Abstract

Agricultural soil polluted by Waste Motor Oil (WMO) due to machinery used for plant production, causes loss of its productivity. WMO is chemical composed of an insoluble mixture of aliphatic, aromatic and polycyclic hydrocarbons. To solve this problem, it is necessary to start biostimulation with a mixture of detergents chemically compatible with WMO hydrocarbons, following by biostimulation applying mineral solution according to the physicochemical properties of the agricultural soil. Therefore, the aim of this work was to improve biostimulation of WMO polluted soil by emulsification with Tween 80®, Triton X-100® and sodium dodecyl sulfate, followed by a mineral solution. In that sense, the agricultural soil polluted by 60,000ppm of WMO in Bartha flasks was first biostimulated applied Tween 80®, Triton X-100® and sodium dodecyl sulfate, and then with a mineral solution. The response variables were carbon dioxide (CO₂) production and final WMO concentration. Gas chromatography was used to determine the hydrocarbon type of the WMO before and after biostimulation of soil polluted by WMO. The experimental data were validated by Tukey HSD ANOVA. The results showed that the agricultural soil impacted by WMO biostimulated applied Tween 80®, Triton X-100® and mineral solution, after 45 days, registered 12.76mg of CO₂/100g of dry soil corresponding a WMO decreasing from 60,000 to 11,000ppm, numerical values statistically different compared to the soil impacted by WMO not biostimulated with detergents and no biostimulated with mineral solution, used as negative control registered 6.96mg of CO₂/100g of dry soil, corresponding to WMO decreased from 60,000 to 56,000ppm. The chromatogram of soil impacted by 60, 000ppm WMO after biostimulation with Tween 80®, Triton X-100® and mineral solution showed the disappearance of short and long chain aliphatic hydrocarbons up to 35 carbons, as well as low and high molecular weight aromatics up to 26 carbons. These results support that in agricultural soil contaminated by WMO biostimulation has to start with a detergent mixture for maximum emulsification that facilitates biostimulation with a mineral solution designed according to the chemical properties of the soil.

Keywords:Soil; Hydrocarbons; Amphoteric; Heterotrophic aerobic microorganisms; Mineralization