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Although diclofenac ranks among the most frequently detected pharmaceuticals in the urban water cycle, its environmental transformation reactions remain imperfectly understood. Biodegradation-induced changes in 15 N/ 14 N ratios (ε N = -7.1‰ ± 0.4‰) have indicated that compound-specific isotope analysis (CSIA) may detect diclofenac degradation. This singular observation warrants exploration for further transformation reactions. The present study surveys carbon and nitrogen isotope fractionation in other environmental and engineered transformation reactions of diclofenac. While carbon isotope fractionation was generally small, observed nitrogen isotope fractionation in degradation by MnO 2 (ε N = -7.3‰ ± 0.3‰), photolysis (ε N = +1.9‰ ± 0.1‰), and ozonation (ε N = +1.5‰ ± 0.2‰) revealed distinct trends for different oxidative transformation reactions. The small, secondary isotope effect associated with ozonation suggests an attack of O 3 in a molecular position distant from the N atom. Model reactants for outer-sphere single electron transfer generated large inverse nitrogen isotope fractionation (ε N = +5.7‰ ± 0.3‰), ruling out this mechanism for biodegradation and transformation by MnO 2 . In a river model, isotope fractionation-derived degradation estimates agreed well with concentration mass balances, providing a proof-of-principle validation for assessing micropollutant degradation in river sediment. Our study highlights the prospect of combining CSIA with transformation product analysis for a better assessment of transformation reactions within the environmental life of diclofenac.

A considerable knowledge gap exists with respect to the fate and environmental relevance of transformation products (TPs) of polar organic micropollutants in surface water. To narrow this gap we investigated the fate of 20 parent compounds (PCs) and 11 characteristic TPs in four wastewater-impacted rivers. Samples were obtained from time-integrated active sampling as well as passive sampling using polar organic chemical integrative samplers (POCIS). Seventeen out of the 20 PCs were detected in at least one of the rivers. All the PCs except acesulfame, carbamazepine, and fluconazole were attenuated along the studied river stretches, with the largest decrease found in the smallest river which had an intense surface water-pore water exchange. Seven TPs were detected, all of which were already present directly downstream of the WWTP outfall, suggesting that the WWTPs were a major source of TPs to the recipients. For anionic compounds, attenuation was the highest in the two rivers with the lowest discharge, while the pattern was not as clear for neutral or cationic compounds. For most compounds the results obtained from active sampling were not significantly different from those using POCIS, demonstrating that the cost and labor efficient POCIS is suitable to determine the attenuation of organic micropollutants in rivers.

Chemical benchmarking was used to investigate the temporal variation of the persistence of chemical contaminants in a Swedish lake. The chemicals studied included 12 pharmaceuticals, an artificial sweetener, and an X-ray contrast agent. Measurements were conducted in late spring, late autumn, and winter. The transformation half-life in the lake could be quantified for 7 of the chemicals. It ranged from several days to hundreds of days. For 5 of the chemicals (bezafibrate, climbazole, diclofenac, furosemide, and hydrochlorothiazide), the measured persistence was lower in late spring than in late autumn. This may have been caused by lower temperatures and/or less irradiation during late autumn. The seasonality in chemical persistence contributed to changes in chemical concentrations in the lake during the year. The impact of seasonality of persistence was compared with the impact of other important variables determining concentrations in the lake: chemical inputs and water flow/dilution. The strongest seasonal variability in chemical concentration in lake water was observed for hydrochlorothiazide (over a factor of 10), and this was attributable to the seasonality in its persistence.

The hyporheic zone—the transition region beneath and alongside the stream bed—is a central compartment for attenuation of organic micropollutants in rivers. It provides abundant sorption sites and excellent conditions for biotransformation. We used a bench-scale flume to study the fate of 19 parent pharmaceuticals (PPs) and the formation of 11 characteristic transformation products (TPs) under boundary conditions similar to those in hyporheic zones. The persistence of PPs ranged from readily degradable with a dissipation half-life (DT50) as short as 1.8 days (acetaminophen, ibuprofen) to not degradable (chlorthalidone, fluconazole). The temporal and spatial patterns of PP and TP concentrations in pore water were heterogeneous, reflecting the complex hydraulic and biogeochemical conditions in hyporheic zones. Four TPs (carbamazepine-10,11-epoxide, metoprolol acid, 1-naphthol, and saluamine) were exclusively formed in the sediment compartment and released to surface water, highlighting their potential to be used as indicators for characterizing hyporheic transformation of micropollutants in streams. The accumulation of certain TPs over the experimental period illustrates that we might face a peak of secondary contamination by TPs far from the point of release of the original contaminants into a stream. Such TPs should be considered as priority candidates for a higher-tier environmental risk assessment.

