PhD 12 : Spectral induced polarization monitoring for in-situ quantification of biochemical reactions

 

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The Institute of Bio- and Geosciences – Agrosphere (IBG-3) conducts research to improve our understanding of biogeochemical and hydrological processes in terrestrial systems. Specific studies focus on environmental controls on biogeochemical cycling of elements, the analysis of exchange processes and nutrient dynamics in the soil-plant-atmosphere continuum. A combination of experiments, modelling and innovative observation technologies is used to bridge the gap between model, process and management scale. Its research contributes to the sustainable and resource-conserving use of soils and water and to the quantification of the effect of climate and land use change on terrestrial ecosystems. We offer a competent and interdisciplinary working environment, as well as an excellent framework in the areas of experiments and modelling.

Objectives of this PhD : Establishment of quantitative relationships between subsurface biochemical reactions and Spectral Induced Polarization (SIP) signals using laboratory millifluidic imaging and subsequent validation using field measurements.

Expected Results: Recent findings suggest that geophysical methods may provide new opportunities for mapping the subsurface spatial distribution of biochemical reaction rates and biofilm development, although it is still difficult to distinguish between the multiple origins of the measured signals. In a first step, this project aims at disentangling the multiple origins of the SIP signal using a novel experimental approach that combines SIP measurements with well-controlled millifluidic experiments where 2D concentration fields and biofilm distribution can be simultaneously and independently monitored using fluorescence imaging techniques. Experiments will be performed using classical laboratory bacterial strains as well as micro-organisms sampled from the Ploemeur site in direct collaboration with microbiologists of the Rennes ecology department. In a second step, a novel borehole SIP imaging approach will be used to quantify biofilm distribution and development at the Ploemeur site. In collaboration with ESR 5 and 9, these field investigations will provide insights into the interaction between flow distribution, chemical gradients, and biofilm distribution. This is of pivotal importance to understand how biofilms can positively (e.g. bioremediation) or negatively (e.g. bioclogging) affect water quality.

Supervisors: FZ Jülich/ Co-Supervisors: CNRS Rennes

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