(Bio)degradation of glyphosate in water-sediment microcosms - A stable isotope co-labeling approach

Glyphosate and its metabolite aminomethylphosphonic acid (AMPA) are frequently detected in water and sediments. Up to date, there are no comprehensive studies on the fate of glyphosate in water-sediment microcosms according to OECD 308 guideline. Stable isotope co-labeled (13)C3(15)N-glyphosate was used to determine the turnover mass balance, formation of metabolites, and formation of residues over a period of 80 days. In the water-sediment system, 56% of the initial (13)C3-glyphosate equivalents was ultimately mineralized, whereas the mineralization in the water system (without sediment) was low, reaching only 2% of (13)C-glyphosate equivalents. This finding demonstrates the key role of sediments in its degradation. Glyphosate was detected below detection limit in the water compartment on day 40, but could still be detected in the sediments, ultimately reaching 5% of (13)C3(15)N-glyphosate equivalents. A rapid increase in (13)C(15)N-AMPA was noted after 10 days, and these transformation products ultimately constituted 26% of the (13)C3-glyphosate equivalents and 79% of the (15)N-glyphosate equivalents. In total, 10% of the (13)C label and 12% of the (15)N label were incorporated into amino acids, indicating no risk bearing biogenic residue formation from (13)C3(15)N-glyphosate. Initially, glyphosate was biodegraded via the sarcosine pathway related to microbial growth, as shown by co-labeled (13)C(15)N-glycine and biogenic residue formation. Later, degradation via AMPA dominated under starvation conditions, as shown by the contents of (13)C-glycine. The presented data provide the first evidence of the speciation of the non-extractable residues as well as the utilization of glyphosate as a carbon and nitrogen source in the water-sediment system. This study also highlights the contribution of both the sarcosine and the AMPA degradation pathways under these conditions.

Pharmaceuticals, Their Metabolites, and Other Polar Pollutants in Field-Grown Vegetables Irrigated with Treated Municipal Wastewater

The reuse of treated municipal wastewater for crop irrigation is a necessity in arid and semiarid regions but a potential entrance for emerging contaminants into the food chain. However, little attention has yet been paid to the detection of micropollutants and possible metabolites in vegetables grown under realistic field conditions. In this study, the uptake of 28 micropollutants and carbamazepine metabolites in 10 different field-grown vegetable species (among them carrot, lettuce, potato, and zucchini) from Jordan was studied. A total of 12 micropollutants and six carbamazepine metabolites, four of which have never been analyzed before in plant-uptake studies, could be detected in all of the samples in concentrations ranging from 1.7 to 216 ng per g of dry weight. In edible tissues, the total concentration of micropollutants decreased in the order of leafy (247-533) > root (73-126) > fruit-bearing (5-76 ng per g of dry weight) vegetables. A preliminary health-risk assessment for nine compounds according to the TTC concept shows no risk for seven of the micropollutats; for ciprofloxacin and 10,11-epoxycarbamazepine, however, more-specific toxicity data would be required for a refined risk assessment.

A false positive finding in liquid chromatography/triple quadrupole mass spectrometry analysis by a non-isobaric matrix component: the case of benzotriazole in urine for human biomonitoring

RATIONALE

Multi-residual methods employing liquid chromatography coupled to triple quadrupole mass spectrometry (LC/MS/MS) with selected reaction monitoring (SRM) are attractive also for human biomonitoring (HBM). A new process is determined that can lead to false positive findings by matrix components that are not isobaric to the analyte of interest.

METHODS

Benzotriazole (1H-BT) was false positively detected in 87 human urine samples analyzed by ultra-high-performance-(UHP)-LC/MS/MS. The quantifier/qualifier ratio (Q/q ratio) did not match. This was further confirmed by negative results with an optimized gradient. Investigations were performed by UHPLC/high-resolution (HR)MS and model compounds to reveal the identity of the disturbing matrix compound and the way that it interfered with 1H-BT detection.

RESULTS

A formula of C7 H5 NO (m/z 120.0444) was found at the retention time of 1H-BT (m/z 120.0556) belonging to an in-source product ion of a heavier co-eluting compound. Product ion spectra and Q/q ratios of model compounds indicated a benzene sub-structure with a carbonyl and amine functional group in the ortho- or para-position. Finally, folic acid was confirmed as the disturbing urine component, exhibiting an in-source fragment with the nominal mass of 1H-BT and the same product ions as used in the SRM mode for UHPLC/MS/MS monitoring.

CONCLUSIONS

Interferences in SRM detection need not be due to co-eluting isobaric matrix compounds, but can originate from in-source fragmentation of heavier ions. Rigid quality control measures are recommended for LC/MS/MS analysis, especially for small molecules in complex sample matrices to overcome the selectivity limits of SRM. Copyright © 2016 John Wiley & Sons, Ltd.

Selectivity of solid phase extraction of freshwater dissolved organic matter and its effect on ultrahigh resolution mass spectra

Solid phase extraction (SPE) is often used for enrichment and clean-up prior to analysis of dissolved organic matter (DOM) by electrospray ionization (ESI) coupled to ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). It is generally accepted that extraction by SPE is not quantitative with respect to carbon concentration. However, little information is available on the selectivity of different SPE sorbents and the resulting effect for the acquired DOM mass spectra. Freshwater samples were extracted by the widely used PPL, HLB and C18 sorbents and the molecular composition and size distribution of the DOM in the extracts and in the permeates was compared to the original sample. Dissolved organic carbon (DOC) recoveries ranged between 20% and 65% for the three tested SPE sorbents. Size-exclusion chromatography coupled to organic carbon detection (SEC-OCD) revealed that limited recovery by PPL and HLB was primarily due to incomplete elution of a fraction of apparent high molecular weight from the solid phase. In contrast, incomplete retention on the solid phase, mainly observed for the C18 cartridge, was attributed to a fraction of low molecular weight. The FT-ICR mass spectra of the original sample and the SPE extracts did not differ significantly in their molecular weight distribution, but they showed sorbent specific differences in the degree of oxygenation and saturation. We concluded that the selective enrichment of freshwater DOM by SPE is less critical for subsequent FT-ICR MS analysis, because those fractions that are not sufficiently recovered have comparatively small effects on the mass spectra. This was confirmed by the extraction of model compounds, showing that very polar and small molecules are poorly extracted, but also have a low response in ESI-MS. Of the three tested SPE cartridges the PPL material offered the best properties for DOM enrichment for subsequent FT-ICR MS analysis as it minimizes too strong and too weak DOM-sorbent interactions.

