Spatial distribution and contamination assessment of heavy metals in urban topsoils from Las Tunas city (Cuba) using XRF

Concentrations of Cr, Co, Ni, Cu, Zn, Pb and Fe in the topsoils (0-10 cm) from Las Tunas city were measured by X-ray fluorescence analysis. The mean Cr, Co, Ni, Zn and Pb contents in the urban topsoil samples (97± 30, 14 ± 2, 35 ± 36, 94 ± 26, 199 ± 87 and 42 ± 29 mg.kg-1 respectively) were compared with mean concentrations for other cities around the world with similar population. Cr content in school grounds, parks and residential areas exceed background level in 20%. Highest content for Ni was determined in residential areas, for Zn in market gardens soils and as for Pb, the highest content ratios were observed for market gardens (2.7) and residential areas (2.3). Spatial distribution maps indicated the same behaviour for Cr-Co-Ni and Pb-Zn, respectively, whereas the spatial distribution of Cu differs from other heavy metals. On the other hand, the metal-to-iron normalisation, using (10-20) cm bottom soil contents as background, showed that topsoils in Las Tunas city are severe enriched with lead and not enriched with the rest of determined metals. The average values of integrated pollution index (IPI) indicated that soils are moderate contaminated by heavy metals (1.17 ≤ IPIave ≤ 1.39), but enrichment index values (EI) shows that metal concentrations on the studied locations are not above the permissible levels for urban agriculture. (Author)