Improved bioremediation of a highly soil impacted by waste motor oil, for safe food

Abstract

The use of automobiles generates waste motor oil (WMO), whose inadequate disposal in agricultural soil is acute problem of loss of this natural resource that results in a drastic reduction in agricultural production. The soil bioremediation is complex and slow task when levels of pollution of 95,000 ppm, exceeds the maximum limit of 4,400 ppm, established by the Mexican standard. However, it is possible to reduce the recovery time of this soils, by the combined of process biostimulation and phytoremediation. Therefore, the objectives of this research were: i) biostimulation of a soil contaminated by 100,000 ppm of WMO, ii) phytoremediation by Phaseolus vulgaris with Methylobacterium symbioticum and Xanthobacter autotrophicus, plus a crude extract of carbon nanoparticles. The response variables were: a) initial and final concentration of WMO and b) P. vulgaris germination percentage, phenology and biomass at seedling stage. The results indicated that biostimulation of soil contaminated by 100,000 ppm of WMO using detergent, followed it of a crude extract of biodetergents and lipases that emulsified and hydrolyzed the insoluble aliphatic hydrocarbons. After a treatment with a crude extract of extracellular enzymes that degrade lignin and hydrolyzed the aromatic fraction of WMO, and the biostimulation with 50% mineral solution, for efficient mineralization of WMO to reduce pollution from 100,000 to 38,354 ppm in 75 days. Phytoremediation by P. vulgaris of remnant of WMO with M. symbioticum and X. autotrophicus, 45 days after sowing, decreased to 4,100, value lower than that maximum established and statistically different from 85,711 ppm of WMO used as negative control. In that sense this soil could be used for agriculture aims having no risk for producing safe food for humans and animals.