Ultra-Short-Chain PFASs in the Sources of German Drinking Water: Prevalent, Overlooked, Difficult to Remove, and Unregulated.

Per- and polyfluoroalkyl substances (PFASs) have been a focal point of environmental chemistry and chemical regulation in recent years, culminating in a shift from individual PFAS regulation toward a PFAS group regulatory approach in Europe. PFASs are a highly diverse group of substances, and knowledge about this group is still scarce beyond the well-studied, legacy long-chain, and short-chain perfluorocarboxylates (PFCAs) and perfluorosulfonates (PFSAs). Herein, quantitative and semiquantitative data for 43 legacy short-chain and ultra-short-chain PFASs (≤2 perfluorocarbon atoms for PFCAs, ≤3 for PFSAs and other PFASs) in 46 water samples collected from 13 different sources of German drinking water are presented. The PFASs considered include novel compounds like hexafluoroisopropanol, bis(trifluoromethylsulfonyl)imide, and tris(pentafluoroethyl)trifluorophosphate. The ultra-short-chain PFASs trifluoroacetate, perfluoropropanoate, and trifluoromethanesulfonate were ubiquitous and present at the highest concentrations (98% of sum target PFAS concentrations). "PFAS total" parameters like the adsorbable organic fluorine (AOF) and total oxidizable precursor (TOP) assay were found to provide only an incomplete picture of PFAS contamination in these water samples by not capturing these highly prevalent ultra-short-chain PFASs. These ultra-short-chain PFASs represent a major challenge for drinking water production and show that regulation in the form of preventive measures is required to manage them.

Occurrence, Distribution, and Environmental Behavior of Persistent, Mobile, and Toxic (PMT) and Very Persistent and Very Mobile (vPvM) Substances in the Sources of German Drinking Water.

Persistent, mobile, and toxic (PMT) and very persistent and very mobile (vPvM) substances have been recognized as a threat to both the aquatic environment and to drinking water resources. These substances are currently prioritized for regulatory action by the European Commission, whereby a proposal for the inclusion of hazard classes for PMT and vPvM substances has been put forward. Comprehensive monitoring data for many PMT/vPvM substances in drinking water sources are scarce. Herein, we analyze 34 PMT/vPvM substances in 46 surface water, groundwater, bank filtrate, and raw water samples taken throughout Germany. Results of the sampling campaign demonstrated that known PMT/vPvM substances such as 1H-benzotriazole, melamine, cyanuric acid, and 1,4-dioxane are responsible for substantial contamination in the sources of German drinking water. In addition, the results revealed the widespread presence of the emerging substances 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and diphenylguanidine (DPG). A correlation analysis showed a pronounced co-occurrence of PMT/vPvM substances associated predominantly with consumer or professional uses and also demonstrated an inhomogeneous co-occurrence for substances associated mainly with industrial use. These data were used to test the hypothesis that most PMT/vPvM substances pass bank filtration without significant concentration reduction, which is one of the main reasons for introducing PMT/vPvM as a hazard class within Europe.

Trifluoroacetate in Precipitation: Deriving a Benchmark Data Set.

Although precipitation is considered to be the most important diffuse source of trifluoroacetate (TFA) to the nonmarine environment, information regarding the wet deposition of TFA as well as general data on the spatial and temporal variations in TFA concentration in precipitation is scarce. This is the first study to provide a comprehensive overview of the occurrence of TFA in precipitation by a systematic and nation-wide field monitoring campaign. In total, 1187 precipitation samples, which were collected over the course of 12 consecutive months at eight locations across Germany, were analyzed. The median, the estimated average, and the precipitation-weighted average TFA concentration of all analyzed wet deposition samples were 0.210, 0.703, and 0.335 µg/L, respectively. For Germany, an annual wet deposition flux of 190 µg/m2 or approximately 68 t was calculated for the sampling period from February 2018 to January 2019. The campaign revealed a pronounced seasonality of the TFA concentration and wet deposition flux of collected samples. Correlation analysis suggested an enhanced transformation of TFA precursors in the troposphere in the summertime due to higher concentrations of photochemically generated oxidants such as hydroxyl radicals, ultimately leading to an enhanced atmospheric deposition of TFA during summer.

