Topics for master theses

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A new view on flow in porous media: Jumps of interfaces monitored with acoustic emission

In contradiction to standard theory, drying and wetting of soils and porous media in general are not continuous processes but sequences of abrupt jumps at the pore scale. To predict fluid invasion we need to measure and understand the dynamics of rap ...

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Comparative characterization of ten bacterial species

Objectives:
10 bacterial species designed to grow in a community will be characterized in detail. Particularly we are interested in swimming ability, biofilm formation, growth on different substrates, growth in homogenous vs. structured environment wi ...

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Dynamics of forced drainage in porous media compared to foam drainage

Summary:
In unsaturated porous media part of the liquid fraction is held in corners of the pore space and around grain contacts, forming thick liquid corner films. At some saturation these corner films form the main pathways of liquid drainage and the ...

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Effects of physical hillslope properties on savanna dynamics

Objective:
Quantify the effect of soil texture and hillslope drainage properties on the dynamics of tree-grass dominance, transpiration and CO2 uptake of savanna ecosystems along a rainfall gradient.

Summary:
This project will employ a fully prognosti ...

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How can we best model depth profiles in spatial analysis of soil property data? — Towards 3D mapping of soil properties

Context
To assess soil functions, e.g. the ability of soils to store water — in order to avoid flooding or to buffer acids or to prevent heavy metals from leaching into ground water — soil properties like texture or organic carbon content must be know ...

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How precise are predictions of soil properties derived from a large-scale polygon soil map?

Context
Planning and decision-making for optimal use of soils requires spatial information on the potentials of soils for particular functions. Soil function potentials are spatially assessed from maps of basic soil properties like organic carbon con ...

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Hydration and diffusion shape biogeochemical processes from aggregate to soil profile scales

Objective:
Quantifying the role of hydration, oxygen and carbon source distribution on the rates of greenhouse gases (e.g., CO2, N2O) across aggregate size classes and soil profile.

Summary:
Microbially-produced greenhouse gases represent substantial ...

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Link between microbiology and soil physics: The Extracellular Polymeric Substances

Spatial and temporal environmental fluctuations are common in nature, especially in microhabitats formed in unsaturated soils. Soils bacteria live in environments dominated by the presence of extensive solid- and air-water interfacial areas where the ...

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Localization of acoustic emissions in snow during snow failure experiments

Acoustic emissions (AE) generated by bond failure or crack formation allow for non-destructive observation of the progressive failure of snow. We performed loading experiments on snow samples and monitored the AE activity before failure. Recording th ...

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Micro-biogeography of bacteria on rough surfaces under controlled hydration conditions MSc Thesis (4-6 months)

Soil bacteria are important for the cycling of nutrients and thus the fertility of soils. Since most bacteria in unsaturated soils live in sessile colonies it is of great interest to understand the conditions under which growth can be limited. One ke ...

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Microbial Population Dynamics on Soil Rough Surfaces Using Patch Networks

Summary:
The astonishing diversity of microbial life in soil has been linked to highly dynamic and heterogeneous soil structure. Recent studies have shown that quantitative description of hydration dynamics in pore network provides some insight into m ...

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Microbial survival strategies in response to extreme dehydration conditions in soils

Natural fields often exhibit extreme and long term desiccation stress resulting in reduced water availability and limited diffusion pathways that are essential for nutrient transport, affecting microbial survivability and strategies. Soil desiccation ...

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Numerical simulations of acoustic emissions in snow

The goal of the project is to perform numerical simulations in order to study the failure process in snow and the concurrently generated acoustic emissions (AE) using a fiber bundle model. The fiber bundle model is to reproduce fully load-controlled ...

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Optimizing complementary surveys for mapping the spatial distribution of Mercury in soils near Visp, Canton of Valais, Switzerland

Context: Lonza Ltd, a manufacturer of chemicals, operates since 1909 a chemical plant in Visp, Canton of Valais, Switzerland. Between 1930 and 1973, about 50 tons of Mercury (Hg) had been discharged as effluent into the environment. The contaminated ...

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Patterns of bacterial coexistence under fluctuating hydration conditions in soil environments

Soil is a complex environment inhabited by a vast diversity of microbial species. At the scale of microorganisms, soil is a collection of microhabitats that can vary in their nutrient availability, water availability, pH, T°, etc. In this project, we ...

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Plant leaves under water stress: frying pan or fire?

Objective:
Assess whether sun-exposed leaves typically die of heat damage as a result of stomatal closure, before carbon starvation becomes an issue.

Summary:
This project has to be carried out in summer, as it will involve leaf temperature measurem ...

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Predictive modelling of basic properties of soils of Baden-Wuerttemberg by digital soil mapping techniques

Context Detailed spatial information on basic soil properties such as pH, soil texture, content of organic matter, carbonates, rock fragments, soil depth, etc. is required foe assessment of soil functions in spatial planning at municipal, regional an ...

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Promotion of bacterial coexistence in pore networks due to boundary condition variation: A case study using the example of carbon source location

Summary:
Previous studies using an individual based model have shown the importance of boundary conditions, especially carbon sources, within soil aggregates for the coexistence of microbial species in pore networks (Ebrahimi & Or 2014). Due to the op ...

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Quantifying bacterial swimming motility on hydrated surface

Swimming motility plays an essential role in the ecology of most bacterial species. Propelled by rotating appendages called flagella, bacteria can move through liquid  towards higher concentrations of nutrients, away from toxins, and generally, dispe ...

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Quantifying soil mechanical heterogeneity post compaction

Objective:
Determine the relationship between soil bulk density and penetration resistance and try to physically quantify the phenomena: Quantify the heterogeneity of soil mechanical parameters as a function of the gradient of bulk density.

Summary:
...

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Reliability of surface evaporative fluxes inferred from the remotely-sensed averaged surface temperature

Summary:
Partitioning of the incoming radiative energy over land surface (often resolved by remotely-sensed surface temperature) has a wide range of applications in hydrological modeling and water resource management. Heterogeneity of surface thermal ...

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Spatial organization of cross-feeding consortia on porous surfaces

Summary:
In soil ecosystems, many microbial species rely on nutrient cross-feeding, that is, the exchange of specific metabolites between interacting species. Such interactions play an essential role in ecosystem functioning, as they help stabilize th ...

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Trophic interactions shaping spatial organization of microbial consortia

Interactions among many microbial species within the same spatial habitat is common in natural systems. The resulting stable multispecies communities are essential for many aspects of ecosystem functioning. To better understand and shape  microbial f ...

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Viscous effects on corner film flow around bubbles during evaporation

Summary:
Capillary held liquid in corners of the pore space form an important constituent of liquid pathways in unsaturated porous media. The hydraulic conductivity of corner films can greatly affect the dynamics of fluid displacement processes, where ...

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What is the best method to create soil property maps by statistical methods? — Comparative mapping of soil properties for a study region in Switzerland

Context
Planning and decision-making for optimal use of soils requires spatial information on the potentials of soils for particular functions. Soil function potentials are spatially assessed from maps of basic soil properties like organic carbon cont ...

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24.05.2017
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