Metabolism of clofibric acid in zebrafish embryos (Danio rerio) as determined by liquid chromatography-high resolution-mass spectrometry

The zebrafish embryo (ZFE) is increasingly used in ecotoxicology research but detailed knowledge of its metabolic potential is still limited. This study focuses on the xenobiotic metabolism of ZFE at different life-stages using the pharmaceutical compound clofibric acid as study compound. Liquid chromatography with quadrupole-time-of-flight mass spectrometry (LC-QToF-MS) is used to detect and to identify the transformation products (TPs). In screening experiments, a total of 18 TPs was detected and structure proposals were elaborated for 17 TPs, formed by phase I and phase II metabolism. Biotransformation of clofibric acid by the ZFE involves conjugation with sulfate or glucuronic acid, and, reported here for the first time, with carnitine, taurine, and aminomethanesulfonic acid. Further yet unknown cyclization products were identified using non-target screening that may represent a new detoxification pathway. Sulfate containing TPs occurred already after 3h of exposure (7hpf), and from 48h of exposure (52hpf) onwards, all TPs were detected. The detection of these TPs indicates the activity of phase I and phase II enzymes already at early life-stages. Additionally, the excretion of one TP into the exposure medium was observed. The results of this study outline the high metabolic potential of the ZFE with respect to the transformation of xenobiotics. Similarities but also differences to other test systems were observed. Biotransformation of test chemicals in toxicity testing with ZFE may therefore need further consideration.

Sunlight photolysis of benzotriazoles - Identification of transformation products and pathways

Benzotriazoles (BTs) are widely used corrosion inhibitors, incompletely removed in municipal wastewater treatment. The photochemical fate of the three BTs 1H-benzotriazole (1H-BT), 4-methyl-1H-benzotriazole (4Me-BT) and 5-methyl-1H-benzotriazole (5Me-BT) and of three microbial metabolites, was studied under simulated sunlight (290-800 nm) at neutral pH in aqueous solution for 24 h. The half-life, the quantum yield and the reaction rate were determined and a total of 36 photolysis products were detected and identified using liquid chromatography-high resolution-mass spectrometry. The half-lives of all six BTs were in the range of 6-24 h under the experimental conditions. Though the quantum yields were comparatively low (0.0007-0.0021), the environmental half-lives ranged from 2.4 to 8 d, suggesting that sunlight photolysis is still a relevant degradation process of BTs in surface waters. The photolysis pathway of 1H-BT under simulated sunlight differed from that suggested for UV-radiation, in that aminophenol is formed directly rather than via aniline. Similar pathways were found for the other BTs, except for 4-hydroxy-1H-benzotriazole (4OH-BT). Most identified transformation products of the BTs showed a high reactivity and appear not to persist in the environment. Upon co-photolysis of BTs with dissolved organic matter (DOM), however, series of reaction products were determined by Fourier transform - ion cyclotron resonance - mass spectrometry (FTICR-MS) which are formed by reaction of photolysis intermediates of the BTs with DOM.

Combined chemoassay and mass spectrometric approach to study the reactive potential of electrophiles towards deoxynucleosides as model for DNA

The modification of DNA by adduct formation is a potential molecular initiating event of genotoxicity. A chemoassay was established to study adduct formation of electrophiles with deoxynucleosides. Liquid chromatography-mass spectrometry was used to determine the reactivity of the model electrophiles para-benzoquinone, hydroquinone, and 1,4-naphthoquinone with deoxynucleoside (deoxyadenosine (dA), deoxyguanosine (dG), deoxycytidine (dC) and thymidine (dT)) to detect formation of adducts via constant neutral loss scan of deoxyribose (116 Da), and to elucidate adduct structures using high resolution mass spectrometry. Of the four deoxynucleosides dG was most susceptible, followed by dC and para-benzoquinone was the most reactive electrophile. With this approach five dG and four dC adducts were detected, formed by Michael addition and subsequent condensation. Also oxidation occurred with reactive oxygen species (ROS). Three of the adducts formed by benzoquinone have not been reported before. This chemoassay combined with mass spectrometry offers a way (a) to screen a large number of chemicals for their genotoxic potential, (b) to determine novel adducts that may be searched for in in vitro and in vivo studies and thus (c) to better understand the reaction of electrophiles with nucleobases.

Determination of moderately polar arsenolipids and mercury speciation in freshwater fish of the River Elbe (Saxony, Germany)

Arsenic and mercury are frequent contaminants in the environment and care must be taken to limit their entrance into the food chain. The toxicity of both elements strongly depends upon their speciation. Total amounts of As and Hg as well as their species were analyzed in muscle and liver of 26 fishes of seven freshwater fish species caught in the River Elbe. The median concentrations of As were 162 μg kg(-1) w.w. in liver and 92 μg kg(-1) w.w. in muscle. The median concentrations of total Hg were 241 μg kg(-1) w.w. in liver and 256 μg kg(-1) w.w. in muscle. While this level of Hg contamination of the freshwater fish in the River Elbe is significantly lower than 20 years ago, it exceeds the recommended environmental quality standard of 20 μg Hg kg(-1) w.w. by a factor of 5-50. However, the European maximum level of 500 μg Hg kg(-1) for fish for human consumption is rarely exceeded. Arsenic-containing fatty acids and hydrocarbons were determined and partially identified in methanolic extracts of the fish by HPLC coupled in parallel to ICP-MS (element specific detection) and ESI-Q-TOF-MS (molecular structure detection). While arsenobetaine was the dominant As species in the fish, six arsenolipids were detected and identified in the extracts of liver tissue in common bream (Abramis brama), ide (Leuciscus idus), asp (Aspius aspius) and northern pike (Esox lucius). Four arsenic-containing fatty acids (AsFA) and two arsenic-containing hydrocarbons (AsHC) are reported in freshwater fish for the first time. With respect to mercury the more toxic MeHg(+) was the major species in muscle tissue (>90% of total Hg) while in liver Hg(2+) and MeHg(+) were of equal importance. The results show the high relevance of element speciation in addition to the determination of total element concentrations to correctly assess the burden of these two elements in fish.

New hydrolysis products of the beta-lactam antibiotic amoxicillin, their pH-dependent formation and search in municipal wastewater

Amoxicillin (AMX) is a widespread β-lactam-antibiotic and, together with some of its transformation products (TPs) originating from hydrolysis, a known environmental contaminant. To shed light on the abiotic degradation of AMX and the stability of its known TPs, laboratory hydrolysis experiments of AMX were carried out at pH 3, 7 and 11. Not only the rate of hydrolysis but also the pattern of TPs was strongly pH-dependent. The time courses of the obtained transformation products were analyzed by UPLC-HR-QToF-MS. AMX penicilloic acid (TP 1), AMX 2',5'-diketopiperazine (TP 2), AMX penilloic acid (TP 3) and 3-(4-hydroxyphenyl)pyrazinol (TP 4) were found at neutral pH. Surprisingly, the first three were not stable but transformed into 23 yet unknown TPs within three to four weeks. Seven TPs were tentatively identified, based on their product ion spectra and, where possible, confirmed with reference standards, e.g. penicillamine disulfide, 2-[amino(carboxy)methyl]-5,5-dimethyl-1,3-thiazolidine-4-carboxylic acid and dehydrocarboxylated amoxicillin penilloic acid. Analysis of samples from municipal wastewater treatment plants confirmed these findings with TP 1 being the dominant TP in the influent and a shift towards TP 2, TP 3 and TP 4 in the effluents. The lab experiments predicted up to 13 consecutive TPs from TP 1, TP 2 and TP 3 under neutral conditions. Their detection from surface waters will be difficult, because their large number and slow formation kinetics will lead to comparatively low environmental concentrations. Nevertheless the abiotic degradation of TP 1, TP 2 and TP 3 to further TPs needs to be considered in future studies of the environmental fate of amoxicillin.

