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Experimental approaches were developed which permit the measurement of carbon isotope effects during partitioning of organic compounds between water and humic substances. Fractionation factors alpha(sorption) = K(OC)12C/K(OC)13C for carbon isotopomers of benzene (1.00044 +/- 0.00015) and toluene (1.00060 +/- 0.00010) were determined from a 10-step batch experiment. Similar fractionation factors were estimated for benzene (1.00017), 2,4-dimethylphenol (1.00035), and o-xylene (< or = 1.00092) from chromatographic experiments. The latter method is based on chromatographic amplification of the fractionation effect (deltadelta13C) in an HPLC column with humic acid (HA) as the stationary phase. Possible implications of the sorption-based isotope fractionation for assessment of natural attenuation processes in contaminated aquifers are discussed. Depending on the aquifer properties (organic carbon content, heterogeneity) together with the plume source, length, and status (stationary or expanding), scenarios may be constructed where sorption-based isotope fractionation competes significantly with that caused by chemical or microbial degradation processes.

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The introduction of ferroelectric and catalytically active materials into the discharge zone of NTP reactors is a promising way to improve their performance for the removal of hazardous substances, especially those appearing in low concentrations. In this study, several coaxial barrier-discharge plasma reactors varying in size and barrier material (glass, Al 2 O 3 , and TiO 2 ) were used. The oxidation of methyl tert-butyl ether (MTBE), toluene and acetone was studied in a gas-phase plasma and in various packed-bed reactors (filled with ferroelectric and catalytically active materials). In the ferroelectric packed-bed reactors, better energy efficiency and CO 2 selectivity were found for the oxidation of the model substances. Studies on the oxidation of a toluene/acetone mixture in air showed an enhanced oxidation of the less reactive acetone related to toluene in the ferroelectric packed-bed reactors. It can be concluded that the change of the electrical discharge behaviour was caused by a larger number of non-selective and highly reactive plasma species formed within the ferroelectric bed. When combining ferroelectric (BaTiO 3 ) and catalytically active materials (LaCoO 3 ), only a layered implementation led to synergistic effects utilising both highly energetic species formed in the ferroelectric packed-bed and the potential for total oxidation provided by the catalytically active material in the second part of the packed bed.