拦河筑坝的水库化进程会改变有机碳的沉积储存。本研究以位于我国西南喀斯特地貌的乌江流域下游两座大型深水水库（思林、彭水水库）为研究对象，利用木质素生物标志物技术对沉积柱中的陆源有机碳进行了定性分析和定量计算，结果表明，木质素含量指标Σ8在0.55 mg/10 g到2.97 mg/10 g之间，Λ8在0.38 mg/100 mg OC到1.42 mg/100 mg OC之间；木质素母源植被信息显示沉积柱中的木质素主要来源于被子植物的草本组织；木质素受白腐菌和棕腐菌共同作用，发生较低程度的去甲基/去甲氧基以及侧链氧化降解。端元模型结果显示，沉积柱中外源有机碳的贡献总体上略大于内源有机碳，其中土壤有机碳贡献最大。河流梯级筑坝作用对沉积物中有机碳的影响表现为外源有机碳的拦截和内源有机碳的积蓄两个方面，并且内外源有机碳分布存在明显的空间异质性。

The impounding process on natural rivers can alter the depositional storage of organic carbon. In this study, the terrestrial organic carbon in the sediment cores in two large deep-water reservoirs (Silin and Pengshui reservoirs) located in the lower reaches of the Wujiang River in the karst landscape of southwest China were used to be analyzed and quantified, by using lignin biomarker technology. The lignin in the sediment cores was mainly derived from the herbaceous tissues of the angiosperms, and the lignin was degraded by demethylation, demethoxylation and oxidative degradation of the side chains by white rot and brown rot bacteria. The end-member model showed that the contribution of exogenous organic carbon to the sediment core was slightly larger than that of endogenous organic carbon, with soil organic carbon contributing the most. The influence of river cascade damming on sedimentary organic carbon is manifested in the interception of exogenous organic carbon and the accumulation of endogenous organic carbon, and there is obvious spatial heterogeneity in the distribution of exogenous and endogenous organic carbon.