官厅水库底泥中碳的分布及累积特征

Distribution and Accumulation Characteristics of Sedimentary Carbon in Guanting Reservoir

水库的拦蓄作用显著改变了天然河流的输运过程,库区底部成为重要的碳积蓄场所.本文通过野外调查和实验测量,研究了官厅水库4个典型区域(近岸区、河口区、浅水区和深水区)底泥柱状样中碳的组成、分布特征以及累积现状.结果表明,不同区域底泥碳含量的差别较大,从大到小依次为近岸区(3.04%)>河口区(2.48%)>浅水区(1.52%)>深水区(1.49%),其中有机碳所占的比例分别为64%、52%、56%和55%.四个区域间无机碳含量的分布没有明显差别,而有机碳含量差异显著.河口区底泥沉积受上游河流淤积作用的影响,有机碳含量随深度变化波动,而其它区域有机碳含量都表现出随深度逐渐减小的特点.受不同区域泥沙淤积、植被类型以及水动力条件变化的影响,底泥的碳埋藏率差别很大,分别为河口区(1300g/(m2·a))、近岸区(156g/(m2·a))、浅水区(70g/(m2·a))和深水区(40g/(m2·a)).

Reservoirs have significantly changed the transportation processes of natural rivers, and their sediment was estimated to have accumulated large amounts of carbon. In this study, field investigations and experimental measurements were carried out to estimate the composition and distribution characteristics of carbon in the sedimentation, vegetation and hydrodynami sediment of Guanting Reservoir. According to the c conditions, the reservoir was divided into four regions. The sediment carbon content in the near shore region, estuary region, shallow water region, and deep water region showed different depositional characteristics and the average value reduced gradually （ 3.04% 〉2. 48% 〉 1.52% 〉 1.49% ） .The proportions of organic carbon in the carbon of the four regions were 64%, 52%, 56% and 55% respectively. There was not much difference of inorganic carbon in the sediment of the four regions, while the organic carbon exhibited great difference. Further, the vertical distribution of organic carbon content in sediments of the estuary region, which were influenced by the sedimentation of upstream river, varied with the depth, whereas the organic carbon content reduced with the depth in sediment cores of the other three regions. Moreover, the carbon accumulation rate differed greatly in the estuary region （ 1300g/（ m^2 · a） ）, near shore region （ 156g/（ m^2 · a） ）, shallow water region （70（g/m^2 ·a））,and deep water region（40g/（m^2 ·a））.