Fitorremediação de solos contaminados por cromo e níquel oriundos de lodo de curtume e mineração por meio de culturas energéticas

Abstract

Leather production and the mining complex play a crucial role in the global economy. In Brazil, the state of Goiás stands out in third place for tanned leather production and holds large reserves of nickel (Ni) and chromium (Cr). However, these activities can lead to the contamination of land with potentially toxic elements (PTEs), such as chromium and nickel. Phytoremediation is a bioremediation technique that involves the direct use of plants for the transfer or stabilization of toxic metals in contaminated soils. Bioenergy is one of the few decarbonization options for the energy system in the short to medium term. Nevertheless, it is often criticized due to indirect land-use changes, the lack of high-quality agricultural land, and competition with food production, while contaminated areas remain unused. The present study aims to provide a sustainable solution to both problems by facilitating soil decontamination through phytoremediation combined with the cultivation of energy crops. The experiments were conducted in a greenhouse at the School of Agronomy of the Federal University of Goiás (Goiânia - GO, Brazil), using soils collected from a tannery sludge spill area (Chapter I) and a chromite mining area in serpentinite rock (Chapter II). The experimental design consisted of randomized blocks with four replications and five treatments, including four energy crops (Capiaçu grass, purple grass, sugarcane, and energy cane) and spontaneous plants. For the purple and Capiaçu grasses, harvesting occurred after six months of cultivation, representing the sum of two cuts; for the sugarcane, energy cane, and spontaneous plants, harvesting took place after 12 months. Biometric characteristics, dry biomass, energy yield, chromium and nickel accumulation in the biomass (shoot and root), and total chromium and nickel content in the soil were analyzed. Data were submitted to analysis of variance (ANOVA), and when differences were observed, the Tukey test was applied, both at a 5% probability level. Biomass production, energy yield, and plant growth were not affected by high levels of chromium and nickel. The highest accumulations of these metals occurred in the roots, evidencing phytostabilization. In conclusion, energy species can be successfully cultivated in contaminated soils for bioenergy purposes.