Transformation Pathways of the Recalcitrant Pharmaceutical Compound Carbamazepine by the White-Rot Fungus Pleurotus ostreatus: Effects of Growth Conditions

The widely used anticonvulsant pharmaceutical carbamazepine is recalcitrant in many environmental niches and thus poses a challenge in wastewater treatment. We followed the decomposition of carbamazepine by the white-rot fungus Pleurotus ostreatus in liquid culture compared to solid-state fermentation on lignocellulosic substrate where different enzymatic systems are active. Carbamazepine metabolites were identified using liquid chromatography-high-resolution mass spectrometry (LC-Q-TOF-MS). In liquid culture, carbamazepine was only transformed to 10,11-epoxy carbamazepine and 10,11-dihydroxy carbamazepine as a dead-end product. During solid-state fermentation, carbamazepine metabolism resulted in the generation of an additional 22 transformation products, some of which are toxic. Under solid-state-fermentation conditions, 10,11-epoxy carbamazepine was further metabolized via acridine and 10,11-dihydroxy carbamazepine pathways. The latter was further metabolized via five subpathways. When (14)C-carbonyl-labeled carbamazepine was used as the substrate, (14)C-CO2 release amounted to 17.4% of the initial radioactivity after 63 days of incubation. The proposed pathways were validated using metabolites (10,11-epoxy carbamazepine, 10,11-dihydroxy carbamazepine, and acridine) as primary substrates and following their fate at different time points. This work highlights the effect of growth conditions on the transformation pathways of xenobiotics. A better understanding of the fate of pollutants during bioremediation treatments is important for establishment of such technologies.

Electrochemistry Combined with LC-HRMS: Elucidating Transformation Products of the Recalcitrant Pharmaceutical Compound Carbamazepine Generated by the White-Rot Fungus Pleurotus ostreatus

Transformation products (TPs) of environmental pollutants must be identified to understand biodegradation processes and reaction mechanisms and to assess the efficiency of treatment processes. The combination of oxidation by an electrochemical cell (EC) with analysis by liquid chromatography-high-resolution mass spectrometry (LC-HRMS) is a rapid approach for the determination and identification of TPs generated by natural microbial processes. Electrochemically generated TPs of the recalcitrant pharmaceutical carbamazepine (CBZ) were used for a target screening for TPs formed by the white-rot fungus Pleurotus ostreatus. EC with LC-HRMS facilitates detection and identification of TPs because the product spectrum is not superimposed with biogenic metabolites and elevated substrate concentrations can be used. A group of 10 TPs formed in the microbial process were detected by target screening for molecular ions, and another 4 were detected by screening on the basis of characteristic fragment ions. Three of these TPs have never been reported before. For CBZ, EC with LC-HRMS was found to be more effective than software tools in defining targets for the screening and faster than nontarget screening alone in TP identification. EC with LC-HRMS may be used to feed MS databases with spectra of possible TPs of larger numbers of environmental contaminants for an efficient target screening.

Selection of organic process and source indicator substances for the anthropogenically influenced water cycle

An increasing number of organic micropollutants (OMP) is detected in anthropogenically influenced water cycles. Source control and effective natural and technical barriers are essential to maintain a high quality of drinking water resources under these circumstances. Based on the literature and our own research this study proposes a limited number of OMP that can serve as indicator substances for the major sources of OMP, such as wastewater treatment plants, agriculture and surface runoff. Furthermore functional indicators are proposed that allow assessment of the proper function of natural and technical barriers in the aquatic environment, namely conventional municipal wastewater treatment, advanced treatment (ozonation, activated carbon), bank filtration and soil aquifer treatment as well as self-purification in surface water. These indicator substances include the artificial sweetener acesulfame, the anti-inflammatory drug ibuprofen, the anticonvulsant carbamazepine, the corrosion inhibitor benzotriazole and the herbicide mecoprop among others. The chemical indicator substances are intended to support comparisons between watersheds and technical and natural processes independent of specific water cycles and to reduce efforts and costs of chemical analyses without losing essential information.

Search for over 2000 current and legacy micropollutants on a wastewater infiltration site with a UPLC-high resolution MS target screening method

A target screening method using ultra high performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS) was developed. The method was applied to 14 groundwater and 11 surface water samples of a former wastewater infiltration site, where raw wastewater was applied until 1985 and treated wastewater is applied since 2005. The measured data are compared with mass spectrometric data of over 2000 organic micropollutants (OMPs), including pharmaceuticals, personal care products, pesticides, industrial chemicals and metabolites of these classes. A total number of 151 and 159 OMPs were detected in groundwater and surface water, respectively, of which 12 have not been reported before in these matrices. Among these 12 compounds were 11 pharmaceuticals and one personal care product. The identity of 55 of the detected OMPs (35%) was verified by analysis of standard compounds. Based on the distribution in the study area, two groups of OMPs were clearly distinguished: current OMPs introduced with treated municipal wastewater since 2005 and legacy OMPs originating from infiltration of untreated wastewater until 1985. A third group included OMPs contained in historic as well as in current wastewater. During infiltration, OMPs with molecular mass >500 g/mol and log DOW > 3.9 were preferentially removed. Speciation had a strong impact with cationic OMPs showing high, neutral OMPs medium and anionic OMPs lowest elimination during infiltration. This target screening method proved useful to study a wide range of compounds, even in retrospect and at sites with poorly documented history and with a complex and variable hydrological situation.

Influence of the perivitelline space on the quantification of internal concentrations of chemicals in eggs of zebrafish embryos (Danio rerio)

The chorion and the perivitelline space which surround unhatched zebrafish embryos (ZFE, Danio rerio) may affect the determination of internal concentrations of study compounds taken up in early life-stages of ZFE. Internal concentration-time profiles were gathered for benzocaine, caffeine, clofibric acid, metribuzin and phenacetin as study compounds over 96 h of exposure starting with ZFE at 4h post-fertilization. Liquid chromatography coupled to tandem-mass spectrometry (LC-MS/MS) was used to determine the concentration of the study compounds from intact (i.e. unhatched), dechorionated and from hatched ZFE. The mass of the study compounds per ZFE was 5-30 ng higher for intact ZFE compared to dechorionated ones. Thus, internal concentrations were overestimated if only intact ZFE were analyzed. Dechorionation of unhatched ZFE after their exposure is proposed to determine the true internal concentration in the embryo. For the compounds studied here the mass of the study compounds determined in unhatched ZFE after a short term (5 min) exposure provided a reasonable estimate of the mass taken up by the chorion and the PVS. This mass can be subtracted from the total mass found in unhatched ZFE to calculate the true internal mass. Estimating the mass in the chorion and the PVS from the concentration of the study compound in the external exposure medium and the volume of the PVS provided no reasonable results.

