Natural organic matter and sunlight accelerate the degradation of 17ss-estradiol in water

Nature based solutions for removal of steroid estrogens in wastewater

Estrogens are a growing problem in wastewater discharges because they are continuously entering the environment and are biologically active at extremely low concentrations. Their effects on wildlife were first identified several decades before, but the environmental limits and the remedial measures are still not completely elucidated. Most conventional treatment processes were not designed with sufficiently long retention times to effectively remove estrogens. Nature-based wastewater treatment technologies such as treatment wetlands (TW) and high-rate algal ponds (HRAP) are economically feasible alternatives for decentralized wastewater treatment and have promise for removing steroid hormones including estrogens. For small communities with populations below 50,000, the overall cost of TWs and HRAPs is considerably lower than that of advanced decentralized treatment technologies such as activated sludge systems (AS) and sequencing batch reactors (SBR). This results from the simplicity of design, use of less materials in construction, lower energy use, operation and maintenance costs, and operation by non-skilled personnel. The nature-based technologies show high removal (>80%) for both natural and synthetic estrogens. Estrogen removal in TWs can be enhanced using alternative media such as palm mulch, biochar, and construction wastes such as bricks, instead of traditional substrates such as sand and gravel. While TWs are effective in estrogen removal, they have the disadvantage of requiring a relatively large footprint, but this can be reduced by using intensified multilayer wetland filters (IMWF). Using filamentous algae in HRAP (high-rate filamentous algal pond; HRFAP) is an emerging technology for wastewater treatment. The algae supply oxygen via photosynthesis and assimilate nutrients into readily harvestable filamentous algal biomass. Diurnal fluctuations in oxygen supply and pH in these systems provide conditions conducive to the breakdown of estrogens and a wide range of other emerging contaminants. The performance of these nature-based systems varies with seasonal changes in environmental conditions (particularly temperature and solar irradiation), however a greater understanding of operating conditions such as loading rate, hydraulic retention time (HRT), pond/bed depth, dissolved oxygen (DO) concentration and pH, which influence the removal mechanisms (biodegradation, sorption and photodegradation) enable TWs and HRAPs to be successfully used for removing estrogens.

Photocatalytic Degradation of Pharmaceutical Residues from Water and Sewage Effluent Using Different TiO2 Nanomaterials

Pharmaceuticals are widely used and often discharged without metabolism into the aquatic systems. The photocatalytic degradation of pharmaceutical compounds propranolol, mebeverine, and carbamazepine was studied using different titanium dioxide nanostructures suspended in water under UV and UV-visible irradiation. Among three different photocatalysts, the degradation was most effective by using Degussa P25 TiO2, followed by Hombikat UV100 and Aldrich TiO2. The photocatalytic performance was dependent on photocatalyst dosage, with an optimum concentration of 150 mg L-1. The natural aquatic colloids were shown to enhance the extent of photocatalysis, and the effect was correlated with their aromatic carbon content. In addition, the photocatalysis of pharmaceuticals was enhanced by the presence of nitrate, but inhibited by the presence of 2-propanol, indicating the importance of hydroxyl radicals. Under optimum conditions, the pharmaceuticals were rapidly degraded, with a half-life of 1.9 min, 2.1 min, and 3.2 min for propranolol, mebeverine, and carbamazepine, respectively. In treating sewage effluent samples, the photocatalytic rate constants for propranolol (0.28 min-1), mebeverine (0.21 min-1), and carbamazepine (0.15 min-1) were similar to those in water samples, demonstrating the potential of photocatalysis as a clean technology for the effective removal of pharmaceuticals from sewage effluent.

Investigation of the Effects of Dioctyl Sulfosuccinate on the Photodegradation of Benzo[a]Pyrene in Aqueous Solutions under Various Wavelength Regimes

