Persistent Transformation Products Research Articles

Assessment of the Presence of Transformation Products of Certain Pharmaceutical Products (Psychotropic Family) by Suspect and Non-Targeted HRMS Screening in Wastewater Treatment Plants.

Aquatic environments are the final receptors of human emissions and are therefore contaminated by molecules, such as pharmaceuticals. After use, these compounds and their metabolites are discharged to wastewater treatment plants (WWTPs). During wastewater treatment, compounds may be eliminated or degraded into transformation products (TPs) or may be persistent. The aim of this study was to develop an analytical method based on high resolution mass spectrometry (HRMS) for the identification of six psychotropic drugs that are widely consumed in France and present in WWTPs, as well as their potential associated metabolites and TPs. Four out of six psychotropic drugs and between twenty-five and thirty-seven potential TPs were detected in wastewater, although this was based on full scan data. TPs not reported in the literature and specific to the study sites and therefore to the wastewater treatment processes were tentatively identified. For the selected drugs, most known and present TPs were identified, such as desmethylvenlafaxine or norcitalopram. Moreover, the short fragmentation study led rather to the identification of several TPs of carbamazepine as ubiquitous persistent TPs.

Seasonal trends and retention of polycyclic aromatic compounds (PACs) in a remote sub-Arctic catchment

Atmospheric deposition is the most dominant source of polycyclic aromatic hydrocarbons (PAHs) in remote and pristine areas. Despite low bioaccumulation potential, PAHs and their persistent transformation products (PAH-derivatives) are chemicals of concern as they can harm human and animal health through chronic low dose exposure. In this study, atmospheric deposition fluxes of polycyclic aromatic compounds (PACs) were measured on a seasonal basis (3-month periods) from 2012 to 2016 in a remote subarctic forest catchment in northern Europe. The target PACs included 19 PAHs and 15 PAH-derivatives (oxygenated, nitrogenated, and methylated PAHs). The deposition fluxes of ƩPAHs and ƩPAH-derivatives were in the same range and averaged 530 and 500 ng m2 day−1, respectively. The fluxes were found to be higher with a factor of 2.5 for ƩPAHs and a factor of 3 for ƩPAH-derivatives during cold (<0 °C) in comparison to warm (>10 °C) periods. PAHs and PAH-derivatives showed similar seasonal patterns, which suggests that these two compound classes have similar sources and deposition mechanisms, and that the source strength of the PAH-derivatives in air follows that of the PAHs. The terrestrial export of PACs via the outlet of the catchment stream was estimated to be 1.1% for ƩPAHs and 1.7% for ƩPAH-derivatives in relation to the annual amounts deposited to the catchment, which suggests that boreal forests are sinks for PACs derived from the atmosphere. Some individual PACs showed higher export than others (i.e. chrysene, cyclopenta(c,d)pyrene, carbazole, quinoline, and benzo(f)quinoline), with high export PACs mostly characterized by low molecular weight and low hydrophobicity (2–3 benzene rings; log Kow<6.0).

Insight into H2O2-mediated catalytic ozonation of cyclophosphamide by zinc peroxide

