Redox induced mobilisation of DOC from riparian wetlands (ReDOCs)

河岸湿地是河流溶解有机碳（DOC）的主要来源。在过去的几十年中，观察到许多北方河流的DOC浓度增加，对湿地土壤和河流水质的碳（C）储存的潜在影响。这些趋势背后的驱动因素，特别是湿地土壤中氧化还原过程的重要性，仍然没有完全理解。在土壤中，有机碳通常与铁（氧）氢氧化物结合或结合。铁（Fe）和有机碳的这些协会可以固定和保护土壤有机质在好氧条件下的矿化。然而，有机碳可以被再动员，如果铁Fe在缺氧条件下被还原，或者如果氧化还原介导的pH值的变化增加其溶解度。因此，氧化还原过程可能是湿地土壤和邻近溪流DOC动态的重要驱动因素。虽然铁-碳协会和他们的氧化还原过程的反应进行了调查的矿质土壤，我们缺乏有关河岸有机土壤和流域尺度的信息。为了解决这一知识差距，实验集水区的研究是必要的，跟踪这些过程的DOC的来源地区的流网络和建模技术，能够从观测数据中提取的因果关系需要加以应用。因此，本项目的目标是机械地了解DOC，铁，和pH值之间的相互作用，为北方和温带流域河岸湿地。我们假设，在流DOC浓度主要是由氧化还原条件驱动的河岸有机土壤，DOC动员是由DOC相关铁的减少，并通过氧化还原介导的pH值的变化。我们进一步提出，这些DOC动员氧化还原条件控制的水位和温度的波动。我们建议结合联合收割机（A）水的调查沿着湿地流断面，寻找DOC分子签名，表明特定的动员过程和（B）新的因果发现方法，以跟踪动员和运输过程的DOC跨尺度。拟议的研究地点是瑞典北方的Krycklan集水区，为拟议的实验和建模工作提供长期的数据记录和良好的现场基础设施。在Krycklan获得的过程理解计划转移到德国集水区使用贝叶斯网络。在后一个地点，进行补充研究，并打算进行合作。该项目为期3年，将与明斯特大学、BHT柏林、莱比锡/马格德堡、瑞典农业科学大学和拜罗伊特大学合作，与一名博士生一起进行。虽然学生专注于在Krycklan和明斯特/莱比锡实验室的实验工作和数据分析，PI Selle（BHT）模型监测和实验数据，并将模型从Krycklan转移到德国集水区。整个团队最终整合知识并创建合成。

Riparian wetlands are major sources of dissolved organic carbon (DOC) to streams. Increasing DOC concentrations were observed for many northern streams during the last decades, with potential implications for carbon (C) storages of wetland soils and streamwater quality. Drivers behind these trends, and particularly the significance of redox processes in wetland soils, are still incompletely understood. In soils, organic C is often associated with or bound to iron (oxy) hydroxides. These associations of iron (Fe) and organic C may immobilise and protect soil organic matter from mineralisation under oxic conditions. However, organic C can be remobilised if ferric Fe is reduced under anoxic conditions or if redox mediated changes in pH increase its solubility. Redox processes are therefore presumably important drivers of DOC dynamics in both wetland soils and the adjacent streams. While Fe-C-associations and their response to redox processes were investigated for mineral soils, we lack information about riparian organic soils and at catchment scales. To address this knowledge gap, experimental catchment studies are needed that trace these processes from the source areas of DOC to the stream network; and modelling techniques able to extract causal links from observational data need to be applied. The objective of this project is thus to mechanistically understand the interplay between DOC, Fe, and pH for boreal and temperate catchments featuring riparian wetlands. We hypothesise that in-stream DOC concentrations are mainly driven by redox conditions within riparian organic soils, where DOC mobilisation is controlled by reduction of DOC associated Fe, and by redox mediated changes in pH. We further propose that these DOC mobilising redox conditions are controlled by fluctuations of water tables and temperature. We propose to combine (A) the investigation of water along wetland-to-stream transects, looking at DOC molecular signatures that indicate specific mobilisation processes and (B) novel causal discovery methods to trace mobilisation and transport processes of DOC across scales. The proposed study site is the Krycklan catchment in northern Sweden, providing long data records and excellent field infrastructure for the proposed experimental and modelling work. Process understanding obtained at Krycklan is planned to be transferred to German catchments using Bayesian networks. At the latter sites, complementary research is conducted and a collaboration is intended. The 3-year project shall be conducted with a doctoral student in a cooperation of Uni Münster, BHT Berlin, UFZ Leipzig/Magdeburg, the Swedish Uni of Agricultural Sciences in Umeå, and Uni Bayreuth. While the student focuses on experimental work and data analysis in Krycklan and the labs at Münster/Leipzig, PI Selle (BHT) models monitoring and experimental data, and transfers models from Krycklan to German catchments. The entire team ultimately integrates knowledge and creates a synthesis.