Age Distribution of the Particulate Organic Carbon (POC) Discharged from Small Mountainous Rivers-- the Influence of Sediment Yield and Soil Residence Time

短而多山的河流支配着北美西缘和整个海洋的沉积物供给。 由于快速的景观剥蚀率和最小的沉积物存储在这些活动的边缘系统，颗粒有机碳（POC）排放不同的被动边缘上较大的河流运输。 最近对加州两条河流的调查表明，它们携带现代和古代颗粒有机碳（POC）的双峰混合物，几乎同样来自现存植被和隆起沉积岩的干酪根。 初步估计，在这些系统中，土壤在发生显著老化之前或在油母质被完全氧化并被现代物质取代之前被侵蚀。 基于这些初步的结果，现代，古代和中年的河流携带的POC之间的平衡被假设为依赖于颗粒在风化层中的停留时间。 为了验证这一假设，本次调查将表征悬浮颗粒有机碳负荷的六条河流，表现出三个数量级范围内的产沙量。 四条河流（Siuslaw，Noyo，Russian和Eel）流经北方加州和俄勒冈州的部分地区。 选择新西兰北岛的Waipaoa河和Waiapu河是因为它们的产沙量极高。 基岩POC也将在每个流域的特点。 本文介绍了OC含量、13 C/12 C（d13 C）和14 C/12 C（？）14 C），将在散装样品，以及密度和大小分级的子样品，以确定干酪根和现代C含量。 将对鳗鱼流域的土壤剖面进行进一步研究，以进一步描绘风化和风化层中的有机碳置换过程。 POC池从基岩C到现代表层材料的演变将在厚层进行研究，与以前的结果从薄土壤剖面进行对比。 本研究结果将有助于进一步了解有机碳从流域向海洋迁移的数量和性质的调控过程。 这项研究还解决了一个关键问题，在长期的地球化学循环，即如何以前埋OC回收。 通过这项调查，可以大大改善对过去环境，特别是活动边缘的沉积有机地球化学记录的解释。

AbstractShort, mountainous rivers dominate the fluvial supply of sediment to the western margin of North America and to the oceans in general. As a result of rapid rates of landscape denudation and minimal sediment storage in these active margin systems, the particulate organic carbon (POC) discharged differs from that transported by larger rivers on passive margins. Recent investigations of two rivers in California indicate they carry a bimodal mixture of modern and ancient particulate organic carbon (POC), derived almost equally from extant vegetation and from the kerogen of uplifted sedimentary rocks. To a first approximation, soils are eroded in these systems before significant aging occurs or before the kerogen can be completely oxidized and replaced by modern material. Based on these preliminary results, the balance between modern, ancient, and intermediate-aged POC carried by rivers is hypothesized to depend on the residence time of particles in the regolith. To test this hypothesis, this investigation will characterize the suspended POC loads of six rivers that exhibit a three-order range of magnitude in sediment yield. Four rivers (Siuslaw, Noyo, Russian, and Eel) drain portions of northern California and Oregon. The Waipaoa and Waiapu rivers on the north island of New Zealand were chosen because of their extremely high sediment yields. Bedrock POC will also be characterized in each of the watersheds. The principle measurements, OC content, 13C/12C(d13C), and 14C/12C (?14C), will be made on bulk samples, as well as density- and size-fractionated subsamples, to determine the kerogen and modern C contents. Additional studies of soil profiles in the Eel watershed will be conducted to further delineate weathering and OC replacement processes in the regolith. The evolution of the POC pool from bedrock C to modern surficial material will be studied in thick horizons, to contrast with previous results from thin soil profiles. The results of this study will further understanding of the processes that regulate the quantity and character of OC transported from drainage basins to the ocean. This study also addresses a key issue in the long-term biogeochemical cycle, namely how previously buried OC is recycled. Interpretation of the sedimentary organic geochemical record of past environments, particularly on active margins, could be significantly improved by this investigation.