Critical evaluation of the 2D-CSIA scheme for distinguishing fuel oxygenate degradation reaction mechanisms

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 (εC and εH) have still been associated with different reaction mechanisms (McKelvie et al. Environ. Sci. Technol. 2009, 43, 2793-2799). Here, we present new laboratory-derived εC and εH 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 Δδ2H/ Δδ13C 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, εC was low (<|-1|¿) and εH 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

Huminstoffe Beitraege

SIGLEAvailable from TIB Hannover: RR 6252(1998,22) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

SAFIRA. Teilprojekt B 3.1: Reduktive Dechlorierung von Chloraromaten mit elektrochemischen Methoden und Membran-gestuetzten Katalysatoren zur in-situ-Behandlung von kontaminierten Grundwaessern Abschlussbericht

The objective of the sub-project was the development and experimental testing of a mainly passive, in situ technology for the abiotic dehalogenation of halogenated organic hydrocarbons (HOCs) within the aquifer. The technology to be developed should be applicable not only for aliphatic HOCs but also for dehalogenation of aromatic halogenated pollutants. During the first two years of the project, the main focus of our research was the development and testing of novel membrane-supported catalysts. The catalytically active component Pd was embedded in highly disperse form into non-porous silicone membranes in order to protect it from ionic catalyst poisons and erosion. At the laboratory scale, the novel catalysts proved their suitability for dehalogenation of various classes of HOCs within the water phase. The membrane-supported catalysts were developed in co-operation with a working group from the GKSS Geesthacht and their novelty was protected in a patent disclosure (DE 19952 732A1). Especially for their use under field conditions, membrane-supported Pd catalysts were produced as hollow fibres where the reaction partner hydrogen was fed from the interior of the fibres. Unfortunately, the high activity of these catalysts was not sustainable under Bitterfeld groundwater conditions - sulphur poisoning occurred due to non-ionic catalyst poisons situated in the aquifer and H_2S produced by sulphate-reducing bacteria. In order to enhance the catalyst stability and therefore their applicability in a scaled-up technology, our studies were then focused on the suppression of microbial activity and on catalyst regeneration. (orig.)Das Ziel des Teilprojektes war die Entwicklung und experimentelle Pruefung eines weitgehend passiven, in-situ-tauglichen Verfahrens zur abiotischen Dehalogenierung von HKW im Aquifer, das auch auf halogenierte aromatische Verbindungen anwendbar ist. In den ersten zwei Jahren des Projektes stand die Entwicklung und Testung von Membran-gestuetzten Palladiumkatalysatoren im Mittelpunkt unserer Untersuchungen, bei denen das Pd in hochdisperser Form in unporoese Silikonmembranen eingebettet ist, um es gegen Vergiftung durch ionische Verbindungen und Erosion zu schuetzen. Im Labormassstab konnte die prinzipielle Eignung Membran-gestuetzter Pd-Katalysatoren zur Dechlorierung von HKW in waessriger Phase nachgewiesen werden. Die Entwicklung des Membrankatalysators erfolgte in Zusammenarbeit mit einer Forschungsgruppe der GKSS. Zum Einsatz der neuartigen und zum Patent angemeldeten Katalysatoren (Offenlegungsschrift DE19952 732A1) unter Feldbedingungen wurden von uns Membrankatalysatoren entwickelt, welche als aktive Katalysatorkomponente palladisierte Hohlfasern enthielten. Die Aktivitaet unserer Katalysatoren wurde unter Feldbedingungen durch im Grundwasser enthaltene sulfidische Schwefelverbindungen beeintraechtigt. Um die Standfestigkeit der Katalysatoren und damit die Aussicht auf eine grosstechnische Verwertung unserer Erfindung zu erhoehen, galt unser Interesse neben der Unterdrueckung der mikrobiellen Sulfidbildung der Regenerierung der Katalysatoren. (orig.)Available from TIB Hannover: F03B236+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman