Vegetal Undercurrents-Obscured Riverine Dynamics of Plant Debris.
Vegetal Undercurrents-Obscured Riverine Dynamics of Plant Debris.
复制标题
植物潜在的植物碎片河流动力学。
DOI：
10.1029/2021jg006726
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发表时间：
2022-03
影响因子：
3.7
通讯作者：
Eglinton, Timothy, I
中科院分区：
文献类型：
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作者：
Schwab, Melissa S.;Hilton, Robert G.;Haghipour, Negar;Baronas, J. Jotautas;Eglinton, Timothy, I
由于其运输，分散和保存有机碳（OC）的潜力，人们一直关注河流中作为悬浮物携带的细粒沉积物，而与河流系统中粗粒沉积物相关的OC的转移和归宿研究较少。在这里，沉积物的沉积学，地球化学和生物分子的特征，从河流深度剖面揭示了不同的池OC内的麦肯齐河流系统不同的水动力学行为。较高的放射性碳（14 C）含量，较低的N/OC比值和升高的植物来源的生物标志物负荷表明，在三角洲上游和三角洲内部的大型通道中，沉水维管植物碎片在活动河床上方进行了系统的运输。零度以下的温度阻碍有机碳的降解，促进流域内植物碎屑的积累和水涝。一旦被卷入河道，持续的水流强度和浮力可以防止植物碎片沉降，并使其悬浮在河床上方的水柱中。弯曲河段内的螺旋流运动集中了内河弯曲处附近的成岩和有机碎屑，形成了含沉积物的羽流。移动到近海，我们观察到缺乏离散的，颗粒OC在大陆架沉积物中，这表明在三角洲和浅海环境中的粗碎屑的优先捕获。在春季洪水期间，水涝植物碎屑运输和高沉积物负荷的交付可能会减少氧气暴露时间和微生物分解，从而增强生物圈OC的封存。暗流丰富的粗，相对新鲜的植物片段似乎是重复出现的功能，突出了一个鲜为人知的，但重要的机制在陆地碳循环。
Much attention has been focused on fine‐grained sediments carried as suspended load in rivers due to their potential to transport, disperse, and preserve organic carbon (OC), while the transfer and fate of OC associated with coarser‐grained sediments in fluvial systems have been less extensively studied. Here, sedimentological, geochemical, and biomolecular characteristics of sediments from river depth profiles reveal distinct hydrodynamic behavior for different pools of OC within the Mackenzie River system. Higher radiocarbon (14C) contents, low N/OC ratios, and elevated plant‐derived biomarker loadings suggest a systematic transport of submerged vascular plant debris above the active riverbed in large channels both upstream of and within the delta. Subzero temperatures hinder OC degradation promoting the accumulation and waterlogging of plant detritus within the watershed. Once entrained into a channel, sustained flow strength and buoyancy prevent plant debris from settling and keep it suspended in the water column above the riverbed. Helical flow motions within meandering river segments concentrate lithogenic and organic debris near the inner river bends forming a sediment‐laden plume. Moving offshore, we observe a lack of discrete, particulate OC in continental shelf sediments, suggesting preferential trapping of coarse debris within deltaic and neritic environments. The delivery of waterlogged plant detritus transport and high sediment loads during the spring flood may reduce oxygen exposure times and microbial decomposition, leading to enhanced sequestration of biospheric OC. Undercurrents enriched in coarse, relatively fresh plant fragments appear to be reoccurring features, highlighting a poorly understood yet significant mechanism operating within the terrestrial carbon cycle.