Urban geochemistry in Kristiansand, Norway

Kristiansand is one of the participating cities in the European URGE project (URban GEochemistry) that aims to map potentially toxic elements (PTEs) in the soil of European cities, identify sources of contamination, use health-based criteria for classification and cooperate with the local health authorities. For more than a century a metallurgical industry, including a large nickel smelter, was in operation in Kristiansand City. Despite the long industrial history of the Ni smelter, elevated Ni values (contaminated 200-<1200 mg/kg) in the surface soil (0-10 cm) are only found in a radius of < 1.5 km from the smelter and no samples within this zone are classified as extremely contaminated (120-<2500 mg/kg). Moderately elevated Ni-values (60-<135 mg/kg) are interpreted as natural elevated concentrations, and are ascribed to the local sulphide-bearing bands occurring within the banded gneiss that dominates the bedrock of Kristiansand. The general scarcity of easily accessible moraine and gravel in the Agder province and Kristiansand municipality has traditionally resulted in extensive reuse of urban soil, which might be reflected in some of the hot spots of PTEs in the suburban areas. None of the 300 samples collected in the area are above the Norwegian uncontaminated to moderately contaminated classification regarding Hg (1-<2 mg/kg) and Cd (1.5-<10 mg/kg). In general, the urban soil quality in Kristiansand is good and represents no hazard to human health. An exception is the residential areas close to the Ni smelter that are characterised by elevated values of As, Cu, Ni and Pb. Precaution has to be taken when old wooden houses are renovated to avoid the generation of new contamination of local soil and discharge to the Kristiansand fjord of PTEs that are in house paint.