Redox Properties and Reactivity of Sorbed Natural Organic Matter

吸附的天然有机物的氧化还原性质和反应性

• 批准号: 338519729
• 负责人: Professor Dr. Stefan Haderlein, since 6/2018
• 金额: --
• 依托单位: Arbeitsgruppe Hydrogeochemie
• 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 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/338519729?language=en
• 关键词: Redox; Properties; Reactivity; Sorbed; Natural

Natural organic matter (NOM) is a major diver of biogeochemical redox processes in soils aquifers. The prominent role of NOM in electron transfer reactions arises from is its ability to act as redox buffer as well as an electron shuttle, enhancing reactions between bulk electron donors and acceptors. Although in natural porous media a major fraction of NOM is present in sorbed state, the effect of redox properties (i.e., the electron exchange capacities and the redox state) on NOM sorption to minerals has not been addressed nor the effect of sorption on the redox properties of sorbed NOM. We hypothesize that the redox properties of adsorbed NOM will differ from those of the same type of NOM in the absence of sorbing surfaces. The research proposed here aims at quantifying these changes to provide the basis for a mechanistic understanding of how sorption processes control redox properties and biogeochemical functions of NOM in aqueous systems. Since sorption of NOM also determines the fraction of mobile and immobilized NOM and their respective redox properties, a detailed insight is needed in order to assess which part of NOM will be available and active for processes such as pollutant transformation, microbial respiration or electron shuttling. We suggest to study experimentally the mechanisms in detail that determine the redox properties and redox state of sorbed NOM. Thus, we propose to address the following major research questions in this proposal: - How does sorption of NOM to solid surfaces per se (i.e., in the absence of electron transfer) change its redox properties (electron accepting/donating capacity, redox state, EH distribution, redox mediation capacity)? - How does the redox state of NOM influence its sorption behavior? - How does electron transfer between the sorbent and NOM change the redox properties of sorbed NOM? - How do bulk properties and pretreatment of NOM (origin, aromaticity, acid/base chemistry) affect sorption and electron transfer processes altogether? To this end, we will study experimentally and systematically the mechanisms that determine the redox properties and redox state of sorbed NOM in laboratory batch experiments at environmentally relevant conditions using novel electrochemical techniques and a range of NOM samples and minerals. As NOM coatings are ubiquitous in aquatic systems answers to these questions will allow us to develop a much deeper understanding of heterogeneous redox processes in the subsurface and are a prerequisite for development of quantitative models for predicting biogeochemical processes at the mineral-water interface.

天然有机质（NOM）是土壤含水层生物地球化学氧化还原过程的主要潜水员。NOM在电子转移反应中的突出作用源于它作为氧化还原缓冲液和电子穿梭器的能力，增强了大量电子给体和受体之间的反应。虽然在天然多孔介质中，大部分NOM以吸附状态存在，但氧化还原特性（即电子交换能力和氧化还原状态）对NOM对矿物质吸附的影响以及吸附对吸附后NOM氧化还原特性的影响尚未得到解决。我们假设，在没有吸附表面的情况下，被吸附的NOM的氧化还原特性将与同类型NOM的氧化还原特性不同。本文提出的研究旨在量化这些变化，为了解吸附过程如何控制水体系中NOM的氧化还原性质和生物地球化学功能提供机制基础。由于NOM的吸附也决定了可移动和固定化NOM的比例及其各自的氧化还原性能，因此需要详细的了解，以评估哪一部分NOM将在污染物转化、微生物呼吸或电子穿梭等过程中可用和活跃。我们建议通过实验详细研究确定被吸附的NOM氧化还原性质和氧化还原状态的机制。因此，我们建议在本提案中解决以下主要研究问题：- NOM吸附到固体表面本身（即在没有电子转移的情况下）如何改变其氧化还原性质（电子接受/给体能力、氧化还原状态、EH分布、氧化还原中介能力）？- NOM的氧化还原状态如何影响其吸附行为？-吸附剂和NOM之间的电子转移如何改变被吸附的NOM的氧化还原性能？-本体性质和预处理（来源，芳香性，酸碱化学）如何影响吸附和电子转移过程？为此，我们将利用新型电化学技术和一系列NOM样品和矿物，在环境相关条件下进行实验室批量实验，实验和系统地研究确定吸附NOM氧化还原特性和氧化还原状态的机制。由于NOM涂层在水生系统中无处不在，这些问题的答案将使我们对地下的非均相氧化还原过程有更深入的了解，并且是开发用于预测矿物-水界面生物地球化学过程的定量模型的先决条件。