Environmental geochemical research for the levels and the sources of toxic metals in the agricultural soils of dimitraeleftherion and platycampos region, Thessaly, Greece

Abstract

The contents of eleven elements (Cu, Pb, Zn, Ni, Co, Mn, Fe, As, V, Cr and Mg) have been assayed in the agricultural soils of Dimitra-Eleftherion and Platycampos region (Thessaly, Greece). One hundred twenty two top soil samples were collected and analysed by ICP-AES after digestion with a mixture of HClO2-HNO3-HCl-HF. Mean concentration of elements (ig g-1) in soil samples were: Cu,43; Pb,16; Zn,78; Ni,216; Co,27; Mn,1032; Fe 4.1%; As,5; V,109; Cr,254; Mg,2.5%. The contamination of the soils was assessed on the basis of comparison with average soil composition, phytotoxic levels and GLC guidelines. All the elements analysed except Pb and As have mean concentrations above the average soil comparison. The metals Zn, Ni and Cr show mean concentrations clearly higher than the phytotoxic levels. The metals Ni, Mn, V and Cr show concentrations that according to G.L.C guidelines the Dimitra-Eleftherion and Platycampos soils are classified as slightly contaminated to contaminated. Correlation analysis (CA) and principal component analysis (PCA) were applied to the data matrix to determine which elements have a common origin. PCA revealed that the studied area was mainly influenced from four sources, namely: natural (factors 1 and 2), traffic (factor 3), agricultural sources (factor 4). Cu, Zn, Co, Mn, Fe and V are associated together in iron and manganese oxideshydroxides; so grouping of these variables in the first factor reflects the adsorption of Cu,Zn,Co and V by the Fe-Mn oxides-hydroxides, as well as their weathering products. The existence of Ni, Co, Cr and Mg in the second factor explains the weathering products of ultrabasic rocks. The third factor is dominated by Pb and is related to the traffic emissions. Finally, the fourth factor is dominated by As and is related to the use of phosphate and other fertilizers.