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The Helmholtz Centre for Environmental Research (UFZ) with its 1,100 employees has gained an excellent reputation as an international competence centre for environmental sciences. We are part of the largest scientific organisation in Germany, the Helmholtz association. Our mission: Our research seeks to find a balance between social development and the long-term protection of our natural resources.

The job

Soils play a crucial role in the global cycle of greenhouse gases. Thus, the gas exchange between soil and atmosphere is of central importance, but its spatial and temporal dynamics are not yet understood sufficiently. Several small-scale methods exist, to determine gas concentration and soil diffusivity (Ds) under laboratory conditions and in the field. However, due to the natural spatial heterogeneity of soils and the temporal dynamics of soil structure, it is hardly possible to transfer these results to the field scale.

The aim of the collaborative DFG project of Dr. Detlef Lazik (UFZ, Halle), Dr. Nina Stoppe-Struck and Prof. Jürgen Böttcher (Leibniz Universität Hannover - LUH) is therefore to develop a measurement methodology and technology for quasi-continuous in situ measurement of spatially averaged gas diffusivities for the field scale (UFZ) as well as to implement these in a defined way in soils (laboratory/field), to test them, and to compare them with established measurement methods (LUH). With respect to the selective diffusion of gases through tubular membranes, a new concept in terms of measurement theory was developed, which is based on varying diffusive gas fluxes between tubular membranes laid parallel in the soil. One of these membrane tubes serves as a linear gas source, the others as sensors for the diffusing gas. Within the sensory tubes, the changing external gas concentrations causes pressure changes, which after convolution with a weight function, allow to infer the diffusivity in the soil. This concept is the starting point for a novel measurement methodology and technology that will be tested and brought to application maturity within the PhD thesis. If successful, this should enable direct measurement of gas diffusion coefficients on a larger scale in the soil.

Your tasks
  • Analysis the state of knowledge of methods for the determination of diffusivity in soil
  • Familiarization with the state of knowledge on measurement methods and technology relevant to the project
  • Theoretical analysis and simulation of the project's underlying membrane- based measurement method and its technology for typical conditions in soil
  • Theory-based determination of suitable parameters for the measurement setup
  • Construction and test of prototypical measurement systems as well as their optimization during the course of the project
  • Development of codes to control the measurement and to determine the diffusivity
  • Parameterization/optimization of the measurement procedure
  • Analysis of experimentally determined diffusivities for defined-structured substrates under controlled conditions in the laboratory and comparison with theoretical models
  • Together with the project partner (LUH): Installation of prototypical measurement systems in soils (laboratory/field) and support/collaboration regarding the operation of the measurement systems, data analysis and result evaluation
  • Writing of reports and publications
  • We offer
  • Excellent technical facilities which are without parallel
  • The freedom you need to bridge the difficult gap between basic research and close to being ready for application
  • Work in inter-disciplinary, multinational teams
  • Excellent links with national and international research networks
  • Excellent support and optimal subject-specific and general training with our HIGRADE graduate school
  • Your profile
  • Completed scientific university studies (Master degree) in physics, geophysics, measurement technology/electronics, environmental sensor technology or soil/geoscientific directions with a focus on measurement technology/physics
  • Good understanding of physical, mathematical, and measurement methodological/technical relationships
  • Skills in at least one of the programming languages Python or C, knowledge of Mathematica is an advantage
  • Basic knowledge in CAD/CAM
  • Professional interest in physical-theoretical and experimental work in laboratory and field and the development of measurement technologies
  • Good German language skills, good command of written and spoken English
  • Determination, independence, teamwork and communication skills
  • Driving license class B
  • From this employer

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