Vanadium as an internal marker to evaluate microbial degradation of crude oil

17[agr ],21[bgr ]-Hopane is used as an internal marker to evaluate the biodegradation and/or weathering of petroleum products. In this study, vanadium, the most abundant heavy metal in crude oil, was investigat- ed as an alternative internal marker to 17[agr ],21[bgr ]-hopane. It was demonstrated that the amounts of dichloromethane-extractable vanadium and 17[agr ],21[bgr ]-hopane were not significantly reduced even after an intensive biodegradation of crude oil. Thus, vanadium was considered to be a possible internal marker for the evaluation of the biodegradation and/or weathering of crude oil. This assumption was tested in beach-simulating tanks where crude oil was biodegraded under conditions that mimic a natural beach environment. Crude oil in the tanks was extracted at appropriate times after the subjection to biodegradation, and the concentrations of various crude oil components including those of vanadium and 17[agr ],21[bgr ]-hopane were determine- d. The concentration changes of the crude oil components determined on the basis of the vanadium concentration agreed well with those determine- d on the basis of the concentration of 17[agr ],-21[bgr ]-hopane. It was concluded that vanadium could be used as an internal marker of crude oil for the estimation of biodegradation and/or weathering.