澜沧江流域糯扎渡水库沉积物有机质来源的定量研究  

Quantifying the Source of Organic Matter in the Sediments of the Nuozhadu Reservoir in the Lancang River Basin

作　　者：韩祥峰 郭明伟 刘坤 王仕禄[1] 王雨春[3] 包宇飞 陈豪 吴嘉曦 HAN Xiangfeng;GUO Mingwei;LIU Kun;WANG Shilu;WANG Yuchun;BAO Yufei;CHEN Hao;WU Jiaxi(State Key Laboratory of Environmental Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,China;University of Chinese Academy of Sciences,Beijing 100049,China;China Institute of Water Resources and Hydropower Research(IWHR),Beijing 100038,China;Huaneng Lancang River Hydropower INC,Kunming 650214,China)

机构地区：[1]中国科学院地球化学研究所环境地球化学国家重点实验室,贵阳550081 [2]中国科学院大学,北京100049 [3]中国水利水电科学研究院,北京100038 [4]华能集团澜沧江水电股份有限公司,昆明650214

出　　处：《地球与环境》2025年第1期54-63,共10页Earth and Environment

基　　金：国家自然科学基金项目(92047204、41877407、U2040211)。

摘　　要：澜沧江流域规划和修建了大量的水库大坝,其沉积物中有机质来源的定量识别对准确估算水库碳汇强度具有重要意义。本研究于2021年5月在澜沧江下游糯扎渡水库不同区域采集了5根沉积物柱芯,测定了总有机碳(TOC)和总氮(TN)含量以及有机碳碳同位素(δ^(13)C_(oc))组成。结果表明,糯扎渡水库沉积物TOC含量变化在0.47%~1.79%之间,平均值为1.05%±0.29%。空间上,库尾沉积物TOC含量低于库中和库首,与流域梯级水库TOC的总体变化趋势一致。TOC与TN之间存在显著的正相关关系,回归线的斜率略大于浮游藻类的雷德菲尔德(Redfield)比,表明糯扎渡水库沉积物有机质主要来自水生浮游藻类。根据沉积物C/N比和碳同位素,利用贝叶斯混合模型定量估算沉积物有机质来源,浮游藻类的贡献最大,平均为38%,其次是土壤有机质,贡献为26%。与前期结果相比,糯扎渡水库是澜沧江梯级水库中一个重要的转折点,上游梯级水库沉积物有机质以外源土壤有机质输入为主,在糯扎渡水库转变为以内源水生浮游藻类的贡献为主。其原因一方面归结于上游梯级水库对陆源输入物质的拦截,使得向下游的输送通量减少,另一原因可能是水库自身产生的有机质增加。考虑到糯扎渡水库营养盐浓度较低,这个转变表明下游更低纬度的梯级水库在有利的光热条件下对流域碳循环的影响更大。Numerous dams have been constructed in the Lancang River Basin,thus,identification and quantification of the organic matter sources in the reservoir sediments is indispensable to estimate the magnitude of reservoir carbon sinks.In this study,five sediment cores were collected from different areas of the Nuozhadu reservoir in the lower Lancang River in May 2021,to measure total organic carbon(TOC)and total nitrogen(TN)contents and carbon isotope of organic carbon(δ^(13)C_(oc)).The results show that TOC concentrations in the sediments of the Nuozhadu reservoir varied between 0.47%and 1.79%with a mean value of 1.05%±0.29%.There were significant and positive correlations between TOC and TN contents,with the slopes of the regression lines being slightly larger than the Redfield ratio of phytoplanktonic algae.These indicate that organic matter in the sediments mainly derived from aquatic planktonic algae and to a lesser extent,terrestrial organic matter.Based on sediment C/N ratios and carbon isotopes,the Bayesian mixing model estimated,with phytoplanktonic contributing the most of sediment organic matter,an average of 38%,followed by soil organic matter,contributing 26%.The Nuozhadu reservoir stood out among the Lancang River cascade reservoirs.Organic matter in the reservoir sediments in the upper reaches was dominated by exogenous soil organic matter.In contrast,the proportion of phytoplanktonic algae in organic matter exceeded the contribution of terrestrial organic matter.This is in part due to the interception of terrestrial-derived materials by the upstream reservoirs,but presumably more importantly the increased organic matter produced by photosynthesis.Considering the low nutrient level in Nuozhadu Reservoir,this transition indicates that downstream cascade reservoirs at lower latitudes have a greater impact on basin carbon cycling under favorable light and thermal conditions.

关 键 词：C/N比 有机碳同位素 水库沉积物来源 定量识别 糯扎渡水库 

分 类 号：X142[环境科学与工程—环境科学]