Pharmaceutical residues are commonly detected organic micropollutants in the aquatic environment. Their actual fate in rivers is still incompletely understood as their elimination is highly substance ...specific and studies often report contradictory results. To elucidate the ceiling of attenuation rates of pharmaceuticals in rivers we carried out a study at a river with favorable conditions for the elimination of organic micropollutants.
Experiments were carried out at a small stream in Germany. Composite samples were taken at both ends of a 12.5 km long river stretch located downstream of a sewage treatment plant and analyzed for 10 pharmaceuticals. Moreover, pore water samples were taken and in situ photolysis experiments at several sites within the river stretch were performed to assess the importance of these individual elimination mechanisms.
Pharmaceutical concentration in the surface water at the first sampling site ranged from 3.5 ng L−1 for propranolol to 1400 ng L−1 for diclofenac. In comparison to carbamazepine which was used as persistent tracer, all other pharmaceuticals were attenuated along the river stretch. Their elimination was higher in a sunny, dry weather period (period I) compared to a period with elevated discharge after a heavy rainfall (period II). Overall, the measured elimination rates ranged from 25% for sulfamethoxazole (period II) to 70% for propranolol (period I). Photolysis was only a relevant elimination process for diclofenac and potentially also for sotalol; for these compounds phototransformation half-life times of some hours were determined in the unshaded parts of the river. Biotransformation in the sediments was also an important attenuation process since the concentrations of the other pharmaceuticals in the sediments decreased relative to carbamazepine with depth. For the chiral betablocker metoprolol this biotransformation was also confirmed by a decrease in the enantiomer fractionation from 0.49 at site A to 0.43 at site B and to <0.40 in the deeper sediments.
Display omitted
► The attenuation of pharmaceuticals in a river was studied under best-case conditions. ► Most investigated pharmaceuticals were efficiently attenuated along the river stretch. ► The biotransformation of metoprolol was confirmed using enantiomer-specific analyses.
Pharmaceutical residues are commonly detected micropollutants in the aquatic environment. Biodegradation in sediments is a potentially significant removal process for these compounds in rivers which ...is constrained by the transfer of water and solutes into the sediment. The aim of this study was to determine the combined effect of flow velocity and sediment dynamics and thus of water-sediment interactions on the attenuation of 6 acidic pharmaceuticals. We carried out experiments with river water and sediment in a bench-scale annular flume at two different hydraulic boundary conditions (flat sediment surface vs moving sediment). The effective biodegradation half-lives of 4 compounds (diclofenac, bezafibrate, ibuprofen, naproxen) were in the range of 2.5 to 18.6 days and were much shorter when the exchange of surface and pore water was fast. For gemfibrozil, a half-life of 10.5 d was determined in the experiment with moving sediment, whereas no degradation was observed with flat sediment bed. These findings can be attributed to the limited transfer of water and solutes into the sediment at low flow velocity and flat sediment bed which rapidly induced anaerobic conditions in the sediment. The only compound that was efficiently removed in deeper, anoxic sediment layers was naproxen. The calculated half-life distances in rivers ranged from 53 to 278 km. Our results indicate that it could be favorable to increase the rate of exchange between surface and pore water during river restoration to enhance the attenuation of organic micropollutants like acidic pharmaceuticals.
•Development and validation of a LC–HRMS (QTOF) method based also on nontarget analysis.•Process evaluation of biological wastewater treatment based on nontarget screening.•Comprehensive workflow for ...nontarget screening – including data acquisition and post-processing.
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.
While substantial knowledge on the occurrence of pharmaceuticals in the environment is available, their behavior and fate in surface waters is still poorly understood. Therefore, the aims of this ...study were to analyze the short-term dynamics of selected pharmaceuticals along a 13.6 km long river stretch downstream of a wastewater treatment plant (WWTP), and to quantify their attenuation by a mass balance approach. Four acidic pharmaceuticals (bezafibrate, clofibric acid, diclofenac, naproxen) with different attenuation properties were measured over a period of three weeks at high temporal resolution, and in situ photolysis experiments were carried out. The average concentrations of pharmaceuticals were between 9 ± 4 and 339 ± 133 ng L−1, corresponding to loads between 1.9 ± 1.2 and 63 ± 37 g d−1 (n = 134). The temporal dynamics of pharmaceuticals was closely related to discharge of the WWTP and precipitation, and highest concentrations were observed at the beginning of a discharge event. During a dry period, naproxen was eliminated along the river stretch with a dissipation time (DT50) of 3.6 ± 2.1 days while the other compounds did not exhibit significant attenuation. As photolysis and other abiotic processes were of limited quantitative relevance, the attenuation of naproxen can most likely be attributed to biotransformation.
