Elementos potencialmente tóxicos em solo de mina de ouro tratado com biocarvão impregnado com ferro.

Abstract

The increasing environmental pollution in the last decades has been causing potentially toxic elements (PTEs), a constant threat to terrestrial and aquatic ecosystems and human health, especially in mining areas. The use of biochar and PTE-tolerant species was used to remedy the soil, arousing great research interest. However, these techniques must be improved. The objective was to evaluate the influence of açaí biochar nonimpregnated (BC) and impregnated with iron (BFe) on the bioavailability of EPTs, a multicontaminated soil in the mining area, in the Amazon. The experiment was conducted in a greenhouse, at the Federal Rural University of the Amazon, with seven treatments and four replications: T1 = contaminated in the soil (SC), T2 = soil in the forest (SM), T3 = SC + SM, T4 = SC + SM + BC, T5 = SC + SM + BFe, T6 = SC + BC, T7 = SC + BFe. The BC raises the pH of soils while BFe has reduced. As the applications of biochar increased the total levels of Ca, Mg, P and K in the soil, but decreased in their availability. Biochar affected the mobility of PTEs in the soil, reducing the levels of oxidizable fraction (linked to organic matter). As plants cultivated with biochar present lower dry matter yield, in addition to a higher concentration of PTEs and lower nutrient content. This suggests that biochar increased the adsorption of basic bases, reducing competition with metallic parts and resulting in greater absorption of PTEs by plants. The use of BC and BFe did not favor the immobilization of PTEs in the soil. BC’s influence As mobility with a reduction in fractions associated with arsenides and sulfates (F5) and an increase in other fractions, mainly associated with very crystalline Fe oxides and hydroxysulfates (F4). BC increased the As the easily soluble solution or what could result in the highest availability of As and the lowest biomass of the plants. The application of BC and BFe in multicontaminated soil must be carried out with caution, considering the chemical attributes of the soil and the characteristics of the EPTs to avoid the adverse impact on the soil ecosystem. According to the factors of phytoextraction and translocation, it can be classified as a species with potential for Zn phytostabilization and tolerant to PTEs, mainly As.