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

摘要河流输送的有机碳（OC）是全球碳收支中一个重要的通量，代表了陆地损失和海洋输入的主要术语。河流和河口也是动态系统，在这里，陆地OC在输出到海洋边缘之前进行化学和同位素转化。全球碳收支目前假设河流通量代表陆地生态系统净初级生产量超过分解量。然而，新的数据表明，流入西北大西洋边缘的河流在OC年龄上表现出广泛的变化，从现代到5000年B.P，颗粒OC （POC）往往比溶解OC （DOC）要早得多。因此，在103-108年的时间尺度上，部分存在于大陆储层中的有机碳正在被重新利用，但由于数据极为有限，无法对不同年龄的有机碳库从陆地向海洋的转移进行定量估计。该提案中需要解决的一个主要问题是“河流中调动了多少年轻、年老和古代的有机碳，以及特定河流和河口在排放到海洋之前对DOC和POC的处理是否取决于有机碳年龄和来源特征？”这将通过使用同位素（D14C, d13C），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土地利用、岩性、大小和流量的范围。将对河流水文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。该项目的研究结果对于理解陆源OC如何促进河流和河口的强烈净异养，限制通过河流/河口运输的土壤OC的损失，以及解释海洋边缘由于OC来源和处理而产生的OC的化学和同位素特征具有重要意义。

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.