Due to the relatively high concentrations of polycyclic aromatic hydrocarbons (PAHs) in oil samples, oil spills in aquatic ecosystems release significant amounts of PAHs. Although remediation efforts often take place during or immediately after an oil spill incident, a portion of the released PAHs remains in the body of water. A natural phenomenon resulting from the direct exposure of PAHs to sunlight is photodegradation. This article investigates the effect of dioctyl sulfosuccinate (DOSS) on the photodegradation of benzo[a]pyrene (BaP), the most toxic PAH in the priority pollutants list of the US Environmental Protection Agency (EPA). DOSS is a surfactant typically used in the remediation of oil spills. Three lamps with maximum emission wavelengths at 350 nm, 419 nm, and 575 nm were individually and simultaneously used to irradiate aqueous solutions of BaP in the absence and the presence of DOSS. When irradiated with the 419 nm lamp or the 575 lamp, BaP showed no photodegradation. Upon irradiation with the 350 nm lamp and with the simultaneous use of the three lamps, the photodegradation of BaP followed first-order kinetics. Independent of the irradiation wavelength, the presence of DOSS increased the half-life of BaP in the aqueous solution. In the case of the 350 nm lamp, the rate constant of photodegradation in the absence and the presence of DOSS varied from (3.79 ± 0.97) × 10-3 min-1 to (1.10 ± 0.13) × 10-3 min-1, respectively. Under simultaneous irradiation with the lamps, the rate constant of photodegradation varied from (1.12 ± 0.35) × 10-3 min (no DOSS) to (3.30 ± 0.87) × 10-4 (with DOSS). Since the largest rate constants of photodegradation were observed in the absence of DOSS, the longer half-lives of BaP in the presence of surfactant were attributed to the incorporation of PAH molecules into the DOSS micelles.

Dark transformation from 17β-estradiol to estrone initiated by hydroxyl radical in dissolved organic matter

The occurrence and fate of 17β-estradiol (E₂) in natural water have gained extensive attention owing to its high ecotoxic risk to wildlife. Dissolved organic matter (DOM) is a ubiquitous water constituent and contributes significantly to E₂ removal, although the reaction mechanism is rarely clarified. The present study aims to investigate E₂ transformation in water containing fresh or aged DOM surrogates at environmentally relevant concentrations in the dark. Experiments along with radical probes of benzene and furfuryl alcohol reveal that reactive radicals, particularly hydroxyl radical (·OH), formed non-photochemically at higher concentrations in aged DOM than in fresh DOM. The contribution of ·OH in E₂ removal is indicated by the decreases in the removal of radical probes in the presence of E₂; moreover, E₂ removal is inhibited in the presence of radical scavengers. The dose-dependent inhibitive effect of substrate concentrations, including E₂ and coexistent propylparaben, shows that the radical concentration is a limiting factor for E₂ removal, which could be enhanced by increasing DOM concentration, dissolved oxygen, and light supply. As the main byproduct, estrone (E₁) is persistent in the current DOM water in the dark, but it can be easily photodegraded when exposed to light. Theoretical analysis reveals that the initial step is ·OH-initiated H- abstraction on the hydroxyl group in the cyclopentane ring of E₂. The formed singlet excited state of E₂ undergoes further intramolecular rearrangement and oxidative dehydrogenation to generate E₁ and the hydroperoxy radical (·HO₂). Considering the universal occurrence of E₂ in DOM-rich aquatic matrices, the present findings have special implications for the biogeochemical cycle and risk assessment of this pollutant in natural aquatic environments, particularly those beyond the photic zone.

Investigation of free and conjugated estrogen fate and emission coefficients in three duck farms

Concentration animal feeding operation (CAFO) is an important source of environmental estrogen. However, to the best of our knowledge, the data on estrogen discharge during duck breeding and growth is insufficient. This study used liquid chromatography with tandem mass spectrometry (LC/MS/MS) to analyze the free and conjugated estrogen concentrations in the surface water, outlet water, groundwater, and duck manure/soil mixture at three duck farms in Taiwan. Natural estrogen species included estrone (E1), 17β-estradiol (E2), estriol (E3), estrone-3-sulfate (E1-3S), 17β-estradiol-3-sulfate (E2-3S), estrone-3-glucuronide (E1-3G), and 17β-estradiol-3-glucuronide (E2-3G), whereas synthetic estrogen included 17α-ethynylestradiol (EE2) and diethylstilbestrol (DES). This study showed that the total estrogen concentrations in the surface water and groundwater were 15.4 and 4.5 ng/L, respectively, which constituted 56% and 58%, respectively, conjugated estrogen. From the pond to the outlet water, the total estrogen concentration decreased by 3.9 ng/L (23% loss) in the duck farms. However, the estrogenic potency was slightly reduced from 0.91 to 0.88 E2 equivalent/L, showing a negligible decrease. From the pond to the outlet water, the field results showed that converting the conjugated estrogen into free estrogen in the duck farm-released water increased their environmental hazard. Primarily E1, with an average concentration of 0.9 ± 1.6 ng/g, was present in the duck manure. The estrogen excreted by the ducks in the pond (from surface water to outlet water) was estimated to be 0.18 kg/million head-year. Although the estrogen concentration in the duck farms was low, the environmental impact of CAFO should not be neglected.

