Climate change triggered planktonic cyanobacterial blooms in a regulated temperate river.

Harmful algae blooms are a rare phenomenon in rivers but seem to increase with climate change and river regulation. To understand the controlling factors of cyanobacteria blooms that occurred between 2017 and 2020 over long stretches (> 250 km) of the regulated Moselle River in Western Europe, we measured physico-chemical and biological variables and compared those with a long-term dataset (1997-2016). Cyanobacteria (Microcystis) dominated the phytoplankton community in the late summers of 2017-2020 (cyano-period) with up to 110 µg Chlorophyll-a/L, but had not been observed in the river in the previous 20 years. From June to September, the average discharge in the Moselle was reduced to 69-76% and water temperature was 0.9-1.8 °C higher compared to the reference period. Nitrogen (N), phosphorus (P) and silica (Si) declined since 1997, albeit total nutrient concentrations remained above limiting conditions in the study period. Cyanobacterial blooms correlated best with low discharge, high water temperature and low nitrate. We conclude that the recent cyanobacteria blooms have been caused by dry and warm weather resulting in low flow conditions and warm water temperature in the regulated Moselle. Under current climate projections, the Moselle may serve as an example for the future of regulated temperate rivers.

From genes to toxins: Profiling Prymnesium parvum during a riverine harmful algal bloom.

Blooms of Prymnesium parvum, a unicellular alga globally distributed in marine and brackish environments, frequently result in massive fish kills due to the production of toxins called prymnesins by this haptophyte. In August 2022, a harmful algal bloom (HAB) of this species occurred in the lower Oder River (Poland and Germany), which caused mass mortalities of fish and other organisms. This HAB was linked to low discharge of the Oder and mining activities that caused a significant increase in salinity. In this context, we report on the molecular detection and screening of this haptophyte and its toxins in environmental samples and clonal cultures derived thereof. Both conventional PCR and droplet digital PCR assays reliably detected P. parvum in environmental samples. eDNA metabarcoding using the V4 region of the 18S rRNA gene revealed a single Prymnesium sequence variant, but failed to identify it to species level. Four clonal cultures established from environmental samples were unambiguously identified as P. parvum by molecular phylogenetics (near full-length 18S rRNA gene) and light microscopy. Phylogenetic analysis (ITS1-5.8S-ITS2 marker region) placed the cultured phylotype within a clade containing other P. parvum strains known to produce B-type prymnesins. Toxin-screening of the cultures using liquid chromatography-electrospray ionization - time of flight mass spectrometry identified B-type prymnesins, which were also detected in extracts of filter residues from water samples of the Oder collected during the HAB. Overall, our investigation provides a detailed characterization of P. parvum, including their prymnesins, during this HAB in the Oder River, contributing valuable insights into this ecological disaster. In addition, the droplet digital PCR assay established here will be useful for future monitoring of low levels of P. parvum on the Oder River or any other salt-impacted and brackish water bodies.

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.

Capturing the oxic transformation of iopromide - A useful tool for an improved characterization of predominant redox conditions and the removal of trace organic compounds in biofiltration systems?

The biological degradation of many trace organic compounds has been reported to be strongly redox dependent. The traditional characterization of redox conditions using the succession of inorganic electron acceptors such as dissolved oxygen and nitrate falls short in accurately describing the critical transition state between oxic and suboxic conditions. Novel monitoring strategies using intrinsic redox tracers might be suitable to close that gap. This study investigated the potential use of the successive biological transformation of the iodinated contrast medium iopromide as an intrinsic tracer of prevailing redox conditions in biofiltration systems. Iopromide degradation in biofiltration systems was monitored by quantifying twelve known biological transformation products formed under oxic conditions. A novel dimensionless parameter (TIOP) was introduced as a measure for the successive transformation of iopromide. A strong correlation between the consumption of dissolved oxygen and iopromide transformation emphasized the importance of general microbial activity on iopromide degradation. However, results disproved a direct correlation between oxic (>1 mg/L O2) and suboxic (<1 mg/L O2) conditions and the degree of iopromide transformation. Results indicated that besides redox conditions also the availability of biodegradable organic substrate affects the degree of iopromide transformation. Similar behavior was found for the compounds gabapentin and benzotriazole, while the oxic degradation of metoprolol remained stable under varying substrate conditions.

Nontarget Analysis via LC-QTOF-MS to Assess the Release of Organic Substances from Polyurethane Coating.

