The source and fate of Pb in contaminated soils at the urban area of Falun in central Sweden

For centuries the city of Falun in central Sweden has been an important industrial region of copper mining, producing sulphuric acid and paint pigment. The mining and chemical industries have generated vast amounts of wastes which have been deposited around the areas. A large part of the city is now built on the wastes. In the last two decades, significant amounts of work on the waste management have been conducted. Previous investigations showed that the soils of the urban areas have been contaminated by the wastes with a rather high level of lead (Pb). What is the speciation of soil-Pb? How does the Pb reach the biosphere? This paper gives answers toward these environmental problems. This study investigates the distribution of Pb in the urban soils by means of chemical and mineralogical methods the quantity and quality of the fallout particles; and traces the potential sources of contamination. The data indicate that in Falun urban soil-Pb speciation, may mainly be associated with some mineral phases, e.g. Fe and Mn oxides, sulphides, Pb-carbonates, as well as retained by organic matters and clay minerals. The concentrations of water soluble Pb are very low. Because of the properties of the Pb-bearing phases, the high concentrations of soil-Pb in the urban area are not likely to have a significant affect on the blood-Pb levels of pre-school children living in the urban areas. Lead and arsenic are found to be associated with iron oxides in the fallout particles collected in the areas. These fine grained particles may have been distributed through wind-related transportation from the industrial wastes dumped in the areas.