Strategies to determine the removal efficiency of micropollutants in wastewater treatment plants (WWTPs) are widely discussed. Especially the evaluation of the potential benefit of further advanced ...treatment steps such as an additional tertiary treatment based on ozonation or activated carbon have come into focus. Such evaluation strategies are often based on the removal behavior of known micropollutants via target or suspected analysis. The utilization of nontarget analysis is considered to lead to a more comprehensive picture as also unknown or not expected micropollutants are analyzed. Here, the results of an evaluation via target and nontarget analysis were compared for biological treatment (BT) processes of eleven full-scale WWTPs and three different post-treatments (PTs): one sand filter (SF) and two granular activated carbon (GAC) filters. The similarity of the determined removals from target and nontarget analysis of the BTs increased significantly by excluding easily degradable "features" from the nontarget evaluation. A similar ranking of the removal trends for the BTs could also be achieved by comparing this new subset of nontarget features with a set of nine readily to moderately biodegradable micropollutants. This observation suggests that a performance ranking of BTs based either on target or nontarget analysis is plausible. In contrast to the BTs, the evaluation of the three PTs revealed that the difference of feature removal between SF and the two GACs was small, but large for the target analytes with substantially higher removal effciencies for the GACs compared to the SF. In addition to the removal behavior, the nontarget analysis provided further information about the number and quantity of transformation products (TPs) in the effluent from the BTs. For all BTs more than half (55–67%) of the features detected in the effluent were not found in the influent. A comparable proportion of TPs was also detected after GAC and sand filtration due to their microbial activities.
Display omitted
•Nontarget analysis (NT) is an appropriate tool to evaluate wastewater processes.•About 50% of the compounds detected after the biological treatment are formed by transformation.•NT revealed that GAC filters have a significant potential for the biological transformation of compounds.
Non-target screening (NTS) including suspect screening with high resolution mass spectrometry has already shown its feasibility in detecting and identifying emerging contaminants, which subsequently ...triggered exposure mitigating measures. NTS has a large potential for tasks such as effective evaluation of regulations for safe marketing of substances and products, prioritization of substances for monitoring programmes and assessment of environmental quality. To achieve this, a further development of NTS methodology is required, including: (i) harmonized protocols and quality requirements, (ii) infrastructures for efficient data management, data evaluation and data sharing and (iii) sufficient resources and appropriately trained personnel in the research and regulatory communities in Europe. Recommendations for achieving these three requirements are outlined in the following discussion paper. In particular, in order to facilitate compound identification it is recommended that the relevant information for interpretation of mass spectra, as well as about the compounds usage and production tonnages, should be made accessible to the scientific community (via open-access databases). For many purposes, NTS should be implemented in combination with effect-based methods to focus on toxic chemicals.
The fate of pharmaceutically active substances in rivers is still only incompletely understood, especially as the knowledge transfer from laboratory experiments to the real world is complicated by ...factors like turbidity, hydrodynamics, or heterogeneity. Therefore, we performed a tracer test with pharmaceutically active substances to study their fate and the importance of individual attenuation mechanisms in situ. The experiment was carried out at a small stream in central Sweden. Two dye tracers and six pharmaceuticals were injected as Dirac pulse and water was sampled at five downstream sites along a 16-km-long river reach. Ibuprofen and clofibric acid were the only compounds which were eliminated along the study reach at half-life times of 10 h and 2.5 d, respectively. Based on the shape of the breakthrough curves and the low hydraulic conductivity of the river bed, we can assume that exchange of river water with the hyporheic zone was minor. Thus, the contribution of processes in the hyporheic zone to the attenuation of pharmaceuticals was low. We hypothesize that ibuprofen and clofibric acid were transformed by in-stream biofilms growing on submerged macrophytes and at the water–sediment interface. Phototransformation and sorption were ruled out as major attenuation processes. No attenuation of bezafibrate, diclofenac, metoprolol, and naproxen was observed.