Metal peroxides, owing to their ability to produce H2O2 in situ, are used for photocatalysis, ozonation, and oxidation of emerging contaminants (ECs) in wastewater. In the present study, catalytic ozonation of ZnO2 was investigated for the first time to our knowledge. The catalytic decomposition of O3 molecules to reactive oxygen species (ROS) was a dominant factor governing the degradation and mineralization of CYP by ZnO2/O3. Percent degradation of CYP by O3 and ZnO2/O3 was 17 and 99, respectively, implying that catalyst enhances the degradation of micropollutants under O3. The transformation products (TPs) of CYP formed after treatment with O3 and ZnO2/O3 as determined by HPLC-MS proves that O3 transforms CYP to still toxic and persistent transformation products (TPs) whereas by ZnO2/O3 significant decrease in TPs was observed suggesting that ZnO2/O3 not only degrades both CYP and TPs. CYP-degradation studies in presence of t-BuOH, MeOH and benzoquinone by ZnO2/O3 proved that OH. in bulk and on the surface of the catalyst and .O2- play significant roles in degrading and mineralizing CYP. CYP-degradation efficiency by ZnO2/O3 was compared to that by ZnO, CaO2, MgO2 and peroxonation, and ZnO2/O3 proved to be more relevant for real-time applications. To study ZnO2/O3 degradation capacity for real-scale applications, tertiary effluents from wastewater spiked with lamotrigine, bezafibrate, valsartan, iohexol, CYP and its TPs were investigated. A significant increase (75–99%) in degradation of the drug mixture was observed by ZnO2/O3 compared to O3 alone, demonstrating the former's potential suitability for effluent-treatment applications.

Combining biological processes with UV/H2O2 for metoprolol and metoprolol acid removal in hospital wastewater

The transformation products (TPs) of water contaminants generated during wastewater treatment can sometimes be equally or even more hazardous than the parent compounds. Therefore, for a comprehensive assessment of removal efficiency of a water treatment technology, it is mandatory to monitor not only the pollutants but also of their TPs. However, this type of evaluation studies is lacking in the case of water combined treatments. In this study, the elimination of metoprolol (MTP), metoprolol acid (MTPA) and the TPs generated was evaluated in pure water and hospital wastewater (HWW) using UV/H2O2 before and after fungal (FG) or conventional activated sludge (CAS). The major transformation pathways were suggested in terms of transformation of the parent compounds through bio-transformation and photo-transformation mechanisms. The results reveal an extended removal of MTP, MTPA and TPs after UV/H2O2 single experiment treating spiked pure water at 2.5 mg/L, without increasing the treated effluents toxicity. However, combined treatments were required to achieve similar removal percentages in spiked real HWW at 2.0 µg/L: while AOPs combined with FG exhibited lower removal efficiencies with generation of persistent intermediates (such as α-HMTP and TP240), AOPs combined with CAS attained the higher persistent TPs removal. In particular, AOP + CAS was classified as the most effective combination for HWW with the highest removal of the parent compounds (86% for MTP and 100% for MTPA), of the intermediates generated (up to 85%) and with a low presence of toxic TPs (such as O-DMTP). This study demonstrates that comprehensive evaluation of the intermediates generated along water treatment technologies is highly recommended to successfully evaluate their removal efficiencies.

Solar photo-Fenton-like process at neutral pH: Fe(III)-EDDS complex formation and optimization of experimental conditions for degradation of pharmaceuticals

This paper demonstrates the effectiveness of Fe(III)-EDDS complex for degradation of pharmaceutical compounds in a solar photo-Fenton-like process at neutral pH in two different aqueous matrixes. Electrochemical experiments were performed to monitor the formation and stability of the complex, as a function of the amount of complexing agent and pH. Eight compounds, including diazepam, dipyrone, fluoxetine, furosemide, nimesulide, paracetamol, progesterone, and propranolol, were analyzed in distilled water and simulated wastewater, at initial concentrations of 500 μg L−1. By applying Doehlert matrix design and the response surface methodology the optimal experimental conditions were found to be 0.28 mmol L−1 Fe(III)-EDDS and 5.00 mmol L−1 H2O2, with a ratio of 1:2 for Fe(III)-EDDS. The most persistent transformation products (TPs) generated during the treatment process were investigated using liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. 16 TPs were identified and classified as having high toxicity (according to the Cramer rules), low biodegradability (according to the START scheme), and possible carcinogenicity and/or mutagenicity. Most of the compounds were degraded in the first minutes of treatment, and most of the identified TPs had been successfully removed at the end of the process.

Studies on the behavior and ecotoxicity of pesticides and their transformation products in a river.