A novel approach was investigated for the assessment of leaching from a one-component polyurethane (1C-PU) coating used for hydraulic structures using nontarget analysis via LC-QTOF-MS. Leaching behavior of the 1C-PU coating was studied using experiments in which the coating was exposed to water for defined periods (6 h, 24 h, 3 d, 14 d). Three hardening durations for the 1C-PU coating were tested (0 h, 24 h, 14 d) as well as two water matrices (ultrapure water and river water), including a successive water renewal. Dissolved organic carbon, total nitrogen bound and nontarget measurements via LC-QTOF-MS showed that under all tested conditions organic substances were leached out of the 1C-PU coating. The shorter the hardening duration and the longer the leaching duration, the higher were the number and quantities of the eluted substances, while the influence of the water matrix was minor with respect to substance elution. Based on the MS2 spectra from the LC-QTOF-MS measurements, 30 substances released from the 1C-PU coating were tentatively identified. These substances belong to five chemical groups: derivatives of (i) N-(tosyl)carbamate, (ii) p-toluenesulfonamide (PTSA), (iii) 4,4'-methylenediphenyl diisocyanate (4,4'-MDI), (iv) toluenediisocyanate (TDI), and (v) oligo(ethylene) ([C2H4O]n) as well as p-toluenesulfonic acid. The identity of seven substances was confirmed by authentic reference standards, all of which exhibited an elevated bacterial toxicity to Aliivibrio fischeri. p-Toluenesulfonic acid was present in a German canal (Teltowkanal) with concentrations of up to 11 µg L-1.

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.

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.

Identification of transformation products during advanced oxidation of diatrizoate: Effect of water matrix and oxidation process.

Removal of micropollutants from reverse osmosis (RO) brines of wastewater desalination by oxidation processes is influenced by the scavenging capacity of brines components, resulting in the accumulation of transformation products (TPs) rather than complete mineralization. In this work the iodinated contrast media diatrizoate (DTZ) was used as model compound due to its relative resistance to oxidation. Identification of TPs was performed in ultrapure water (UPW) and RO brines applying nonthermal plasma (NTP) and UVA-TiO2 as oxidation techniques. The influence of main RO brines components in the formation and accumulation of TPs, such as chloride, bicarbonate alkalinity and humic acid, was also studied during UVA-TiO2. DTZ oxidation pattern in UPW resulted similar in both UVA-TiO2 and NTP achieving 66 and 61% transformation, respectively. However, DTZ transformation in RO brines was markedly lower in UVA-TiO2 (9%) than in NTP (27%). These differences can be attributed to the synergic effect of RO brines components during NTP. Moreover, reactive species other than hydroxyl radical contributed to DTZ transformation, i.e., direct photolysis in UVA-TiO2 and direct photolysis + O3 in NTP accounted for 16 and 23%, respectively. DTZ transformation led to iodide formation in both oxidation techniques but it further oxidized to iodate by ozone in NTP. In total 14 transformation products were identified in UPW of which 3 were present only in UVA-TiO2 and 2 were present exclusively in NTP; 5 of the 14 TPs were absent in RO brines. Five of them were new and were denoted as TP-474A/B, TP-522, TP-586, TP-602, TP-628. TP-522 (mono-chlorinated) was elucidated only in presence of high chloride titer-synthetic water matrix in NTP, most probably formed by active chlorine species generated in situ. TPs accumulation in RO brines was markedly different in comparison to UPW. This denotes the influence of RO brines components in the formation of reactive species that could further attack DTZ/TPs and/or scavenging performed by these brine components that could limit further TPs degradation. Five plausible degradation pathways are proposed for DTZ transformation in UPW.

Development and validation of a generic nontarget method based on liquid chromatography - high resolution mass spectrometry analysis for the evaluation of different wastewater treatment options.

A comprehensive workflow for using nontarget approaches as process evaluation tools was implemented, including data acquisition based on a LC-HRMS (QTOF) system using direct injection and data post-processing for the peak recognition in "full scan" data. Both parts of the approach were not only developed and validated in a conventional way using the suspected analysis of a set of spiked known micropollutants but also the nontarget analysis of a wastewater treatment plant (WWTP) effluent itself was utilized to consider a more environmental relevant range of analytes. Hereby, special focus was laid on the minimization of false positive results (FPs) during the peak recognition. The optimized data post-processing procedure reduced the percentage of FPs from 42% to 10-15%. Furthermore, the choice of a suitable chromatography for biological treated wastewater systems was also discussed during the method development. The workflow paid also attention to differences in the performance levels of the LC-HRMS system by implementation of an adaption system for intensity variations comparing different measurements dates or different instruments. The application of this workflow on wastewater samples from a municipal WWTP revealed that more than 91% compounds were eliminated by the biological treatment step and that the received effluent contained 55% newly formed potential transformation products.

Electrochemical oxidation of tramadol in low-salinity reverse osmosis concentrates using boron-doped diamond anodes.

