Influence of Mass-Transfer Limitations on Carbon Isotope Fractionation during Microbial Dechlorination of Trichloroethene

详细信息    查看全文

• 作者：Christoph Aeppli ; Michael Berg ; Olaf A. Cirpka ; Christof Holliger ; Ren P. Schwarzenbach ; Thomas B. Hofstetter
• 刊名：Environmental Science & Technology
• 出版年：2009
• 出版时间：December 1, 2009
• 年：2009
• 卷：43
• 期：23
• 页码：8813-8820
• 全文大小：275K
• 年卷期：v.43,no.23(December 1, 2009)
• ISSN：1520-5851

文摘

Mass transfer of organic contaminants from nonaqueous phase liquids to the aqueous phase can significantly modulate the observable carbon isotope fractionation behavior associated with contaminant transformation. We evaluated the effects of kinetic interphase mass transfer between tetradecane and water on the observable ¹³C enrichment factor, _obs, pertinent to the reductive dechlorination of trichloroethene (TCE) by Sulfurospirillum sp. in laboratory batch model systems containing organic, aqueous and gaseous phases. We propose a conceptual model, which includes the kinetics of tetradecane−water and gas−water mass transfer, microbial growth, and isotope-sensitive parameters describing dehalorespiration, for quantifying variable ¹³C enrichment factors. While the C isotope fractionation of TCE reduction to cis-dichloroethene (cDCE) in the absence of phase-transfer effects can be characterized by a constant -value of −18.8 ± 0.6‰, mass-transfer limitations impede describing this process with a constant enrichment factor typically used in Rayleigh equations. Owing to the masking of kinetic isotope effects by the transfer of TCE from tetradecane to the aqueous phase, _obs-values gradually changed from −18.4‰ to −5.9‰. Such variations may complicate the interpretation of compound-specific isotope analysis in the assessment of chloroethene biodegradation in field applications.