New Solid-State NMR Techniques for Analyzing Insoluble Organic Matter

在分析和表面化学以及地质和古生物学项目的支持下，爱荷华州立大学的Klaus Schmidt-Rohr教授及其同事将开发并应用先进的固态核磁共振方法来识别至少40个特定的官能团，并估计它们在天然有机物中的浓度。这将通过基于异核偶极耦合或化学位移各向异性的一组有效的新的光谱编辑脉冲序列来实现。此外，给定官能团的较大环境将在二维和三维相关实验中被识别，并通过自旋扩散在1到50纳米尺度上识别不均匀。核磁共振动力学测量将使搜索软流动区域成为可能，这些区域已被用来解释有机污染物在土壤有机质中的分配。在项目接近尾声时，将为土壤和海洋有机质的例子建立改进的结构模型。核磁共振波谱将用于阐明自然环境中出现的不溶性有机物质的化学和超分子结构，如土壤和海洋有机物、干酪根或沥青材料。为此，正在开发先进的固体核磁共振方法，可以识别和量化有机固体中的大量化学基团。此外，还将对纳米尺度的微区进行表征。核磁共振方法将用于表征污染物的化学结合部位；帮助了解养分向土壤中的释放；指明加强土壤中的碳固存以减少大气中“温室气体”的方法；以及阐明土壤、干酪根和化石燃料形成的化学过程。这将有助于更深入地了解天然有机物的化学史、其在全球碳循环中的作用以及人类活动对环境的影响。

In this project supported by the Analytical and Surface Chemistry and the Geology and Paleontology Programs, Professor Klaus Schmidt-Rohr and coworkers at Iowa State University, advanced solid-state NMR methodologies will be developed and applied to identify at least 40 specific functional groups and estimate their concentrations in natural organic matter. This will be achieved by means of a set of efficient new spectral-editing pulse sequences based on heteronuclear dipolar couplings or chemical-shift anisotropies. Furthermore, the larger environment of a given functional group will be identified in two- and three-dimensional correlation experiments, and inhomogeneities on a 1- to 50-nm scale by spin diffusion. NMR dynamics measurements will enable the search for soft mobile regions that have been invoked to explain the partitioning of organic contaminants into soil organic matter. Near the end of the project, improved structural models for examples of soil and marine organic matter will be generated. Nuclear magnetic resonance spectroscopy will be used to elucidate the chemical and supramolecular structures of insoluble organic substances that are presented by the natural environment, such as soil and marine organic matter, kerogen, or bituminous materials. To this end, advanced solid-state nuclear magnetic resonance methods are being developed that can identify and quantify a large number of chemical groups in organic solids. In addition, nanometer-scale domains will be characterized. The NMR methods will be used to characterize the chemical binding sites of contaminants; to help understand nutrient release into soil; to indicate methods for enhanced carbon sequestration in soil to reduce "greenhouse gases" in the atmosphere; and to shed light on the chemical processes of soil, kerogen, and fossil-fuel formation. This will help to provide deeper insights into the chemical history of natural organic matter, its role in the global carbon cycle, and the results of human activities on the environment.