Accumulation and translocation capacity of As, Co, Cr and Pb by forage plants

Over the last decades environmental levels of As, Cr, Pb and Co heavily increased. They are naturally present in ecosystems but also released by numerous human activities. The high concentration inside the environment has caused not wanted accumulation inside the biosphere. Their toxicity has contaminated several food chains with consequent damage. Animal slurries are particularly rich in Co, while the Cr main sources of pollution are represented by phosphate fertilizers and metallurgical industry emissions, which can contain over 1000 mg kg-1 Cr. Activities like mining, industrial emissions and application of insecticides and fertilisers have contributed to increase levels of heavy metals in soils (Alloway, 1994). Consequently these soils cannot be used for crop production without cleaning up and before measuring the metal concentration (Buxton, 1996; Niu et al., 2006). Researches demonstrated that crop cultivation can accumulate metals in their parts (Khattak et al., 1991; Hartley and Lepp, 2008). Medicago sativa has been tested for its metal uptake capacity. In a soil contaminated with 0-40 mg Cr kg-1 and other metals, Peralta- Videa et al. (2001, 2002, 2003) have shown that M. sativa is able to germinate and grow. Bioconcentration factors (BCF) and translocation factors (TF) can be used to estimate plant ability to accumulate metals from soils. The overall objectives of the present research were: (i) to determine the concentration of As, Co, Cr and Pb in plant biomass of Trifolium incarnatum (Crimson clover), Medicago sativa (Alfalfa), and mix for forage growing on a contaminated soil; (ii) to compare the metal concentrations in the aboveground biomass to those in roots and in soils (BCF, TF); (iii) to verify the removal efficiency from the soil, by comparing soil metal concentration before and after plant growing and harvesting.