Surfactant-enhanced in-situ enzymatic oxidation: A bioremediation strategy for oxidation of polycyclic aromatic hydrocarbons in contaminated soils and aquifers

Polycyclic aromatic hydrocarbons (PAHs) degradation by laccases has been often evaluated on optimal conditions, in presence of expensive mediators. However, the application of this process on remediation of contaminated areas are not clearly understood. The aim of this work is to provide an alternative strategy closer to a real application. Batch experiments were performed on contrasted PAH contaminated model and a real (groundwater) solution at room temperature for 2 and 5 days, respectively. Analyses of anthracene, benzo(a) pyrene, naphthalene and laccase activity were performed. In model solution at pH 7 without ABTS, 50.59% of anthracene and 42.15% of benzo(a)pirene were removed. The laccase-mediated oxidation was then applied to four groundwater contaminated samples from abandoned gas station areas. The harsh chemical and biological conditions of groundwater may have influenced enzyme stability, and consequently PAH oxidation rates. After 5 days of incubation, groundwater sample 2 resulted in 94.37% of anthracene oxidation, producing anthraquinone. The final anthracene concentration was lower than the intervention value of international groundwater protection and cleanup policies, demonstrating the capability of laccases to mediate PAH oxidation until safe concentration, when applied directly into groundwater and, thus, making the proposed strategy an interesting alternative to remedy polluted sites.