To clarify the properties of pesticide transformation products (TPs) for which the risk to aquatic organisms should be evaluated, I monitored the concentrations of paddy pesticides and their TPs in the Sakura River, Japan, during the rice-growing season in 2007-2010. I also conducted algal growth inhibition tests of herbicides and their TPs using a diatom and a green alga and acute toxicity tests of insecticides and their TPs using a caddisfly and a daphnid. Moreover, on the basis of the results of pesticide monitoring and toxicity tests, I attempted to evaluate the risk of these compounds to the riverine organisms as well as the risk of mixtures of insecticides and their TPs for caddisflies and cladocerans. The TPs were detected in the river water depending on the half-lives of the parent compounds and of the TPs in water and soil. The toxicities of the parent compound and its TPs may be related to their hydrophobicities and chemical structures. Some toxic and persistent TPs that formed rapidly in water and soil posed a risk to the organisms over a long period. The physicochemical properties and chemical structures of a parent compound and its TPs can be key factors in evaluating the pesticide TP risk to aquatic organisms in rivers.

Identification of potentially mobile and persistent transformation products of REACH-registered chemicals and their occurrence in surface waters

Transformation of industrial chemicals might be a significant source of hitherto unknown persistent and mobile organic contaminants (PMOC, PM chemicals) present in the aquatic environment. Herein we depicted a three-step strategy consisting of (I) the prioritization of potential PMOC precursors among REACH-registered chemicals, (II) their lab scale transformation through hydrolysis, photolysis, MnO2 oxidation, and biotransformation and subsequent structural elucidation of derived transformation products, and finally (III) the assessment of their environmental relevance. The proposed procedure was utilized to investigate eleven chemicals, for nine of which a concentration reduction was observed. For six of these chemicals transformation products were at least tentatively identified and partially confirmed with a commercially available reference standard. Retrospective assessment of high-performance liquid chromatography - high-resolution mass spectrometry data as well as a target screening method for the identified TPs and some of the prioritized REACH chemicals revealed the widespread presence of the following chemicals in the environment: 2-pyrrolidone (hydrolysis product of vinylpyrrolidone), TP 216 (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-acetic acid, biotransformation product of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-ethanol), and 1,3-diphenylguanidine (prioritized chemical with experimental evidence of environmental stability). 2-Pyrrolidone was detected in 23/25 investigated surface water samples and present in concentrations of up to 400 ng/L. TP 216 was detected in 20/25 surface water samples and an additional sampling of a waste water treatment plant and the receiving surface water confirmed that TP 216 is formed in waste water treatment plants. The vulcanisation agent 1,3-diphenylguanidine was present in all investigated samples. A leaching experiment with a tire suggested that tires and thus tire wear particles are a potential source of 1,3-diphenylguanidine. With these data the depicted approach was proven successful and suitable for true unknowns like TP 216, and thus an alternative to non-target screenings or suspect-screenings with predicted TPs to identify environmentally relevant transformation products.

Pharmaceutical removal from different water matrixes by Fenton process at near-neutral pH: Doehlert design and transformation products identification by UHPLC-QTOF MS using a purpose-built database

This work evaluates the Fenton process in the removal of eight pharmaceuticals (gemfibrozil, nimesulide, furosemide, paracetamol, propranolol, dipyrone, fluoxetine, and diazepam), present at an initial concentration of 500 μg L−1 for each compound, from three different water matrixes (distilled water, simulated wastewater, and hospital wastewater). The Fenton process conditions (iron and hydrogen peroxide concentrations, and pH) were optimized for the distilled water matrix by Doehlert design associated with response surface methodology. These corresponded to initial Fe2+ and hydrogen peroxide concentrations of 12.5 and 533 mg L−1, respectively, and pH 5.0. Mineralization rates and pharmaceutical degradation were monitored for all water matrixes and different experimental conditions employed. Unique iron addition, using low (12.5 mg L−1) and increased concentrations (37.5 mg L−1) were evaluated. These preliminary results motivated the study of the Fenton process employing successive iron additions and using an excess of hydrogen peroxide in the reaction medium. Multiple iron addition favored higher oxidation of the initial contaminants. Finally, the most persistent transformation products generated during the Fenton process were identified by liquid chromatography coupled with quadrupole-time of flight mass spectrometry (UHPLC-QTOF MS) using a purpose-built database that allowed monitoring 97 transformation products in a single injection. In this study, 12 transformation products (TPs) were tentatively identified employing this purpose-built database. Most TPs generated were classified as of high toxicity (Cramer rules) and showed ready biodegradability (START biodegradability).

