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Bioremediation of contaminated soil: Focus on bioavailability and isotope fractionation
Stable isotope fractionation analysis is an emerging technology for the qualitative and quantitative assessment of organic contaminant biodegradation in the environment. Stable isotope fractionation is caused by the enzymatic discrimination of heavier isotopes during biotransformation processes and leads to a relative enrichment of the heavier isotope in the residual substrate pool. Present fractionation factors are determined in well-mixed laboratory systems and normally neglect the influence of pollutant bioavailability on isotope fractionation; Bioavailability for degradation of organic contaminants can be seen as an interactive process that is determined by the rate of physical mass transfer to microbial cells relative to their intrinsic catabolic activity. At substrate mass-transfer-limited conditions (a situation often encountered in the subsurface) the pollutant supply does not meet the intrinsic degradation capacity of the microorganisms and will theoretically lead to both a significantly reduced discrimination of the heavier stable isotopes and concomitantly reduced stable isotope fractionation factors.
The aim of the diploma work is to compare stable isotope fractionation at bioavailability limited and non-limited conditions in batch culture systems or model soil columns, using toluene as a model compound and a well-known (aerobic) toluene degrading strain Pseudomonas putida mt-2. During this study a main focus will be laid on the two main processes thought to influence bioavailability and isotope fractionation: (i) Influence of the quantity of biomass influencing the biodegradation activity (of both growing and resting cells) and (ii) the rate of
toluene mass transfer to the biophase.
This interdisciplinary project touches biochemistry, microbiology, environmental chemistry, and chemical analytics. It will give a broad theoretical background and provide practical experience in microbiological techniques, gas chromatography and other state of the art laboratory methods.
The working place:
Being an international competence centre for environmental research, UFZ is investigating the interaction between man and environment in used and disturbed landscapes. UFZ develops concepts and methods to assure a healthy environment for future generations. The Helmholtz Centre for Environmental Research GmbH-UFZ located in Leipzig, Halle and Magdeburg is a member of the Helmholtz-Association (HGF).
Informationen om uppsatsförslag är hämtad från Nationella Exjobb-poolen.