溶解无机碳及其同位素组成特征对初期水库过程的响应——以新建水库(洪家渡)为例

RESPONSE OF DISSOLVED INORGANIC CARBON AND ITS ISOTOPIC SPATIAL AND TEMPORAL CHARACTERISTICS TO THE EARLIER RESERVOIR PROCESS:A CASE STUDY ON A NEW RESERVOIR(HONGJIADU)

水坝拦截引起的生物地球化学影响越来越引起人们的重视。本文以我国西南喀斯特地区新建的洪家渡水库为例,详细分析了该水库入库水体、出库水体和水库坝前水体的溶解无机碳含量(D IC)及其同位素组成(1δ3CD IC)特征。结果表明:河流经水库作用后水体无机碳体系发生显著变化。洪家渡水库入库水体D IC和1δ3CD IC值的年均分别为2.14 mmol/L和-6.6‰,库区表层水体为2.12 mmol/L和-6.5‰,出库水体为2.22mmol/L及-8.6‰。总体上,入库水体D IC含量低于出库水体,而溶解无机碳同位素组成却比出库水体偏正。就全年平均而言,出库水体的D IC浓度比入库水体和库区表层水体中分别高出3.7%和4.7%;同时,其D IC的同位素组成相对更偏负,出库水体中δ13CD IC值比入库水体和库区表层水体分别偏负30.3%和32.3%。在垂直剖面上,水体中D IC含量随着深度的增加而增高,1δ3CD IC值随水深的增加而偏负。由于水库为底层泄水,使得出库水体中D IC含量增高,而δ13CD IC值偏负。河流受水坝拦截后,水化学特征发生显著改变,逐渐向湖沼型方向演化。

Recently, an increasing attention has been paid to the effect of the biogeochemistry of artificial reservoirs. The Hongjiadu reservoir is a newly-built one, which is located in Guizhou Province, Southwest China. In this study, systematical investigations were carried out in April, July and October in 2006 and January in 2007. The characteristics of dissolved inorganic carbon （DIC） and its isotopic composition（δ^13CDIC） in the inflow rivers, water column in the reservoir and outflow water were analyzed in detail. The results showed that the river inorganic carbon system could be changed markedly by the reservoir process. The annual average DIC and δ^13CDIC in the inflow, the surface water before the dam and the outflow were 2. 14 mmol/L and -6. 6‰0, 2. 12 mmol/L and -6. 5‰, 2. 22 mmol/L and -8. 6‰, respectively. As a whole, the DIC concentrations were lower in the inflow than in the outflow, whereas the isotopic composition of DIC （δ^13CDIC） in the inflow was more negative than in the outflow. On annual average, the DIC concentrations in the outflow are 3.7% and 4. 7% higher, and its δ^13CDIC values are 30. 3% and 32. 3% more negative than those in the inflow and the surface water before the dam, respectively, In the water column, the DIC concentrations increase with water depth, with its isotopic composition （δ^13CDIC ） showing a trend to become more negative with depth.