Transformation Products of Fluoxetine Formed by Photodegradation in Water and Biodegradation in Zebrafish Embryos ( Danio rerio).

The present study investigates the transformation of the antidepressant fluoxetine (FLX) by photo- and biodegradation and shows similarities and differences in transformation products (TPs). TPs were identified using LC-high-resolution mass spectrometry with positive and negative electrospray ionization. In a sunlight simulator, photodegradation was carried out using ultrapure water (pH 6, 8, and 10) and surface water (pH 8) to study the effect of direct and indirect photolysis, respectively. The well-known metabolite norfluoxetine (NFLX) proved to be a minor TP in photolysis (≤2% of degraded FLX). In addition, 26 TPs were detected, which were formed by cleavage of the phenolether bond ( O-dealkylation) which primarily formed 3-(methylamino)-1-phenyl-1-propanol (TP 166) and 4-(trifluoromethyl)phenol, by hydroxylation of the benzyl moiety, by CF3 substitution to benzoic aldehyde/acid, and by adduct formation at the amine group ( N-acylation with aldehydes and carboxylic acids). Higher pH favors the neutral species of FLX and the neutral/anionic species of primary TPs and, therefore, photodegradation. In zebrafish embryos, the bioconcentration factor of FLX was found to be 110, and about 1% of FLX taken up by the embryos was transformed to NFLX. Seven metabolites known from photodegradation and formed by hydrolysis, hydroxylation, and N-acylation as well as three new metabolites formed by N-hydroxylation, N-methylation, and attachment of an amine group were identified in zebrafish embryos. The study highlights the importance of considering a broad range of TPs of FLX in fresh water systems and in ecotoxicity tests and to include TP formation in both environmental processes and metabolism in organisms.

Efficient synthesis of readily water-soluble sulfonic Acid carbamates.

A series of various readily water-soluble carbamates were synthesized with good yields. These compounds are useful chemical tracers for assessing the cooling progress in a georeservoir during geothermal power plant operation. Acylation of primary amines was carried out as well as using a solution of sodium bicarbonate and without the presence of salt. Products were characterized by 1H-NMR and 13C-NMR. Purity was confirmed through elemental analysis.

Efficient synthesis and reaction kinetics of readily water soluble esters containing sulfonic groups.

A series of various readily water soluble esters were synthesized by a very efficient procedure. These compounds can be useful as thermosensitive tracers for studying the cooling progress in a low enthalpy georeservoir exploitable by double flash geothermal power plant systems. The kinetics of their hydrolysis was investigated. Acylation of primary alcohols or phenols was carried out by a method based on a single-phase solvent system consisting of ethyl acetate acting as an organic solvent and triethylamine acting as a catalyst. Products were characterized by 1H-NMR, and 13C-NMR.

Metabolites are overlooked in environmental risk assessments and monitoring of pharmaceuticals: The case study of pantoprazole.

The proton-pump inhibitor pantoprazole (PPZ) is one of the most consumed pharmaceuticals worldwide. Despite its high usage, reported PPZ concentrations in environmental water samples are comparatively low, which can be explained by the extensive metabolism of PPZ in the human body. Since most previous studies did not consider human PPZ metabolites it can be assumed that the current environmental exposure associated with the application of PPZ is substantially underestimated. In our study, 4'-O-demethyl-PPZ sulfide (M1) was identified as the predominant PPZ metabolite by analyzing urine of a PPZ consumer as well as the influent and effluent of a wastewater treatment plant (WWTP) using liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS). M1 was found to be ubiquitously present in WWTP effluents (max. concentration: 3 000 ng/L) and surface waters in Germany. On average, the surface water concentrations of M1 were approximately 30 times higher than those of the parent compound PPZ. Laboratory scale experiments demonstrated that activated carbon can considerably adsorb M1 und thus improve its removal during wastewater and drinking water treatment. Laboratory ozonation experiments showed a fast oxidation of M1, accompanied by the formation of several ozonation products. Certain ozonation products (identities confirmed via synthesized reference standards) were also detected in water samples collected after ozonation in a full-scale WWTP. Overall lower signal intensities were observed in the effluents of a sand filter and biologically active granular activated carbon filter, suggesting that the compounds were significantly removed during these post-ozonation treatment stages.

