Dynamic (redox) interfaces in soil - Carbon turnover in microbial biomass and flux into soil organic matter

现有的土壤有机质（SOM）形成模型认为植物物质是土壤有机质的主要来源。然而，最近的结果从核磁共振分析SOM和自己的孵化研究，表明微生物残留物也有助于在很大程度上SOM的形成。扫描电子显微镜观察表明，土壤矿物表面覆盖着许多小的片状碎片（100 - 500 nm），这些碎片来自微生物细胞壁残留物。我们将研究人工土壤系统（石英，蒙脱石，氧化铁，细菌和碳源）中连续产生的界面，这些片状碎片的形成和命运。我们将量化不同类型的土壤生物对斑块碎片形成的相对贡献，并阐明氧化还原条件和铁矿物学对斑块碎片形成和周转的影响。在成土作用期间，将通过研究来自退缩的达玛冰川前区的年代序列的土壤样品来跟踪片状碎片的发展。我们将在环境扫描电子显微镜中通过纳米尺度分析和微尺度凝聚实验来表征片状碎片的化学和物理性质。研究结果将有助于理解地球化学界面的过程和特征。

Existing models of soil organic matter (SOM) formation consider plant material as the main source of SOM. Recent results from nuclear magnetic resonance analyses of SOM and from own incubation studies, however, show that microbial residues also contribute to a large extent to SOM formation. Scanning electron microscopy showed that the soil mineral sur-faces are covered by numerous small patchy fragments (100 - 500 nm) deriving from microbial cell wall residues. We will study the formation and fate of these patchy fragments as continuously produced interfaces in artificial soil systems (quartz, montmorillonite, iron oxides, bacteria and carbon sources). We will quantify the relative contributions of different types of soil organisms to patchy fragment formation and elucidate the effect of redox con-ditions and iron mineralogy on the formation and turnover of patchy fragments. The develop-ment of patchy fragments during pedogenesis will be followed by studying soil samples from a chronosequence in the forefield of the retreating Damma glacier. We will characterize chemical and physical properties of the patchy fragments by nanothermal analysis and microscale condensation experiments in an environmental scanning electron microscope. The results will help understanding the processes at and characteristics of biogeochemical interfaces.