Biocarvão de lodo de esgoto na imobilização de elementos potencialmente tóxicos em vertissolo contaminado

Abstract

The volume of waste produced by industrial and urban activities has resulted in the enrichment of potentially toxic elements (TPEs) in the environment. Many of these TPEs, in low concentrations, are essential to soil, plants, animals and human health, however high concentrations can become toxic, others, even in low concentrations do not present any beneficial functions, characterized by accumulation, persistence and potential risks to organisms. To mitigate the potential risks, the use of adsorbent materials has been well evaluated as an alternative for soil remediation, such as biochar, derived from agricultural waste, food, forestry and sewage sludge, pyrolyzed under different temperature conditions. This study aims to evaluate the effect of biochar from sewage sludge in the immobilization of TPEs in a Vertissol contaminated by metals in the municipality of Santo Amaro, Bahia, Brazil. Soils at a depth of 0.20 m were obtained from the surroundings of a former mining-metallurgical plant in the municipality and chemically characterized. For the analysis of the material, an experimental design was set up entirely at random, where biochars were added in pots, with the Vertissolo, at three pyrolysis temperatures (BL350º, BL450º and BL600°C) as well as a control, in five repetitions. This material was incubated for 120 days and then chemically characterized and chemical fractionation of the EPTs was performed. For the elements Cd, Co, Pb and Zn, the higher pyrolysis temperatures BL450 and BL600, were more efficient in immobilizing the element, keeping the highest concentrations in the F3 and F4 fractions. The addition of the treatments for Cr had negative effects. The temperatures of BL450 and BL600, increased the concentration of Cu to the F3 fraction. For Ni, the addition of BL600 had the greatest positive effect on the immobilization of the element, maintaining the F3 fractions.