Impacts of activated carbon amendments, added from the start or after five months, on the microbiology and outcomes of crude oil bioremediation in soil

Abstract

The use of activated carbon (AC) amendments to reduce exposure risks for hydrophobic contaminants like polycyclic aromatic hydrocarbons (PAHs) by adsorption is an innovative soil remediation approach. However, AC amendment side-effects on the pollution biodegradation are poorly understood. This study assessed for optimized nutrient ratio conditions, effects of 5% soil wet weight AC amendments, if added from the beginning or after five months, on the outcomes of one year of crude oil polluted soil bioremediation. CO2, residual hydrocarbon concentrations and microbial community structure analysis revealed how AC amendment hindered crude oil biodegradation much more, if added from the start, as compared to after 5 months, i.e. after the initial phase of biodegradation. Putative crude oil degrading microorganisms from the genera Marinobacter, Parvibaculum, Salinibacterium, Muricauda, and Alcanivorax were more sensitive to the AC amendment than those from the genus Rhodococcus. Rhodococci possess hydrophobic cell walls which may enable them to accumulate hydrocarbons in the AC amended soil, despite of their reduced availability. AC amendment from the start had the highest alkane and total US EPA PAH residues, but was more effective than one year of bioremediation, with or without AC amendment after 5 months, in reducing PAH availability in the soil.