Integrated Modeling of Cadmium and Zinc Contamina- tion in Groundwater and Surface Water of the Kempen Region, The Netherlands

Regional modeling of subsurface cadmium and zinc transport in a diffusely polluted area in the south of the Netherlands is the subject of this study. The atmospheric deposition of cadmium and zinc was caused by three zinc-ore smelters (point sources of emission). Agriculture and other sources of heavy metals are small compared to the atmospheric deposition in the vicinity of the smelters. A coupled unsaturated and saturated zone flow and transport model was used to assess and predict reactive transport of cadmium and zinc in three different catchments in the area. For cadmium an extensive set of modeling results is presented, for zinc only preliminary results. The modeling started with a spatial reconstruction of the historic atmospheric deposition followed by an unsaturated zone transport model to calculate cadmium leaching to groundwater. After this, a 3-dimensional reactive transport model was used for the saturated zone. The calculated cadmium concentrations were compared with two datasets of shallow groundwater analyses for validation of the model. The range of modeled and measured concentrations is the same. The modeling results indicate that the amount of cadmium in the groundwater has been doubled in the past twelve years. In the saturated zone, cadmium becomes strongly retarded, despite the low reactivity of the sandy sediments. The maximum depth of modeled and measured concentrations is about 20 meter beneath surface level. In 2002 about 10% of the total estimated leached cadmium has been discharged in seepage areas. The integrated modeling system developed here can be used to run future scenarios to predict resulting concentrations in groundwater and surface water.