Photodegradation of free estrogens driven by UV light: Effects of operation mode and water matrix

Estrogens are endocrine disrupting chemicals that have been frequently detected in diverse water matrices (e.g. surface water, wastewater and drinking water) and caused a series of health risks. This study was aimed at investigating the photochemical degradation of free estrogens estrone (E1), 17β-estradiol (E2), estriol (E3), and 17α-ethyl estradiol (EE2) upon the monochromatic irradiation (253.7 nm). Concerning the practical installation of photolysis treatment, exposing the impacts of photoreactor operation mode (stationary or up-flow) and the water matrix (ultrapure water or natural surface water) on the photolytic behaviour of estrogens was of high importance. The pseudo-first-order rate constants showed that E1 was the most susceptible to UV radiation among chosen estrogens due to its high molar absorption coefficient of 402.4 M^-1 cm^-1 and quantum yield of 0.065 mol E^-1 at λ = 253.7 nm. Moreover, the up-flow mode and the surface water matrix collected from a lake in Regent's Park (London) were found to favour the photodegradation of estrogens due to the introduction of more dissolved oxygens and promotion of reactive oxygen species (ROS) formation. These findings may shed light on the photochemical behaviour of estrogens in some specific scenarios.

Toward Selective Oxidation of Contaminants in Aqueous Systems

The presence of diverse pollutants in water has been threating human health and aquatic ecosystems on a global scale. For more than a century, chemical oxidation using strongly oxidizing species was one of the most effective technologies to destruct pollutants and to ensure a safe and clean water supply. However, the removal of increasing amount of pollutants with higher structural complexity, especially the emerging micropollutants with trace concentrations in the complicated water matrix, requires excessive dosage of oxidant and/or energy input, resulting in a low cost-effectiveness and possible secondary pollution. Consequently, it is of practical significance but scientifically challenging to achieve selective oxidation of pollutants of interest for water decontamination. Currently, there are a variety of examples concerning selective oxidation of pollutants in aqueous systems. However, a systematic understanding of the relationship between the origin of selectivity and its applicable water treatment scenarios, as well as the rational design of catalyst for selective catalytic oxidation, is still lacking. In this critical review, we summarize the state-of-the-art selective oxidation strategies in water decontamination and probe the origins of selectivity, that is, the selectivity resulting from the reactivity of either oxidants or target pollutants, the selectivity arising from the accessibility of pollutants to oxidants via adsorption and size exclusion, as well as the selectivity due to the interfacial electron transfer process and enzymatic oxidation. Finally, the challenges and perspectives are briefly outlined to stimulate future discussion and interest on selective oxidation for water decontamination, particularly toward application in real scenarios.

Solvent- and Wavelength-Dependent Photolysis of Estrone

The direct photolysis of estrone in solvents ranging from water to cyclohexane is reported. The photodegradation is dominated by lumiestrone, an epimer of estrone resulting from the inversion of the methyl group at carbon 13, regardless of solvent and photolysis wavelength in the range 254-320 nm. Solvent addition products are also observed in lesser amounts. The photodegradation rate in water is an order of magnitude slower than in nonaqueous solvents. Short wavelength excitation enhances photodegradation. Together, these results suggest complicated photophysics underlie the photochemistry with implications for the remediation of environmental estrogens.