Application of a multivariate analysis method for non-target screening detection of persistent transformation products during the cork boiling wastewater treatment

Cork boiling wastewater is a very complex mixture of naturally occurring compounds leached and partially oxidized during the boiling cycles. The effluent generated is recalcitrant and could cause a significant environmental impact. Moreover, if this untreated industrial wastewater enters a municipal wastewater treatment plant it could hamper or reduce the efficiency of most activated sludge degradation processes. Despite the efforts to treat the cork boiling wastewater for reusing purposes, is still not well-known how safe these compounds (original compounds and oxidation by-products) will be. The purpose of this work was to apply an HPLC-high resolution mass spectrometry method and subsequent non-target screening using a multivariate analysis method (PCA), to explore relationships between samples (treatments) and spectral features (masses or compounds) that could indicate changes in formation, degradation or polarity, during coagulation/flocculation (C/F) and photo-Fenton (PhF). Although, most of the signal intensities were reduced after the treatment line, 16 and 4 new peaks were detected to be formed after C/F and PhF processes respectively. The use of this non-target approach showed to be an effective strategy to explore, classify and detect transformation products during the treatment of an unknown complex mixture.

Formation and degradation of N-oxide venlafaxine during ozonation and biological post-treatment

While ozonation is considered an efficient treatment to eliminate trace organic compounds (TrOCs) from secondary wastewater effluents, the presence and persistence of transformation products (TPs) resulting from ozonation of TrOCs is a major concern that should be assessed prior to effluent discharge to the environment. Venlafaxine (VLX), an environmentally relevant tertiary amine-containing TrOC, was chosen as the model for this study. TP analysis confirmed that the lone electron pair of the non-protonated amine are the predominant site of oxidant attack, and therefore strongly affected by pH value and VLX speciation. N-oxide VLX (NOV), the primary ozone-induced TP, was formed and degraded simultaneously during ozonation of VLX-containing secondary effluent and reached a maximum yield of 0.44 to 0.85 (NOV-to-VLX0 ratio), depending on pH and hydroxyl (OH) radical presence. Rate constants for the reaction of NOV with ozone (3.1×102M−1s−1) and OH radicals (5.3×109M−1s−1) were determined. A simple kinetic model was developed to fit the kinetics of formation and degradation of NOV during ozonation in secondary effluents, based on a known ozone-reaction kinetic equation. The biodegradability of NOV (degradation rate of 39%) was significantly lower than that of the parent compound (VLX, 92%) after 71days, as evaluated by modified Zahn–Wellens tests, suggesting that N-oxide products are not better removed than the parent compound in a simulated biological post-treatment, which may even result in partial reformation of the parent compound. Lessons learned from this study were supported by a pilot-scale demonstration at the Shafdan wastewater-treatment plant, confirming the presence of NOV after ozonation and its persistence in biological post-treatment. Removal of such persistent TP will require higher dosages or promotion of OH-radicals during ozonation. Nevertheless, further assessment of the toxicity of persistent TPs relative to the parent compound is needed for complete evaluation of concerned TPs.

