Micropollutants In Aquatic Environment Research Articles

Enhanced removal of selected ionizable micro-pollutants from drinking water by adsorption on activated carbon fiber filters under electrochemical assistance

Micro-pollutants have raised serious concerns for drinking water safety because of their great harm to the ecological environment and public health. Traditional water purification technologies, including coagulation and sand filtration, are commonly insufficient to treat micro-pollutants. Adsorption process through carbon-based material has the potential to remove micro-pollutants from aqueous solution. However, the adsorption efficiency is restrained by insufficient adsorption capacity of the adsorbent. Ionization is a common character of most micro-pollutants in aquatic environment, which enables the possibility to improve adsorption capacity by enhance the electrostatic interaction through electrochemical ways. In this work, the activated carbon fiber (ACF) filter possessing high inherent adsorption capacity was prepared and the electrochemical assistance was adopted to improve the adsorption capacity by enhancing the electrostatic attraction between ionizable micro-pollutant and the adsorbent. The adsorption behavior under electrochemical assistance was well fitted by the pseudo-second-order kinetic model. The initial adsorption rates v0 for dichloroacetic acid (DCAA), levofloxacin (LVFX) and ciprofloxacin (CIP) reached 10.8 mg·g−1·h−1 (2.0 V), 48.3 mg·g−1·h−1 (−2.0 V) and 39.4 mg·g−1·h−1 (−2.0 V), respectively, which were 1.1–2.0 times higher than those without electrochemical assistance. The Langmuir model well fitted the adsorption isotherms of the three pollutants under electrochemical assistance. The calculated adsorption capacities (qm) of DCAA, LVFX and CIP under electrochemical assistance were 1.9, 1.3 and 1.1 times higher than those without electrochemical assistance. Furthermore, the adsorption of DCAA of 100 μg·L−1 by ACF filters under continuous flow-through mode was further investigated. The DCAA concentration in effluent maintained lower than the World Health Organization (WHO) limitation of 50 μg·L−1 for 3150 bed volumes under electrochemical assistance, which was 2.4 times higher than that without electrochemical assistance. This work provided a new approach for the efficient removal of ionizable micro-pollutants during drinking water treatment.

Distribution, source and contamination of rare earth elements in sediments from lower reaches of the Xiangjiang River, China

Rare earth elements (REEs) are emerging micropollutants in aquatic environments. In this study, concentrations of REEs and major elements, and mineralogical compositions of sediments from lower reaches of the Xiangjiang River (China) were analyzed using ICP-MS technique. The results suggested that sediments were characterized by terrigenous compositions TiO2, SiO2, Al2O3, K2O, Na2O and P2O, and contained high concentrations of REEs with mean total REE concentrations (∑REE) of 318.7 mg/kg. REEs were moderately enriched in upper river sediments, and slightly or less enriched in downriver sediments. The normalized REE distribution pattern for sediments was characterized by flat shalelike and Eu depleted V-shape REE patterns, which indicated REEs in sediments were lithologically contributed from sedimentary rocks and granites distributed in the watershed respectively. REEs in sediments were hosted mainly in Fe–Mn oxides, and sulfide and organic matters that were characterized by middle REEs (MREE) enrichments relative to light REEs (LREE) and heavy REEs (HREE), and the distribution and differentiation of REEs in sediments were controlled by clays, Fe–Mn oxides, organic matters and finer grains; and also by accessory minerals (e.g., zircon) from granite. The distribution features of REEs in sediments and BCR extraction results suggested that the sediment REE enrichment resulted from additional REE input from anthropogenic sources, including those in discharges from sulfide-ore smelting industries at Zhuzhou city and from phosphate fertilizer plants at Xiangtan city along the river. Thus, sediments were contaminated with REEs in moderate degree in upper river area, and REE contamination was then formed by superimposing anthropogenic REEs on lithological residues. Finally, concentrations of Ce > 100 mg/kg, Gd > 8.12 mg/kg, ∑REE >274.9 mg/kg, ∑LREE >252.3 mg/kg and ∑HREE >28.8 mg/kg here were recommended as the REE contamination levels that represented as REE indices for identifying and rating REE contamination in this mining impacted river.

An Ultrasensitive and Universal Surface Plasmonic Biosensor for Detection of Micropollutants in Aquatic Environments.

