Spatial and temporal observations of adsorption and remobilization of heavy metal ions in a sandy aquifer matrix using Magnetic Resonance Imaging.

The exploration of the transport and matrix interactions of heavy metal ions in the subsurface environment under natural conditions is an important field of research in environmental science and technology. Most commonly, column tests are used for a first assessment of the transport behavior. Classical column tests fall short with regard to the spatial and temporal resolution; however, these detailed data are needed for proper upscaling. Hence, providing spatially and temporally resolved data on the distribution of environmentally relevant concentrations of heavy metal ions in a water-wet aquifer matrix poses a major challenge to analytical chemistry. In this contribution, we present the results of Magnetic Resonance Imaging (MRI) studies in which submilligram quantities of heavy metal ions where either fed conventially through the column or locally injected into saturated sand packings. The subsequent transport and mobilization was monitored at a high spatial and temporal resolution. The results from a local injection show that the test design of column tests has not yet come to an end and that column tests under MRI-control may be used as a model system for, e.g., remediation techniques.