Uptake of Cd and Pb by natural vegetation in soils polluted by mining activities.

Abstract

The remediation of heavy metal-contaminated sites using hyperaccumulating plants represents a promising alternative to currently used methods. The potential of five species was examined to determine their tolerance and ability to accumulate metals for phytoremediation purposes, in polluted soils. The area studied is located in the SE of Spain and is heavily affected by the effects of mining activities. The total contents of heavy metals were determined in soil and plant samples and their soluble and bioavailable contents in soil samples. Average soil concentrations ranged from 2 mg kg-1 to 165 mg kg -1 for Cd and from 550 mg kg-1 to 3990 mg kg-1 for Pb. The concentration found in vegetable species studies ranged from 1.1 mg kg-1(d.w) to 172 mg kg-1 (d.w) for Cd in roots and from 1.4 mg kg-1 (d.w) to 2.7 mg kg-1 (d.w) for Cd in leaves. Finally, lead content in plant samples ranged from 45 mg kg-1 (d.w) to 1089 mg kg-1 (d.w) in roots and from 52 mg kg-1 (d.w) to 960 mg kg-1 (d.w) in leaves. Among the plant species collected, Dittrichia viscosa and Arthrocnemum rnacrostachyum were the best Cd and Pb accumulators from contaminated soils. The other plant species analyzed showed a lower heavy metal content and transfer factors values of less than 1, so that they can be considered as hypertolerant to heavy metals but not hyperaccumulators.