Dynamics of CO2 Evolution during Bioremediation of Clayey and Sandy Soils Contaminated with Used Lubricating Oil

The aim of the study was to evaluate the biodegradation of petroleum hydrocarbons in two Brazilian contaminated soil types (clayey S1 and sandy S2) at a loading rate of 30,000 and 45,000 mg/kg. A model soil of 300 g with used lubricating oil was amended with commercially available hydrocarbon degrading microbial consortium: Amnite p1300 as the bioaugmentation (T1), other treatments consist of nutrients amendments - (NH4)2SO4 and K2HPO4 (NPK) as biostimulation (T2), unammended soil - natural attenuation as (T3) and the control soil treated with sodium azide (NaN3) as (T4) were evaluated on the microbial community and the degradation of used lubricating oil. Three microcosm replicated flasks per treatment were incubated, and the performance of each treatment was examined by monitoring CO2 evolution, microbial activity, and oil degradation rate. In Soil 1, T1 produced the highest values of CO2 of (1600.20 mg/kg) and (1347.60 mg/kg) while the least values were recorded in the control (T4) with 89.52 and 102 mg/kg in oil contaminated with 3 and 4.5 % respectively. A similar trend was obtained in the bioaugmented treatment soil (S2) with the highest CO2 production in T1. The best percentage oil degradation was also recorded where the utmost CO2 production was obtained.