Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

GeoPET is the application of positron emission tomography (PET) for direct, non-destructive, quantitative spatiotemporal measurement and visualization of fluid transport in natural geological media on drill-core scale. Data on heterogeneous flow and diffusion can be extracted from PET experiments which can be used to parameterize reactive transport models that better reflect the heterogenous nature of geochemical transport processes.
GeoPET functions through the use of positron emitting radioactive isotopes. The emitted positron quickly annihalates with electrons inside the matrix setting the physical resolution limit of the PET technique at about 1 mm spatial resolution. Upon annihilation two gamma photons are sent out in opposite directions that are detected coincidentally and thus hold information about the location of the original decay. This can be used to keep track of solute species, particles and solids. Through the use of [F-18]KF (halflife: 1.8 h) we are able to visualize heterogenous flow in geological media on drill-core scale and to extract flow fields and porosity data from the yielded data. Using Na-22 (halflife: 250 d) longer-term diffusion experiments can be perfomed and matrix-diffusion coefficients can be extracted from the data. Furthermore, through the development of appropriate labeling strategies we have visualized the transport of [I-124]MWCNTs and the initial stages of [Cu-64]CuS leaching.
In case of the technologically interesting application of in-situ copper bioleaching we have imaged matrix diffusion and the heterogenous flow through a Kupferschiefer sandstone fractured core sample. The extracted flow velocity fields and diffusion coefficients were used to parameterize a reactive transport model in the COMSOL-PHREEQC interface (iCP) to simulate mineral dissolution/precipitation, porosity change, as well as, copper extraction in the sequential leaching process employed within the BIOMOre project including water washing, acid washing and ferric iron acid leaching.