Organic residues and biochar to immobilize potentially toxic elements in soil from a gold mine in the Amazon

Abstract

Waste from gold mining (Au) is a threat to the ecosystem and human health because it contains high levels of potentially toxic elements (PTEs). Organic waste and biochar can be used to recover contaminated soils from mining areas because they have the potential to immobilize PTEs and improve soil fertility, enabling revegetation. The objective of this study was to investigate the efficiency with which organic residues and biochar immobilize PTEs in a multicontaminated soil of a small-scale Au mine in the state of Pará. The soil from a gold mining area was mixed with different proportions (v/v) of coffee ground residues (Bcoffee), Brazil nut tegument residues (BN), açai palm stone residues (A), and Brazil nuts biochar residues to determine which treatment is best for immobilizing PTEs. The treatments with the addition of BN and A resulted in low pH and high contents of organic matter (OM) and phosphor (P) The BN increased the available levels of Ba and reduced the available levels of Ni. The addition of coffee ground residues and biochar increased the uptake of Ba, Pb, and Ni in lettuce plants compared to treatments with BN and A. Plants grown with A showed higher dry matter yield and lower absorption and translocation of PTEs. Thus, the addition of BN and A residues in PTE phytostabilization programs in PTE-multicontaminated soils is a potential possibility.