Collaborative Research: Assessing the Variability and Modification of Age, Character and Reactivity of Organic Carbon Delivered by Rivers and Estuaries to an Ocean Margin

合作研究：河流和河口向海洋边缘输送有机碳的年龄、特征和反应性的变化和改变的评估摘要有机碳（OC）的河流输送是全球碳收支中的一个重要通量，代表着陆地损失和海洋输入的主要条件。 河流和河口也是动态系统，在这些系统中，陆地有机碳在输出到海洋边缘之前发生化学和同位素转化。 目前全球碳收支假设河流通量代表陆地生态系统净初级生产力超过分解的部分。 然而，新的数据表明，流向西北大西洋边缘的河流的OC年龄范围很广，从现代到5,000年B. P.，其中颗粒OC（POC）通常比溶解的OC（DOC）老得多。 因此，在103-108年的时间尺度上，居住在大陆水库中的有机碳的一部分正在重新动员，但极其有限的数据集排除了不同年龄的有机碳池从陆地到海洋的转移的定量估计。本提案中要解决的一个主要问题是“有多少年轻、古老和古老年龄的OC在河流中被动员，以及在排放到海洋之前，特定河流和河口中DOC和POC的处理是否取决于OC年龄和来源特征？“这将通过使用同位素（D14 C，d13 C），有机生物标志物（干酪根，微生物脂肪酸，植物木质素和碳氢化合物）和建模方法检查河流/河口系统的区域子集来解决。选择用于研究的系统将涵盖美国东北部的土地利用、岩性、大小和流量。将对河流水文过程的不同阶段进行采样，以评估径流和停留时间作为控制因素的关键作用。 从这个项目的结果将是重要的了解如何陆源有机碳燃料的河流和河口的强烈净异养，限制通过河流/河口运输的土壤有机碳的损失，并解释化学和同位素签名的OC在海洋边缘由于OC的来源和处理。

Collaborative Research: Assessing the Variability and Modification of Age, Character and Reactivity of Organic Carbon Delivered by Rivers and Estuaries to an Ocean MarginAbstractRiverine transport of organic carbon (OC) is a significant flux in the global C budget, representing major terms for both terrestrial losses and marine inputs. Rivers and estuaries are also dynamic systems where terrestrial OC is transformed chemically and isotopically prior to its export to the ocean margins. The global C budget currently assumes that riverine flux represents the excess of terrestrial ecosystem net primary production over decomposition. New data, however, show that rivers discharging to the NW Atlantic margin exhibit a broad range in OC ages, from modern to 5,000 yrs B.P., with particulate OC (POC) often being much older than dissolved OC (DOC). Therefore, part of the OC residing in continental reservoirs on 103-108 year timescales is being remobilized, but the extremely limited dataset precludes quantitative estimates of the transfer of different-aged OC pools from land to the oceans. A major question to be addressed in this proposal is "How much OC of young, old, and ancient ages is mobilized in rivers, and is the processing of DOC and POC in specific rivers and estuaries prior to discharge to the ocean dependent on OC ages and source characteristics?" This will be addressed by examining a regional subset of river/estuarine systems using isotopic (D14C, d13C), organic biomarker (kerogen, microbial fatty acids, plant lignin, and hydrocarbons), and modeling approaches. The systems chosen for study will cover a spectrum of land-use, lithology, size and discharge in the northeastern U.S. Different stages of the rivers' hydrographs will be sampled to assess the key roles of runoff and residence times as controlling factors. Results from this project will be important for understanding how land-derived OC fuels the intense net heterotrophy of rivers and estuaries, for constraining the losses of soil OC via river/estuarine transport, and for interpreting the chemical and isotopic signatures of OC in ocean margins due to both OC sources and processing.