Oxidative degradation and mineralization of the endocrine disrupting chemical bisphenol-A by an eco-friendly system based on UV-solar/H2O2 with reduction of genotoxicity and cytotoxicity levels

A solar-driven advanced oxidation process at a lab scale was studied for the degradation and mineralization of the known endocrine disrupting chemical (EDC), bisphenol A (BPA). Preliminary tests were performed varying the irradiation source, BPA/H₂O₂ ratio, temperature, initial H₂O₂ concentration, initial solution pH, and initial BPA concentration, then, the operational conditions of the UV-solar/H₂O₂ were optimized by a response surface methodology (RSM), providing the following responses: UV-solar/H₂O₂ process at pH 3.0, [BPA]₀ = 25 mg L^-1, [H₂O₂] = 350 mg L^-1, T = 50 °C, achieving BPA degradation of 77.4% and BPA mineralization of 38.2%, H₂O₂ consumption of 230 mg L^-1. From the optimized condition, different pH ranges were tested (3.0; 5.0; 7.0; 9.0; and 11.0), where, at solution pH 5.0 the best removal rates were achieved (89.2% BPA degradation and 49.0% BPA mineralization). The BPA amount in solution was monitored by High Performance Liquid Chromatography (HPLC) and a study of the intermediate reaction by-products was performed by Gas Chromatography-Mass Spectrometry (GC-MS) analyses, highlighting the lower amount of by-products identified when the solution pH 5.0 was employed, rather than the solution pH 3.0. Genotoxicity tests with Zebrafish (Danio rerio) and cytotoxicity tests with Allium cepa were performed aiming to evaluate errors in the cells and nuclear abnormalities of the tested organisms induced by BPA raw samples, as well as by the BPA samples treated by the UV-solar/H₂O₂ process. Therefore, the bio-toxicity levels for an animal and a vegetal bio-indicator were reduced by applying a renewable source of energy as the irradiation source for the UV/H₂O₂ process, representing an efficient and eco-friendly alternative for BPA treatment in aqueous solutions.

Alkylphenols and Chlorophenols Remediation in Vertical Flow Constructed Wetlands: Removal Efficiency and Microbial Community Response

This study aims to investigate the effect of two different groups of phenolic compounds (the alkylphenols nonylphenol (NP) and octylphenol (OP), and the chlorophenol pentachlorophenol (PCP)) on constructed wetlands (CWs) performance, including on organic matter, nutrients and contaminants removal efficiency, and on microbial community structure in the plant bed substrate. CWs were assembled at lab scale simulating a vertical flow configuration and irrigated along eight weeks with Ribeira de Joane (an urban stream) water not doped (control) or doped with a mixture of NP and OP or with PCP (at a 100 μg·L−1 concentration each). The presence of the phenolic contaminants did not interfere in the removal of organic matter or nutrients in CWs in the long term. Removals of NP and OP were >99%, whereas PCP removals varied between 87% and 98%, mainly due to biodegradation. Microbial richness, diversity and dominance in CWs substrate were generally not affected by phenolic compounds, with only PCP decreasing diversity. Microbial community structure, however, showed that there was an adaptation of the microbial community to the presence of each contaminant, with several specialist genera being enriched following exposure. The three more abundant specialist genera were Methylotenera and Methylophilus (methylophilaceae family) and Hyphomicrobium (hyphomicrobiaceae family) when the systems were exposed to a mixture of NP and OP. When exposed to PCP, the three more abundant genera were Denitromonas (Rhodocyclaceae family), Xenococcus_PCC_7305 (Xenococcaceae family) and Rhodocyclaceae_uncultured (Rhodocyclaceae family). To increase CWs efficiency in the elimination of phenolic compounds, namely PCP which was not totally removed, strategies to stimulate (namely biostimulation) or increase (namely bioaugmentation) the presence of these bacteria should be explore. This study clearly shows the potential of vertical flow CWs for the removal of phenolic compounds, a still little explored subject, contributing to promote the use of CWs as nature-based solutions to remediate water contaminated with different families of persistent and/or emergent contaminants.

Reevaluation of the contributions of reactive intermediates to the photochemical transformation of 17β-estradiol in sewage effluent

