Redox induced mobilisation of DOC from riparian wetlands (ReDOCs)

氧化还原诱导河岸湿地 DOC 的动员 (ReDOC)

• 批准号: 502259606
• 负责人: Professor Dr. Klaus-Holger Knorr
• 金额: --
• 依托单位: Department Seenforschung
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/502259606?language=en
• 关键词: Redox; induced; mobilisation; DOC; riparian

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.

河岸湿地是河流溶解有机碳(DOC)的主要来源。在过去的几十年里，观察到了许多北部溪流中DOC浓度的增加，这可能会对湿地土壤的碳(C)储量和溪水水质产生影响。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，仍然不完全清楚。在土壤中，有机碳通常与铁(氧)氢氧化物结合或结合。铁(Fe)和有机碳的这些组合可能在氧化条件下固定和保护土壤有机质免受矿化。然而，如果铁在缺氧条件下被还原，或者如果氧化还原引起的pH变化增加了有机碳的溶解度，则有机碳可以被重新动员。因此，氧化还原过程可能是湿地土壤和邻近溪流中DOC动态变化的重要驱动因素。虽然对矿物土壤的Fe-C-缔合及其对氧化还原过程的响应进行了研究，但我们缺乏关于河岸有机土壤和集水尺度的信息。为了解决这一知识鸿沟，需要进行试验性流域研究，从DOC的源头区域追踪这些过程到河流网络；需要应用能够从观测数据中提取因果联系的建模技术。因此，该项目的目标是从机械上了解以河岸湿地为特征的北方和温带集水区DOC、Fe和pH之间的相互作用。我们假设河流中DOC的浓度主要是由河岸有机土壤中的氧化还原条件驱动的，在河岸有机土壤中，DOC的动员受控于DOC相关铁的还原，以及氧化还原介导的pH变化。我们进一步提出这些DOC动员氧化还原条件是由水位和温度的波动控制的。我们建议结合(A)湿地到河流横断面的水调查，寻找指示特定动员过程的DOC分子特征，以及(B)追踪跨尺度DOC的动员和运输过程的新的因果发现方法。拟议的研究地点是瑞典北部的Krykerlan集水区，为拟议的实验和建模工作提供大量数据记录和出色的实地基础设施。计划利用贝叶斯网络将在克里克兰获得的过程理解转移到德国的集水区。在后两个地点，进行了补充研究，并打算进行合作。该项目为期3年，将与明斯特大学、柏林BHT大学、德国莱比锡大学/马格德堡大学、乌梅萨的瑞典农业科学大学和拜罗伊特大学的一名博士生合作进行。虽然学生专注于克里克兰和明斯特/莱比锡的实验室的实验工作和数据分析，但PiSelle(BHT)对监测和实验数据进行建模，并将模型从克里克兰转移到德国流域。整个团队最终整合了知识，创造了一个综合体。