Collaborative Research: Episodic, ENSO-Orchestrated Carbon Sequestration in Amazonian River Basins by Erosion-Sedimentation Processes

这个跨学科小组的建议涉及一个三步过程，可能代表亚马逊前陆盆地的一个主要碳汇。作为假设，该建议表明：1)在拉尼娜相关的大风暴期间，安第斯山脉广泛的山坡破坏和河道迁移调动了大量的低有机碳（OC）含量的新鲜有机质和沉积物；2)在河流内部，矿物表面通过吸附获得了正常的OC负荷，因为它们从山地烃源盆地迅速被抽离到邻近的前陆沉积中心；3)沉积的沉积物将“新鲜”碳保存在有机矿物复合体中，并通过深埋在点坝和“裂缝-展”沉积物中，这些沉积物几乎没有与生物圈和大气交换的潜力。项目描述（C.1.2）中给出的计算表明，这一过程每次可以在亚马逊前陆封存约3亿吨碳。当外推到全球其他潮湿的热带地区时，这些估计相当于平均每年“丢失的碳汇”的50-100%或拉尼娜期间典型观测到的大气二氧化碳异常的50-100%。为了探索这些假设，研究人员将研究1)极端事件下河流沉积物动员、运输和沉积的速率和机制，2)有机碳与侵蚀和沉积地点沉积物的关联，以及3)通过吸收和深埋过程，OC从快速（5 y）转移到较慢（50 y）周转池。我们将结合对卫星图像的GIS分析来绘制与单个大风暴相关的变化（山坡破坏和河流迁移）；泥沙输运过程的野外调查；对存档和新收集的样品进行实验室分析，以确定有机碳浓度、来源和周转时间；沉积特征;以及搬运/沉积的时间和速率（地质年代学）。拟议的项目是一个合作的、多学科的、多国的研究工作，它建立在以前和目前由美国国家科学基金会资助的关于亚马逊河流域十年尺度沉积物通量和有机碳动态的研究结果的记录之上。斯特劳德水研究中心和加州大学戴维斯分校的科学家们将与华盛顿大学的科学家们进行的沉积物通量、地质年代学、地球化学和过程测绘（GIS）研究密切配合，调查这些地貌过程中调动的有机碳的数量、来源和封存。此外，本项目得益于与法国发展研究所（IRD）的密切合作，我们将在旱季和雨季在玻利维亚和秘鲁的安第斯山脉和前陆盆地进行实地考察。其他合作伙伴包括国立农业大学和加州大学圣巴巴拉分校。这些持续的国际合作为目前研究极端风暴事件运输和沉积碳的提案提供了相当大的科学和后勤优势，并节省了成本。如果这项研究工作证实了最初的假设，那么这种大陆尺度的、气候驱动的侵蚀-沉积过程将被证明是具有全球意义的大量的、以前未被认识到的天然碳汇。此外，这些过程可能会通过人为加速的侵蚀-沉积而潜在地导致类似数量的碳的吸收。此外，这项研究对任何对沉积物和土壤中有机碳保存的地球化学过程感兴趣的人都有好处，或者在极端的、enso组织的洪水期间，滑坡、沉积物运输、河道-洪泛平原相互作用和沉积盆地动力学的时间/速率/机制。地貌学、生物地球化学和有机地球化学之间的紧密联系对整个地球科学具有更广泛的影响，提供了新的视角，将促进新的地球化学和地理信息系统技术的发展。加强与ird的合作，支持建立富有成效和可见的国际跨学科科学伙伴关系。例如，我们之前与IRD的合作研究使我们对土著居民的河岸食物来源中的汞污染动力学有了新的认识。pi有公开宣传的记录，这个项目将产生对教育工作者和研究人员有用的数据产品，包括我们自己的教学和对科学家和普通观众的公开演讲。此外，这将为美国和南美的许多本科生和一些研究生提供宝贵的研究经验，包括为这些学生在会议上发表和展示结果提供资金。

0404169 Aufdenkampe This interdisciplinary group proposal addresses a three-step process that could represent a majorcarbon sink in Amazonian foreland basins. Stated as hypotheses, the proposal suggests: 1) extensiveAndean hillslope failure and channel migration during large La Nina associated storms mobilizes vastquantities of fresh organic matter and sediment with low organic carbon (OC) content ; 2) within theriver, mineral surfaces acquire normal OC loadings via sorption as they are rapidly evacuated from themountainous source basins to adjacent foreland depocenters; and 3) deposited sediments preserve "fresh"carbon within organo-mineral complexes and by deep burial in point bars and "crevasse-splay" depositsthat have little potential for exchange with the biosphere and atmosphere. Calculations presented in theProject Description (C.1.2) suggest that this process could sequester ~ 300 Mtonnes of carbon per event inthe Amazonian foreland. When extrapolated globally to other humid tropical regions, these estimates areequivalent to 50-100% of the average annual "missing carbon sink" or 50-100% of atmospheric CO2anomalies typically observed during La Nina.To explore these hypothesis, proposers will study 1) the rates and mechanics of sedimentmobilization, transport, and deposition of river sediment during extreme events, 2) the associations oforganic carbon with sediments at erosional and depositional sites, and 3) the transfer of OC from rapid(5 y) to slower (50 y) turnover pools, via sorption and deep burial processes. We will employ acombination of GIS analysis of satellite images to map changes associated with individual large storms(hillslope failures and river