Combined Carbon and Hydrogen Isotope Fractionation Investigations for Elucidating Benzene Biodegradation Pathways

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• 作者：Anko Fischer ; Ilka Herklotz ; Steffi Herrmann ; Martin Thullner ; Sander A. B. Weelink ; Alfons J. M. Stams ; Michael Schlö ; mann ; Hans-Hermann Richnow ; Carsten Vogt
• 刊名：Environmental Science & Technology
• 出版年：2008
• 出版时间：June 15, 2008
• 年：2008
• 卷：42
• 期：12
• 页码：4356 - 4363
• 全文大小：376K
• 年卷期：v.42,no.12(June 15, 2008)
• ISSN：1520-5851

文摘

Recently, combined carbon and hydrogen isotope fractionation investigations have emerged as a powerful tool for the characterization of reaction mechanisms relevant for the removal of organic pollutants. Here, we applied this approach in order to differentiate benzene biodegradation pathways under oxic and anoxic conditions in laboratory experiments. Carbon and hydrogen isotope fractionation of benzene was studied with four different aerobic strains using a monooxygenase or a dioxygenase for the initial benzene attack, a facultative anaerobic chlorate-reducing strain as well as a sulfate-reducing mixed culture. Carbon and hydrogen enrichment factors (b5;_C, b5;_H) varied for the specific pathways and degradation conditions, respectively, so that from the individual enrichment factors only limited information could be obtained for the identification of benzene biodegradation pathways. However, using the slope derived from hydrogen vs carbon isotope discriminations or the ratio of hydrogen to carbon enrichment factors (9b; = Δ_H/Δ_C ≈ b5;_H/b5;_C), benzene degradation mechanisms could be distinguished. Although experimentally determined 9b; values partially overlapped, ranges could be determined for different benzene biodegradation pathways. Specific 9b; values were <2 for dihydroxylation, between 7 and 9 for monohydroxylation, and >17 for anaerobic degradation. Moreover, variations in 9b; values suggest that more than one reaction mechanism exists for monohydroxylation as well as for anaerobic benzene degradation under nitrate-reducing, sulfate-reducing, or methanogenic conditions. Our results show that the combined carbon and hydrogen isotope fractionation approach has potential to elucidate biodegradation pathways of pollutants in field and laboratory microcosm studies.