title: Critical evaluation of the 2D-CSIA scheme for distinguishing fuel oxygenate degradation reaction mechanisms.
abstract: Although the uniform initial hydroxylation of methyl tert-butyl ether (MTBE) and other oxygenates during aerobic biodegradation has already been proven by molecular tools, variations in carbon and hydrogen enrichment factors (ε(C) and ε(H)) have still been associated with different reaction mechanisms (McKelvie et al. Environ. Sci. Technol. 2009, 43, 2793-2799). Here, we present new laboratory-derived ε(C) and ε(H) data on the initial degradation mechanisms of MTBE, ethyl tert-butyl ether (ETBE), and tert-amyl methyl ether (TAME) by chemical oxidation (permanganate, Fenton reagents), acid hydrolysis, and aerobic bacteria cultures (species of Aquincola, Methylibium, Gordonia, Mycobacterium, Pseudomonas, and Rhodococcus). Plotting of Δδ(2)H/ Δδ(13)C data from chemical oxidation and hydrolysis of ethers resulted in slopes (Λ values) of 22 ± 4 and between 6 and 12, respectively. With A. tertiaricarbonis L108, R. zopfii IFP 2005, and Gordonia sp. IFP 2009, ε(C) was low (<|-1|‰) and ε(H) was insignificant. Fractionation obtained with P. putida GPo1 was similar to acid hydrolysis and M. austroafricanum JOB5 and R. ruber DSM 7511 displayed Λ values previously only ascribed to anaerobic attack. The fractionation patterns rather correlate with the employment of different P450, AlkB, and other monooxygenases, likely catalyzing ether hydroxylation via different transition states. Our data questions the value of 2D-CSIA for a simple distinguishing of oxygenate biotransformation mechanisms, therefore caution and complementary tools are needed for proper interpretation of groundwater plumes at field sites.
authors.affiliation: Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research - UFZ, Permoserstrasse 15, 04318 Leipzig, Germany. monica.rosell@ub.edu
authors.forename: Mònica
authors.initials: M
authors.lastname: Rosell
authors.forename: Rafael
authors.initials: R
authors.lastname: Gonzalez-Olmos
authors.forename: Thore
authors.initials: T
authors.lastname: Rohwerder
authors.forename: Klara
authors.initials: K
authors.lastname: Rusevova
authors.forename: Anett
authors.initials: A
authors.lastname: Georgi
authors.forename: Frank-Dieter
authors.initials: FD
authors.lastname: Kopinke
authors.forename: Hans H
authors.initials: HH
authors.lastname: Richnow
mesh_terms: D001420:Bacteria, Aerobic / Q000378:metabolism*; D001673:Biodegradation, Environmental; D005019:Ethyl Ethers / Q000737:chemistry / Q000378:metabolism*; D006851:Hydrochloric Acid / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry; D006868:Hydrolysis; D007501:Iron / Q000737:chemistry; D017895:Manganese Compounds / Q000737:chemistry; D008738:Methyl Ethers / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry; D014106:Tosylarginine Methyl Ester / Q000737:chemistry / Q000378:metabolism*
chemical_list: D005019:Ethyl Ethers; C045076:Fenton's reagent; D017895:Manganese Compounds; D008738:Methyl Ethers; D010087:Oxides; C048856:permanganic acid; C043243:methyl tert-butyl ether; C098546:ethyl tert-butyl ether; D014106:Tosylarginine Methyl Ester; D006861:Hydrogen Peroxide; D007501:Iron; D006851:Hydrochloric Acid