Aplicação de biochar de eucalipto e peróxido de cálcio (CaO2) no tratamento de solo contaminado por diesel

Abstract

In a context where fossil fuels continue to play a crucial role in human development, diesel is a significant energy component used in B razil. However, leaks that may occur during its transportation and storage pose a threat to the environmental quality of the soil. In this scenario, biochar, known for its soil improvement benefits, a nd oxygen-releasing compounds, used as a prolonged source of oxygen, emerge as potential agents for the degradation of hydrocarbons in soils contaminated by diesel. The purpose of this study was to evaluate the effectiveness of a treatment using biochar from eucalyptus biomass (Eucalyptus sp.) and calcium peroxide (CaO2) in soil from compacted barriers contaminated by diesel. Bench-scale bioreactors were prepared, including the following treatments: eucalyptus biochar at 5% (BC), calcium peroxide at 1% (Pe), and a combination of both (BP). Throughout the assay, the quantification of total heterotrophic bacteria (THB) and diesel-degrading bacteria (DDB) was performed using the spread plate method. Periodic samplings were conducted to analyze the supernatant, considering parameters such as pH, conductivity, salinity, chemical oxygen demand (COD), and hardness. At the end of the assay, the remaining total petroleum hydrocarbons (TPH) in the soil were quantified by gas chromatography. The soil toxicity after treatment, as well as that of biochar and CaO2, was assessed using lettuce seeds (Lactuca sativa), the bacteria Vibrio fischeri, and the microcrustacean Artemia sp.. There was a greater degradation of total petroleum hydrocarbons in the BP treatment compared to the control (42 ± 7% and 28 ± 10%, respectively). However, CaO2 proved to be toxic to the microbial community, while biochar stimulated its development, with 3.6 ± 0.1 × 106 CFU of THB/g of soil, whereas the control obtained 1.3 ± 0.7 × 104 CFU of THB/g of soil. The toxicity of soil elutriates after the BP treatment was reduced. Furthermore, soil additives showed no toxicity to lettuce (the lowest germination index found was 86.16% for CaO2), but calcium peroxide showed toxicity to the luminescent bacterium V. fischeri, r esulting i n a EC50 o f 0.23%. The treatment with eucalyptus biochar and CaO2 showed potential for the degradation of total petroleum hydrocarbons. However, additional studies are needed to elucidate the underlying mechanisms and consider their applicability in the field.