Photodegradation of the natural steroid 17β-estradiol (E2), an endocrine-disrupting hormone that has been widely detected in aquatic environments, was investigated in wastewater effluents at various pH ranges under simulated solar irradiation. The rate of E2 degradation in the sewage effluents was stable at pH 6.0-7.0 but suddenly increased from pH 8.0-10.0. The second-order reaction rate constants of E2 with ³EfOM* and CO₃^•- were measured to increase 11.0-fold and 18.0-fold from pH 6.0 to 10.0, respectively. Two main reasons are proposed for this sharp increase. First, the change in the ionization state of E2 made it susceptible to oxidation by triplet-state effluent organic matter (³EfOM*) and carbonate radicals (CO₃^•-). Second, the steady-state concentration of CO₃^•- increased with increasing pH. Indirect photolysis was suggested to be the main degradation pathway in the sewage effluents, and ³EfOM* was proposed to play a major role at pH 8.0-9.0, while CO₃^•- played a significant role at pH 10.0. In this study, EfOM was shown for the first time to inhibit the oxidation of E2 initiated by ³EfOM* and CO₃^•-. Thus, we suggest that EfOM plays a dual role in the photodegradation of E2: EfOM can not only be activated as ³EfOM* to degrade E2 but also can inhibit the degradation of E2 by reducing the E2 oxidation intermediate back to E2. The estrogenic activity of the photodegradation products was also studied. The in vitro estrogenic activity of E2 solutions decreased approximately as fast as the E2 photodegradation occurred in the effluent water at various pH values, suggesting that solar photodegradation in sewage effluents reduces the risk of endocrine disruption in waters impacted by E2 and subject to continuing inputs. The results of this study are important for predicting the environmental fate of endocrine-disrupting chemicals and developing methods for their removal from aquatic environments.

Oxolinic acid in aquaculture waters: Can natural attenuation through photodegradation decrease its concentration?

Quinolones, such as oxolinic acid (OXA), are antimicrobials commonly used in aquaculture. Thus, its presence in the aquatic environment surrounding aquaculture facilities is quite easy to understand. When present in aquatic environment, pharmaceuticals may be subjected to several attenuation processes that can influence their persistence. Photodegradation, particularly for antibiotics, can have significant importance since these compounds may be resistant to microbial degradation. OXA photodegradation studies reported in literature are very scarce, especially using aquaculture waters, but are markedly important for an appropriate risk assessment. Results hereby presented showed a decrease on photodegradation rate constant from 0.70 ± 0.02 h^-1 in ultrapure water to 0.42 ± 0.01 h^-1 in freshwater. The decrease on photodegradation rate constant was even more pronounced when brackish water was used (0.172 ± 0.003 h^-1). In order to understand which factors contributed to the observed behaviour, environmental factors, such as natural organic matter and salinity, were studied. Results demonstrated that dissolved organic matter (DOM) may explain the decrease of OXA photodegradation observed in freshwater. However, a very sharp decrease of OXA photodegradation was observed in solutions containing NaCl and in synthetic sea salts, which explained the higher decrease observed in brackish water. Moreover, under solar radiation, the use of an ¹O₂ scavenger allowed us to verify a pronounced retardation of OXA decay, suggesting that ¹O₂ plays an important role in OXA photodegradation process.

Simultaneous removal of harmful algal cells and toxins by a Ag2CO3-N:GO photocatalyst coating under visible light

The frequent harmful algae blooms (HABs) in eutrophic waters pose serious threats to the water environment and health of human beings and animals. In this study, a new type of photocatalytic coating was prepared by loading Ag₂CO₃-N:GO (AGON) on the polyurethane sponge modified by silica sol via a dip coating method for the photocatalytic inactivation of Microcystis aeruginosa (M. aeruginosa) and degradation of Microcystin-LR (MC-LR). The factors including photocatalyst loading dosage, natural organic matter (NOM), and alkalinity were studied. The effects on the physiological characteristics of M. aeruginosa and reactive oxygen species (ROS) were also investigated to reveal the photocatalytic inactivation mechanisms. The results showed that the AGON coating-4 (the initial concentration of AGON suspension used for loading is 4 g/L) exhibited the optimum photocatalytic performance under visible light, which can completely remove chlorophyll a after 5 h of irradiation. And the NOM and alkalinity in water have relatively negative effects on the photocatalytic inactivation of algae. The prepared AGON coating also exhibited excellent photocatalytic performance in the degradation of MC-LR under visible light. It only needed 20, 60 and 120 min to completely degrade 0.1, 0.3 and 0.5 mg/L MC-LR, respectively. However, the mixed systems of algae and MC-LR required a longer time to achieve photocatalytic degradation. The O₂^- were the predominant reactive oxygen species, causing the damage of cell membranes and walls and the leakage of cellular content, which eventually led to the irreversible damage to algal cells. What's more, the coating can be reused several times due to its good cyclability and stability. Therefore, the AGON coating has promising prospects for the treatment of algal blooms in eutrophic waters.

