Solid and dissolved organic matter redox properties as controls of anaerobic Respiration in organic soils

在湿地、泥炭地、沉积物和其他水饱和系统中，有机物的厌氧分解在数量上是重要的。因此，基于热力学约束，有机物氧化（OM）的替代电子受体的存在与否决定了甲烷生成的竞争性。通常认为无机电子受体，如硝酸盐、铁和硫酸盐，大多不足以解释所观察到的二氧化碳（CO2）的产生，溶解（DOM）和固体有机物（SOM）作为电子受体的作用越来越得到承认。然而，对OM氧化还原性质的研究较少，缺乏OM的电子接受能力（EAC）和给电子能力（EDC）范围及其与OM性质的关系的数据。这些数据将需要在厌氧碳矿化模型中实现OM氧化还原过程。此外，要了解自然发生的氧化还原波动的影响，还需要了解DOM和DOM的典型再氧化动力学。此外，初步研究表明，DOM和SOM的氧化还原状态不能假设相似，可能有必要对两者进行评估。最后，尚不清楚OM的氧化还原性质是否与给定环境系统中的热力学有关，正如使用无机电子受体的碳矿化所证明的那样。本研究通过以下方法解决了这些重要的知识缺口：1)对不同质量和来源的泥炭材料进行受控培养，2)在受控条件下进行培养，计算碳矿化的电子收支，3)受控的OM动力学再氧化实验，4)将OM的氧化还原状态与溶解的H2浓度联系起来，作为热力学条件的指标。从这个项目中，我期望对我们目前对富有机质系统和厌氧条件下有机碳矿化的理解做出重大贡献。

Anaerobic decomposition of organic matter is quantitatively important in wetlands, peatlands, sediments, and other water saturated systems. Thereby, based on thermodynamic constraints, presence or absence of alternative electron acceptors for oxidation of organic matter (OM) determines the competitiveness of methanogenesis. As commonly considered inorganic electron acceptors, such as nitrate, iron, and sulfate mostly do not suffice to explain observed production of carbon dioxide (CO2), the role of dissolved (DOM) and solid organic matter (SOM) as electron acceptors is increasingly acknowledged. Nevertheless, (OM) redox properties has been in the focus of only a small number of studies and we are lacking data on ranges of electron accepting (EAC) and donating capacities (EDC) of OM and their relation to OM properties. Such data would be needed to implement OM redox processes into models of anaerobic carbon mineralization. Additionally, knowledge about typical re-oxidation kinetics of DOM and DOM would be needed to understand the impact of naturally occurring redox fluctuations. Moreover, preliminary work suggests that the redox state of DOM and SOM cannot be assumed similar and an assessment of both may be necessary. Finally, it is yet unknown if redox properties of OM are related to thermodynamics in a given environmental system, as has been demonstrated for carbon mineralization using inorganic electron acceptors. This proposal addresses these important knowledge gaps, by conducting i) controlled incubations of a range of peat materials of different quality and origin, ii) incubations under controlled conditions to calculate electron budgets for carbon mineralization, iii) controlled, kinetic OM re-oxidation experiments, and iv) incubations to relate the redox state of OM to dissolved H2 concentrations as an indicator for thermodynamic conditions. From this project, I expect a substantial contribution to our current understanding of organic carbon mineralization in organic-rich systems and under anaerobic conditions.