Simple yet ultrasensitive and accurate quantification of a variety of analytical targets by virtue of a universal sensing device holds promise to revolutionize environmental monitoring, medical diagnostics, and food safety. Here, we propose a novel optical surface plasmon resonance (SPR) system in which the frequency-shifted light of different polarizations returned the laser cavity to stimulate laser heterodyne feedback interferometry (LHFI), hence amplifying the reflectivity change caused by the refractive index (RI) variations on the gold-coated SPR chip surface. In addition, the s-polarized light was further used as the reference to compensate the noise of the LHFI-amplified SPR system, resulting in nearly 3 orders of magnitude enhancement of RI resolution (5.9 × 10-8 RIU) over the original SPR system (2.0 × 10-5 RIU). By exploiting nucleic acids, antibodies, and receptors as recognition materials, a variety of micropollutants were detected with ultralow detection limits, ranging from a toxic metal ion (Hg2+, 70 ng/L) to a group of commonly occurring biotoxin (microcystins, 3.9 ng microcystin-LR/L) and a class of environmental endocrine disruptors (estrogens, 0.7 ng 17β-estradiol/L). This sensing platform exhibits several distinct characteristics, including dual improvement of sensitivity and stability and common-path optical construction without needing optical alignment, demonstrating a promising avenue toward environmental monitoring.

Suspended particulate matter-associated environmental corticosteroids in the Pearl River, China: Occurrence, distribution, and partitioning

Suspended particulate matter (SPM) plays an important role in the geochemical behavior and fate of organic micropollutants in aquatic environments. However, the presence of trace emerging endocrine disruptors such as environmental corticosteroids (ECs) in SPM is less well understood. This study focused on the occurrence, distribution, and partitioning of SPM-associated ECs in the Pearl River system, China. Ubiquitous particulate ECs were found in the surface water of the rivers at average concentrations (dry weight) between 0.46 ng/g (flumethasone) and 8.83 ng/g (clobetasone butyrate). The total EC (∑ECs) concentrations of the 24 selected target compounds varied from <1.03 ng/g to 62.3 ng/g, with an average and median of 17.6 ng/g and 13.7 ng/g, respectively. Higher SPM-bound EC levels were commonly observed in winter (dry season), and spatially, their relatively high contamination in urban tributary networks decreased while flowing to mainstreams and then gradually attenuated from upstream to the estuary. Despite the approximately 90 % mass distribution of ∑ECs in the aqueous phase, approximately 50 % of their effect burden was derived from the suspended particulate fractions. For the first time, in situ SPM-water partitioning coefficients (Kp) and their organic carbon-normalized ones (Koc) of ECs were determined in surface waters, and a field-derived preliminary linear equation was proposed to estimate Koc for ECs using basic physicochemical parameters n-octanol/water partitioning coefficient (Kow), which is of importance with regard to the assessment of transport, fate, and risk of these emerging hazardous chemicals. Furthermore, the significant logKoc-logKow relationship for ECs reveals that nonspecific hydrophobic partitioning is a major association mechanism between SPM and ECs. Moreover, hydrogen bonding is suggested to be a prevailing specific binding mechanism and provides more contribution to nonhydrophobic interactions between ECs and particulate organic matter than environmental estrogens.

The different toxicological effects and removal efficiencies of norfloxacin and sulfadiazine in culturing Arthrospira (Spirulina) platensis

Norfloxacin (NFX) and sulfadiazine (SDZ) are two widely used antibiotics belonging to fluoroquinolone and sulfonamide groups, respectively, and have become the commonly detected micropollutants in aquatic environments. However, only few works have been conducted to investigate the highly probable inhibition of these antibiotic pollutants to Arthrospira platensis, which is an important species of cyanobacteria that is one of primary producers in aquatic ecosystems and should be remarkably sensitive to environmental pollutants due to its prokaryotic characteristics. Hence, the toxicological effects and removal efficiencies of NFX and SDZ in culturing A. platensis were studied by analyzing the biomass growth, photosynthetic pigments, primary biocomponents, and antibiotics concentration. The corresponding variations of these characteristics showed the higher sensitivity of A. platensis to NFX than to SDZ, indicating the specifically targeted effect of NFX on A. platensis, which could be confirmed in silico by the higher binding affinity of NFX with the critical enzyme. The obtained results illustrated the roles of NFX and SDZ on the growth of A. platensis, thus providing the great support in employing A. platensis to reduce hazards from contaminated water and recover biomass resources.

