在全球变化与人类活动双重压力下,极端风暴事件对河口沉积过程和碳汇能力的影响愈发突出。然而,传统单次取心方法难以对风暴事件导致的侵蚀-堆积过程及其碳埋藏净效应进行准确评估。本研究以中国杭州湾大鱼山岛为典型区域,针对同一站位分别于2021年(台风“灿都”前)和2022年开展了重复取心。通过沉积物粒度、构造以及放射性核素分析与对比,揭示了一次由台风“灿都”触发的剧烈的“侵蚀-堆积”事件;并结合元素组成与有机地球化学指标,定量评估了该事件的碳埋藏净效应。研究表明,尽管风暴层本身表现为高效的有机碳保存,但强烈的侵蚀作用造成了1 950±523 g·m^-2的有机碳净亏损。此发现揭示了沉积记录中事件沉积层的“幸存者偏差”,基于单次取心的研究结果会系统性地高估风暴对河口碳埋藏的贡献。本研究发展的“重复取心-核素示踪”方法,为准确评估非稳态条件下的河口沉积过程与碳埋藏能力提供了新的范式。

Under the dual pressures of global change and human activities, the impact of extreme storm events on estuarine sedimentary processes and carbon sink capacity has become increasingly prominent. However, traditional single-core methods face challenges in quantitatively characterizing the erosion-deposition processes and net carbon burial effects induced by storm events. In this study, we conducted repetitive coring at a fixed station near the Dayushan Island in the Hangzhou Bay, China in 2021 (before Typhoon Chanthu) and 2022. Through analysis of sedimentary structures, grain size and radionuclides, we identified an intense erosion-deposition event triggered by Typhoon Chanthu. Combined with elemental composition and organic geochemical indicators, we further quantitatively assessed its net impact on carbon burial. The results demonstrate that despite the efficient organic carbon preservation within the storm layer, the related intense erosion resulted in a net organic carbon deficit of 1 950±523 g·m^-2. This finding highlights a preservation bias of the storm layers in sedimentary records, leading to a systematic overestimation of the storm contribution to estuarine carbon burial in studies relying on single cores. The “repetitive coring-radionuclides tracing” methodology developed in this study provides a new paradigm for accurately assessing estuarine sedimentary processes and carbon cycling under non-steady-state conditions.