HR: 14:40h
AN: H23J-05    [Abstracts]
TI: How Groundwater Discharge Influences the Time Scales of Contaminant Release From Streambed Sediments
AU: * Schmidt, C
EM: christian.schmidt@ufz.de
AF: UFZ – Helmholtz Centre for Environmental Research, Department of Hydrogeology, Permoserstrasse 15, Leipzig, 04318, Germany
AU: Kalbus, E
EM: edda.kalbus@ufz.de
AF: UFZ – Helmholtz Centre for Environmental Research, Department of Hydrogeology, Permoserstrasse 15, Leipzig, 04318, Germany
AU: Martienssen, M
EM: marion.martienssen@ufz.de
AF: UFZ – Helmholtz Centre for Environmental Research, Department of Hydrogeology, Theodor-Lieser-Strasse 4, Halle, 06120, Germany
AU: Schirmer, M
EM: mario.schirmer@ufz.de
AF: UFZ – Helmholtz Centre for Environmental Research, Department of Hydrogeology, Permoserstrasse 15, Leipzig, 04318, Germany
AB: Streambed sediments can act as long-term storage zones for organic contaminants originating from the stream water. Although contamination levels in German rivers have generally declined in recent years, streambed sediments might still be considerably contaminated. Groundwater discharge through the sediments can induce an advective contaminant transport so that contaminants are released back from the sediment to the stream water. In our study, groundwater fluxes were quantified along a reach of 220m length of a small man-made stream in the industrial area of Bitterfeld (Germany). The stream was used for waste water discharge from the chemical industry nearby until the early 1990s. The study focuses on the long-term behaviour of chlorinated benzenes (MCB, DCBs) which are the major contaminants at the study site. The groundwater fluxes were obtained with fine spatial resolution using streambed temperatures. Groundwater discharge ranged from 11.0 to 455.0 Lm^-2 d^-1. According to locations with high and low groundwater discharge, time-integrating passive samplers were installed in the streambed to monitor the vertical distribution of current contaminant concentrations. Batch experiments were conducted to obtain the kinetic parameters of the desorption process and the water-sediment distribution coefficients as input data for a transport model of the streambed. We applied a numerical one-dimensional advective transport model to simulate the timescales of contaminant release and their dependence on the magnitude of groundwater discharge. As initial condition a homogeneous contaminant distribution in the streambed sediment layer was assumed. The mass fluxes from the streambed to the water are determined by the flow velocity of the groundwater and the sediment water distribution coefficient of the specific substance. The long-term predictive modeling indicated that the time required to reduce the concentrations and the resulting mass fluxes to the water by 90% of the initial values will be in the scale of decades for high-discharge locations and centuries for low-discharge locations, respectively.
DE: 1829 Groundwater hydrology
DE: 1830 Groundwater/surface water interaction
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: 2007 Fall Meeting