The electrochemical treatment of low-salinity reverse osmosis (RO) concentrates was investigated using tramadol (100 µM) as a model substance for persistent organic contaminants. Galvanostatic degradation experiments using boron-doped diamond electrodes at different applied currents were conducted in RO concentrates as well as in ultra-pure water containing either sodium chloride or sodium sulfate. Kinetic investigations revealed a significant influence of in-situ generated active chlorine besides direct anodic oxidation. Therefore, tramadol concentrations decreased more rapidly at elevated chloride content. Nevertheless, reduction of total organic carbon (TOC) was found to be comparatively low, demonstrating that transformation rather than mineralization was taking place. Early stage product formation could be attributed to both direct and indirect processes, including demethylation, hydroxylation, dehydration, oxidative aromatic ring cleavage and halogenation reactions. The latter led to various halogenated derivatives and resulted in AOX (adsorbable organic halogens) formation in the lower mg/L-range depending on the treatment conditions. Characterisation of transformation products (TPs) was achieved via MS(n) experiments and additional NMR measurements. Based on identification and quantification of the main TPs in different matrices and on additional potentiostatic electrolysis, a transformation pathway was proposed.

Occurrence of venlafaxine, other antidepressants and selected metabolites in the Rhine catchment in the face of climate change.

Fate and occurrence of 4 selective serotonin reuptake inhibitors, one serotonin-noradrenergic reuptake inhibitor and one noradrenergic-dopamineric reuptake inhibitor and their human metabolites were determined in a German municipal wastewater treatment plant as well as in the Rhine River and selected tributaries. The enantiomeric fractions of venlafaxine and its metabolites were not altered during wastewater treatment and were similar in all river samples underlining that no appreciable biodegradation occurs. In the Rhine catchment area highest concentrations were detected for venlafaxine, citalopram and their human metabolites. Projected future climate change would lead to an increased portion of treated wastewater in rivers due to reduced discharges during low flow situations by the end of the 21st century. However, the effect of climate change on the pattern and concentrations of antidepressants is predicted to be of minor importance in comparison to altered consumption quantities caused by demographic developments and changes in life styles.

Reactive transport of iomeprol during stream-groundwater interactions.

The transport and biochemical transformations of the iodinated X-ray contrast medium (ICM) iomeprol were studied at the stream/groundwater interface. During a one-month field experiment piezometric pressure heads, temperatures, and concentrations of redox-sensitive species, iomeprol and 15 of its transformation products (TPs) were collected in stream- and groundwater. The data set was analyzed and transformation processes and rates identified by comparing conservative and reactive transport simulations. ICM and TP transformations were simulated as a cometabolic process during organic carbon degradation. Using iomeprol/TPs ratios as calibration constrain mitigated the uncertainties associated with the high variability of the ICM wastewater discharge into the investigated stream. The study provides evidence that biodegradation of ICM occurs at the field-scale also for predominantly denitrifying conditions. Under these anaerobically dominated field conditions shortest simulated half-life (21 days) was in the same range as previously reported laboratory-determined half-lives for aerobic conditions.

Kinetic and mechanistic investigations of the oxidation of tramadol by ferrate and ozone.

The kinetics and oxidation products (OPs) of tramadol (TRA), an opioid, were investigated for its oxidation with ferrate (Fe(VI)) and ozone (O(3)). The kinetics could be explained by the speciation of the tertiary amine moiety of TRA, with apparent second-order rate constants of 7.4 (±0.4) M(-1) s(-1) (Fe(VI)) and 4.2 (±0.3) × 10(4) M(-1) s(-1) (O(3)) at pH 8.0, respectively. In total, six OPs of TRA were identified for both oxidants using Qq-LIT-MS, LTQ-FT-MS, GC-MS, and moiety-specific chemical reactions. In excess of oxidants, these OPs can be further transformed to unidentified OPs. Kinetics and OP identification confirmed that the lone electron pair of the amine-N is the predominant site of oxidant attack. An oxygen transfer mechanism can explain the formation of N-oxide-TRA, while a one-electron transfer may result in the formation of N-centered radical cation intermediates, which could lead to the observed N-dealkylation, and to the identified formamide and aldehyde derivatives via several intermediate steps. The proposed radical intermediate mechanism is favored for Fe(VI) leading predominantly to N-desmethyl-TRA (ca. 40%), whereas the proposed oxygen transfer prevails for O(3) attack resulting in N-oxide-TRA as the main OP (ca. 90%).

Occurrence of iodinated X-ray contrast media and their biotransformation products in the urban water cycle.

