Search

Worldwide, ozonation of secondary wastewater effluents is increasingly considered in order to decrease the load of organic contaminants before environmental discharge. However, despite the constantly growing knowledge of ozonation over the past few years, the characterization of transformation products (TPs) is still a major concern, particularly because such TPs might remain biologically active. It has been shown for selected tertiary amine pharmaceuticals that they react with ozone and form the corresponding N-oxides. This study therefore applies liquid chromatography-high resolution mass spectrometry (LC-HRMS) to assess the overall N-oxide formation during the pilot-scale ozonation of a secondary wastewater effluent from a major city in Germany. Sample analysis by LC-HRMS revealed the occurrence of 1,229 compounds, among which 853 were precursors attenuated by ozone and 165 were TPs. Further examination of precursors and TPs using Kendrick mass and Kendrick mass defect analysis revealed 34 pairs of precursors and products corresponding to a mono-oxygenation. Among these, 27 pairs (16% of all TPs) were consistent with N-oxides since the TP had a higher retention time than the precursor, a characteristic of these compounds. Using high resolution tandem mass spectrometry, 10 of these N-oxides could be identified and were shown to be stable during a subsequent filtration step. [ABSTRACT FROM AUTHOR]

Anaerobic degradation processes play an important role in contaminated aquifers. To indicate active blodegradation processes signature metabolites can be used. In this study field samples from a high-resolution multilevel well in a tar oil-contaminated, anoxic aquifer were analyzed for metabolites by liquid chromatography-tandem mass spectrometry and time-of-flight mass spectrometry. In addition to already known specific degradation products of toluene, xylenes, and naphthalenes, the seldom reported degradation products benzothiophenemethylsuccinic acid (BTMS), benzofuranmethyl-succinic acid (BFMS), methylnaphthyl-2-methylsuccinic acid (MNMS), and acenaphthene-5-carboxylic acid (AC) could be identified (BFMS, AC) and tentatively identified (BTMS, MNMS). The occurrence of BTMS and BFMS clearly show that the tumarate addition pathway, known for toluene and methylnaph-thalene, is also important for the anaerobic degradation of heterocyclic contaminants in aquifers. The molar concentration ratios of metabolites and their related parent compounds differ over a wide range which shows that there is no simple and consistent quantitative relation. However, generally higher ratios were found for the more recalcitrant compounds, which are putatively cometabolically degraded (e.g., 2-car-boxybenzothiophene and acenaphthene-5-carboxylic acid), indicating an accumulation of these metabolites. Vertical concentration profiles of benzylsuccinic acid (BS) and methyl-benzylsuccinic acid (MBS) showed distinct peaks at the fringes of the toluene and xylene plume indicating hot spots of biodegradation activity and supporting the plume fringe concept. However, there are some compounds which show a different vertical distribution with the most prominent concentrations where also the precursor compounds peaked. [ABSTRACT FROM AUTHOR]