Remediação de solo contaminado com uma mistura comercial de diesel-biodiesel (B12): uma avaliação em microcosmos dos efeitos da adição de compostos (in)orgânicos

Abstract

Fossil fuels have been protagonists in soil pollution, especially diesel-biodiesel blends, the most used fuel in Brazil. One of the alternatives for treating soils contaminated with fuels is the bioremediation processes, which can be improved by biostimulation techniques. In this study, the dynamics of the degradation of commercial S10 diesel with 12% biodiesel (B12) in soil was investigated, supplemented with organic and inorganic compounds, seeking to determine the effects on indigenous microbiota indicators and to achieve better levels of contaminant attenuation. Three treatments were evaluated over 93 days: natural attenuation (control), addition of organic compound (COB), addition of soybean hulls (SHB) and addition of NPK (IB). During the experiment, basal soil respiration, variations in the number of total heterotrophic and degrading B12 bacteria, soil pH, carbon and nitrogen concentrations (total, inorganic and organic), and finally, efficiency in removal of petroleum hydrocarbons in the diesel range (THP-DRO) in each treatment. Basal soil respiration showed the highest cumulative C-CO2 releases in the following order: COB> SHB> Control> IB, all of which were significantly different (p <0.05). The numbers of total heterotrophic bacteria and degrading bacteria increased over the course of treatments. The soil pH increased after the addition of B12 in relation to the soil without contamination, and there were variations throughout the experiment for all treatments, except COB. The phytotoxicity of the soil indicated that only the SHB treatment reached satisfactory levels of toxicity reduction, followed by the control. Nitrogen and soil carbon had significant variations (p <0.05) over time and between treatments, with biostimulated treatments showing more N-total than the control. Organic carbon tended to decrease over time, except for the SHB treatment, where there was no variation (p> 0.05). Contrary to expectations, biostimulation was not able to improve the attenuation of the contaminant. The analysis of TPH DRO showed that the Control treatment showed the greatest removal of the contaminant (96.12%), followed by COB (87.25%,), IB (84.21%) and SHB (68.05%), after 93 days.