Tolerance and accumulation of heavy metals by Brassicaceae species grown in contaminated soils from Mediterranean regions of Spain

Cultivation of crops in or close to contaminated sites may result in both growth inhibition and tissue accumulation of heavy metals, with resulting possible risks to humans or livestock health if these tissues are ingested. In this work, growth inhibition and accumulation of Cd, Cu, Pb and Zn for three Brassica crop species ( B. oleracea L., B. carinata A. Br. and B. juncea (L.) Czern.) and the autochthonous Cu-accumulating species Hirschfeldia incana (L.) Lagrèze-Fossat were studied, in two contaminated soils from the Murcia region of Spain and one from Valencia, over a 80-day period (40 days for H. incana) in pot experiments. Growth parameters indicated a tolerance index averaged for the two contaminated soils (relative to non-contaminated substrate) of the Brassica species in the order: B. juncea (mean value 97.6%) > B. carinata cv. 117 (74.2%) > B. carinata cv. 2920 (66.5%) ≈ B. oleracea (65.6%), with an average of 72% for H. incana. Above-ground tissue metal concentrations indicated a possible risk to human and livestock health from Cd and Pb for B. oleracea and H. incana. H. incana did not show a marked shoot accumulation of Cu, possibly due to inhibition of Cu uptake by the high soil levels of Zn and Pb. Its shoot tissue concentrations of Pb and Zn were related more closely to the total soil metal concentrations than to the DTPA-extractable, concentrations of these elements.