Phytoextraction of Heavy Metals from Soil Polluted with Waste Mining by Using Forage Plants in Successive Cultures

Abstract

During two years, was studied the phytoextraction potential of some perennial species (Medicago sativa and Trifolium pretense, Festuca arundinacea and Lolium perenne), for Zn, Cd, and Pb from soils polluted with waste mining. The experiment was done on kernozem soil with adding of 20 kg waste mining/m2 and 8 kg biosolid/m2. The results showed that in all experiments, rye-grass is a good extractor for Zn and Cd, and leguminous species for Pb. Both leguminous species, especially M. sativa, presented a high tolerance for lead toxicity, even with 3-4 times greater values than maximum allowable level from actual legislation. In all cases, regardless of the experimental variant, raygrass (Lolium perenne) is a good accumulator of Zn and Cd, and red clover (Trifolium pratense) of Pb. The values of metal bioaccumulation increase gradually with their concentration in soil. Quality of very good extractor of Pb displayed by Trifolium pratense species are kept even in case of excessive pollution with Pb, when it exceed 3.4 times the maximum permissible norms. This proves, as Medicago sativa species, a good tolerance and resistance to toxicity of this metal. In case of addition of natural zeolite-volcanic tuff there was no increase in the rate of Zn bioaccumulation. Only in case of Cd at Lolium perenne and Pb at Trifolium pratense appear the favourable effect of metallic ions bioavailability in soil for plants.

Keywords

• heavy metals
• leguminous and gramineous species
• phytoextraction
• zinc