Decontamination of soil containing oil by natural attenuation, phytoremediation and chemical desorption.

An experiment was performed for 240 days to evaluate the oil removal through natural attenuation (NA) and phytoremediation (PH) combined with surfactant (SF), in soil up to 76,585 mg kg -1 of total petroleum hydrocarbons (TPH). A completely randomized design was applied using a 4 × 6 factorial arrangement, with four concentrations of oil and six recovery technologies. The technologies were combinations of Leersia hexandra (Lh) grass, NA (native microorganisms), and doses of Tween ® 80. The results recorded treatment means with statistical differences (Tukey, p  ≤ 0.05 and 0.01). Oil in presence of 5% SF stimulated the formation of grass roots. The SF promoted a significant increase in the biomass of grass stems and leaves but did not contribute to oil removal or microbial density. Unexpectedly, the PH inhibited the removal of oil and induced a decrease in fungi, hydrocarbonoclastic bacteria, and heterotrophic fungi. NA combined with 2.5% SF removed 95% of 48,748 mg of TPH. The best technology for soil decontamination was bioremediation through hydrocarbonoclastic bacteria stimulated with 2.5% SF.