(Redox-)Biogeochemistry on the Microscale - Biofilms and Model Systems

我们观察到环境中的还原和氧化过程不能用经典的地球化学模型来解释。通常情况下，根据各自的化学需求，不应该同时发生的反应是耦合的。然而，一个基本的方面往往没有被考虑，主要是由于我们的实验可能性的限制，是环境系统的异质性。创新实验方法的发展，特别是基于同步加速器的x射线光谱显微镜和基于实验室的原位方法，如环境敏感荧光探针与共聚焦激光扫描显微镜的耦合，现在成为研究这种非均质性的有前途的工具。本项目将系统研究氧化还原活性生物膜的结构和亚微米尺度化学非均质性对生物地球化学反应的影响。它将重点关注不同氧化还原循环（Fe, Mn， S）之间的耦合-基于宏观条件-不应该发生。这些耦合对养分和污染物循环的影响将被研究。除了研究天然和人工生物膜外，微流体模型系统将有助于在受控的实验室条件下获得对潜在过程的基本理解。本项目的目标是：1)在微观尺度上表征和参数化氧化还原活性生物膜的结构和化学异质性。这包括有机化学成分（如氧化还原活性官能团），无机成分和化学条件，重点是铁，锰和S种。2)识别、绘制和量化发生在微生态位中的生物地球化学过程，包括营养物质或污染物的吸附、矿物沉淀和溶解，以及生物膜不同成分之间的电子转移反应。3)通过实验证明微观尺度的异质性是否会导致与时间波动（如水位波动）相同的现象。4)识别可能引起先前描述的结构和化学异质性的单个参数（即pH、电位、金属浓度、氧化还原电位）。5)表征微生物外聚合物的有机化学组成，研究其电子电导率和作为氧化还原缓冲系统的潜力。6)在宏观尺度上评估先前确定的微环境反应的重要性。

We observe reduction and oxidation processes in the environment that cannot be explained by classical geochemical models. Often reactions are coupled that - based on their individual chemical requirements - should not occur together. However, one fundamental aspect that often has not been considered, mostly due to limitations in our experimental possibilities, is the heterogeneity of environmental systems.Die development of innovative experimental approaches, in particular in the fields of synchrotron-based X-ray spectromicroscopy and lab-based in-situ approaches such as the coupling of environmentally sensitive fluorescence probes with confocal laser scanning microscopy now became promising tools to study such heterogeneities.In this project, the influence of structural and chemical sub-micron scale heterogeneity in redox-active biofilms on biogeochemical reactions will be studied systematically. It will focus on the coupling between different redox-cycles (Fe, Mn, S) that - based on the macroscopic conditions - should not occur. The influence of these couplings on nutrient and contaminant cycling will be studied. In addition to studying natural and artificial biofilms, microfluidic model systems will help to gain a fundamental understanding of the underlying processes under controlled laboratory conditions.The goals of this project are:1) to characterize and parameterize both structural and chemical heterogeneities of redox-active biofilms at the micro-scale. This includes the organochemical composition (e.g. redox-active functional groups), inorganic constituents and chemical conditions with a focus on Fe, Mn and S species.2) to identify, to map and to quantify biogeochemical processes that occur in micro-niches, including the adsorption of nutrients or contaminants, mineral-precipitation and -dissolution, but also electron transfer reactions between the different constituents of the biofilm.3) to prove experimentally whether micro-scale heterogeneities can result in the same phenomena as temporal fluctuations, e.g. fluctuations in water levels.4) to identify individual parameters (i.e. pH, potential, metal concentrations, redox potential) that could induce the previously described structural and chemical heterogeneities.5) to characterize the organochemical composition of microbial exopolymers to study their potential for electron conductance and for acting as redox-buffer systems.6) to assess the importance of the previously determined reactions in microenvironments on the macroscopic scale.