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

点击翻译按钮获取中文摘要

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.