17β-Estradiol removal routes by moving bed biofilm reactors (MBBRs) under various C/N ratios

This study evaluated the contribution of biotic and abiotic routes to the 17β-estradiol (E2) removal in moving bed biofilm reactors (MBBRs), and uncovered the interrelation between the E2 removal routes and biofilm characteristics, which was not researched in previous literature. Three MBBRs with different C/N ratios (0 for C/N₀; 2 for C/N₂; and 5 for C/N₅) were operated in continuous mode. A 65-day degradation demonstrated that the MBBRs had high potential to remove E2 regardless of the C/N (E2 removal greater than 99% for all MBBRs; P > 0.05). Further batch tests showed that the E2 removal mainly resulted from heterotrophic activities for all MBBRs, accounting for approximately 85% for all MBBRs (P > 0.05), followed by nitrification (10-11%) and adsorption (4-5%). Importantly, lower adhesive force likely led to higher E2 adsorption onto biofilms. Besides, enhanced ammonia oxidizing rate (AOR) was consistent with the high contribution of nitrification to the E2 attenuation. Importantly, heterotrophic activity was positively correlated with its contribution to E2 removal (r = 0.99, P < 0.05). To sum, the results obtained in this study helped to understand the E2 removal routes in nitrifying biofilm systems.

Photodegradation of sulfadiazine in different aquatic environments - Evaluation of influencing factors

The presence of antibiotics, such as sulfadiazine (SDZ), in the aquatic environment contributes to the generation of antimicrobial resistance, which is a matter of great concern. Photolysis is known to be a major degradation pathway for SDZ in surface waters. Therefore, influencing factors affecting SDZ photodegradation in different aquatic environments were here evaluated in order to have a better knowledge about its persistence in the environment. Photodegradation of SDZ was found to be more efficient at higher pH (t_1/2 = 6.76 h, at pH = 7.3; t_1/2 = 12.2 h, at pH = 6.3), in the presence of humic substances (HS) (t_1/2 between 1.76 and 2.42 h), as well as in the presence of NaCl (t_1/2 = 1.00 h) or synthetic sea salts (t_1/2 = 0.78 h). Using ˙OH and ¹O₂ scavengers, it was possible to infer that direct photolysis was the main pathway for SDZ photodegradation in ultrapure water. Furthermore, results under N₂ purging confirmed that ¹O₂ was not relevant in the phototransformation of SDZ. Then, the referred observations were used for the interpretation of results obtained in environmental matrices, namely the final effluent of a sewage treatment plant (STPF), fresh and brackish water (t_1/2 between 2.3 and 3.48 h), in which SDZ photodegradation was found to be much faster than in ultrapure water (t_1/2 = 6.76 h).

Comparing the effects of different types of inorganic nanoparticles on 17β-estradiol adsorption by graphene oxide

This study compared the effects of five types of inorganic nanoparticles (INPs) on the 17β-estradiol (E2) adsorption to graphene oxide (GO). The results showed that INPs increased the equilibrium time for the adsorption of E2 to GO. Higher Brunauer-Emmett-Teller (BET) surface area of INPs resulted in lower diffusion rate of E2, and thus the adsorption rate constant (k₂) calculated from pseudo-second-order kinetic model negatively correlated with the BET surface area of INPs (p = 0.037). In addition, INPs decreased the adsorption amount of E2 to GO, and the inhibition effects declined in the order of Al₂O₃ > ZnO > TiO₂ > SiO₂ > Fe₂O₃. This is determined by the interactions between GO and INPs. The positively charged ZnO and Al₂O₃ strongly heteroaggregate with GO via electrostatic attraction, and then significantly inhibited E2 adsorption to GO. In contrast, the homoaggregation of GO was superior to its heteroaggregation with negatively charged SiO₂ and TiO₂, and then lower inhibition of E2 adsorption to GO was induced. Fe₂O₃ with less negative charge (-8.48 mV) led to the lowest inhibition effect on E2 adsorption to GO because of its preferable homoaggregation. The results were further confirmed by Derjaguin-Landau-Verwey-Overbeek calculation, transmission electron microscopy, and sedimentation experiments. This study revealed how the properties of INPs influence their effects on the adsorption of E2 by GO, and the findings are critical to understand the behavior and fate of GO and pollutants in natural aquatic environment.