Mass spectrometric detection, identification, and fragmentation of arseno-phytochelatins

Phytochelatins (PC) are cystein-rich oligopeptides in plants for coordination with toxic metals and metalloids via their thiol groups. The composition, structure, and mass spectrometric fragmentation of arseno-PC (As-PC) with PC of different degree of oligomerization (PC2-PC5) in solution were studied using liquid chromatography coupled in parallel to inductively coupled plasma mass spectrometry and electrospray ionization quadrupole time-of-flight mass spectrometry. As-PC were detected from As(PC2) to As(PC5) with an increasing number of isomers that differ in the position of thiol groups bound to As. Thermodynamic modeling supported the identification process in case of these isomers. Mass spectrometric fragmentation of the As-PC does not follow the established pattern of peptides but is governed by the formation of series of As-containing annular cations, which coordinate to As via S, N, or O. Structure proposals for 30 As-PC fragment ions in the range m/z 147.92 to m/z 1290.18 are elaborated. Many of these fragment ions are characteristic to several As-PC and may be suited for a screening for As-PC in plant extracts. The mass spectrometric data offer the perspective for a future more sensitive determination of As-PC by means of liquid chromatography tandem mass spectrometry with multiple reaction monitoring.

Triclocarban, triclosan and its transformation product methyl triclosan in native earthworm species four years after a commercial-scale biosolids application

Triclocarban (TCC), triclosan (TCS) and methyl triclosan (Me-TCS) were detected in soil and the native population of earthworms of an agricultural field in Ottawa, Canada, about four years after a commercial-scale application of biosolids. In soil that received biosolids, TCC and TCS were detected at median concentrations of 13.0 and 1.5 ng/g soil (d.w.), respectively, while Me-TCS, the transformation product of triclosan, was detected at a six-fold higher median concentration than its precursor. In earthworms collected at the biosolids-amended field-plot about four years post application, Me-TCS was also detected at higher concentrations (26 to 114 ng/g tissue d.w.) than TCS (16-51 ng/g) and TCC (4-53 ng/g). These data provide evidence that not only parent compounds but also their transformation products need to be considered in faunal bioaccumulation studies. Moreover, the preliminary results for pooled earthworm samples from different ecological groups suggest that the degree of bioaccumulation of biosolids-associated contaminants may depend on the habitat and feeding behavior of the organisms.

Identification of plant metabolites of environmental contaminants by UPLC-QToF-MS: the in vitro metabolism of triclosan in horseradish

Plants can extensively transform contaminants after uptake through phase I and phase II metabolism to a large diversity of products. UPLC-QToF-MS was used to detect and identify metabolites of the bacteriostatic agent triclosan in a horseradish hairy root culture. Thirty-three metabolites of triclosan were recognized by a stepwise approach of mass defect filtering, multivariate data analysis, and isotope pattern filtering from a data set of several thousands of signals in the exposed culture. Structure proposals were elaborated for 23 triclosan metabolites on the basis of their MS data. The majority were identified as conjugates (phase II metabolites) such as saccharides or sulfosaccharides. Additionally, a disulfosaccharide was identified as a plant metabolite for the first time. Besides that, also conjugates of a phase I metabolite, hydroxytriclosan, were determined in horseradish tissue extracts. Dehalogenation products of triclosan were not observed. The large number of metabolites detected and identified in this study emphasizes the importance of a comprehensive analytical approach in studies on the uptake and fate of organic contaminants in plants.

Ozonation products of carbamazepine and their removal from secondary effluents by soil aquifer treatment--indications from column experiments

Ozonation is known as an efficient treatment to reduce the concentration of many trace organic compounds from WWTP effluents, but the formation of unknown and possibly persistent and toxic transformation products has to be considered. In this paper tertiary treatment of wastewater by the combination of ozone and soil aquifer treatment was investigated with respect to the removal of the antiepileptic drug carbamazepine (CBZ, 10 μg/L) and its transformation products. Batch tests and pilot experiments confirmed efficient removal of carbamazepine from secondary effluent by ozone. With typical ozone consumption of 0.7 mg O3/mg DOC0, approx. 50% of the transformed CBZ was detected as its primary product 1-(2-benzaldehyde)-4-hydro-(1H,3H)-quinazoline-2-one (BQM). Structure proposals and a formation pathway were elaborated for a total of 13 ozonation products of CBZ. In subsequent biological treatment BQM turned out to be more effectively biodegraded than CBZ. Its aldehyde group was quickly oxidized to a carboxylic acid (BaQM), which was removed in sand column experiments. Most of the minor ozonation products of CBZ persisted in sand column experiments with residence times of 5-6 days. Non-target screening of column effluent revealed no formation of persistent biotransformation products.

Quantification of Al2O3 nanoparticles in human cell lines applying inductively coupled plasma mass spectrometry (neb-ICP-MS, LA-ICP-MS) and flow cytometry-based methods

In order to quantify and compare the uptake of aluminum oxide nanoparticles of three different sizes into two human cell lines (skin keratinocytes (HaCaT) and lung epithelial cells (A549)), three analytical methods were applied: digestion followed by nebulization inductively coupled plasma mass spectrometry (neb-ICP-MS), direct laser ablation ICP-MS (LA-ICP-MS), and flow cytometry. Light and electron microscopy revealed an accumulation and agglomeration of all particle types within the cell cytoplasm, whereas no particles were detected in the cell nuclei. The internalized Al₂O₃ particles exerted no toxicity in the two cell lines after 24 h of exposure. The smallest particles with a primary particle size (x_BET) of 14 nm (Alu1) showed the lowest sedimentation velocity within the cell culture media, but were calculated to have settled completely after 20 h. Alu2 (x_BET = 111 nm) and Alu3 (x_BET = 750 nm) were calculated to reach the cell surface after 7 h and 3 min, respectively. The internal concentrations determined with the different methods lay in a comparable range of 2-8 µg Al₂O₃/cm² cell layer, indicating the suitability of all methods to quantify the nanoparticle uptake. Nevertheless, particle size limitations of analytical methods using optical devices were demonstrated for LA-ICP-MS and flow cytometry. Furthermore, the consideration and comparison of particle properties as parameters for particle internalization revealed the particle size and the exposure concentration as determining factors for particle uptake.

Biotransformation of the antibiotic agent flumequine by ligninolytic fungi and residual antibacterial activity of the transformation mixtures

Flumequine, a fluoroquinolone antibiotic, is applied preferably in veterinary medicine, for stock breeding and treatment of aquacultures. Formation of drug resistance is a matter of general concern when antibiotics such as flumquine occur in the environment. Thus, biodegradation of flumequine in solution was investigated using five different ligninolytic fungi. Irpex lacteus, Dichomitus squalens, and Trametes versicolor proved most efficient and transformed more than 90% of flumequine within 6 or even 3 days. Panus tigrinus and Pleurotus ostreatus required up to 14 days to remove >90% of flumequine. Analyses of the metabolites by liquid chromatography-mass spectrometry suggest different transformation pathways for the different fungal strains. Structure proposals were elaborated for 8 metabolites. 7-Hydroxy-flumequine and flumequine ethyl ester were identified as common metabolites produced by all ligninolytic fungi. The largest variety of metabolites was formed by D. squalens. Residual antibacterial activity of the metabolite mixtures was tested using gram-positive and gram-negative bacteria. While for the less efficient P. tigrinus and P. ostreatus cultures the antibacterial activities corresponded to the residual concentrations of flumequine, a remarkable antibacterial activity remained in the D. squalens cultures although flumequine was transformed to more than 90%. Obviously, antibacterially active transformation products were formed by this fungal strain.