Metabolic, cellular and defense responses to single and co-exposure to carbamazepine and methylmercury in Dreissena polymorpha

Carbamazepine (CBZ) and Hg are widespread and persistent micropollutants in aquatic environments. Both pollutants are known to trigger similar toxicity mechanisms, e.g. reactive oxygen species (ROS) production. Here, their effects were assessed in the zebra mussel Dreissena polymorpha, frequently used as a freshwater model in ecotoxicology and biomonitoring. Single and co-exposures to CBZ (3.9 μg L−1) and MeHg (280 ng L−1) were performed for 1 and 7 days. Metabolomics analyses evidenced that the co-exposure was the most disturbing after 7 days, reducing the amount of 25 metabolites involved in protein synthesis, energy metabolism, antioxidant response and osmoregulation, and significantly altering cells and organelles' structure supporting a reduction of functions of gills and digestive glands. CBZ alone after 7 days decreased the amount of α-aminobutyric acid and had a moderate effect on the structure of mitochondria in digestive glands. MeHg alone had no effect on mussels' metabolome, but caused a significant alteration of cells and organelles’ structure in gills and digestive glands. Single exposures and the co-exposure increased antioxidant responses vs control in gills and digestive glands, without resulting in lipid peroxidation, suggesting an increased ROS production caused by both pollutants. Data globally supported that a higher number of hyperactive cells compensated cellular alterations in the digestive gland of mussels exposed to CBZ or MeHg alone, while CBZ + MeHg co-exposure overwhelmed this compensation after 7 days. Those effects were unpredictable based on cellular responses to CBZ and MeHg alone, highlighting the need to consider molecular toxicity pathways for a better anticipation of effects of pollutants in biota in complex environmental conditions.

Risk-based screening for prioritisation of organic micropollutants in Swedish freshwater

Concerns about environmental contamination by organic micropollutants (OMPs) are increasing, due to their potential bioaccumulative and toxic properties. This study evaluated the risk posed by OMPs to aquatic ecosystems in Swedish freshwaters. The assessment was based on measured environmental concentrations (MEC) of OMPs in surface waters upstream and downstream of Swedish wastewater treatment plants (WWTPs). A novel optimised risk quotient (RQf) was used to identify potential high-risk substances in the aquatic environment. A secondary objective was to assess the impact of WWTP effluent on aquatic ecosystems using a novel impact factor (I) based on the risk quotient (RQ). Among the 126 substances investigated, four compounds (metformin, N,N-dimethyltetradecylamine, oxazepam, and venlafaxine) were identified as likely to pose a risk to aquatic ecosystems in Swedish surface waters (RQf>1), and five compounds (clindamycin, gemfibrozil, sertraline, o-desmethylvenlafaxine, and diclofenac) were identified as posing a moderate risk to aquatic ecosystems ( 0.1 <RQf<1). WWTP effluent appeared to pose an environmental risk for all recipient sites, but the impact of calculated RQ was site-specific. These results can be used by authorities to prioritise OMPs and contaminated hotspots, in order to decrease negative impacts on aquatic ecosystems. SynopsisA novel optimised risk assessment approach for identification of high-concern organic micropollutants in aquatic environments.

Analysis of micropollutants in a marine outfall using network analysis and decision tree

The presence of micropollutants (MPs), including pharmaceutical, industrial, and pesticidal compounds, threatens both human health and the aquatic ecosystem. The development and extensive use of new chemicals have also inevitably led to the accumulation of MPs in aquatic environments. Recreational beaches are especially vulnerable to contamination, affecting humans and aquatic animals via the absorption of MPs in water during marine activities (e.g., swimming, sailing, and windsurfing). Additionally, marine outfalls in an urbanized coastal city can cause serious chemical and microbial pollution on recreational beaches, leading to an increase in adverse effects on public health and the ecological system. Therefore, the aim of this study was to, with the use of network and decision tree analyses, identify the features and factors that influence the change in MP concentrations in a marine outfall. These analyses were conducted to inspect the relationship between each MP and its hierarchical structure as well as hydrometeorological variables. Additionally, a risk analysis was conducted in this study in which the MPs were prioritized based on their optimized risk quotient values. During our monitoring of MP concentrations over time at the marine outfall, high concentrations of pharmaceutical and industrial compounds were detected when the tide level was low after rainfall. Furthermore, results of the risk analysis and the prioritization revealed that a total of 18 substances identified in our study posed a risk to the ecosystem; these include major ecotoxicologically hazardous substances such as telmisartan, mevinphos, and methiocarb. Results of the network analysis demonstrated distinct trends for pharmaceutical and industrial substances, whilst those for pesticide compounds were irregular. Additionally, the hierarchical structures for most MPs consisted of rainfall, tide level, and antecedent dry hours; this implies that these factors influence MP dynamics. These findings will be helpful for establishing chemical contamination management plans for recreational beaches in the future.

