Analysis of solute transport in a heterogeneous aquifer: the Krauthausen field experiment

A field-scale natural gradient tracer experiment with bromide, uranin and l ithium was conducted in a heterogeneous aquifer at Krauthausen, Germany. Th e temporal and spatial evolution of the solute plumes was monitored over 39 8 days for bromide and 449 days for uranin and lithium. The spatial variabi lity of basic aquifer parameters, hydraulic conductivity, and sorption para meters of the aquifer material was investigated in detail. Local Darcian ve locities were measured using NH4Br82 as a radioactive tracer in 33 observat ion wells. Vertical and horizontal correlation lengths of hydraulic propert ies were determined using variogram analysis. The magnitude of the local Da rcian velocities was found to be lognormally distributed. In addition, the groundwater flow direction showed a clear trend in the vertical direction. The horizontal correlation length of the magnitude of Darcian velocity agre ed with the correlation length of K estimated from grain size data. Batch e xperiments on aquifer sediments showed that sorption of uranin and lithium could be described by a Freundlich isotherm. The Freundlich n parameter of uranin sorption showed little variation with depth. The time evolution of t he bromide plume was quantified in terms of spatial moments. The longitudin al effective dispersivity estimated from spatial moment analysis was within the range of calculated effective dispersivities, taking into account the uncertainty of estimates of the 1n K statistics. (C) 2000 Elsevier Science B.V. All rights reserved.