Emerging pesticide metabolites in groundwater and surface water as determined by the application of a multimethod for 150 pesticide metabolites

A recently developed multimethod for the determination of 150 pesticide metabolites was exemplarily applied to 58 samples of groundwater and surface water. 37 of these metabolites were detected in at least two samples with a concentration ≥0.025 μg/L. The detected metabolites were ranked according to their concentration and frequency of detection. Findings are clearly dominated by metabolites of chloroacetanilide herbicides, but metabolites of sulfonylurea and thiocarbamate herbicides and other herbicides (dichlobenil) together with metabolites of some fungicides (tolylfluanid, chlorothalonil, trifloxystrobin) were also prominent. A number of 17 of the ranked metabolites are denoted as emerging metabolites because no reports on their previous detection in groundwater or surface water were found. Most of them, however, were correctly predicted to occur in the summary reports of the European pesticide approval process. Median total concentrations of the analysed pesticide metabolites summed up to 0.62 μg/L in groundwater and 0.33 μg/L in surface waters. While the concentration of the individual metabolites is usually low (<0.1 μg/L) the diversity of metabolites found in one sample can be large; between two and six metabolites were detected most frequently (maximum of 12 metabolites). Runoff from urban surfaces was investigated in this study and also here previously undetected pesticide (biocide) metabolites were detected. The emerging pesticide metabolites detected in environmental water samples in this study require more extended monitoring.

Metabolization of the bacteriostatic agent triclosan in edible plants and its consequences for plant uptake assessment

Persistent environmental contaminants may enter agricultural fields via the application of sewage sludge, by irrigation with treated municipal wastewater or by manuring. It has been shown that such contaminants can be incorporated into crop plants. The metabolism of the bacteriostatic agents triclocarban, triclosan, and its transformation product methyl triclosan was investigated after their uptake into carrot cell cultures. A fast metabolization of triclosan was observed and eight so far unknown phase II metabolites, conjugates with saccharides, disaccharides, malonic acid, and sulfate, were identified by liquid chromatography-mass spectrometry. Triclocarban and methyl triclosan lack a phenolic group and remained unaltered in the cell cultures. Phase I metabolization was not observed for any of the compounds. All eight triclosan conjugates identified in the cell cultures were also detected in extracts of intact carrot plants cultivated on triclosan contaminated soils. Their total amount in the plants was assessed to exceed the amount of the triclosan itself by a factor of 5. This study shows that a disregard of conjugates in studies on plant uptake of environmental contaminants may severely underestimates the extent of uptake into plants and, eventually, the potential human exposure to contaminants via food of plant origin.

Uptake of galaxolide, tonalide, and triclosan by carrot, barley, and meadow fescue plants

Many xenobiotics entering wastewater treatment plants are known to be persistent during wastewater treatment and tend to adsorb to sewage sludge. The application of sewage sludge as fertilizer in agriculture may pose the risk of an incorporation of xenobiotics in the cultivated plants and, finally, an inclusion into the food chain. This study was performed to investigate the uptake of common sewage sludge contaminants, galaxolide, tonalide, and triclosan, by plants used for human consumption and livestock feeding. Barley, meadow fescue, and four carrot cultivars were sown and grown in spiked soils under greenhouse conditions. After harvesting the plants, roots and leaves were analyzed separately, and the respective bioconcentration factors were calculated. In carrots, a concentration gradient of the xenobiotics became evident that decreased from the root peel via root core to the leaves. A significant influence of the differing root lipid contents on the uptake rates cannot be supported by our data, but the crucial influence of soil organic carbon content was confirmed. Barley and meadow fescue roots incorporated higher amounts of the target substances than carrots, but translocation into the leaves was negligible. The results indicated that an introduction of persistent semi- and nonpolar xenobiotics into the food chain via edible plants like carrots could be of certain relevance when sludge is applied as fertilizer. Due to low rates found for the translocation of the xenobiotics into the aerial plant parts, the entrance pathway into food products via feeding livestock is less probable.

Abstract 5732: Mercapturic acid excretion and N7-GA-Gua DNA adduct formation after low dose oral application of acrylamide to rats

Acrylamide (AA), a genotoxic carcinogen (IARC class 2A), is a food contaminant formed by thermal treatment of food. The margin of exposure (MOE) of AA, representing the distance between the bench mark dose associated with 10% tumor incidence in rats and the estimated average human exposure, is considered to be low and of human health concern. After uptake, AA is partly converted by CYP450 2E1 into the genotoxic epoxide glycidamide (GA). GA forms DNA adducts, primarily at N7 of guanine (N7-GA-Gua). AA and its genotoxic metabolite GA are conjugated to glutathione and excreted via urine as mercapturic acids (MA), namely N-acetyl-S-(2-carbamoylethyl)-cysteine (AAMA), and N-acetyl-S-(2-hydroxy-2-carbamoylethyl)-cysteine (GAMA) which are used as biomarkers for exposure. Female Sprague Dawley (SD) rats were kept on an AA free diet. AA was given by gavage in a broad dosage range, covering single doses of 0.1-10,000 µg/kg bw. Formation of urinary MAs and of N7-GA-Gua DNA adducts in liver, kidney and lung was measured 16 h after application. The lowest dosage of 0.1 µg AA/kg bw did not result in significantly enhanced MA excretion, as compared to untreated controls, found to excrete about 0.8 nmol MA. Since the animals may have ingested at best 0.4 nmol AA/d with the diet, this findings suggests a background level of endogenously formed AA. At the lowest dosage (0.1 µg AA/kg bw), N7-GA-Gua adducts above the limit of detection (LOD, 0.2 adducts/10exp8 nucleotides) were not detected in any organ tested. At 1 µg/kg bw, enhanced adduct levels were found in kidney (around 1 adduct/10exp8 nucleotides) and lung (&lt; 1 adduct/10exp8 nucleotides), but not in liver. At 10 and 100 µg/kg bw, adducts were found in all three organs, at levels not significantly different to those found at 1 µg AA/kg bw (about 1-2 adducts/10exp8 nucleotides). Taken together, the results of this in vivo study allow to conclude that exposure to single doses of AA in the range of human dietary exposure leads to N7-GA-Gua adduct levels in tissues of SD rats at the low end of steady state background DNA lesions of various origin in human and rat tissues. This study was supported by ISIC, the Institute for Scientific Information on Coffee.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5732. doi:1538-7445.AM2012-5732

N7-glycidamide-guanine DNA adduct formation by orally ingested acrylamide in rats: a dose-response study encompassing human diet-related exposure levels