Assessment of the photocatalytic transformation of pyridinium-based ionic liquids in water

We studied some ionic liquids (ILs) belonging to the pyridinium class under photocatalytic treatment. In particularly, we analysed how the length of the alkyl chain, the kind of inorganic ion and the type of substituents could influence the disappearance rate, the mineralization extent, the acute toxicity and the transformation mechanism. For such, we selected some pyridinium derivatives with different alkyl chain but the same anion, namely tetrafluoroborate (1-ethylpyridinium, 1-butylpyridinium, 1-hexylpyridinium), with two alkyl substituents (4-methyl-1-butylpyridinium) and with a different substituent (1-cyanopropylpyridinium). Then, on a selected IL (1-butylpyridinium), we evaluate the role of different inorganic anions (bromine and chlorine). The results show that irrespective to the alkyl chain or the number of substituents, the transformation involved an attack to the alkyl chain, proceeded through the formation of harmless compounds and the mineralization was easily achieved within 4h. Nitrogen was mainly released as ammonium ion. When introducing a cyano group, the extent of nitrate ions and the number of possible transformation route increased. Conversely, the type of inorganic ion deeply affected the transformation pathways and the extent of mineralization. Actually, in the presence of bromide as anion, IL was only partially mineralized and the formation of highly persistent transformation products occurred.

Effect of operational and water quality parameters on conventional ozonation and the advanced oxidation process O3/H2O2: Kinetics of micropollutant abatement, transformation product and bromate formation in a surface water

The efficiency of ozone-based processes under various conditions was studied for the treatment of a surface water (Lake Zürich water, Switzerland) spiked with 19 micropollutants (pharmaceuticals, pesticides, industrial chemical, X-ray contrast medium, sweetener) each at 1 μg L−1. Two pilot-scale ozonation reactors (4–5 m3 h−1), a 4-chamber reactor and a tubular reactor, were investigated by either conventional ozonation and/or the advanced oxidation process (AOP) O3/H2O2. The effects of selected operational parameters, such as ozone dose (0.5–3 mg L−1) and H2O2 dose (O3:H2O2 = 1:3–3:1 (mass ratio)), and selected water quality parameters, such as pH (6.5–8.5) and initial bromide concentration (15–200 μg L−1), on micropollutant abatement and bromate formation were investigated. Under the studied conditions, compounds with high second-order rate constants kO3>104 M−1 s−1 for their reaction with ozone were well abated (>90%) even for the lowest ozone dose of 0.5 mg L−1. Conversely, the abatement efficiency of sucralose, which only reacts with hydroxyl radicals (OH), varied between 19 and 90%. Generally, the abatement efficiency increased with higher ozone doses and higher pH and lower bromide concentrations. H2O2 addition accelerated the ozone conversion to OH, which enables a faster abatement of ozone-resistant micropollutants. Interestingly, the abatement of micropollutants decreased with higher bromide concentrations during conventional ozonation due to competitive ozone-consuming reactions, except for lamotrigine, due to the suspected reaction of HOBr/OBr− with the primary amine moieties. In addition to the abatement of micropollutants, the evolution of the two main transformation products (TPs) of hydrochlorothiazide (HCTZ) and tramadol (TRA), chlorothiazide (CTZ) and tramadol N-oxide (TRA-NOX), respectively, was assessed by chemical analysis and kinetic modeling. Both selected TPs were quickly formed initially to reach a maximum concentration followed by a decrease of their concentrations for longer contact times. For the studied conditions, the TP's concentrations at the outlet of the reactors ranged from 0 to 61% of the initial parent compound concentration, CTZ being a more persistent TP against further oxidation than TRA-NOX. Finally, it was demonstrated in both reactors that the formation of bromate (BrO3−), a potentially carcinogenic oxidation by-product, could be controlled by H2O2 addition with a general improvement on micropollutant abatement. Post-treatment by granular activated carbon (GAC) filtration enabled the reduction of micropollutants and TPs concentrations but no changes in bromate were observed. The combined algae assay showed that water quality was significantly improved after oxidation and GAC post-treatment, driven by the abatement of the spiked pesticides (diuron and atrazine).

