URBAN AND AGRICULTURAL SOIL ECOTOXICITY AND HEAVY METAL CONTAMINATION

Soils represent the final destination of pollutants coming from both air and water inputs. Heavy metals are of primary concern as they persist in the environment, move up the food chain and could cause several disorders. The aim of this study was to compare the metal contamination and ecotoxicity of two soils at different use, urban and agricultural. Different toxicity tests were performed both with whole soil and its aqueous extract by a battery of ecotoxicological test with organisms belonging to different trophic levels: bacteria (Vibrio fischeri), algae (Selenastrum capricornutum), plants (Sorghum saccharatum, Lepidium sativum, Sinapis alba) and crustaceans (Daphnia magna, Heterocypris incongruens). Moreover the genotoxic effects were assessed by Vicia faba micronucleus assay. The content of some trace metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) and their available fractions were also determined. Urban soil exerted a moderate toxicity upon V. fischeri and a clear biostimulation upon S. alba, instead of soil aqueous extract produced only algae growth biostimulation. Higher genotoxic effects observed for urban soil could be attributable to lead content and availability. Agricultural soil was mainly contaminated by Cu which could be responsible of bacteria bioluminescence inhibition. Agricultural soil aqueous extract revealed high toxicity on S. capricornutum growth; moreover genotoxic effects were not evidenced. The integration of toxicity data in the ecotoxicological risk index showed a clear difference between investigated soils, with the highest risk values for agricultural one.