Nano-scale biogeochemistry of organic carbon across a long-term mineralogical gradient

土壤是全球范围内陆地有机碳(C)的最大储存库。鉴于预测的气候变化，土壤？it’积累和保留C的能力受到了越来越多的关注。关于气候变化的《京都议定书》要求对控制土壤中碳的稳定和释放的机制有一个基本的了解。然而，土壤中碳长期稳定的潜在地球生物学机制仍然没有得到很好的理解，以及地球最上层碳封存的潜力？S表面仍然是未知的。目前土壤有机碳转换的概念模型建立在破坏性的宏观分析方法上，并不完全面向过程，通常无法提供关于矿物学与有机碳功能之间联系的明确分子水平信息，以及有机碳组合的空间特征。拟议项目的目标是设计新颖的实验性和非破坏性高分辨率光谱显微镜（STXM和NEXAFS）方法，使我们能够获得有关以下方面的第一手过程导向生物地球化学证据：(1)在微观和亚微观水平上矿物、多价金属离子、有机C官能团和有机组合的其他建筑特征的原位空间排列；(2)关于吸附原子和表面相互作用的局部结构和组成环境、空间分配的微观和纳米尺度异质性以及有机组合的其他分子水平特征的特定元素信息。特别令人感兴趣的是在成土过程中沿着矿物学梯度发展的长期变化。我们计划对将从默塞德-加利福尼亚的长期土壤时序中收集的样本进行拟议的调查，其中潜在的地貌单元的年龄范围从3到3000凯尔。智力优势：该项目旨在开发创新的分析方法，包括使用基于同步加速器的直接显微和光谱技术。这些新方法将揭示分子和原子水平上的高分辨率信息，为空间组织和表面生物地球化学相互作用导致的有机碳稳定提供详细的机制理解。该项目将是首个此类项目，并将推进有关有机碳长期稳定和全球生物地球化学碳循环的知识，该循环是由碳、土壤矿物质和临界带突出土壤性质的复杂相互作用驱动的。对于更广泛的科学界来说，项目成果将显著加强对地球气候变化和环境的研究。s个C循环。更广泛的影响：该项目将建立当地的教学、学习和研究能力。本科、研究生和研究生阶段的学生将接受使用各种新技术及其应用的培训。将特别努力积极招收非传统、少数民族和女学生。分析方法的创新性提供了开发短期协作实践培训项目的可能性。基于同步加速器的红外和x射线光谱显微技术在环境地球生物学中的潜力和应用对处于职业发展初期的环境科学家。我们还计划组织一个关于？基于同步加速器的环境中有机矿物组合的微纳米尺度制图？结合国际地球科学会议，努力将这些光谱显微镜技术作为新兴的环境研究技术介绍给更广泛的受众。该项目的结果将通过年度报告和同行评议的国际期刊出版物向科学界通报。该项目加入了美国西部许多其他生态系统研究项目，并将结果直接传达给参与教育、研究和政策制定的组织。

Soil represents the largest reservoir of terrestrial organic carbon (C) on the global scale. In light of predicted climate change, the soil?s ability to accumulate and retain C has received growing interest. The Kyoto Protocol on climate change demands a fundamental understanding of mechanisms that control C stabilization and release from soils. Yet, the underlying geobiological mechanisms for the long-term stabilization of C in soils are still not well understood, and the potential for C sequestration in the uppermost layers of the Earth?s surface remains unknown. Current conceptual models of soil organic C turnover build on destructive macroscopic analytical approaches are not fully process-oriented, and usually fail to provide explicit molecular-level information about the linkage between mineralogy and organic C functionalities, as well as the spatial features of organomineral assemblages. The objective of the proposed project is to design novel experimental and non-destructive high resolution spectromicroscopic (STXM and NEXAFS) approaches that enable us to obtain first-hand process-oriented biogeochemical evidence regarding: (i) the in situ spatial arrangement of minerals, polyvalent metal-ions, organic C functionalities and other architectural features of organomineral assemblages at the microscopic and sub-microscopic level, and (ii) element-specific information about local structural and compositional environments of adsorbing atoms and surficial interactions, micro- and nano-scale heterogeneity in spatial allocations and other molecular-level features of organomineral assemblages. Of particular interest are the long-term changes along a mineralogical gradient developed during pedogenesis. We plan to conduct the proposed investigation on samples that will be collected from a long-term soil chronosequence at Merced-California, where the underlying geomorphologic units range in age from 3 to 3000 Kyr. Intellectual merit: This project aims to develop innovative analytical approaches involving the use of synchrotron-based direct microscopic and spectroscopic techniques. These novel methods will reveal high-resolution information on a molecular- and atomic-level providing a detailed mechanistic understanding of organic C stabilization due to spatial organization and surficial biogeochemical interactions. This project will be the first of its kind and advance knowledge about long-term stabilization of organic C and global biogeochemical C cycling driven by the complex interaction of C, soil minerals and the emergent soil properties in the critical zone. For the broader scientific community, project outcomes will significantly strengthen climate change and environmental research of Earth?s C cycles. Broader impacts: This project will build local capacity in teaching, learning and research. Students at the undergraduate, graduate and post-graduate levels will be trained using a wide array of new technologies and their applications. A particular effort will be made to actively recruit non-traditional, minority and female students. The innovative nature of the analytical approach affords the possibility of developing a short collaborative hands-on training program on ?The potentials and applications of synchrotron-based infrared and X-ray spectromicroscopic techniques in environmental geobiology? to environmental scientists who are at early stage of career development. We also plan to organize a symposium on ?Synchrotron-based micro- and nano-scale mapping of organomineral assemblages in the environment? make an effort to introduce these spectromicroscopy techniques to a wider audience as emerging environmental research techniques in conjunction with international geosciences meetings. The results of the project will be communicated to the scientific community through annual presentations and publications in peer reviewed international journals. This project joins a number of others ecosystems research programs in Western US, and communicate results directly to organizations involved in education, research and policy making.