Acrylamide (AA) is formed during the heating of food and is classified as a genotoxic carcinogen. The margin of exposure (MOE), representing the distance between the bench mark dose associated with 10% tumor incidence in rats and the estimated average human exposure, is considered to be of concern. After ingestion, AA is converted by P450 into the genotoxic epoxide glycidamide (GA). GA forms DNA adducts, primarily at N7 of guanine (N7-GA-Gua). We performed a dose-response study with AA in female Sprague-Dawley (SD) rats. AA was given orally in a single dosage of 0.1-10 000 μg/kg bw. The formation of urinary mercapturic acids and of N7-GA-Gua DNA adducts in liver, kidney, and lung was measured 16 h after application. A mean of 37.0 ± 11.5% of a given AA dose was found as mercapturic acids (MAs) in urine. MA excretion in urine of untreated controls indicated some background exposure from endogenous AA. N7-GA-Gua adduct formation was not detectable in any organ tested at 0.1 μg AA/kg bw. At a dose of 1 μg/kg bw, adducts were found in kidney (around 1 adduct/10(8) nucleotides) and lung (below 1 adduct/10(8) nucleotides) but not in liver. At 10, respectively, 100 μg/kg bw, adducts were found in all three organs, at levels close to those found at 1 μg AA/kg, covering a range of about 1-2 adducts/10(8) nucleotides. As compared to DNA adduct levels from electrophilic genotoxic agents of various origin found in human tissues, N7-GA-Gua adduct levels within the dose range of 0.1-100 μg AA/kg bw were at the low end of this human background. We propose to take the background level of DNA lesions in humans more into consideration when doing risk assessment of food-borne genotoxic carcinogens.

Determination of 14 monoalkyl phosphates, dialkyl phosphates and dialkyl thiophosphates by LC-MS/MS in human urinary samples

Human urine was analyzed for nine dialkyl (DAP) and five monoalkyl phosphates (MAP) by LC-MS/MS. Some phosphoric acid esters are industrial chemicals and other hydrolysis products of trialkyl or triaryl phosphates, used as pesticides, flame retardants or plasticizers. Five MAP and two DAP were detected here for the first time in human urine. Monobutyl, diethyl, diphenyl and diethylhexyl phosphate were determined with median concentrations in the μg/L-range. The total urinary concentration of the 14 DAP and MAP summed up to a median of 20μg/L. Inclusion of MAP in future biomonitoring studies should provide a more comprehensive picture of the exposure of humans to organophosphorus compounds.

Long term laboratory column experiments to simulate bank filtration: factors controlling removal of sulfamethoxazole

Microbial removal of the poorly degradable antibiotic sulfamethoxazole (SMX) from surface water was investigated in laboratory columns to identify critical factors for SMX removal during bank filtration, such as the substrate concentration, redox conditions and the availability of biodegradable DOC. About 60% of SMX at a start concentration of 0.25 μg/L in surface water were removed within 14 d of column passage under aerobic conditions while no removal occurred under anoxic conditions. The adaptation time was very long and was not completed after 2 years of operation. Adaptation was faster and SMX degradation was improved at an elevated concentration of SMX (4.5 μg/L) with 90% removal in 3.5 d under aerobic conditions. SMX removal was less effective under anoxic conditions (27% in 14 d) but increased again under anaerobic conditions (51% in 14 d). According to the half-lives for SMX determined from the column data (1-9 d aerobic, 49 d anoxic and 16 d anaerobic) it is essential to provide several weeks up to months of travel time in bank filtration to allow for the degradation of SMX, and likely, also for other poorly degradable compounds. Thus, the occurrence of SMX in groundwater samples does not indicate persistency of SMX but reflects insufficient residence time or unfavorable respective redox conditions. Adaptation times of years may also be required for new bank filtration sites to develop their full removal potential towards trace pollutants. Long operation time, a comparable concentration level and similar redox conditions as in the field appear to be essential to obtain realistic results with laboratory column experiments that can be transferred to real bank filtration sites.

Compensation of matrix effects by postcolumn infusion of a monitor substance in multiresidue analysis with LC-MS/MS

This study systematically compares matrix effects in liquid chromatography (LC) coupled by electrospray ionization (ESI) in the positive mode with tandem mass spectrometry (MS/MS) for 129 pesticides in 20 plant matrixes. In total, 2388 analyte/matrix combinations were evaluated. Permanent postcolumn infusion (PCI) of analyte standards was used to quantify matrix effects over the whole chromatographic run time. This allowed the analyte signal suppression or enhancement, by different coeluting matrix components, to be assessed throughout the duration of an entire chromatographic run, i.e., independent of a specific retention time. Matrix effects occurring at a certain retention time in one matrix were surprisingly similar for different analytes with diverse physicochemical properties. On the basis of this finding, a new approach for matrix effect compensation in multiresidue analysis was developed in which one single monitor substance is permanently added postcolumn. Signal intensities of all analytes obtained by LC-MS/MS analysis of sample extracts are then corrected for the matrix effect recorded by the monitor substance. With the use of this approach, strong matrix effects could be reduced and apparent recoveries increased from 45% to 85% on average. With dependence on the particular sample matrix, between 69% and 100% of the analytes showed recoveries between 60% and 140% after correction. Thus this approach may significantly reduce the number of cases in which standard addition is required to confirm violations of maximum residue levels.

The carbon versus mass diagram to visualize and exploit FTICR-MS data of natural organic matter

A two-dimensional diagram is proposed, in which the carbon number of each formula is plotted against its nominal mass, to visualize large sets of molecular formula data that can be derived from data generated by ultrahigh-resolution Fourier transform ion cyclotron resonance-MS. In such a carbon versus mass (CvM) diagram, each formula (C(c)H(h)O(o)) is unambiguously described by c, its (nominal) mass and the parameter i = c + o. Calculations of chemically allowable formulas illustrate that organic molecules occupy only certain spaces in such a diagram. The extension of these spaces increases with molecular mass in x-direction (hydrogenation) and y-direction (oxygenation). The data sets of molecules determined in natural organic matter(NOM) occupy only a certain range of the allowable space. The intensity of the mass spectrometric signals can be included as the third dimension into a CvM diagram. Separate CvM diagrams can be plotted for NOM molecules that include different heteroatoms. The benefits of the CvM diagram are illustrated by application onto data sets of fulvic acids from riverine and marine origin, of secondary organic aerosol, including organosulfates and organonitrates, as well as of ozonation of fulvic acids. The CvM diagram is a useful tool to visualize the elemental regularities in NOM isolates as well as the differences between isolates. It may also be applicable to large sets of molecular formula data generated in other disciplines such as petroleum biogeochemistry or metabolomics.

