Waterlot, C.;Bidar, G.;Pelfrene, A.;Roussel, H.;Fourrier, H.;Douay, F.

Université Lille Nord de France, Lille 59044 (France);Département des Sites et Sols Pollués, Agence de I'Environment et de la Matrise de I'Energie (ADEME), Angers 49000 (France);Groupe ISA, Equipe Sols et Environnement, Laboratoire Génie Civil et géo Environnement (LGCgE) Lille Nord de France (EA 4515), Lille 59046 (France)

bioconcentration factor;environmental availability;metal toxicity;sequential extraction;soil physico-chemical property

Soil contamination by metals from anthropogenic activities (e.g., mining and smelting) is a major concern for the environment and human health. Environmental availability of cadmium (Cd), lead (Pb), zinc (Zn), copper (Cu), and indium (In) in 27 urban soils located around two former Pb and Zn smelters in Northern France were studied by analysing the chemical forms of these metals and evaluating their phytoavailability. These metals were determined using flame or electrothermal absorption atomic spectrometry (FAAS or ETAAS), depending on their concentration levels. After optimisation of the ETAAS method, characteristic mass of In in water and aqua regia were 9.9 and 18 pg, respectively, showing the high sensitivity of the analytical procedure. Metal partitioning was conducted using a four-step sequential extraction procedure. The results showed that Cd and Zn were mainly in the acid-extractable and reducible forms in the urban soils studied. In contrast, Pb and In were largely in the reducible fraction. However, in some samples, the amount of In extracted in the residual or exchangeable fraction was higher than that in the reducible fraction. Copper was mainly found in the reducible and residual fractions. A pot experiment was conducted in a glasshouse with seven soils (six contaminated and one uncontaminated) and two plant species, ryegrass and lettuce. The results showed transfer of metals from the contaminated soils to the shoots of ryegrass and the edible part of lettuce. The metal bioconcentration factor was in the order of Cd >> Cu > In > Zn >> Pb for lettuce leaves, whereas for ryegrass shoots, three orders were found, Cd > Zn > Cu >> In > Pb, Cd >= In > Zn > Cu >> Pb, and Zn > Cd > Cu > In > Pb, depending on the physico-chemical properties of the soils, such as pH, cation exchange capacity, carbonates, and organic matter. It was established that the metal toxicity was related to the contamination levels and the physico-chemical properties, including pH, organic matter, and in a lesser extent, Ca, Mg, and phosphorus contents, of the soils. However, it was shown that lettuce could grow on soils having high Cd and CaCO₃ contents. Cadmium was one of the most available metals while Pb was always the least available in the soils studied.