It is challenging to measure the persistence of chemicals under field conditions. In this work, two approaches for measuring persistence in the field were compared: the chemical mass balance approach, and a novel chemical benchmarking approach. Ten pharmaceuticals, an X-ray contrast agent, and an artificial sweetener were studied in a Swedish lake. Acesulfame K was selected as a benchmark to quantify persistence using the chemical benchmarking approach. The 95% confidence intervals of the half-life for transformation in the lake system ranged from 780-5700 days for carbamazepine to <1-2 days for ketoprofen. The persistence estimates obtained using the benchmarking approach agreed well with those from the mass balance approach (1-21% difference), indicating that chemical benchmarking can be a valid and useful method to measure the persistence of chemicals under field conditions. Compared to the mass balance approach, the benchmarking approach partially or completely eliminates the need to quantify mass flow of chemicals, so it is particularly advantageous when the quantification of mass flow of chemicals is difficult. Furthermore, the benchmarking approach allows for ready comparison and ranking of the persistence of different chemicals.

Of the tens of thousands of chemicals in use, only a small fraction have been analyzed in environmental samples. To effectively identify environmental contaminants, methods to prioritize chemicals for analytical method development are required. We used a high-throughput model of chemical emissions, fate, and bioaccumulation to identify chemicals likely to have high concentrations in specific environmental media, and we prioritized these for target analysis. This model-based screening was applied to 215 organosilicon chemicals culled from industrial chemical production statistics. The model-based screening prioritized several recognized organosilicon contaminants and generated hypotheses leading to the selection of three chemicals that have not previously been identified as potential environmental contaminants for target analysis. Trace analytical methods were developed, and the chemicals were analyzed in air, sewage sludge, and sediment. All three substances were found to be environmental contaminants. Phenyl-tris(trimethylsiloxy)silane was present in all samples analyzed, with concentrations of ∼50 pg m(-3) in Stockholm air and ∼0.5 ng g(-1) dw in sediment from the Stockholm archipelago. Tris(trifluoropropyl)trimethyl-cyclotrisiloxane and tetrakis(trifluoropropyl)tetramethyl-cyclotetrasiloxane were found in sediments from Lake Mjøsa at ∼1 ng g(-1) dw. The discovery of three novel environmental contaminants shows that models can be useful for prioritizing chemicals for exploratory assessment.

As ombrotrophic peat bogs receive only atmospheric input of contaminants, they have been identified as suitable natural archives for investigating historical depositions of airborne pollutants. To elucidate their suitability for determining the historical atmospheric contamination with perfluoroalkyl substances (PFAS), two peat cores were sampled at Mer Bleue, a bog located close to Ottawa, Canada. Peat cores were segmented, dried, and analyzed in duplicate for 25 PFASs (5 perfluororalkyl sulfonates (PFSAs), 13 perfluoroalkyl carboxylates (PFCAs), 7 perfluororalkyl sulfonamido substances). Peat samples were extracted by ultrasonication, cleaned up using a QuEChERS method, and PFASs were measured by HPLC-MS/MS. Twelve PFCAs and PFSAs were detected regularly in peat samples with perfluorooctane sulfonate (85-655 ng kg(-1)), perfluorooctanoate (150-390 ng kg(-1)), and perfluorononanoate (45-320 ng kg(-1)) at highest concentrations. Because of post depositional relocation processes within the peat cores, true or unbiased deposition fluxes (i.e., not affected by post depositional changes) could not be calculated. Apparent or biased deposition rates (i.e., affected by post depositional changes) were lower than measured/calculated deposition rates for similar urban or near-urban sites. Compared to PFAS production, PFAS concentration and deposition maxima were shifted about 30 years toward the past and some analytes were detected even in the oldest segments from the beginning of the 20th century. This was attributed to PFAS mobility in the peat profile. Considerable differences were observed between both peat cores and different PFASs. Overall, this study demonstrates that ombrotrophic bogs are not suited natural archives to provide authentic and reliable temporal trend data of historical atmospheric PFAS deposition.

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.

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 (DT(50)) 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.

