The UFZ
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