花溪河水溶解无机碳同位素的季节变化

Seasonal Variations in Dissolved Inorganic Carbon and δ^(13)C of the Huaxi River

对乌江上游支流花溪河水进行了一年的监测,测定了DIC含量和δ13 CDIC。结果显示DIC含量在1.73～4.53mmol/L之间,δ13 CDIC的变化范围-9.6‰～-3.6‰,反映了碳酸盐岩的主要控制作用,δ13 CDIC和DIC含量之间存在负相关关系,表明有机质分解作用、生物作用对河水DIC也有着重要影响。冬季河水主要来自花溪水库,水体与大气CO2同位素平衡时间较长,加之少量地下水直接的补给使河水具有一年中较高δ13 CDIC和DIC含量。春季光合作用增强,δ13 CDIC达到一年中最高,DIC含量下降。夏季水体DIC库受有机质分解作用控制,δ13 CDIC达到一年中的最低值,由于雨水的稀释作用使得DIC含量处于一年中较低水平。在夏季晚期光合作用和CO2的逃逸使得δ13 CDIC升高变化但DIC含量下降。秋季有机质的降解导致δ13 CDIC的负向变化,同时伴随DIC含量的升高。

The Huaxi River,one of the tributaries of the Wujiang River,had been monitored for one year to determine the DIC concentrations and δ13CDIC.The results showed that DIC ranges from 1.73 to 4.53 mmol/L,and δ13CDIC varies from-9.6 ‰ to-3.6 ‰,reflecting the main control of carbonates,negative correlation between δ13CDIC and DIC indicated that the decomposition of organic matter and biological activities of the river also have an important influence on the DIC pool.Groundwater recharge and the dissolution of atmospheric CO2 in the winter led to higher δ13CDIC and DIC concentrations.With the onset of spring,enhancement of photosynthesis would cause an increase in δ13CDIC,a decrease in DIC concentrations,and the highest δ13CDIC value.During the summer,the decomposition of organic matter is a predominant control on shifts in the DIC pool,δ13CDIC reaches the lowest value,and due to the dilution effect of rainfall makes the DIC concentrations at the lower level.During the late summer,photosynthesis and elevated CO2 escape would cause an increase in δ13CDIC and a decrease in DIC concentrations.Decomposition of organic matter in the autumn would lead to a negative shift of δ13CDIC,accompanied by an increase in DIC concentrations.