Distribution in the environment of degradative capacities for gasoline attenuation

A methodology allowing the detailed assessment of the capacities of microfl orae to degrade gasoline in aerobic conditions has been developed. It consi sted in the determination of the degradation of a gasoline model mixture in liquid cultures in optimal conditions. The gasoline model mixture containe d 23 representative hydrocarbons of gasoline (GM23). The kinetics and exten t of biodegradation were evaluated by continuous overall monitoring of CO2 production and final chromatographic analysis (usually after about 30 days) of the consumption of each hydrocarbon. The methodology was used with soil and water samples from polluted and non polluted sites. The experimentatio n aimed at assessing the distribution of the degradative capacities in the environment and the prospects for natural attenuation of gasoline. Nine mic roflorae were tested. The intrinsic biodegradability (existence of mechanis ms of biodegradation) appeared total for GM23 as shown by the results obtai ned with several microflorae. The degradative capacities of microflorae fro m non polluted samples were high (total degradation rates at least 85%). In complete degradation was observed essentially for trimethylalkanes (2,2,4-t rimethylpentane and 2,3,4-trimethylpentane) and for cyclohexane. In several cases, samples from polluted sites exhibited more extensive degradative ca pacities, with total degradation of all hydrocarbons being observed for thr ee out of the six samples.