Comprehensive target analysis and TOP assay of per- and polyfluoroalkyl substances (PFAS) in wild boar livers indicate contamination hot-spots in the environment.

The suitability of wild boar liver as a bioindicator of per- and polyfluoroalkyl substances (PFAS) in the terrestrial environment was investigated. Samples from 50 animals in three different areas associated with (1) contaminated paper sludges distributed on arable land (PS), (2) industrial emissions of PFAS (IE) and (3) background contamination (BC) were analyzed for 66 PFAS, including legacy PFAS, novel substitutes and precursors of perfluoroalkyl acids (PFAAs). Additionally, the Total Oxidizable Precursor (TOP) assay was performed to determine the formation potential of PFAAs from precursors. In total, 31 PFAS were detected with site-specific contamination profiles. PFAS concentrations in livers from area PS and IE (567 and 944 µg kg-1 wet weight, respectively) were multiple times higher than from area BC (120 µg kg-1). The dominating PFAS were the legacy compounds perfluorooctane sulfonic acid (PFOS) in areas PS and BC (426 and 82 µg kg-1, respectively) and perfluorooctanoic acid (PFOA) in area IE (650 µg kg-1). In area IE, the compounds 4,8-dioxa-3H-perfluorononanoic acid (DONA) and hexafluoropropylene oxide dimer acid (HFPO-DA) - which are used as substitutes for PFOA - were determined at 15 and 0.29 µg kg-1, respectively. The formation potential of PFAAs was highest in area PS, but generally lower than the contamination with PFAAs. The pattern of perfluoroalkyl carboxylic acids (PFCAs) in wild boar liver reflects the contamination of the local soil at the two hot-spot areas IE and PS. This first comparison of PFAS contamination between wild boars and soil suggests that wild boar livers are suitable bioindicators for PFAS contamination in the terrestrial environment. Moreover, in terrestrial samples from area IE, legacy PFAS were found to be retained for a longer period as compared to riverine samples (suspended particulate matter and chub filet).

Differences in the internal PFAS patterns of herbivores, omnivores and carnivores - lessons learned from target screening and the total oxidizable precursor assay.

Per- and polyfluorinated alkyl substances (PFAS) are a group of anthropogenic chemicals, which are not (fully) biodegradable and accumulate in different environmental compartments worldwide. A comprehensive, quantitative analysis - consisting of target analysis (66 different analytes, including e. g. ultrashort-chain perfluorinated carboxylic acids (PFCAs), precursor compounds and novel substitutes) and the Total Oxidisable Precursor (TOP) assay (including trifluoroacetic acid (TFA)) - were conducted to analyse the PFAS concentrations and patterns in 12 mammalian and two bird species from different areas of Germany and Denmark. The PFAS contamination was investigated in dependance of the trophic class (herbivores, omnivores, carnivores), ecological habitat (terrestrial, (semi-) aquatic) and body tissue (liver, musculature). PFAS concentrations were highest in carnivores, followed by omnivores and herbivores, with ∑PFAS concentration ranging from 1274 µg/kg (Eurasian otter liver) to 22 µg/kg (roe deer liver). TFA dominated in the herbivorous species, whereas perfluorooctanesulfonic acid (PFOS) and the long-chain PFCAs covered the majority of the PFAS contamination in carnivorous species. Besides trophic class, ecological habitat also affected the PFAS levels in the different species, with terrestrial herbivores and omnivores showing higher PFAS concentration than their aquatic counterparts, whereas for carnivores this relationship was reversed. The TOP assay analysis indicated similar trends, with the PFCA formation pattern differing significantly between the trophic classes. TFA was formed predominantly in herbivorous and omnivorous species, whereas in carnivorous species a broad spectrum of PFCAs (chain-length C2-C14) was formed. Musculature tissue of six species exhibited significantly lower PFAS concentrations than the respective liver tissue, but with similar PFAS patterns. The comprehensive approach applied in the present study showed, that primarily the trophic class is decisive for the PFAS concentration, as herbivores, omnivores and carnivores clearly differed in their PFAS concentrations and patterns. Additionally, the TOP assay gave novel insights in the PFCA formation potential in biota samples.

