Yutian Ke, Damien Calmels, Julien Bouchez, Aurélie Noret, Marc Massault, Benjamin Chetelat, Hongming Cai, Jiubin Chen, Cécile Quantin, Jérôme Gaillardet
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引用次数: 0
摘要
人工水库显著改变了悬浮颗粒物(SPM)从河流到海洋的自然运输,从而通过颗粒有机碳(POC)在十年至千年时间尺度上的动态变化重塑了全球碳循环。本文研究了长江上游金沙江流域梯级水库(CMRs)运行对POC组成、运移和命运的扰动。cmr给SPM和POC的输送带来了新的扰动,加剧了三峡大坝的影响。我们分析了POC的元素、稳定和放射性成因同位素组成,以及上下CJ收集的SPM的无机化学成分。自cmr建设以来,人工水库的POC固存量约为660万吨/年(MtC yr - 1),其中380万吨/年为生物圈来源的POC (POCbio)。值得注意的是,在TGD中捕获的POC通量从1.6 MtC / yr - 1下降到0.4 MtC / yr - 1,而cmr捕获了0.7 MtC / yr - 1。这一转变突出了POC埋藏地点从三峡库区和河口向上游水库的迁移。大型山地河流水库中陆相POC的快速埋藏有望通过减少长时间向河口输送造成的矿化而加强POC的保存。泥沙负荷的显著减少和水库滞留导致POC比例的增加,极大地改变了输出POC的组成和通量,影响了下游和河口的碳循环。
Regulation of Particulate Organic Carbon by Cascade Mega-Reservoirs in the Changjiang Basin: Enhanced Sequestration and Altered Downstream Composition
Artificial reservoirs significantly alter the natural transport of suspended particulate matter (SPM) from rivers to oceans, thereby reshaping the global carbon cycle through changes in particulate organic carbon (POC) dynamics over decadal to millennial timescales. Here, we investigate dam-induced perturbation of POC composition, transport, and fate within the Changjiang (CJ) River basin in response to the operation of cascade mega-reservoirs (CMRs) along the Jinshajiang (JSJ) in the upper CJ. The CMRs have introduced new perturbations to SPM and POC delivery, compounding the effects of the Three Gorges Dam (TGD). We analyzed elemental, stable, and radiogenic isotopic compositions of POC, as well as the inorganic chemistry of SPM collected from both the upper and lower CJ. Since the construction of CMRs, POC sequestration in artificial reservoirs reaches approximately 6.6 megatons carbon per year (MtC yr−1), 3.8 MtC yr−1 of which being POC of biospheric origin (POCbio). Notably, the flux of POC trapped in the TGD declined from 1.6 to 0.4 MtC yr−1, while CMRs sequestered 0.7 MtC yr−1. This shift highlights the relocation of POC burial sites from the TGD and estuary to upstream reservoirs. The rapid burial of terrestrial POC in large mountainous river reservoirs is expected to enhance POC preservation by minimizing mineralization caused by prolonged transport to estuaries. The significant reduction in sediment load and the increased proportion of POCbio due to reservoir retention have substantially altered the composition and flux of exported POC, impacting downstream and estuarine carbon cycles.
期刊介绍:
Global Biogeochemical Cycles (GBC) features research on regional to global biogeochemical interactions, as well as more local studies that demonstrate fundamental implications for biogeochemical processing at regional or global scales. Published papers draw on a wide array of methods and knowledge and extend in time from the deep geologic past to recent historical and potential future interactions. This broad scope includes studies that elucidate human activities as interactive components of biogeochemical cycles and physical Earth Systems including climate. Authors are required to make their work accessible to a broad interdisciplinary range of scientists.