Evaluation of the short-term fate and transport of chemicals of emerging concern during soil-aquifer treatment using select transformation products as intrinsic redox-sensitive tracers.

In this study, known products from oxic transformation of the X-ray contrast medium iopromide were introduced for the first time as intrinsic tracer for in situ characterization of the transition zone between oxic and suboxic conditions during the initial phase of soil-aquifer treatment (SAT). Two wet-dry cycles of a full-scale infiltration basin were monitored to characterize hydraulic retention times, redox conditions, removal of bulk organic parameters and the fate of chemicals of emerging concern (CECs). Tracer tests at the site showed an average hydraulic retention time of <20h before collection in drainage pipes located approximately 1.5m below surface. Dissolved oxygen at different depth rapidly depleted and only increased towards the end of the flooding event. Transformation of iopromide and all known intermediates to persistent transformation products (TPs) usually occurring during oxic biodegradation was very limited in samples from suction cups immediately underneath the basin. But transformation was complete in samples collected from the drainage outlet indicating that dissolved oxygen had been introduced to the system before sample collection in the combined drainage outlet. Similar to iopromide and its TPs, removal of several CECs (diclofenac, bezafibrate, mecoprop, TCEP) was inefficient after 90cm infiltration (<35%) but significantly enhanced in the combined drainage outlet (>80%). These results highlight that the analysis of iopromide along with its intermediates and persistent TPs can serve as a promising probing tool to determine overall efficiency of CEC biodegradation and to identify potential in situ oxygen limitations.

Identification of transformation products of rosuvastatin in water during ZnO photocatalytic degradation through the use of associated LC–QTOF–MS to computational chemistry

Rosuvastatin (RST), a synthetic statin, is a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, with a number of pleiotropic properties, such as anti-inflammation, antioxidation and cardiac remodelling attenuation. According to IMS Health, rosuvastatin was the third best-selling drug in the United States in 2012. RST was recently found in European effluent samples at a detection frequency of 36%. In this study, we evaluate the identification process of major transformation products (TPs) of RST generated during the heterogeneous photocatalysis process with ZnO. The degradation of the parent molecule and the identification of the main TPs were studied in demineralised water. The TPs were monitored and identified by liquid chromatography-quadrupole time-of-flight mass spectrometry (LC–QTOF–MS/MS). Ten TPs were tentatively identified and some of them originated from the hydroxylation suffered by the aromatic ring during the initial stages of the process. Structural elucidation of some of the most abundant or persistent TPs was evaluated by computational analysis, which demonstrated that this approach can be used as a tool to help the elucidation of structures of unknown molecules. The analysis of the parameters obtained from ab initio calculations for different isomers showed the most stable structures and, consequently, the most likely to be found.

Biotransformation of Benzotriazoles: Insights from Transformation Product Identification and Compound-Specific Isotope Analysis

Benzotriazoles are widely used domestic and industrial corrosion inhibitors and have become omnipresent organic micropollutants in the aquatic environment. Here, the range of aerobic biological degradation mechanisms of benzotriazoles in activated sludge was investigated. Degradation pathways were elucidated by identifying transient and persistent transformation products in batch experiments using liquid chromatography-high-resolution tandem mass spectrometry (LC-HR-MS/MS). In addition, initial reactions were studied using compound-specific isotope analysis (CSIA). Biodegradation half-lives of 1.0 days for 1H-benzotriazole, 8.5 days for 4-methyl-1H-benzotriazole, and 0.9 days for 5-methyl-1H-benzotriazole with activated sludge confirmed their known partial persistence in conventional wastewater treatment. Major transformation products were identified as 4- and 5-hydroxy-1H-benzotriazole for the degradation of 1H-benzotriazole, and 1H-benzotriazole-5-carboxylic acid for the degradation of 5-methyl-1H-benzotriazole. These transformation products were found in wastewater effluents, showing their environmental relevance. Many other candidate transformation products, tentatively identified by interpretation of HR-MS/MS spectra, showed the broad range of possible reaction pathways including oxidation, alkylation, hydroxylation and indicate the significance of cometabolic processes for micropollutant degradation in biological wastewater treatment in general. The combination of evidence from product analysis with the significant carbon and nitrogen isotope fractionation suggests that aromatic monohydroxylation is the predominant step during the biotransformation of 1H-benzotriazole.