Sulfonamide antibiotics are widely used in human and veterinary medicine. After their application, they are excreted in unchanged as well as in metabolized form. Due to incomplete elimination in wastewater treatment plants, they can be emitted into surface water. The environmental fate of both parent compounds and metabolites is currently unknown. The aim of this study was to determine the biodegradation potential of river sediment for the sulfonamide sulfamethoxazole (SMX) and its two major human metabolites N4-acetyl-SMX and SMX-N1-glucuronide using a water sediment test system. Each compound was tested in a separate series together with sterile and "water only" controls. All three compounds were efficiently removed from the test system by biodegradation in the sediment. Only for SMX-N1-glucuronide, a substantial removal in the absence of sediment was determined. Dissipation times from the aqueous phase (DT50) between 8.5 and 17.2 days were measured. Sorption to sediment was of minor importance due to the slightly basic pH of the test system. By the application of a mathematical model, biodegradation half-lives in sediment between 3.3 and 25.6 h were calculated for SMX and its metabolites. The results of this study highlight the capability of native river sediment for degrading sulfonamide antibiotics, but also the potential of human metabolites to retransform into parent SMX under environmental conditions. Based on this study, it is unlikely that SMX or its metabolites will persist or accumulate in river sediments under pH conditions where sorption is of minor importance.

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.

Aerosol particles that are emitted from aeration tanks of wastewater treatment plants (WWTPs) can be enriched with environmentally relevant wastewater constituents. In this study, aerosol particles were sampled simultaneously at the pre-aeration tank of a municipal WWTP and at two urban locations approximately 1 km away from the WWTP to evaluate the significance of these aerosol emissions. Moreover, aerosol particles were sampled at a small wastewater irrigation facility and at a rural site. In aerosol particles and wastewater, six sterols (cholesterol, coprostanol, campesterol, beta-sitosterol, stigmasterol, stigmastanol) and anionic surfactants (expressed in terms of methylene blue active substances, MBAS) were quantified. The results showed significantly higher concentrations of sterols and MBAS at the WWTP than atthe urban locations. At the WWTP, average concentrations of cholesterol (848 +/- 321 pg m(-3)), coprostanol (1132 +/- 565 pg m(-3)), and MBAS (132 +/- 43 ng m(-3)) in aerosol were approximately twice as high. This can be attributed to emissions from the treatment tank. Coprostanol, a unique tracer for wastewater, was detected only occasionally at the urban locations. The results of this study show that the aeration of wastewater is a continuously operating local source for organic compounds in aerosol. The wastewater irrigation facility was a minor source of aerosol-bound sterols (coprostanol, 287 +/- 218 pg m(-3)) and anionic surfactants (64 +/- 32 ng m(-3)). Except for coprostanol, all compounds were also present in samples of rural aerosol.

To date, studies about historic PAH (polycyclic aromatic hydrocarbons) deposition at a regional scale have rarely been published. To address this research gap, we sampled 17 ombrotrophic peatlands across eastern Canada. The peat cores from hollows were dated with 210Pb for the period of about 1850-2000 and analyzed fortheir PAH concentration, so PAH deposition could be reconstructed. Peat samples were extracted by accelerated solvent extraction (ASE). The extracts were purified by column chromatography with aluminum oxide and silica gel. PAH were measured by gas chromatography-tandem mass spectrometry (GC-MS/MS). Overall reconstructed deposition rates of sigma-11 PAH ranged from 4 to 1432 microg m(-2) year(-1). Three different long-term trends in PAH deposition could be distinguished: sites with two separated periods of maximum PAH deposition, sites with one period of maximum PAH deposition, and sites with no clearly separated period of maximum PAH deposition. Increasing PAH depositions were caused by rapid industrialization accompanied by extensive use of fossil fuels; decreasing PAH depositions were caused by substitution of these fuels and movements of PAH emitting industry to different regions. At all sites either phenanthrene (20-60%) or benzo[b+k]fluoranthene (10-40%) was the predominant PAH. Detailed analysis of three bogs suggested that combustion of coal and vehicle exhausts mainly contributed to the peat PAH burden. The temporal trends of PAH deposition indicated that increases in the PAH deposition rates followed the industrial development in Canada, particularly in the periods 1880-1910 and 1940-1960. Recent abatement efforts were reflected in decreased PAH deposition rates to about 15% of the maximum.

Aeration tanks of wastewater treatment plants (WWTP) are a potential source of atmospheric aerosol particles. Several groups of organic compounds (sterols, polycyclic aromatic hydrocarbons, estrogens) were analyzed in aerosol particles sampled at a municipal WWTP, and the particle size distribution was measured directly with optical particle counters. Aerosol emissions from an activated treatment tank equipped with fine bubble diffusers were low; however, at the preaeration tank equipped with coarse bubble diffusers, sterol concentrations up to 14 ng m(-3) were measured. Directly next to the tank, sterols were associated mainly to particles with aerodynamic diameter >1.35 microm. The results suggest that coprostanol could be a useful tracer for monitoring the emission of aerosol particles from WWTPs. Moreover, wastewater treatment could contribute substantially to the atmospheric concentrations of cholesterol and 24-ethylcholesterol. Aeration tanks with fine bubble diffusers are no major source of atmospheric aerosol particles, whereas coarse bubbling devices seem to emit considerable amounts of aerosol particles.