Mobilization of hydrophobic contaminants from soils by enzymatic depolymerization of soil organic matter

The effect of hydrolytic exoenzymes on the release of hydrophobic organic contaminants (HOC) from two different surface soils was studied in laboratory batch experiments. Incubation of the soils with cellulase with an activity fivefold above the inherent soil activity enhanced the release of hydrophobic contaminants (polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB) and hydroxylated PCB) by 40-200%. Xylanase and invertase did not show measurable effects at comparable relative activity levels. This suggests that cellulose substructures are important for the retention of HOC in soil organic matter (SOM). Hydrolytic exoenzymes, and the microorganisms that release them, contribute to the mobilization of HOC from soil, by shifting the sorption equilibrium in the course of SOM transformation into dissolved organic matter or by facilitating HOC diffusion as a consequence of reduced rigidity of SOM. We conclude that not only biodegradation but also sorption and desorption of HOC in soil can be influenced by (micro-) biology and the factors that determine its activity.

Polar pollutants in municipal wastewater and the water cycle: occurrence and removal of benzotriazoles

1H-benzo-1,2,3-triazole (BTri) and its methylated analogues (tolyltriazole, TTri) are corrosion inhibitors used in many industrial applications, but also in households in dishwashing agents and in deicing fluids at airports and elsewhere. BTri and one of the TTri-isomers (4-TTri) are typical examples of polar and poorly degradable trace pollutants. Benzotriazole elimination in four wastewater treatment plants (WWTP) in Berlin ranged from 20 to 70% for 5-TTRi over 30 to 55% for BTri to insignificant for 4-TTri. WWTP effluent concentrations were in the range of 7-18 microg/L of BTri, 1-5 microg/L of 4-TTri and 0.8-1.2 microg/L of 5-TTri. BTri and 4-TTri proved to be omnipresent in surface waters of the rivers Rhine and Elbe with concentrations increasing from <0.05 microg/L to around 0.5 microg/L of BTri and 0.2-0.5 microg/L of 4-TTri over 600-700 km. Bank filtration is an important process to generate raw water for drinking water production from surface waters. Even after residence times of several months BTri and 4-TTri were determined in concentrations of a few hundred ng/L in bank filtration water. Isotherm data from batch experiments indicate that activated carbon filtration should be suitable to avoid intrusion of TTri into drinking water in partially closed water cycles. For BTri, however, sorption to activated carbon appears to be too weak and ozonation may be mandatory to remove it from raw waters.

Modelling the degradation of micropollutants in wastewater: parameter estimation and application to pilot (laboratory-scale) MBR data in the case of 2,6-NDSA and BTSA

The paper summarises the definition of an extended biokinetic model dedicated to micropollutant degradation in wastewater treatment and the parameter estimation methodology for this model. Additionally it describes results on experimental parameter estimation for two target micropollutants, naphthalene disulfonate (2,6-NDSA) and benzothiazole sulfonic acid (BTSA). Subsequently the parameterised model is applied to real operational data from two laboratory-scale (MBR) installations. The work presents the full chain of theoretical model development, model analysis and practical application to case study data for micropollutants.

Membrane bioreactors for municipal wastewater treatment - a viable option to reduce the amount of polar pollutants discharged into surface waters?

The potential of a lab-scale membrane bioreactor (MBR) to remove polar pollutants from municipal wastewater was studied for industrial and household chemicals over a period of 22 months parallel to a conventional activated sludge (CAS) treatment. For half of the compounds, such as benzotriazole, 5-tolyltriazole (5-TTri), benzothiazole-2-sulfonate and 1,6-naphthalene disulfonate (1,6-NDSA), removal by MBR was significantly better than in CAS, while no improvement was recorded for the other half (1,5-NDSA, 1,3-NDSA, 4-TTri and naphthalene-1-sulfonate). The influence of operational conditions on trace pollutant removal by MBR was studied but no significant effects were found for variation of hydraulic retention time (7h-14h) and sludge retention time (26d-102d), suggesting that the lowest values selected have already been high enough for good removal. It is shown that the seemingly inconsistent results reported here and in previous studies regarding the comparison of trace pollutant removal in MBR and CAS are highly consistent. MBR is neither superior for well degradable compounds that are already extensively degraded in CAS treatment nor for recalcitrant compounds that are not amenable to biodegradation. For most compounds of intermediate removal in CAS treatment (15-80%), among them pharmaceuticals, personal care products and industrial chemicals, the MBR is clearly superior and reduces the effluent concentration by 20-50%. Despite of this clear benefit of MBR, the effect is not pronounced enough to serve as a sole argument for employing MBR in municipal wastewater treatment.

Environmental influences on the partitioning and diffusion of hydrophobic organic contaminants in microbial biofilms

A biofilm reactor was used to investigate kinetic and thermodynamic aspects of the sorption of polycyclic aromatic hydrocarbons (PAH) as model compounds for hydrophobic organic contaminants (HOC) to intact microbial biofilms. Effective diffusion coefficients are in the range of 10(-10) cm2 x s(-1) resulting in equilibration times of more than 3 days for a biofilm of 100 microm thickness. Diffusion in the biofilm was strongly temperature-dependent and increased by a factor of 3 (phenanthrene) to 6 (fluoranthene, pyrene) between 5 and 35 degrees C. Drying and rewetting of the biofilm as well as the inclusion of Ca2+ ions and of humic acids all strengthened the biofilm rigidity and slowed down the diffusion of PAH. The later two factors also influenced the thermodynamics of the process as they supported the partitioning of PAH into the biofilm. Humic acid inclusion from solution into the biofilm illustrates that a microbial biofilm can act as a primer allowing for the buildup of a particulate organic phase from dissolved organic matter. PAH metabolites (3-hydroxy-phenanthrene and 1-hydroxy-2-naphthoic acid) showed lower partition coefficients as compared to their parent compounds and 3-hydroxy-phenanthrene also showed a higher diffusion constant, indicating that these transformation products would be easily released into the water phase upon formation during PAH biodegradation in a biofilm. These results allow the quantification of the influence of environmental conditions on a biofilm's function as a sink or as a diffusion barrier for PAH from aqueous solution, and they indicate the importance of kinetic aspects of this partitioning process.

Molecular and structural characterization of dissolved organic matter from the deep ocean by FTICR-MS, including hydrophilic nitrogenous organic molecules

Dissolved organic matter isolated from the deep Atlantic Ocean and fractionated into a so-called hydrophobic (HPO) fraction and a very hydrophilic (HPI) fraction was analyzed for the first time by Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) to resolve the molecular species, to determine their exact masses, and to calculate their molecular formulas. The elemental composition of about 300 molecules was identified. Those in the HPO fraction (14C age of 5100 year) are very similar to much younger freshwater fulvic acids, but less aromatic and more oxygenated molecules are more frequent. This trend continues toward the HPI fraction and may indicate biotic and abiotic aging processes that this material experienced since its primary production thousands of years ago. In the HPI fraction series of nitrogenous molecules containing one, two, or three nitrogens were identified by FTICR-MS. Production spectra of the nitrogenous molecules suggest that the nitrogen atoms in these molecules are included in the (alicyclic) backbone of these molecules, possibly in reduced form. These mass spectrometric data suggest that a large set of stable fulvic acids is ubiquitous in all aquatic compartments. Although sources may differ, their actual composition and structure appears to be quite similar and largely independent from their source, because they are the remainder of intensive oxidative degradation processes.

