The effect of biodegradation and water washing on the occurrence of alkylphenols in crude oils

摘要

Hlodegraded oils from California and Nigeria wereanalysedtoassess the impact of biodegradation upon alkylphe- 101 occurrence in crude oils. The extent of biodegradation in the 13 Californian samples ranged from very mild (full n- Ilkane distribution present) to moderate (complete degradation of Cis + n-alkanes and significant reduction of acyclic soprenoids) corresponding to a range of <1-4 on the biodegradation scale of Peters and Moldowan [Peters, K.E.. -1oldowan, J.M.. 1993. The Biomarker Guide: Interpreting Molecular Fossils in Petroleum and Ancient Sediments. >rentice Hall. Englewood Cliffs, NJ (363 pp)J. Degradation in the four Nigerian oils ranged from very mildnon- legraded (stage lor less) to complete removal of n-alkanes and acyclic isoprenoids (stage 5). The data from the natu- 'ally-degrcided sample suites were compared to the results of an in-vitro aerobic biodegradation experiment conducted vith a North Sea oil. Biodegradation resulted in significant reduction in total alkyl phenol abundance and preferential lepletion ofCJ and C2 alkylated compounds in the Nigerian and laboratory degraded samples. These effects were most >ronounced in oils in which the methylated naphthalenes had been biodegraded (biodegradation stage 4 or 5). There vas no clear relationship between alkylphenol abundance or molecular distributions and the extent of biodegradation n the Californian samples, although alkylphenol distributions in the biodegraded samples were generally dominated by he C1 compounds. Simple oil/water partition calculations showed that these distributions were consistent with the : .ffect~ of water washing.