Removal performance and optimisation of pharmaceutical micropollutants from synthetic domestic wastewater by hybrid treatment

Occurrence of pharmaceutical micropollutants in aquatic environments has been one amongst serious environmental problems. During this study, two reactors, including a sequencing batch reactor (SBR) + powdered composite adsorbent (CA) (first reactor, SBR + CA) and a sequencing batch reactor (second reactor, SBR), were designed to treat synthetic wastewater. Powdered CA was added with a dosage of 4.8 g L−1 to the first reactor. Tap water was contaminated with chemical oxygen demand (COD), ammonia and three pharmaceuticals, namely, atenolol (ATN), ciprofloxacin (CIP) and diazepam (DIA) to produce synthetic wastewater. The SBR + CA illustrated a better performance during synthetic municipal wastewater treatment. Up to 138.6 mg L−1 (92.4%) of COD and up to 114.2 mg L−1 (95.2%) of ammonia were removed by the first reactor. Moreover, optimisation of pharmaceuticals removal was conducted through response surface methodology (RSM) and artificial neural network (ANN). Based on the RSM, the best elimination of ATN (90.2%, 2.26 mg L−1), CIP (94.0%, 2.35 mg L−1) and DIA (95.5%, 2.39 mg L−1) was detected at the optimum initial concentration of MPs (2.51 mg L−1) and the contact time (15.8 h). In addition, ANN represented a high R2 value (>0.99) and a rational mean squared error (<1.0) during the optimisation of micropollutants removal by both reactors. Moreover, adsorption isotherm study showed that the Freundlich isotherm could justify the abatement of micropollutants by using CA better than the Langmuir isotherm.

Efficient reduction of carbamazepine using UV-activated sulfite: Assessment of critical process parameters and elucidation of radicals involved

For a successful reclamation of aquatic systems, advanced reduction processes (ARP) have recently attracted a lot of attention for the elimination of emerging pharmaceutical compounds. This study investigates the synergistic effect between UV and sulfite (UV/sulfite) for the degradation of carbamazepine (CBZ) and elucidates the critical process parameters and degradation mechanisms. No efficient degradation of CBZ is observed when applying sulfite alone, and only little degradation for UV irradiation alone (8.2% in 30 min reaction time), but the combined use of UV/sulfite ARP improves CBZ degradation significantly (99.62% in the same reaction time) through the formation of reductive radicals (eaq−, H, SO3−). The process is demonstrated to follow a pseudo first order kinetic model, with degradation rate constants of CBZ increasing linearly with increasing sulfite dosage and UV irradiance. It is shown that the degradation of CBZ by UV/sulfite is much more favourable in alkaline conditions than in acidic conditions due to the more favourable distribution between SO32− and HSO3−, which are the precursors of the radicals generated during the UV/sulfite process. It is demonstrated that hydrated radicals (eaq−) are responsible for CBZ degradation, excluding the function of hydrogen atoms (H) and sulfite radicals (SO3−). Inhibition experiments, conducted by introducing radical scavengers (NO3− and NO2−) into the system, further demonstrate the crucial contribution of eaq− on the degradation of CBZ. The energy consumption is evaluated for different UV intensities and sulfite concentrations and indicates that a dose of 0.4 mM sulfite in combination with a 18 W UV lamp is the most economic. This study emphasizes the dominant impact of eaq− on CBZ degradation in UV/sulfite-ARP systems and highlights the potential of this process to efficiently eliminate recalcitrant micropollutants in aquatic environments.