Combining target analysis with sum parameters-a comprehensive approach to determine sediment contamination with PFAS and further fluorinated substances.

Recent studies aiming at a fluorine mass balance analysis in sediments combined the determination of extractable organic fluorine (EOF) with target analysis. They reported high fractions of unidentified organic fluorine (UOF) compounds, as the target analysis covers only a limited number of per- and polyfluoroalkyl substances (PFAS). For this reason, in this study, a comprehensive approach was used combining target analysis with an extended PFAS spectrum, the EOF and a modified total oxidisable precursor (TOP) assay, which includes trifluoroacetic acid, to determine the PFAS contamination in sediments (n=41) and suspended solids (n=1) from water bodies in Northern Germany (Lower Saxony). PFAS are ubiquitous in the sediments (detected in 83% of the samples). Perfluorinated carboxylic acids (PFCAs) were found in 64% of the samples; perfluorinated sulfonic acids (PFSAs) were detected less frequently (21%), with the highest concentration observed for perfluorooctanesulfonic acid (PFOS). Levels of precursors and substitutes were lower. Applying the TOP assay resulted in an increase in PFCAs in 43% of the samples analysed. In most cases, target analysis and the TOP assay could not account for the EOF concentrations measured. However, as the fraction of UOF decreased significantly, the application of the TOP assay in fluorine mass balance analysis proved to be an important tool in characterising the PFAS contamination of riverine sediments.

Ultrashort-chain perfluoroalkyl substance trifluoroacetate (TFA) in beer and tea - An unintended aqueous extraction.

Trifluoroacetate (TFA) is an ultrashort-chain perfluoroalkyl substance, which is ubiquitously present in the aqueous environment. Due to its high mobility, it accumulates in plant material. The study presented here shows for the first time that TFA is a widely spread contaminant in beer and tea / herbal infusions. In 104beer samples from 23countries, TFA was detected up to 51 µg/L with a median concentration of 6.1 µg/L. An indicative brewing test and a correlation approach with potassium (K) indicate that the main source of TFA in beer is most likely the applied malt. It could be proven that the impact of the applied water is negligible in terms of TFA, which was supported by the analysis of numerous tap water samples from different countries. The unintended extraction of TFA was also demonstrated for tea / herbal infusions with a median concentration of 2.4 µg/L.

Under the radar - Exceptionally high environmental concentrations of the high production volume chemical sulfamic acid in the urban water cycle.

