GEOCHEMICAL DISTRIBUTION OF POTENTIALLY HARMFUL ELEMENTS IN PERIURBAN SOILS OF A MEDITERRANEAN REGION: MANRESA (CATALONIA, SPAIN)

The contents for six elements (Ba, Cu, Ni, Pb, V and Zn) have been assayed in soils of Manresa, an area famous for its environmental sceneries in Central Catalonia region. This area is affected by a rapid transition from a traditionally agricultural-based economy to an increasingly industrial-based economy, and has formed a complete industrial structure. Twenty-seven soils (topsoil and subsoil) were sampled and heavy metals concentrations were analysed with an inductively coupled plasma-mass spectrometer (ICP-AES) after acid digestion with HNO3 and HCl and Xray fluorescence (XRF). The background values, calculated after the removal of concentrations above the upper whisker for studied metals were in mg.kg(-1): Ba: 904, Cu: 43.9, Ni: 38.7, Pb: 35.4, V: 110 and Zn: 131. The enrichment factor also shows enriched samples for Cu, Pb and Zn. The degree of soil contamination was assessed on the basis of geoaccumulation index and upper whisker method. Five percent of the soils was contaminated by at least one trace metal. The heavy metal showing the greatest number of samples with slight enrichment anomalies was Pb. The following data sets were influenced mainly by natural element dispersion and accumulation processes. Only Cu and Pb should be associated to anthropogenic pollution. However, Cu, Pb and Zn are grouped in very similar way with a general pattern increase in the NE direction for Pb and Zn and N for Cu. The relationships between the X-ray fluorescence and aqua regia methods were highly significant for Cu, Ni, Pb and Zn.