Bioavailable Nickel and Zinc in Polluted Soil Alter the Growth of Non-pioneer Trees in the Brazilian Atlantic Forest

Background and aimsThe Brazilian Atlantic forest has been affected by the deposition of Ni and Zn, among other heavy metals adsorbed from atmospheric particles, which can be incorporated into the soil. If available in the soil, they can be absorbed by plant roots. The study aimed at testing experimentally the hypotheses: 1) Ni and Zn depositions increase their bioavailable fractions in the soil; 2) pioneer tree species demonstrate a greater potential to absorb Ni and Zn from the soil and less growth changes than non-pioneer species.MethodsThe experiment was carried out with six pioneer and non-pioneer species native to the Atlantic Forest, grown for 90 days in soil from an urban fragment of the Atlantic Forest, according to the treatments: soil with balanced fertilization (control) and soil enriched with Ni, Zn and Ni+Zn. At the end, the concentrations of Ni and Zn were determined in four soil fractions (F1: soluble; F2: linked oxides/hydroxides; F3: organic matter: F4: residual metals) and in leaves, stems/branches and roots. Mobility factors in soil, concentration ratios between treatments and respective controls, translocation index and relative growth rate in height, leaf number and total biomass were also calculated.ResultsThe results showed that Ni and Zn concentrations increased significantly in the bioavailable soil fractions (F1, F2). The absolute content of Ni and Zn in the plants directly reflected the soil level in the available forms.ConclusionsThe metal accumulation in the species occurred regardless of the successional group to which they belonged. Non-pioneer species showed greater susceptibility to the metals.