Elevated concentrations of sulfamate, the anion of sulfamic acid, were found in surface waters and finished drinking water in Germany with concentrations up to 580 µg/L and 140 µg/L, respectively. Wastewater treatment plant (WWTP) effluent was identified as the dominant source of sulfamate in the urban water cycle, as sulfamate concentrations correlated positively (0.77 > r < 0.99) with concentrations of the wastewater tracer carbamazepine in samples from different waterbodies. Ozonation and activated sludge experiments proved that sulfamate can be formed from chemical and biological degradation of various precursors. Molar sulfamate yields were highly compound-specific and ranged from 2% to 56%. However, the transformation of precursors to sulfamate in WWTPs and wastewater-impacted waterbodies was found to be quantitatively irrelevant, since concentrations of sulfamate in these compartments are already high, presumably due to its primary use as an acidic cleaning agent. Sulfamate concentrations in the influent and effluent of studied WWTPs ranged from 520 µg/L to 1900 µg/L and from 490 µg/L to 1600 µg/L, respectively. Laboratory batch experiments were performed to assess the recalcitrance of sulfamate for chemical oxidation. In combination with the results from sampling conducted at full-scale waterworks, it was shown that common drinking water treatment techniques, including ozonation and filtration with activated carbon, are not capable to remove sulfamate. The results of biodegradation tests and from the analysis of samples taken at four bank filtration sites indicate that sulfamate is attenuated in the sediment/water interface of aquatic systems and during aquifer passage under aerobic and anaerobic conditions. Sulfamate concentrations decreased by between 62% and 99% during aquifer passage at the bank filtration sites. Considering the few data on short term ecotoxicity, about 30% of the presented sulfamate levels in ground and surface water samples did exceed the predicted no-effect concentration (PNEC) of sulfamate, and thus effects of sulfamate on the aquatic ecosystem of wastewater-impacted waterbodies in Germany cannot be excluded so far. Toxicological estimations suggest that no risk to human health is expected by concentrations of sulfamate typically encountered in tap water.

Qualitative and quantitative use of micropollutants as source and process indicators. A review.

Nowadays, micropollutants such as pharmaceuticals, pesticides and personal care products can be found ubiquitously in the anthropogenically influenced water cycle. As micropollutants have virtually no natural background concentrations they are significantly more sensitive in detecting processes and flow paths than classic inorganic tracers and indicators and at the same time they are often highly source specific. Therefore, using micropollutants as environmental indicators for anthropogenic activities is a common and frequently applied method today. As they interact in many ways with environmental matrices they can be used for source apportionment as well as to estimate flow paths and residence times in waterbodies. This review gives a systematic overview over the large variety of micropollutants used as indicators in the aquatic environment over the last decades together with the prerequisites on their use. Their application is subdivided into their qualitative (compound presence or absence) and quantitative (volume flows) use and shows the numerous possibilities from gaining basic information on the water regime up to advanced applications such as wastewater-based epidemiology.

Robust trace analysis of polar (C2-C8) perfluorinated carboxylic acids by liquid chromatography-tandem mass spectrometry: method development and application to surface water, groundwater and drinking water.

A simple and robust analytical method for the determination of perfluorinated carboxylic acids (PFCAs) with C2 to C8 chains, based on solid-phase extraction (SPE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS), was developed, validated and applied to tap water, groundwater and surface water. Two stationary phases for LC (Obelisc N and Kinetex C18) and two materials with weak anion-exchange properties for SPE (Strata X-AW and Oasis WAX) were evaluated. Robust separation and retention was achieved with the reversed phase column and an acidic eluent. Quantitative extraction recoveries were generally achieved for PFCAs with C > 3, but extraction efficiencies were different for the two shortest chained analytes: 36 to 114% of perfluoropropanoate (PFPrA) and 14 to 99% of trifluoroacetate (TFA) were recovered with Strata X-AW, while 93 to 103% of PFPrA and 40 to 103% of TFA were recovered with Oasis WAX. The sample pH was identified as a key parameter in the extraction process. One-step elution-filtration was introduced in the workflow, in order to remove sorbent particles and minimise sample preparation steps. Validation resulted in limits of quantification for all PFCAs between 0.6 and 26 ng/L. Precision was between 0.7 and 15% and mean recoveries ranged from 83 to 107%. In groundwater samples from sites impacted by per- and polyfluoroalkyl substances (PFASs), PFCA concentrations ranged from 0.056 to 2.2 µg/L. TFA and perfluorooctanoate were the predominant analytes. TFA, however, revealed a more ubiquitous occurrence and was found in concentrations between 0.045 and 17 µg/L in drinking water, groundwater and surface water, which were not impacted by PFASs.

Closing the gap - inclusion of ultrashort-chain perfluoroalkyl carboxylic acids in the total oxidizable precursor (TOP) assay protocol.

