An evaluation of mobile mud dynamics in the Mississippi River deltaic region
An evaluation of mobile mud dynamics in the Mississippi River deltaic region
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DOI：
10.1016/j.margeo.2004.05.028
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发表时间：
2004-08-30
期刊：
影响因子：
2.9
通讯作者：
Duncan, D
中科院分区：
文献类型：
--
作者：
Corbett, DR;McKee, B;Duncan, D
大河流是陆地和海洋环境之间的主要界面。数量相对较少的河流在输送到沿海海洋的淡水和悬浮物质中所占的比例不成比例。由于三角洲和大陆架被认为是海洋沉积物中有机碳的主要储存库，因此向这些沿海系统的沉积物输送在全球碳循环中发挥着关键作用。这些环境中的颗粒物质通常会沉积并重新悬浮数次，然后才会永久堆积或从货架上运输出去。这种沉积物循环是影响沿海环境中发生的生物地球化学过程的重要组成部分。 2000 年 4 月和 10 月在密西西比河附近的大陆架进行的两次航行期间，收集了水和沉积物样本，用于分析悬浮固体和颗粒反应性放射性核素（(210)Pb、(137)Cs、(7)Be 和 (234)Th），以评估陆地和海洋物质的迁移和归宿。通过比较这些示踪剂的分布，可以深入了解颗粒材料在货架上的路径和停留时间。这些短寿命放射性示踪剂的库存显示出超过两个数量级的变化，表明采样事件之间沉积物沉积的巨大变化。短寿命放射性示踪剂表明，在初始沉积之前，河流传播的物质从河口输送到了不到 30 公里的地方。然而，(7)Be 和 (137)Cs 的季节性变化表明，在高能量（例如风/波浪）冬季月份，沉积物显着重新流动，并且沉积物可能从研究区域输出。此外，(7)Be和过量(234)Th的深度剖面表明两个陆架位置（靠近河流和开放陆架环境）的沉积物沉积速率在0.8和3.9 cm月(-1)（0.4-2.1 g cm(-2)月(-1)）之间。这些速率远大于在同一地点通过 (210)Pb 在十年时间尺度（1.3-2.0 cm 年(-1) 或 0.6-1.5 g cm(-2) 年(-1)）观察到的速率。这进一步证实了活跃的沉积物改造和潜在的陆架出口，正如在其他河流主导的海洋边缘所观察到的那样。 (C) 2004 Elsevier B.V. 保留所有权利。
Large rivers are the primary interface between terrestrial and ocean environments. A relatively small number of rivers account for a disproportionate amount of the freshwater and suspended materials that are delivered to the coastal ocean. Sediment delivery to these coastal systems plays a key role in the global carbon cycle since deltas and continental shelves are considered to be the main repositories of organic carbon in marine sediments. Particulate material in these environments are typically deposited and resuspended several times before permanent accumulation or transport off the shelf. This sediment cycling is an important component influencing biogeochemical processes that occur in coastal environments. During two cruises in April and October 2000 on the shelf adjacent to the Mississippi River, water and sediment samples were collected for analysis of suspended solids and particle reactive radionuclides ((210)Pb, (137)Cs, (7)Be and (234)Th) to evaluate the transport and fate of terrestrial and marine material. A comparison of the distribution of these tracers provides insight about the pathways and residence times of particulate materials on the shelf. Inventories of these short-lived radiotracers showed variations of more than two orders of magnitude, indicating dramatic variations in sediment deposition between sampling events.Short-lived radiotracers indicate that river-borne materials are transported less than similar to 30 km from the river mouth before initial deposition. However, seasonal variations in (7)Be and (137)Cs indicate significant remobilization of sediment and potential export of sediment out of the study area during the high energy (e.g., wind/wave) winter months. In addition, depth profiles of (7)Be and excess (234)Th indicate sediment deposition rates between 0.8 and 3.9 cm month(-1) (0.4-2.1 g cm(-2) month(-1)) at two shelf locations (near river and open shelf environments). These rates are much greater than those observed on decadal time scales (1.3-2.0 cm year(-1) or 0.6-1.5 g cm(-2) year(-1)) via (210)Pb at the same sites. This further substantiates active sediment reworking and potential export off the shelf as has been observed in other river-dominated ocean margins. (C) 2004 Elsevier B.V. All rights reserved.