Sources of terrestrially-derived organic carbon in lower Mississippi River and Louisiana shelf sediments: Implications for differential sedimentation and transport at the coastal margin
Sources of terrestrially-derived organic carbon in lower Mississippi River and Louisiana shelf sediments: Implications for differential sedimentation and transport at the coastal margin
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DOI：
10.1016/s0304-4203(01)00088-3
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发表时间：
2002-02
期刊：
影响因子：
3
通讯作者：
T. Bianchi;S. Mitra;B. McKee
中科院分区：
文献类型：
--
作者：
T. Bianchi;S. Mitra;B. McKee
在这项研究中，我们研究了陆地有机碳源的时间和空间变异性在较低的密西西比河和路易斯安那州陆架沉积物（在11个巡航超过22个月的时间），以进一步了解排序动态和选择性运输的维管植物材料的主要分散系统内的河流。下游河流沉积物的δ 13 C值介于−21.90‰至−24.64‰之间（平均值为−23.20±1.09‰），这些值通常比陆架沉积物（−22.5‰至−21.2‰）更贫。下游河流中的Λ8值（Λ8=氧化100 mg有机碳产生的香草基酚、丁香基酚和肉桂基酚的总和）范围为0.71至3.74（平均值=1.78±0.23）。虽然Λ 8与河流流量之间没有显著的关系（p>0.05），但最高值出现在1999年4月的洪峰流量期间，对应于观测到的最高C/N值17.41。陆架沉积物的Λ 8值为0.68 ~ 1.36（平均值为0.54±0.30），显著低于下游河流沉积物的平均值（p<0.05）。S/V（肉桂基/香草基）和C/V（肉桂基/香草基）比的范围在货架上，分别为0.11至0.95和0.01至0.08，与下游河流中发现的相似。这些低的C/V比率表明木质和非木质碳源的混合物。Goni等人的近期工作[Nature 389（1997）275; Geochim.宇宙化学。Acta 62（1998）3055]，其中不包括采样断面内的主要传播系统的密西西比河，显示了非木本维管植物的签名在路易斯安那州的货架上。这表明，riverine-derived木本组织优先解决了水柱，在较低的河流和内陆架，C3与C4非木本材料在其他地区的货架和斜坡的选择性扩散之前。这项工作进一步证明了差异沉降的颗粒，采样位置内的分散系统，和河流流量的重要性，当检查河流占主导地位的边缘生态地球化学循环。
In this study, we examined the temporal and spatial variability of terrestrial organic carbon sources in lower Mississippi River and Louisiana shelf sediments (during 11 cruises over a 22-month period) to further understand the sorting dynamics and selective transport of vascular plant materials within the primary dispersal system of the river. Bulk δ13C values in lower river sediments ranged from −21.90‰ to −24.64‰ (mean=−23.20±1.09‰), these values were generally more depleted than those found in shelf sediments (−22.5‰ to −21.2‰). The Λ8(Λ8=sum of vanillyl, syringyl and cinnamyl phenols produced from the oxidation of 100 mg of organic carbon) values in the lower river ranged from 0.71 to 3.74 (mean=1.78±0.23). While there was no significant relationship between Λ8and river discharge (p>0.05), the highest value occurred during peak discharge in April 1999—which corresponded to the highest observed C/N value of 17.41. The Λ8values on the shelf ranged from 0.68 to 1.36 (mean=0.54±0.30) and were significantly lower (p<0.05) than the average value for lower river sediments. The range of S/V (syringyl/vanillyl) and C/V (cinnamyl/vanillyl) ratios on the shelf, 0.11 to 0.95 and 0.01 to 0.08, respectively, were similar to that found in the lower river. These low C/V ratios are indicative a mixture of woody and non-woody carbon sources. Recent work by Goni et al. [Nature 389 (1997) 275; Geochim. Cosmochim. Acta 62 (1998) 3055], which did not include sampling transects within the primary dispersal system of the Mississippi River, showed a non-woody vascular plant signature on the Louisiana shelf. This suggests that riverine-derived woody tissues preferentially settle out of the water column, in the lower river and inner shelf, prior to the selective dispersal of C3versus C4non-woody materials in other regions the shelf and slope. This works further demonstrates the importance of differential settlement of particles, sampling location within the dispersal system, and river discharge, when examining biogeochemical cycles in river-dominated margins.