An improved protocol of the total oxidizable precursor (TOP) assay was developed for precursors to C2-C14 perfluoroalkyl carboxylic acids (PFCAs) and C4-C8 and C10 perfluoroalkyl sulfonic acids (PFSAs). The proposed protocol was tested and validated for contaminated soil samples. The perfluoroalkyl acids (PFAAs) present in the soil extract solutions after oxidation with persulfate were separated from the inorganic salts by vacuum-assisted drying of the digestion solution followed by solid-liquid extraction of the PFAAs with acetonitrile from the dry residue. Ion chromatography (for C2-C4 PFCAs) and reversed phase liquid chromatography (for all other PFASs), both coupled to tandem mass spectrometry, were used for quantification. High procedural recoveries of PFAAs between 68% and 123% with RSDs between 0.2% and 25% (n = 3) were achieved. The method was validated using selected polyfluoroalkyl phosphoric acid esters (PAPs) and bis-[2-(N-ethyl perfluorooctane-1-sulfonamido)ethyl] phosphoric acid ester (diSAmPAP) as model precursors in pure solutions and in the presence of soil matrix. The oxidation led to characteristic and reproducible PFCA patterns (in the case of PAPs) or PFOA (in the case of diSAmPAP) with total reaction yields between 92 ± 4% and 123 ± 13% (n = 3). The impact of the soil matrix on transformation yields was negligible. In a soil core from a PFAS-polluted agricultural site, precursors were concentrated in the upper 40 cm with long-chain precursors being prevalent. After oxidative digestion, the total molar PFAA-concentrations increased by factors of 1.6 to 5.0. More than 40 cm below ground precursors of TFAA, PFPrA and PFBA accounted for ∼50% of the reaction products, underlining the importance of their inclusion in mass balances based on the TOP assay.

Evaluation of EOC removal processes during artificial recharge through a reactive barrier.

A reactive barrier that consisted of vegetable compost, iron oxide and clay was installed in an infiltration basin to enhance the removal of emerging organic compounds (EOCs) in the recharge water. First-order degradation rates and retardation factors were jointly estimated for 10 compounds using a multilayer reactive transport model, whose flow and conservative transport parameters were previously estimated using hydraulic head values and conservative tracer tests. Reactive transport parameters were automatically calibrated against the concentration of EOCs measured at nine monitoring points. The degradation rate of each compound was estimated for three zones defined according to the redox state, and retardation coefficients were estimated in two zones defined according to the organic matter content. The fastest degradation rates were obtained for the reactive barrier, and the estimated values were similar to or higher than those estimated in column and/or field experiments for most of the compounds (8/10). Estimated retardation coefficients in the reactive barrier were higher than in the rest of the aquifer in most cases (8/10) and higher than those values estimated in previous studies. Based on the results obtained in this study the reactive barrier seems to be able to enhance the removal of EOCs.

Biodegradation of the artificial sweetener acesulfame in biological wastewater treatment and sandfilters.

A considerable removal of the artificial sweetener acesulfame (ACE) was observed during activated sludge processes at 13 wastewater treatment plants (WWTPs) as well as in a full-scale sand filter of a water works. A long-term sampling campaign over a period of almost two years revealed that ACE removal in WWTPs can be highly variable over time. Nitrifying/denitrifying sequencing batch reactors (SBR) as well as aerobic batch experiments with activated sludge and filter sand from a water works confirmed that both activated sludge as well as filter sand can efficiently remove ACE and that the removal can be attributed to biologically mediated degradation processes. The lab results strongly indicated that varying ACE removal in WWTPs is not associated with nitrification processes. Neither an enhancement of the nitrification rate nor the availability of ammonium or the inhibition of ammonium monooxygenase by N-allylthiourea (ATU) affected the degradation. Moreover, ACE was found to be also degradable by activated sludge under denitrifying conditions, while being persistent in the absence of both dissolved oxygen and nitrate. Using ion chromatography coupled with high resolution mass spectrometry, sulfamic acid (SA) was identified as the predominant transformation product (TP). Quantitative analysis of ACE and SA revealed a closed mass balance during the entire test period and confirmed that ACE was quantitatively transformed to SA. Measurements of dissolved organic carbon (DOC) revealed an almost complete removal of the carbon originating from ACE, thereby further confirming that SA is the only relevant final TP in the assumed degradation pathway of ACE. A first analysis of SA in three municipal WWTP revealed similar concentrations in influents and effluents with maximum concentrations of up to 2.3 mg/L. The high concentrations of SA in wastewater are in accordance with the extensive use of SA in acid cleaners, while the degradation of ACE in WWTPs adds only a very small portion of the total load of SA discharged into surface waters. No removal of SA was observed by the biological treatment applied at these WWTPs. Moreover, SA was also stable in the aerobic batch experiments conducted with the filter sand from a water works. Hence, SA might be a more appropriate wastewater tracer than ACE due to its chemical and microbiological persistence, the negligible sorbing affinity (high negative charge density) and its elevated concentrations in WWTP effluents.

