significant correlation with dissolved organic carbon(DOC).