BACKGROUND: Vegetable oils are used as environmentally friendly and cost-efficient amendments for the treatment of contaminated soils, primarily as solvents for the mobilization of polycyclic aromatic hydrocarbons (PAH). In the present study, the efficacies of food-grade and of waste oils, i.e. thermally ‘abused’ cooking oils, in increasing physical and potential microbial accessibility of soil-sorbed PAH were evaluated.
RESULTS: Abused oils were found to be slightly less efficient for PAH mobilization than their unheated counterparts. After 168 h of extraction, residual concentrations amounted to between 5% and 20% of initial PAH (16 EPA-compounds). The non-bioaccessible PAH fraction was reduced by up to 84% using canola or sunflower oil in a bioaccessibility-limited soil. For all oils, removal efficacy increased with PAH hydrophobicity, including the carcinogenic Benzo(a)pyrene. Simple octanol-, soil organic carbon–and triolein–water partitioning coefficients did not serve to explain these observations. Increased oil viscosity induced by heating appears to be the priming factor in decreasing extraction efficacy rather than a profound change in the oil constituents' molecular properties, as expressed by Hildebrand solubility parameters.
CONCLUSION: The present results show that waste vegetable oils can be used efficiently for the extractive or biological treatment of PAH-contaminated soils, offering a cost-efficient and sensible alternative for the use of foodstuff. Copyright © 2012 Society of Chemical Industry