Small, mobile, persistent: Trifluoroacetate in the water cycle - Overlooked sources, pathways, and consequences for drinking water supply.

Elevated concentrations of trifluoroacetate (TFA) of more than 100 µg/L in a major German river led to the occurrence of more than 20 µg/L TFA in bank filtration based tap waters. Several spatially resolved monitoring programs were conducted and discharges from an industrial company were identified as the point source of TFA contamination. Treatment options for TFA removal were investigated at full-scale waterworks and in laboratory batch tests. Commonly applied techniques like ozonation or granulated activated carbon filtration are inappropriate for TFA removal, whereas TFA was partly removed by ion exchange and completely retained by reverse osmosis. Further investigations identified wastewater treatment plants (WWTPs) as additional TFA dischargers into the aquatic environment. TFA was neither removed by biological wastewater treatment, nor by a retention soil filter used for the treatment of combined sewer overflows. WWTP influents can even bear a TFA formation potential, when appropriate CF3-containing precursors are present. Biological degradation and ozonation batch experiments with chemicals of different classes (flurtamone, fluopyram, tembotrione, flufenacet, fluoxetine, sitagliptine and 4:2 fluorotelomer sulfonate) proved that there are yet overlooked sources and pathways of TFA, which need to be addressed in the future.

Use of two artificial sweeteners, cyclamate and acesulfame, to identify and quantify wastewater contributions in a karst spring.

The identification and differentiation of different sources of contamination are crucial aspects of risk assessment in water resource protection. This is especially challenging in karst environments due to their highly heterogeneous flow fields. We have investigated the use of two artificial sweeteners, cyclamate and acesulfame, as an indicator set for contamination by wastewater within the rural catchment of a karst spring. The catchment was investigated in detail to identify the sources of artificial sweeteners and quantify their impact. Spring water was analysed following two different but typical recharge events: (1) a rain-on-snow event in winter, when no wastewater overflow from the sewer system was observed, and (2) an intense rainfall event in summer triggering an overflow from a stormwater detention basin. Acesulfame, which is known to be persistent, was quantified in all spring water samples. Its concentrations decreased after the winter event with no associated wastewater spillage but increased during the summer event following a recent input of untreated wastewater. Cyclamate, which is known to be degradable, was only detected following the wastewater inflow incident. The cyclamate signal matched very well the breakthrough of faecal indicator bacteria, indicating a common origin. Knowing the input function, cyclamate was used quantitatively as a tracer in transport modelling and the impact of 'combined sewer overflow' on spring water quality was quantified. Signals from artificial sweeteners were compared to those from bulk parameters (discharge, electrical conductivity and turbidity) and also to those from the herbicides atrazine and isoproturon, which indicate 'old' and 'fresh' flow components, respectively, both originating from croplands. High concentration levels of the artificial sweeteners in untreated wastewater (cyclamate and acesulfame) and in treated wastewater (acesulfame only) make them powerful indicators, especially in rural settings where wastewater input is relatively low, and in karst systems where dilution is often high.