Formation and properties of mineral-organic soil interfaces as revealed by X-ray photoelectron spectroscopy

X 射线光电子能谱揭示矿物-有机土壤界面的形成和性质

• 批准号: 392159791
• 负责人: Professor Dr. Robert Mikutta
• 金额: --
• 依托单位: Professur für Bodenkunde und Bodenschutz
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/392159791?language=en
• 关键词: Formation; properties; mineral; organic; soil

Mineral-organic interfaces represent organic matter-enriched transition zones between mineral surfaces and pore spaces. Many soil processes, including adsorption and desorption reactions, occur at these interfaces and are controlled by their physicochemical properties. A decade ago, Kleber et al. (Biogeochemistry 2007, 85, 9-24) proposed the so-called ´multilayer´ model, which assumes the presence of chemically distinct zones within natural organic matter coatings on mineral surfaces. The model assumes that organic coatings are composed of an inner contact zone followed by a zone of hydrophobic interactions and an outer kinetic zone, each zone containing distinct organic matter components (´chemical zonation´). Although the model is currently considered as ´state of knowledge´ in terms of the composition of soil mineral-organic associations, it has never been validated experimentally. Our proposed research will consequently address the chemical composition of organic coatings as a function of environmental conditions. We analyse the morphology of organic coatings on mineral surfaces and their chemical structure using atomic force microscopy and X-ray photoelectron spectroscopy (XPS). XPS allows for (i) the depth-dependent chemical characterisation of organic coatings using step-wise argon cluster ion beam milling and (ii) the chemical analysis of organic coatings in fully hydrated state (cryo-XPS). Additionally, we explore the effect of specific environmental parameters such as pH and solution composition on the formation and composition of organic multilayers. Our experiments also account for the chemical zonation within organic coatings as influenced by sequential sorption and sorptive fractionation processes of natural organic matter as well as reorganization of organic molecules at mineral-organic interfaces. The proposed research will be the first test of the validity of the multilayer model and provides the scientific fundament for an improved understanding of the chemical composition of natural mineral-organic interfaces.

矿物-有机界面代表矿物表面与孔隙空间之间有机质富集的过渡带。许多土壤过程，包括吸附和解吸反应，发生在这些界面上，并由它们的物理化学性质控制。十年前，Kleber等人（Biogeochemistry 2007，85，9-24）提出了所谓的“多层”模型，该模型假设矿物表面天然有机物涂层内存在化学上不同的区域。该模型假设有机涂层由内部接触区、疏水相互作用区和外部动力学区组成，每个区含有不同的有机物质组分（“化学分区”）。虽然该模型目前被认为是“知识状态”方面的土壤矿物有机协会的组成，它从来没有得到实验验证。因此，我们提出的研究将解决有机涂层的化学成分作为环境条件的函数。利用原子力显微镜和X射线光电子能谱（XPS）分析了矿物表面有机涂层的形貌和化学结构。XPS允许（i）使用逐步氩团簇离子束研磨的有机涂层的深度依赖性化学表征和（ii）完全水合状态的有机涂层的化学分析（低温XPS）。此外，我们探讨了特定的环境参数，如pH值和溶液组成的有机多层膜的形成和组成的影响。我们的实验还占有机涂层内的化学分区的影响，顺序吸附和吸附分馏过程的天然有机物，以及重组的有机分子在矿物有机界面。该研究将首次检验多层模型的有效性，并为更好地理解天然矿物-有机界面的化学组成提供科学基础。