Assessing impediments to hydrocarbon biodegradation in weathered contaminated soils

► Impediments to TPH degradation were assessed using chemical and molecular assays. ► High TPH concentrations (68.9 g kg−1) affected alkB bacterial community diversity. ► The lack of TPH degradation following ENA was due to limited TPH bioavailability. ► The presence of alkB genes does not always guarantee bioremediation success.