Transport von synthetischen und anorganischen Nanopartikeln (EINP) im Boden

We will explore the mechanisms of EINP (nAg0, nAu0 and nTiO2) transport in soil under unsaturated conditions. The ultimate goal is to predict their mobility in the subsurface based on soil properties, particle characteristics and flow conditions. There is experimental evidence (first project phase) that the mobility of EINP exhibit a highly non-linear behavior in the state space defined by solution chemistry, average water content and particle properties including various coatings. The role of different interfaces (water-solid and water-air) is known to be critical but yet unclear and may lead to an increased catching. We will conduct column experiments at the mm-scale of single grains and micro-aggregates. The transport of EINP is monitored for various unsaturated flow conditions (steady state and fluctuations) using a nano-X-ray CT system (new investment at UFZ). In this way EINP-concentrations within volumes <1µm3 can be visualized in the context of the flow field. This will allow for quantifying the distribution of EINP among the various interfaces and the bulk water phase. Of special interest is the dynamics during transient conditions as typical for soils and the process of particle retention and remobilization.
Based on the pore scale analysis, the prediction of EINP transport at the larger scale should be possible based structural properties of the material (observable by hierarchical X-ray CT at various resolutions) and the EINP properties. Column experiments at the dm-scale of soil horizons will demonstrate in how far such a prediction is possible.
The experiments will be performed using metallic and oxidized particles of various types (starting with nAg0 and nTiO2) and differently masked (MASK, SOILMOBILE). Particle properties will be analyzed in cooperation with the project partners using SEM, DLS (SOILMOBILE), ESEM, AFM, HDC-UV-FD-ICP-MS (MASK) and Raman-Spectroscopy (PORESURFACE) before and after passage through the porous medium to test the masking and catching hypotheses. They will be characterized in terms of size and surface area and type of coating. This will provide valuable insight in how far general conclusions can be drawn on the relation between particle properties and their mobility in soil.