Laboratory-scale incubation experiments in water/sediment systems were conducted to test the transformation behavior of the anticonvulsant gabapentin (GBP) under different environmental conditions ...(aerobic, anaerobic, with abiotic controls). GBP was transformed by biological processes as it was eliminated quickly under aerobic conditions (dissipation time 50% of initial concentration (DT50): 2–7 days) whereas no decrease was observed under anaerobic conditions. Measurements via high resolution mass spectrometry (LC-Orbitrap-MS) revealed eight biological transformation products (TPs). Three of them were identified with reference standards (GBP-Lactam, TP186, TP213), while for the other five TPs tentative structures were proposed from information by MS2/MS3 experiments. Furthermore, the quantitatively most relevant TP GBP-Lactam was formed via intramolecular amidation (up to 18% of initial GBP concentration). Incubation experiments with GBP-Lactam revealed a higher stability against biotic degradation (DT50: 12 days) in contrast to GBP, while it was stable under anaerobic and abiotic conditions. Besides GBP, GBP-Lactam was detected in surface water in the μg L−1 range. Finally, GBP and GBP-Lactam were found in potable water with concentrations up to 0.64 and 0.07 μg L−1, respectively. According to the elevated environmental persistence of GBP-Lactam compared to GBP and its presumed enhanced toxicity, we recommend to involve GBP-Lactam into monitoring programs.
Display omitted
•In water/sediment systems Gabapentin was biodegraded under aerobic conditions and was persistent under anaerobic conditions.•The transformation pathway of Gabapentin could be elucidated.•Gabapentin and gabapentin-Lactam were detected in surface water, ground water and drinking water.
Benzotriazole UV stabilizers (BUVSs) are widely applied in plastics to prevent discoloration and to enhance product stability. This study describes for the first time the occurrence of nine different ...lipophilic BUVSs (UV-326, UV-320, UV-329, UV-350, UV-328, UV-327, UV-928, UV-234 and UV-360) in sediment, suspended particulate matter (SPM) and bream liver samples of German rivers. All investigated BUVSs were detected in sediments and SPM at concentrations in the low ng/g dry weight (dw) range. The so far rarely analyzed compound UV-360 as well as UV-326 were the predominant BUVSs in sediments and SPM from the river Rhine reaching maximum concentrations of 62 and 44 ng/g dw, respectively. Five BUVSs were also confirmed to bioaccumulate in bream liver, but neither UV-360 nor UV-326 was detected above the limit of quantification (LOQ). In contrast, highest concentrations in bream liver were determined for UV-327 (65 ng/g dw) and UV-328 (40 ng/g dw).
A retrospective time trend analysis of BUVSs in SPM from two sites (river Rhine, 2005 to 2013; river Saar, 2006 to 2013) revealed increasing contamination levels of UV-329 and decreasing levels of UV-320 and UV-350. At one site (river Rhine) time trends of BUVS concentrations were also investigated in bream liver (1995–2013) and supported a considerably reduced exposure to UV-350.
A first assessment of the environmental fate of BUVSs by sediment-water batch systems revealed a rapid partitioning into the sediment and no considerable degradation within 100 d.
Display omitted
•Benzotriazole UV filters (BUVSs) are ubiquitous contaminants in German rivers.•BUVSs were detected in sediment, suspended particulate matter and bream liver samples.•Time trend analysis was performed for an estimation of future contamination levels.•Increasing contamination levels were observed for UV-329, UV-234 and UV-928.•None of the BUVSs were degraded in sediment-water batch systems within 100 d.
This study describes for the first time the occurrence of nine benzotriazole UV filters in sediment, suspended particulate matter and bream liver samples of German rivers and provides new insights on expected future contamination levels and persistency by retrospective time trend monitoring and laboratory batch experiments.
•The most relevant pantoprazole-related compound (M1) for monitoring was identified.•M1 occurs ubiquitously in surface water and wastewaters in Germany.•Environmental concentrations of M1 were much ...higher than those of parent compound.•Activated carbon filtration considerably improves the removal of M1 from wastewater.•Several ozonation products of M1 in wastewater were characterized.
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.
Display omitted
PDF