A LC tandem MS method was developed for the simultaneous determination of four iodinated X-ray contrast media (ICM) and 46 ICM biotransformation products (TPs) in raw and treated wastewater, surface water, groundwater, and drinking water. Recoveries ranged from 70% to 130%, and limits of quantification (LOQ) varied between 1 ng/L and 3 ng/L for surface water, groundwater and drinking water, and between 10 ng/L and 30 ng/L for wastewater. In a conventional wastewater treatment plant, iohexol, iomeprol, and iopromide were transformed to >80%, while iopamidol was transformed to 35%. In total, 26 TPs were detected above their LOQ in WWTP effluents. A significant change in the pattern of ICM TPs was observed after bank filtration and groundwater infiltration under aerobic conditions. Predominately, these TPs are formed at the end of the microbial transformation pathways in batch experiments with soil and sediment. These polar ICM TPs, such as iohexol TP599, iomeprol TP643, iopromide TP701A, and iopromide TP643, were not or only partially removed during drinking water treatment. As a consequence, several ICM TPs were detected in drinking water, at concentration levels exceeding 100 ng/L, with a maximum of 500 ng/L for iomeprol TP687.

Biotransformation of selected iodinated X-ray contrast media and characterization of microbial transformation pathways.

Iodinated X-ray contrast media (ICM) are commonly detected in the aquatic environment at concentrations up to the low microgram per liter range. In this study, the biotransformation of selected ICM (diatrizoate, iohexol, iomeprol, and iopamidol) in aerobic soil-water and river sediment-water batch systems was investigated. In addition, microbial transformation pathways were proposed. Diatrizoate, an ionic ICM, was not biotransformed, while three nonionic ICM were transformed into several biotransformation products (TPs) at neutral pH. Iohexol and iomeprol were biotransformed to eleven TPs and fifteen TPs, respectively, while eight TPs were detected for iopamidol. Since seven of the TPs detected during biotransformation had not been previously identified, mass fragmentation experiments were completed to elucidate the chemical structures. Oxidation of primary alcoholic moieties, cleavage of the N-C bonds (i.e., deacetylation and removal of hydroxylated propanoic acids), and decarboxylation are potential reactions that can explain the formation of the identified TPs. Iohexol and iomeprol had similar biotransformation rates, while iopamidol was biotransformed slower and to a lesser extent. A LC tandem MS method confirmed the presence of ICM TPs in aqueous environmental samples. Fifteen of the ICM TPs were even detected in drinking water with concentrations up to 120 ng/L.

Multistep approach for the structural identification of biotransformation products of iodinated X-ray contrast media by liquid chromatography/hybrid triple quadrupole linear ion trap mass spectrometry and (1)H and (13)C nuclear magnetic resonance.

This study investigated the application of a hybrid triple quadrupole linear ion trap mass spectrometer (Qq-LIT-MS) in combination with NMR to elucidate the chemical structures of 27 biotransformation products (TPs) of the nonionic iodinated X-ray contrast media (ICM), iohexol, iomeprol, and iopamidol, formed in contact with soil. The combination of MS(2) and MS(3) spectra with Qq-LIT-MS was essential to determine the MS fragmentation pathways crucial for structural elucidation. (1)H and (13)C NMR analyses were needed to confirm the chemical structures of TPs proposed by MS fragmentation. Biotransformation occurred exclusively at the side chains of the iodinated X-ray contrast media, while the iodinated benzene ring remained unaltered. Several of the newly identified TPs of the ICM were found in surface water, groundwater, and even drinking water. Concentrations as high as 1450 +/- 110 ng/L (iomeprol TP629) were detected in groundwater that is influenced by wastewater infiltration, and as high as 289 +/- 41 ng/L (iomeprol TP643) in drinking water.

Transformation of the X-ray contrast medium iopromide in soil and biological wastewater treatment.

In water/soil systems, the iodinated contrast medium iopromide was quantitatively biotransformed into several transformation products (TPs). Twelve TPs were identified via HPLC-UV and LC tandem MS. The chemical structures of the TPs were elucidated via fragmentation in MS2 and MS3 of LC tandem MS with a linear ion trap and 1H and 13C NMR analyses. All TPs exhibited transformations at the side chains containing either carboxylic moieties and/or primary and secondary amide moieties, while the triiodoisophthalic acid structure remained unaltered. A transformation pathway was proposed based on the sequence of TP formation in aerobic batch experiments. Additionally, the occurrence of iopromide TPs was investigated in native water samples. All TPs identified were found in municipal WWTP effluents because of their formation during biological wastewater treatment with maximum concentrations of up to 3.7 +/- 0.9 microg/L (TP 819). Predominantly, those TPs were present at higher concentrations in WWTP effluents which were formed at the beginning of the transformation pathway. Furthermore, four TPs formed at the end of the transformation pathway (TP 759, 701A/B, and 643) were also found in bank filtrate up to 0.050 microg/L and in groundwater of an wastewater irrigation area up to 4.6 microg/L.