N-doped Cu-MOFs for efficient electrochemical determination of dopamine and sulfanilamide

Fast and efficient tracking of micropollutants in aquatic environment by developing novel electrode materials is of great significance. Herein, a polyvinylpyrrolidone (PVP) assisted strategy is applied for synthesis of nitrogen doped Cu MOFs (N-Cu-MOF) for micropollutants electrochemical detection. The designed N-Cu-MOFs possess uniform octahedral shape with large surface area (1184 m2 g−1) and an average size of roughly 450 nm, exhibiting the excellent electroanalytical capability for the detection of multipollutants. In the case of dopamine (DA) and sulfonamides (SA) as typical microcontaminants, the designed N-Cu-MOFs exhibited wide linear ranges of 0.50 nM–1.78 mM and low detection limit (LOD, 0.15 nM, S/N = 3) for the determination of DA, as well as a linear range of 0.01–58.3 μM and LOD (0.003 μM, S/N = 3) for monitoring SA. The improved performance is attributed to the heteroatom introduction and good dispersion stability of N-Cu-MOF with PVP-decorated. The good electroanalytical ability of N-Cu-MOF for detection of DA and SA can provide a guide to efficient and rapid monitor other micropollutants and construct novel electrochemical sensors.

Toxicity assessment of four pharmaceuticals in aquatic environment before and after ferrate(VI) treatment

Micro-pollutants in aquatic environment are an emerging challenge to the human health and ecosystems. This study was to investigate the acute toxicity before and after ferrate(VI) treatment for four pharmaceuticals (simvastatin, ivermectin, fluoxetine and oxytetracycline) at concentrations of 10 and 100 μg/L, respectively. Zebrafish animal model and Vibrio fischeri luminescent test were employed to achieve the study targets. It is the first effort using the stated methods to assess toxicity of the selected pharmaceuticals before and after ferrate(VI) treatment when biochemical responses of catalase (CAT), tumour necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β) and B-cell lymphoma 2 (Bcl-2) were assessed in the zebrafish model. The results firstly revealed a significant change in the gene expression of CAT (p < 0.001), TNF-α SOD 1 (p < 0.01), and Bcl-2 (p < 0.05) for simvastatin at low concentrations, which exhibited high toxicity in comparison with other pharmaceuticals. Ferrate(VI) treatment significantly reduced the toxicity of simvastatin by partially removing it during the treatment process and ferrate(VI) itself did not produce additional toxicity in the effluent.

Molecularly Imprinted Polymers for Compound-Specific Isotope Analysis of Polar Organic Micropollutants in Aquatic Environments.

Compound-specific isotope analysis (CSIA) of polar organic micropollutants in environmental waters requires a processing of large sample volumes to obtain the required analyte masses for analysis by gas chromatography/isotope-ratio mass spectrometry (GC/IRMS). However, the accumulation of organic matter of unknown isotopic composition in standard enrichment procedures currently compromises the accurate determination of isotope ratios. We explored the use of molecularly imprinted polymers (MIPs) for selective analyte enrichment for 13C/12C and 15N/14N ratio measurements by GC/IRMS using 1 H-benzotriazole, a typical corrosion inhibitor in dishwashing detergents, as example of a widely detected polar organic micropollutant. We developed procedures for the treatment of >10 L of water samples, in which custom-made MIPs enabled the selective cleanup of enriched analytes in organic solvents obtained through conventional solid-phase extractions. Hydrogen bonding interactions between the triazole moiety of 1 H-benzotriazole, and the MIP were responsible for selective interactions through an assessment of interaction enthalpies and 15N isotope effects. The procedure was applied successfully without causing isotope fractionation to river water samples, as well as in- and effluents of wastewater treatment plants containing μg/L concentrations of 1 H-benzotriazole and dissolved organic carbon (DOC) loads of up to 28 mg C/L. MIP-based treatments offer new perspectives for CSIA of organic micropollutants through the reduction of the DOC-to-micropollutant ratios.

TREATMENT ALTERNATIVES FOR MICROPOLLUTANT REMOVAL IN WASTEWATER

Present of micropollutants in aquatic environments has become an alarming environmental problem for both living creatures and environment. Micropollutants, also called as emerging contaminants arise from natural substances and increasing variety of anthropogenic events. Micropollutants consist of pharmaceuticals, personal care products, steroid hormones, industrial chemicals, pesticides, polyaromatic hydrocarbons and other recently seen compounds. These emerging contaminants are commonly found in very low concentration in different water bodies ranging from a few ng/L to several μg/L. Many existing Wastewater Treatment Plants (WWTPs) in all over the world are not especially designed for removing micropollutants. Low concentration and diversity of micropollutants complicate the dedection and analysis procedures during the treatment processes. Furthermore, entering micropollutants to the WWTPs continuously and stable structure of many micropollutants make difficult to eliminate these emerging compounds sufficiently. Therefore, many micropollutants of unknown concentration pass to aquatic environment from WWTPs. The occurence of micropollutants with a significant levels in aquatic environments disrupt the aquatic ecosystems with a number of adverse effects including short-term and long-term toxicity such as endocrine disrupting effects. Besides the known negative effects of micropollutants there are great number of micropollutants whose effects on living organisms are still unknown. As a result, removing these compounds is of a great importance both to protect environmental ecosystem and human health. Considering that the conventional methods are insufficient for removing the micropollutants other alternative treatment methods including coagulation–flocculation, activated carbon adsorption (powdered activated carbon and granular activated carbon), advanced oxidation processes (AOPs), membrane processes and membrane bioreactor can be applied for better removal. In this study, alternative treatments methods and removal efficiencies of each treatment methods on different micropollutants were investigated and all alternative treatment methods were compared between each other in terms of micropollutant removal rates.

