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

有机物的厌氧分解在湿地、泥炭地、沉积物和其他水饱和系统中具有重要的定量意义。因此，基于热力学约束，存在或不存在的替代电子受体的有机物（OM）的氧化决定了产甲烷的竞争力。由于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被认可。然而，（OM）的氧化还原性能一直是只有少数研究的重点，我们缺乏数据的范围内的电子接受（EAC）和捐赠能力（EDC）的OM和它们的关系OM性能。这些数据将需要实施OM氧化还原过程到厌氧碳矿化模型。此外，需要了解DOM和DOM的典型再氧化动力学，以了解自然发生的氧化还原波动的影响。此外，初步的工作表明，DOM和SOM的氧化还原状态不能假设相似，两者的评估可能是必要的。最后，它还不知道，如果氧化还原性能的OM在一个给定的环境系统中的热力学，已被证明为碳矿化使用无机电子受体。该提案解决了这些重要的知识空白，通过进行i）不同质量和来源的泥炭材料的范围内的受控孵育，ii）在受控条件下孵育，以计算碳矿化的电子预算，iii）受控的动力学OM再氧化实验，以及iv）孵育，以将OM的氧化还原状态与溶解的H2浓度相关，作为热力学条件的指标。从这个项目中，我希望我们目前的有机碳矿化在有机丰富的系统和厌氧条件下的理解作出重大贡献。

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.