Differences in the molecular composition of fulvic acid size fractions detected by size-exclusion chromatography-on line Fourier transform ion cyclotron resonance (FTICR-) mass spectrometry

Size-exclusion chromatography was coupled to electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (SEC-FTICR-MS) to separate a fulvic acid isolate into three size fractions and to determine the elemental composition of fulvic acids in these fractions. Molecular formulas of about 3000 ions in the mass range of 200-700 Da were derived, many of which occur in all three fractions and follow the same system of elemental composition. Product ion spectra generated by SEC coupled to quadrupol-time-of-flight-MS (Q-TOF-MS) confirmed that the ions of all three fractions are basically polycarboxylates with hardly any other functional moiety. However, SEC-FTICR-MS revealed that the ions generated from the high molecular weight (HMW) fraction are enriched in carboxyl groups and are more aromatic as compared with the low molecular weight (LMW) fraction. These findings support the idea that the HMW fulvic acids are formed from LMW fulvic acids. The shift in the relative frequency of ions from the LMW to the HMW fraction is in line with different interaction mechanisms: HMW fulvic acids may be aggregates held together by electrostatic interaction of the carboxylate groups via hydrogen bonds or with polyvalent cations or by hydrophobic interaction of their carbon backbone, or consist of LMW fulvic acids covalently bound to each other or to (aliphatic) alcohols.

Experimental and modeling approach to study sorption of dissolved hydrophobic organic contaminants to microbial biofilms

A biofilm reactor was developed to investigate the sorption of polycyclic aromatic hydrocarbons (PAH) as model compounds for hydrophobic organic contaminants (HOC) to intact microbial biofilms at environmentally realistic concentrations. When operated as a differential column batch reactor, the system can be used to study the thermodynamics as well as the kinetics of the exchange of HOC between an aqueous phase and microbial biofilms. Organic carbon normalized partition coefficients (K(oc)) for phenanthrene, fluoranthene and pyrene were at the lower end of those known for other organic sorbents. Intra-biofilm diffusion coefficients (D) were calculated from decrease in solute concentration over time using a model for diffusion through a plane sheet and ranged from 0.23 to 0.45x10(-9)cm(2)s(-1) for the three PAH. These diffusion coefficients are about four orders of magnitude lower than those reported in literature for free aqueous solution. These data and the experimental approach presented here are useful to assess the importance of microbial biofilms for exchange processes of HOC in heterogeneous systems such as water distribution systems, membranes and aquifers, sewer systems or surface soils.

Determination of benzotriazole corrosion inhibitors from aqueous environmental samples by liquid chromatography-electrospray ionization-tandem mass spectrometry

The first method for the determination of commonly used corrosion inhibitors in environmental water samples by liquid chromatography-electrospray ionization-tandem mass spectrometry is presented. Benzotriazole (BTri) and the two isomers of tolyltriazole (5- and 4-TTri) are separated in an isocratic run. By gradient elution, BTri, 4-TTri, 5-TTri, and xylyltriazole can be determined simultaneously with three benzothiazoles, but here TTri isomers coelute. The instrumental detection limit of 2 pg allows the determination of the three most important benzotriazoles from municipal wastewater and most surface waters by direct injection into the HPLC system without previous enrichment. When solid-phase extraction is employed with mean recovery rates of 95-113%, the limit of quantification for benzotriazoles range from 10 ng/L in groundwater to 25 ng/L in untreated wastewater. BTri and TTri were determined in municipal wastewater in microgram per liter concentrations. Elimination in wastewater treatment appears to be poor, and BTri and TTri can be followed through a water cycle from treated municipal wastewater through surface water to bank filtrate used for drinking water production. The TTri isomers show markedly different biodegradation behavior with 4-TTri being more stable.

Rapid and sensitive determination of ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid in water samples by ion-pair reversed-phase liquid chromatography–electrospray tandem mass spectrometry

A new method is presented for the quantitative determination of ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) from aqueous samples without an enrichment step. It consist of the formation of the Fe(III) complexes of EDTA and DTPA, liquid-chromatography with a volatile ion-pairing agent and determination by electrospray ionization-tandem mass spectrometry (ESI-MS/MS). Limits of quantification (LOQ) of 1.0 and 0.6 microgL(-1) for EDTA and DTPA were obtained, allowing the direct injection of most aqueous environmental samples without any preceding enrichment. With a more recent mass spectrometer, the LOQ could be further decreased by almost one order of magnitude. Parallel analysis of real samples by a standardized method employing enrichment, derivatization and GC-MS analysis yielded comparable results. The method was applied to the determination of both complexing agents in several wastewater, surface water and drinking water samples, showing that EDTA is an omnipresent contaminant in partially closed water cycles.

Comparison of sulfonated and other micropollutants removal in membrane bioreactor and conventional wastewater treatment

Membrane bioreactors (MBRs) were compared with conventional activated sludge systems (CAS) for micropollutant degradation, in laboratory-scale spiking experiments with synthetic and real domestic wastewater. The target micropollutants were polar in nature and represented a broad range in biodegradability. The experimental data indicated that MBR treatment could significantly enhance removal of the micropollutants 1,6- and 2,7-naphthalene disulfonate (NDSA) and benzothiazole-2-sulfonate. 1,5-NDSA, EDTA and diclofenac were not removed in either the MBR or the CAS. The other compounds were equally well degraded in both systems. For 1,3-naphthalene disulfonate, the existence of a minimum threshold level for degradation could be demonstrated. Although MBRs could not always make a difference in the overall removal efficiencies achieved, they showed reduced lag phases for degradation and a stronger memory effect, which implies that they may respond quicker to variable influent concentrations. Finally, micropollutant removal also turned out to be less sensitive to system operational variables.

Discharge of three benzotriazole corrosion inhibitors with municipal wastewater and improvements by membrane bioreactor treatment and ozonation

A set of three benzotriazole corrosion inhibitors was analyzed by liquid chromatography-mass spectrometry in wastewaters and in a partially closed water cycle in the Berlin region. Benzotriazole (BTri) and two isomers of tolyltriazole (TTri) were determined in untreated municipal wastewater with mean dissolved concentrations of 12 microg/L (BTri), 2.1 microg/L (4-TTri), and 1.3 microg/L (5-TTri). Removal in conventional activated sludge (CAS) municipal wastewater treatment ranged from 37% for BTri to insignificant removal for 4-TTri. In laboratory batch tests 5-TTri was mineralized completely and 4-TTri was mineralized to only 25%. This different behavior of the three benzotriazoles was confirmed by following the triazoles through a partially closed water cycle, into bank filtrate used for drinking water production, where BTri (0.1 microg/L) and 4-TTri (0.03 microg/ L) but no 5-TTri were detected after a travel time of several months. The environmental half-life appears to increase from 5-TTri over BTri to 4-TTri. Treatment of municipal wastewater by a lab-scale membrane bioreactor (MBR) instead of CAS improved the removal of BTri and 5-TTri but could not avoid their discharge. Almost complete removal was achieved by ozonation of the treatment plant effluent with 1 mg O3/mg DOC.