Chromatographic determination and toxicological potential evaluation of selected micropollutants in aquatic environment—analytical problems

In this study, the analytical procedures for the improved extraction and determination of the selected micropollutants (anthracene, pentachlorophenol, octylphenol, benzo(a)pyrene, and diclofenac) in aqueous environment are proposed. These methods were based on application of gas chromatography coupled with mass spectrometry and solid phase extraction for isolation of tested analytes from water samples. Compared to standard procedures currently used in the range presented in this paper, the authors’ modifications of analytical procedures allowed increasing the recovery rate of analytes. Within modification of procedures, hyamine, methanol were used. The substances increase solubility of analytes in water, for instance. Toxicological potential of samples containing tested micropollutants in different environmental matrix was evaluated. Proposed analytical procedures allow the quantitative determination of five different compounds in aquatic environment with satisfactory repeatability and precision of measurements. Applied modifications of analytical procedures had an influence on the increase of recovery degree of compounds. Extraction of micropollutants from effluent exceeded 60% and depended on compounds concentration in the samples, excluding the determination for lower concentration of anthracene. The limits of quantitation LOQ (in ng/L) were as follows: 6.5 for anthracene and octylphenol, 8.5 for diclofenac, and 10 for pentachlorophenol and benzo(a)pyrene. It was found that Microtox® assay allows the quick evaluation of toxicological potential of selected micropollutants. The toxicological potential (expressed as EC50, in mg/L) of deionized water samples containing micropollutants was equal to: 12.8; 2.2; 1.4; 6.6; 23.1 for anthracene, pentachlorophenol, octylphenol, benzo(a)pyrene, and diclofenac, respectively. However, the toxicity was also dependent on environmental matrix. The explanation of this phenomenon requires further research.

Development of a Passive Sampler for Monitoring of Carbamate and s-Triazine Pesticides in Surface Waters

A new sampling system has been developed for the measurement of time-averaged concentrations (TWA) and diffusion coefficients of organic micropollutants in aquatic environments. The system is based on the diffusion of targeted organic compounds through a rate-limiting membrane and the subsequent accumulation of these species in a bound, hydrophobic solid-phase material. Two separate prototype systems are described. One is suitable for the sampling of carbamates such as carbaryl, carbofuran, 3-hydroxycarbofuran, baygon, propham, clorpropham, and the other one for s-triazines such as atrazine, prometryn, propazine, simazine, terbuthylazine, terbutryn, metribuzin, cyanazine, and metamitron pesticides. The systems use solid-phase material (47-mm C18 Empore disk) as the receiving phase but are fitted with rate-limiting membranes of either polysulfone or polycarbonate. For the two designs investigated, the cumulative uptake of all target analytes was considered over exposure periods of 7 days. The determined sampling rates ranged from 0.1323 to 0.0465 L day−1 with both membranes. The best system was the one with the polysulfone membrane allowing a better cumulative uptake.

Tracking transformation processes of organic micropollutants in aquatic environments using multi-element isotope fractionation analysis

The quantitative description of enzymatic or abiotic transformations of man-made organic micropollutants in rivers, lakes, and groundwaters is one of the major challenges associated with the risk assessment of water resource contamination. Compound-specific isotope analysis enables one to identify (bio)degradation pathways based on changes in the contaminants’ stable isotope ratios even if multiple reactive and non-reactive processes cause concentrations to decrease. Here, we investigated how the magnitude and variability of isotope fractionation in some priority pollutants is determined by the kinetics and mechanisms of important enzymatic and abiotic redox reactions. For nitroaromatic compounds and substituted anilines, we illustrate that competing transformation pathways can be assessed via trends of N and C isotope signatures.