THE USE OF HOPANES TO TRACK IN-SITU VARIATIONS IN PETROLEUM COMPOSITION IN SURFACE SEDIMENTS

Alterations in the composition of a Light Arabian crude oil has been s tudied in situ during 12 months in an artificially contaminated site. After 12 months of experimentation, C-17/Pr and C-18/Ph ratios could n ot be used, because the isoprenoids were no longer stable. In contrast , a high degree of stability of biomarkers, especially hopanes, was ob served. These are very useful tools to assess alterations in other les s stable classes of saturated compounds (n-alkanes and isoprenoids) co ntained in petroleum. Marked degradation of both n-alkanes and isopren oids (using 17 alpha 21 beta C-30 hopane as ''internal standard'') has been evidenced. The use of biomarkers also made it possible to observ e a burying process which occurred down to 6 cm deep after 12 months o f experimentation. (C) 1997 Elsevier Science Ltd.