Evaluation of hydrocarbons and organochlorine pesticides and their tolerant microorganisms from an agricultural soil to define its bioremediation feasibility
The concentrations of hydrocarbons and organochlorine pesticides (OCPs), nutrients and tolerant microorganisms in an agricultural soil from a locality in Tepeaca, Puebla, Mexico, were determined to define its feasibility for bioremediation. The OCPs detected were heptachlor, aldrin, trans-chlordane, endosulfán I, endosulfán II, 1,1,1-bis-(4-chlorophenyl)-2,2-trichloroethane (4,4′-DDT), 1,1-bis-(4-chlorophenyl)-2,2-dichloroethene (4,4′-DDE) and endrin aldehyde, with values of 0.69–30.81 ng g−1. The concentration of hydrocarbons in the soil of Middle Hydrocarbons Fraction (MHF), C10 to C28, was 4608–27,748 mg kg−1 and 1117–19,610 mg kg−1 for Heavy Hydrocarbons Fraction (HHF), C28 to C35, due to an oil spill from the rupture of a pipeline. The soil was deficient in nitrogen (0.03–0.07%) and phosphorus (0 ppm), and therefore it was advisable to fertilize to bio-stimulate the native microorganisms of soil. In the soil samples, hydrocarbonoclast fungi 3.72 × 102 to 44.6 × 102 CFU g−1 d.s. and hydrocarbonoclast bacteria (0.17 × 105 to 8.60 × 105 CFU g−1 d.s.) were detected, with a tolerance of 30,000 mg kg−1 of diesel. Moreover, pesticideclast fungi (5.13 × 102 to 42.2 × 102 CFU g−1 d.s.) and pesticideclast bacteria (0.15 × 105 to 9.68 × 105 CFU g−1 d.s.) were determined with tolerance to 20 mg kg−1 of OCPs. Fungi and bacteria tolerant to both pollutants were also quantified. Therefore, native microorganisms had potential to be stimulated to degrade hydrocarbons and pesticides or both pollutants. The concentration of pollutants and the microbial activity analyzed indicated that bioremediation of the soil contaminated with hydrocarbons and pesticides using bio-stimulation of native microorganisms was feasible.