Disponibilidade de cádmio em solos tratados com resíduos de sisal (Agave sisalana)

Abstract

Soil contamination by heavy metals from numerous existing human activities is an issue that needs to be mitigated. From this perspective and through scientific advances in the area of environmental pollution and soil science, organic waste began to be characterized as materials capable of retaining metals in their biomass due to the presence of chemical sites and electrically attractive functional groups in their composition. In this sense, the objective was to evaluate the biosorption potential of cadmium (Cd2+) in soils contaminated by this metal, through the addition of three different sisal residues, originating from the process of defibrating its leaves to obtain fibers, aiming to analyze the relationship between residues and soil fertility. The experiment was conducted in a greenhouse under a completely randomized design (DIC) in a 3x5x4 factorial scheme [3 types of waste [Mucilage (MUC), Fibrils (FIB) and Fiber powder (PFIB)] 5 doses [0 (control), 1, 2, 3, and 4 (%m/m)] in 4 different times (30, 60, 90 and 120 days)] with 3 repetitions. The soil samples were contaminated with 30 mg kg -1 of Cd2+ and subsequently the residues, in different doses, were added to the experimental units. To analyze metal availability, the extracting solution DTPA [(0.005 mol L-1) (1:2, m/v) was used, with the soil from the different units collected in 4 periods (30, 60, 90 and 120 days). The quantification of Cd2+ availability in the soil, after extraction, was determined by atomic absorption spectrometry. The data were subjected to analysis of variance and, when significant (p≤0.05), a regression analysis was performed. As there are two quantitative factors (dose and days), a response surface figure was created when the factors interacted. Finally, a principal component analysis (PCA) was performed to estimate the residue-fertility relationship. The factors dose and days statistically influenced the availability of Cd2+ in the soil, so that the 4% dose corresponded to the greatest reductions in availability. MUC showed the highest capacity for Cd2+ biosorption, with maximum adsorption of 52.80% at dose 4% and FIB 38.53%. The 3% and 4% doses of MUC were positively correlated with soil fertility parameters. Thus, it is concluded that sisal MUC and FIB can be considered potential alternatives for use in the remediation of soils contaminated by Cd2+ via biosorption.