PhD project offered by the IMPRS-gBGC in July 2021

Anchor

Reconstruction of subsurface flow networks in the critical zone using natural organic tracers

Kai U. Totsche , Susan Trumbore , Gerd Gleixner

Project description

Dissolved Organic Matter (DOM) resembles a vast variety of soluble and colloidal organic substances comprising among others microbial products, root exudates, microbiota, lysis products and humified materials released from the soil organic matter pool. Major source of DOM are the forest floor and the top-soil horizons. While many compounds within the organic matter pool are so far unknown, molecular organic signatures relating to type of plants or plant societies as well as land use and land management have been identified. As part of theses substances are persistent, they are prone to transport with the fluids phases. If a set of components are identified that can be uniquely related to the location or origin and to the type of vegetation/land uses, such a collection of substances could serve as “natural tracers” for the reconstruction of the subsurface network of flow paths in hydrogeologic settings with fracture type networks in the vadose and the saturated zone. To achieve this goal, chemical analytical methods are required that allow for the simultaneous detection of a variety of substances in the aqueous phase. Among these analytical methods comprehensive Tandem-Gas-Chromatography (GCxGC) seems to be promising, as it is compound specific, sensitive rather rapid, and requires only less sample pretreatment.
GCxGC characterizes thermostable aqueous organic mixtures by separating compounds according to their volatility and polarity. Such a dual separation system increases the peak capacity and reduces coelution. Moreover, it produces 2D-chromatograms (“contour plots”) that allow to identify the composition of an aqueous sample using advanced image analysis tools.
Within the project, comprehensive GCxGC combined with image analysis is used to analyze and evaluate spatially and temporally resolved seepage and water samples from the different sampling locations and sampling depths at the Hainich Critical Zone exploratory. Based on the spatio-temporal suite of 2D chromatograms, the objective is to identify natural substances that may serves as suite the subsurface tracers for the reconstruction of transport pathways.

Requirements

Applications to the IMPRS-gBGC are open to well-motivated and highly-qualified students from all countries. Prerequisites for this PhD project are
  • a Master’s degree in bio(geo)chemistry, environmental science, geosciences, or chemistry
  • experience in spectroscopic techniques like GC, HPLC and FTIR
  • excellent oral and written communication skills in English
The Max Planck Society seeks to increase the number of women in those areas where they are underrepresented and therefore explicitly encourages women to apply. The Max Planck Society is committed to increasing the number of individuals with disabilities in its workforce and therefore encourages applications from such qualified individuals.

2D-chromatogram of a forest floor leachate analyzed with comprehensive GCxGC chromatography. Each black dot represents a single organic substance
2D-chromatogram of a forest floor leachate analyzed with comprehensive GCxGC chromatography. Each black dot represents a single organic substance


>> more information about the IMPRS-gBGC + application