Ozonation of wastewater: Removal and transformation products of drugs of abuse

In this study amphetamine, methamphetamine, methylenedioxymethamphetamine (MDMA), cocaine (COC), benzoylecgonine (BE), ketamine (KET) and oxycodone (OXY) in wastewater at concentrations of 100μgL−1 were subjected to ozone to determine their removals as a function of ozone dose and to identify significant oxidation transformation products (OTPs) produced as a result of ozonation. A method based on high resolution mass spectrometry and differential analysis was used to facilitate and accelerate the identification and structural elucidation of the transformation products. The drug removal ranged from 3 to 50% depending on the complexity of the matrix and whether a mixture or individual drugs were ozonated. Both transient and persistent oxidation transformation products were identified for MDMA, COC and OXY and their chemical formulae were determined. Three possible structures of the persistent transformation product of MDMA (OTP-213) with chemical formula C10H16O4N, were determined based on MSn mass spectra and the most plausible structure (OTP-213a) was determined based on the chemistry of ozone. These results indicate that ozone is capable of removing drugs of abuse from wastewater to varying extents and that persistent transformation products are produced as a result of treatment.

Photodegradation kinetics and transformation products of ketoprofen, diclofenac and atenolol in pure water and treated wastewater

Pharmaceutical compounds such as ketoprofen, diclofenac and atenolol are frequently detected at relatively high concentrations in secondary effluents from wastewater treatment plants. Therefore, it is important to assess their transformation kinetics and intermediates in subsequent disinfection processes, such as direct ultraviolet (UV) irradiation. The photodegradation kinetics of these compounds using a medium pressure (MP) lamp was assessed in pure water, as well as in filtered and unfiltered treated wastewater. Ketoprofen had the highest time- and fluence-based rate constants in all experiments, whereas atenolol had the lowest values, which is consistent with the corresponding decadic molar absorption coefficient and quantum yield. The fluence-based rate constants of all compounds were evaluated in filtered and unfiltered wastewater matrices as well as in pure water. Furthermore, transformation products of ketoprofen, diclofenac and atenolol were identified and monitored throughout the irradiation experiments, and photodegradation pathways were proposed for each compound. This enabled the identification of persistent transformation products, which are potentially discharged from WWTP disinfection works employing UV photolysis.

Transformation Products in the Life Cycle Impact Assessment of Chemicals

The current life cycle impact assessment (LCIA) of chemicals focuses only on the fate and effects of the parent compound, neglecting the potential impact of transformation products. Here, we assess the importance of including the potential impact of transformation products in the calculation of characterization factors (CF). The developed method is applied to freshwater ecotoxicity for 15 pesticides and perchloroethylene, which are all known to have potentially persistent transformation products. The inclusion of transformation products resulted in a median increase in CF that varied from negligible to more than 5 orders of magnitude. This increase, however, can be highly uncertain, particularly due to a lack of toxicity data for transformation products and a lack of mode of action-specific data. We show in a case study that replacement of atrazine with other pesticides for application on corn results in a median impact score of 2 orders of magnitude lower when the fate and effects of only the parent compounds are included. When transformation products are included, the reduction in median impact score would likely be lower (less than 1 order of magnitude). An uncertainty analysis showed that the difference in impact scores of atrazine and the atrazine replacements was not statistically significant when only the parent chemical was considered. When transformation products were included, the uncertainty in impact scores was even greater.