migration); field surveys of sediment transport processes; and laboratoryanalysis of archived and newly collected samples to determine organic carbon concentrations, sources andturnover times; sediment characteristics; and transport/deposition timing and rates (geochronology).The proposed project is a collaborative, multi-disciplinary, multi-national research effort thatbuilds upon a record of prior and current NSF-funded results of decadal-scale sediment fluxes and organiccarbon dynamics within river basins of the Amazon. In close coordination with sediment-flux,geochronological, geochemical, and process-mapping (GIS) studies conducted by scientists from Univ. ofWashington, scientists at Stroud Water Research Center and Univ. of California Davis will investigate thequantities, sources, and sequestration of organic carbon mobilized during by these geomorphologicalprocesses. In addition, this project benefits from a close working collaboration with the French Institut deRecherche pour le Developpement (IRD), with whom we will conduct fieldwork in the Andes andforeland basins of Bolivia and Peru during both the dry and wet seasons. Additional collaborations arewith the Univ. Nacional Agraria La Molina (UNALM) and the Univ. of California Santa Barabara. Thesecontinuing international collaborations offer considerable scientific and logistical advantages and costsavings for this current proposal to study the carbon transported and deposited by extreme storm events.If this research effort substantiates the primary hypothesis, such continental-scale, climate-driven,erosion-sedimentation processes will be demonstrated to represent substantial, previously unrecognizednatural carbon sinks of global significance. Furthermore, these processes could potentially result in thesequestration of similar quantities of carbon by anthropogenically accelerated erosion-sedimentation.Additionally, this research benefits anyone interested in the geochemical processes of organic carbonpreservation in sediment and soils or the timing/rates/mechanics of landsliding, sediment transport,channel-floodplain interaction, and sedimentary basin dynamics during extreme, ENSO-orchestratedfloods.The strong bridging between the disciplines of geomorphology, biogeochemistry and organicgeochemistry has broader impacts on earth science as a whole, by offering new perspectives that willfacilitate the development of new geochemical and GIS techniques. Enhanced collaboration with IRDsupports a productive and visible international, interdisciplinary scientific partnership. For example, ourprevious collaborative research with IRD resulted in new understandings of mercury contaminationdynamics within riparian food sources to indigenous human populations. The PIs have a record of publicoutreach, and this project will generate data products useful to educators and researchers, including ourown teaching and public presentations to both scientists and general audiences. Furthermore, this willprovide valuable research experience to many undergraduate and some graduate students in the USA andSouth America, including funds for these students to publish and present results at meetings.