Reduction of pH on the Bioavailability of Potentially Toxic Elements for Plants Grown in Iron Mining Tailing

The rupture of the Fund & atilde;o dam (Mariana, Brazil) resulted in various environmental and socio-economic impacts on riverside communities. However, the effects of iron mining tailings on the cultivation of vegetables and annual crops still need to be clarified, especially regarding the bioavailability of potentially toxic elements (PTEs), which may be exacerbated by the acidification of the tailings. Thus, this study aimed to assess the acidification of the tailings on the growth and availability, uptake, and accumulation of PTEs (Fe, Mn, Ni, Pb, Zn, Ba, Cd, Co, Cr, and Cu) in plants. Tailings samples were collected from the banks of the Gualaxo do Norte River (Mariana, MG, Brazil), and were characterized physically and chemically. Experiments on the availability, uptake, and accumulation of PTEs were conducted in a greenhouse, using four plant species: tomato (Solanum lycopersicum L.), lettuce (Lactuca sativa L.), radish (Raphanus sativus L.), and sorghum (Sorghum bicolor [L.] Moench), in a completely randomized design with three treatments (non-acidified tailings (pH 7.23), acidified tailings (pH 5.00), and reference soil (pH 5.33)), each with five replications. The availability and accumulation of PTEs were quantified. Most of the analyzed PTEs showed higher concentrations in plants grown in the reference soil. Conversion to fresh mass was performed when examining the levels of PTEs in the edible parts of the cultivated crops. In both acidified and non-acidified tailings, the levels of PTEs were within the standards permitted by Brazilian legislation. The cultivation of tomato, radish, and sorghum is restricted when grown in tailing at normal or acidified pH levels, while lettuce has no restrictions. Overall, the tailings did not pose risks regarding the PTEs content in plants for consumption, even when acidified to pH 5.00. However, they exhibited Mn phytotoxic levels, which, combined with the high presence of silt and sand, affected the development of the plants.