Demonstrating formation of potentially persistent transformation products from the herbicides bromoxynil and ioxynil using liquid chromatography‐tandem mass spectrometry (LC‐MS/MS)

It is shown that potentially persistent transformation products can be formed from the herbicides bromoxynil (3,5-dibromo-4-hydroxybenzonitrile) and ioxynil (3,5-diiodo-4-hydroxybenzonitrile), and possible leaching to groundwater is discussed. A similar process to the formation of BAM (2,6-dichlorobenzamide) from the herbicide dichlobenil (2,6-dichlorobenzonitrile) can be anticipated as bromoxynil and ioxynil are analogues of dichlobenil and they are degraded by the enzymes nitrilase, nitrile hydratase and amidase. A biodegradation study using cultured Variovorax sp. DSM 11402, a species commonly found in soil, demonstrated that ioxynil and bromoxynil were fully transformed into their corresponding amides in 2-5 days. These amides were not further degraded within 18 days, and formation of other degradation products was not observed. These results are in agreement with biodegradation experiments with dichlobenil. In soil, dichlobenil is transformed into its only observed degradation product BAM, which is persistent and mobile, and has been found in 19% of 5000 samples of Danish groundwater. Variovorax sp. is known to degrade the non-halogenated analogue benzamide, suggesting that degradation of the three amides may be hindered by the halogenated substituents (meta-Br; meta-I; ortho-Cl). This hypothesis is supported by QSAR modelling of fundamental properties. Using a new optimised liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, the sorption and desorption properties of bromoxynil and ioxynil were characterised in sandy topsoil at four concentration levels. The estimated sorption coefficient K(d) was 1.4 L kg(-1) for bromoxynil and 5.4 L kg(-1) for ioxynil, indicating weak to moderate sorption to topsoil. Desorption of the herbicides showed that they were strongly and irreversible bound to the soil (K(des) > K(d)). The amount of herbicide desorbed depended on the initial concentration level. At low levels, K(des) values were higher, indicating stronger binding than at higher levels. The isocratic LC-MS/MS method developed for simultaneous detection of bromoxynil, ioxynil and their main degradation products is described. Using negative electrospray ionisation (ESI-), the detection limits were 0.4-1.0 microg L(-1), with relative standard deviations of 4-10% (n = 10) using direct injection without clean-up steps. The standard curves showed linearity in the range 5-100 microg L(-1) with r(2) > 0.992.

Organochlorine compounds and their reactions in the atmosphere

To estimate the influence of the chlorinated hydrocarbons on the quality of the environment, primarily chemico-ecological and toxico-ecological data are required. In addition to their level of production, range of application, and distribution tendency, a knowledge of their transformation under environmental conditions is desirable. On one hand, the change of a substance under biotic and abiotic environmental conditions provides an indication of whether an enrichment of the environment with the relevant chemical may be anticipated in the long term on the other hand, these investigations allow possible persistent transformation products to be characterized. In contrast to the biological degradation pathways and transformation processes of environmental chemicals, whose course is accompanied by only very small amounts of energy, energy sources with an inexhaustible capacity and constant intensity are available for abiotic conversions. Temperature and uv radiation become the most important manifestations of the largest energy source of our environment, the sun, whose direct or indirect effect is especially important during an ecological assessment of chlorinated hydrocarbons. It is also important to know in which ecological systems these chemicals occur, because both dynamic and catalytic effects can be traced back primarily to the respective state of the molecule and the interaction with the surroundings. In this connection the task posed is an investigation of the reactions of chlorinated hydrocarbons under simulated atmospheric conditions. Such simulations are made more difficult by virtue of the complexity of these reactions. The atmosphere may be portrayed as a large chemical reactor in which complicated reactions take place under the action of the sun's uv radiation and are catalyzed by trace substances and whereby large amounts of substances are reacted. Numerous equilibria are established under the influence of chemical, photochemical, and physical factors. To study individual reaction mechanisms, it is necessary to create conditions which correspond to those in the atmosphere, or a partial simulation to enable the experimental results to be interpreted with some degree of probability.