Change of magnetic mineralogy related to groundwater fluctuation and hydrocarbon contamination

在前空军基地(捷克)的一次飞行员研究中。我们观察到松散沉积物中受碳氢化合物(HC)污染的地下水的波动导致磁性的变化。磁铁矿含量有系统地增加，接近波动带的上限，这种影响以前从未描述过。因此，在拟议的项目中，我们希望(A)扩大实地研究，以更详细地定位和量化这种影响，以及(B)通过模拟受控水位波动(WLF)进行实验室实验，以揭示磁场变化的特征(浓度、时间动力学、空间范围)，并深入了解重要的驱动过程。我们假设形成铁(I)磁性矿物有三个关键因素：(A)细菌活性，(B)HC含量，(C)水含量。在实验室里，我们想要研究短期和长期(长达一年)的过程，并改变以下参数：细菌群落(铁氧化/还原细菌和无菌条件)，WLF的范围和频率，HC的类型和含量。这项研究应由德国和捷克在环境磁学和地球微生物学方面拥有可靠专业知识的小组联合进行。这项工作对于开发检测环境中例如由于污染引起的HC的简单方法具有重要意义。

During a pilot study at a former military airbase (in Czech Rep.) we observed a change of magnetic properties due to fluctuations of hydrocarbon (HC) contaminated groundwater in unconsolidated sediments. A systematic increase of magnetite content was observed towards the upper limit of the fluctuation zone, an effect that has not been described before. In the proposed project we therefore want to (a) extend the field studies to localize and quantifiy this effect in more detail and (b) perform laboratory experiments by simulating controlled water level fluctuations (WLF) in order to reveal the character of magnetic changes (concentration, temporal dynamics, spatial extent) and to gain insight into the important driving processes. We assume that there are three key factors for the formation of ferro(i)magnetic minerals: (a) bacterial activity, (b) HC content, (c) water content. In the laboratory we want to study short and long-term (up to >1 year) processes and vary the following parameters: bacterial communities (iron oxidizing/reducing bacteria and sterile conditions), extent and frequency of WLF, type and content of HC. The study shall be jointly conducted by German and Czech groups with sound expertise in environmental magnetism and geomicrobiology. The work has relevance for developing simple methods for detection of HC in the environment, e.g. due to contamination.