Urban geochemistry: A study of element distributions in the soils of Tallinn (Estonia)

First results are presented from the 'Urban geochemistry of Tallinn', a project supported by the Scientific and Environmental Affairs Division of NATO. The distribution of chemical elements in 532 samples of the topsoils from the territory of the biggest industrial centre of Estonia (pop. 500,000) is interpreted. Statistical analysis and mapping of major and trace elements at the territory of the Tallinn region and of the city were performed and background values and local anomalies of chemical elements on the territory were determined. The investigation focussed on the determination of zones with anomalously high concentrations of elements and the relationships of soil contamination with different pollution sources. The increase of the element concentrations has natural as well as anthropogenic origins. A detailed comparative analysis of the element distributions and the results of a factor analysis showed that the distribution of the major chemical elements depended mainly on the composition of the underlying sedimentary rocks. The territory of Tallinn is characterised by relatively high and widespread concentrations of Ba, Cr, Ga, Ni, Ti and Zn. Especially intensive local concentrations were determined for As, Cr, Mn, Ni, Pb, S, V and Zn, which are typical for the local pollution of the soils by industrial sources. The levels of As, Cr, Mn and V are more than three times. Pb and Zn are more than five times higher in the geochemical anomalies than for background levels. For the Tallinn region two major associations of elements connected with industrial pollutions of the soil are typical: the first association includes Ba, Cr, Mn, Ni and partly Fe and the second one includes As, Pb and Zn. For the city of Tallinn an increase of Ag, Ba, Be, La, Pb, Sn and Zn concentration in the soil was detected. Ba, Cr, Mn and Ni occur in high concentrations in the soils around Maardu. Different types of contamination sources can be identified in Tallinn and its suburbs.