Potentially Toxic Elements in Urban Soils of Havana, Cuba

Abstract

Urban soils are characterised by a strong anthropogenic influence. Potentially toxic elements were studied in various horizons of 35 urban soils in Havana, Cuba, classified as Urbic or Garbic Technosols. Pseudo-total, available, and acid-oxalate extractable concentrations were determined. The pseudo-total concentrations were generally higher than the average values for the world’s soils but similar to those published for urban soils. In a few cases, very high values of copper or lead were found. Nickel and chromium concentrations exceeded the maximum allowable concentrations for agricultural soils in 22% and 12% of samples. Vanadium concentrations were always very high. There was minimum enrichment of most samples in Co, Mn, As, Cd, Cr, Cu, and Ni, but outliers reached moderate or significant enrichment. Enrichment was significant for V, while for Pb, Zn, and Hg the median values denoted moderate enrichment, but outliers reached significant enrichment in Zn and extremely high enrichment in Pb and Hg. The available elements amounted to between 0.07% of the pseudo-total vanadium and 30% lead and cadmium. The published toxicity limits for bioavailable Cd, Mn, Ni, and Pb were exceeded in 14%, 39%, 10%, and 56% of samples, respectively. The concentrations of pseudo-total total iron, cobalt, chromium, and nickel, and available cobalt, nickel and titanium were significantly lower in soils with gleyic properties (reducing conditions)