Chromium, nickel, cadmium, and lead accumulation in maize, sunflower, willow, and poplar

Our study investigated the accumulation of chromium, nickel, lead and cadmium by maize (Zea mays L.), sunflower (Helianthus annuus L.), willow (Salix x smithiana Willd.), and poplar (Populus nigra L. x P. maximowiczii), and the realtionship between the contaminants in soil and in plants. The experiment was performed in contaminated soil (former waste incineration plant) at the Hradec Králové (Czech Republic) site. Plant and soil samples were collected from three plots with different risk element contents (higher amounts of Cd, Cu, Hg, Zn, Cr, Ni, and Pb). The total and available soil metal concentrations in soil were investigated. Only a low portion of risk elements were available for plants (6% Ni, 14% Cd, 1.3 % Pb, and less than 1% of Cr). Chromium, nickel, and lead showed a similar trend to element accumulation where the highest amount was found in plant roots, higher in herbs than in trees (6.83 mg Cr·kg⁻¹, 5.04 mg Ni·kg⁻¹, and 7.76 mg Pb·kg⁻¹). The highest cadmium concentration was found in leaves of willow (1.87 mg Cd·kg⁻¹) and roots of willow (3.05 mg Cd·kg⁻¹). The correlation between the concentration of risk elements in soil and in plants was the highest in the case of lead reaching up to R= 0.89. Results also indicated that translocation of Cr, Ni, Cd, and Pb from roots to aboveground biomass of willow and poplar was low (89-98% of risk elements was retained in roots). The highest translocation from plant roots to aboveground biomass of maize and sunflower was found in the case of Cd and Pb (57 and 83% of Cd, 56 and 76% of Pb). The behaviour of these elements concerning soil and plants differed among fields with unknown history of contamination and type of contaminants.