Assessment of the heavy metal contamination of soils in Kondopoga and Kostomuksha (Republic of Karelia)

Surveys were carried out in Kondopoga and Kostomuksha, where the main industries are pulp-and-paper making and iron ore mining and concentration, respectively. Samples were taken from the top 0-10 cm soil layer in sites belonging to different land use categories and the content of heavy metals (Pb, Cu, Zn, Ni, Co, Cr, Mn) in the samples was determined by atomic absorption spectrophotometry (Aqua Regia extract). In addition, subsidiary soil pits were made for sampling at 0-5, 5-10, and 10-20 cm depths. These samples were analyzed for physico-chemical properties and heavy metal content. The results showed a relatively low level of heavy metal pollution of soil in the mentioned towns. Surveys in Kondopoga revealed limited general-use areas containing some elements in concentrations exceeding Russian national maximum allowable (MAC) and tentative allowable (TAC) levels (Pb - 6x MAC, Cu - 9x TAC, Zn - 16x TAC), and with labile copper and zinc concentrations up to 2x-3x MAC. Soils of Kostomuksha exhibited relatively low levels of the analyzed heavy metals with concentrations generally not exceeding the regional background in all land use categories. It was only occasionally that pollutant concentrations (Pb, Ni, Cu, Zn) reached 1-2x MAC/TAC. The resultant data can be used in the monitoring of urban soils and for working out recommendations for environmental protection.