In the Biostimulation of Soil Impacted by Hydrocarbons the Detergent Emulsifies Them the Elimination Depends on Microorganisms Induced by Mineral Solution

Abstract

The objective of this work was to analyze the role of Roma® detergent in the biostimulation of soil impacted by Waste motor oil (WMO). WMO is a soil contaminant that contains insoluble hydrocarbons, so it must necessarily be biostimulated with a detergent to emulsify it. However, some research erroneously assumes that the detergent, in addition to emulsifying the hydrocarbons, also helps to mineralize them. For this, the soil and sand were polluted by 60,000 ppm of WMO in respirometer-type microcosms, there biostimulated by Roma®, a mineral solution and hydrogen peroxide (H₂O₂) at 0.5%. Carbon dioxide (CO₂) and WMO concentration was quantified by Soxhlet and detergent by the methylene blue method. The experimental data were validated by Tukey HSD ANOVA. The biostimulated soil by Roma®, the mineral solution at 50 % and H₂O₂, generated the highest generation of 17.6 mg CO₂ 100 g dry sand-¹, at 72 days and the maximum decrease of WMO up to 12,364 ppm, compared to the biostimulated soil only with Roma ® that registered 11.29 mg CO₂·100 g dry sand-¹ and decreased WMO to 34,708 ppm. In the sterile sand polluted by WMO biostimulated by Roma®, the CO₂ registered a value of 1.1 mg · 100 g of dry sand-¹. In soil biostimulated by Roma® alone, 0.4 to 0.31 mL ·100 g of dry soil-¹ was registered. These results demonstrate that Roma® detergent only emulsifies WMO for oxidation by aerobic heterotrophic microorganisms if biostimulated with a 50% mineral solution. This work shows that the detergent, according to its chemical composition, only emulsifies the WMO and maintains that it is the first obligatory action of the biostimulation and the oxidation of the WMO depends directly on the aerobic heterotrophic microorganism’s native to the soil if they are biostimulated by a mineral solution.