Removal of 17β-Estradiol by Activated Charcoal Supported Titanate Nanotubes (TNTs@AC) through Initial Adsorption and Subsequent Photo-Degradation: Intermediates, DFT calculation, and Mechanisms

A low-cost composite of activated charcoal supported titanate nanotubes (TNTs@AC) was developed via the facile hydrothermal method to remove the 17β-estradiol (E2, a model of pharmaceutical and personal care products) in water matrix by initial adsorption and subsequent photo-degradation. Characterizations indicated that the modification occurred, i.e., the titanate nanotubes would be grafted onto the activated charcoal (AC) surface, and the micro-carbon could modify the tubular structure of TNTs. E2 was rapidly adsorbed onto TNTs@AC, and the uptake reached 1.87 mg/g from the dual-mode model fitting. Subsequently, the adsorbed E2 could be degraded 99.8% within 2 h under ultraviolet (UV) light irradiation. TNTs@AC was attributed with a unique hybrid structure, providing the hydrophobic effect, π−π interaction, and capillary condensation for E2 adsorption, and facilitating the electron transfer and then enhancing photocatalytic ability for E2-degradation. In addition, the removal mechanism of E2 was elucidated through the density functional theory calculation. Our study is expected to provide a promising material for environmental application.

Advanced oxidative processes in the degradation of 17β-estradiol present on surface waters: kinetics, byproducts and ecotoxicity

Endocrine disruptors represent risks to aquatic ecosystem and humans, and are commonly detected in surface water. Photochemical treatments can be used to remove 17β-estradiol (E2), but few studies have analyzed the kinetics, intermediates, and 17β-estradiol degradation pathways in natural matrices. In this study, the photochemical behavior of E2 under ultraviolet irradiation (UVC, 254 nm) associated with oxidants (H₂O₂ or O₃) or photocatalyst (TiO₂) was investigated to evaluate the degradation potential and the transformation pathway in a natural surface water matrix. Additionally, computational modeling analyses with Ecological Structure Activity Relationships (ECOSAR) software were performed to predict the toxicity from the E2 and its transformation byproducts. E2 degradation kinetics showed adjusted to the pseudo-first-order kinetic model, being k_UV/O3 > k_UV/TiO2 > k_UV/H2O2 > k_UV. Eight transformation byproducts were identified by liquid chromatography with time-of-flight mass spectrometry (HPLC/TOF-MS) in natural surface water samples. These byproducts formed as the result of opening the aromatic ring and adding the hydroxyl radical. The E2 degradation pathway was proposed based on the byproducts identified in this study and in previous studies, suggesting the formation of aliphatic and hydroxylated byproducts. E2 treatment presented both very toxic and not harmful byproducts.

Assessing the human risk and the environmental fate of pharmaceutical Tramadol

Tramadol (TRA) is a widely used human pharmaceutical and a well-established emerging pollutant and its potential genotoxic and cytotoxic effects on humans as well as its fate in aqueous systems demand full investigation. The present study is a multidisciplinary approach and provides important insights on the potential risks of Tramadol on humans accompanied by its photolytic transformation under simulated solar irradiation. The present study revealed that Tramadol can induce genotoxic and cytotoxic effects under the specific experimental conditions, significantly depended on the tested concentration. In addition, the photolytic transformation of Tramadol was investigated in detail under simulated solar irradiation in two different water matrices: ultrapure water (UW) and treated wastewater (WW). Differences in the degradation rates were observed between UW and WW, being slower in WW. The results showed that more than 70% of Tramadol was removed after 240 min in UW ([TRA] = 10 mg L^-1, I = 500 W m^-2). After this period, TOC removal was found to be about 40%. Transformation of N atoms into NO₃^- and NH₄⁺ followed a similar trend reaching up to 38% release. Τramadol degraded mainly by HO radicals and ¹O₂ through a self-sensitizing process while direct photolysis was also significant. Hydroxylation, demethylation and N-oxidation of the parent compound were found to be the main degradation pathways confirming the important role of HO and ¹O₂ in the photolytic process. Toxicity measurements showed a noticeable increase of the inhibition for Vibrio fischeri at the first stages which coincide with the formation of the major TPs.

Characterization of an efficient estrogen-degrading bacterium Stenotrophomonas maltophilia SJTH1 in saline-, alkaline-, heavy metal-contained environments or solid soil and identification of four 17β-estradiol-oxidizing dehydrogenases

The efficient bioremediation of estrogen contamination in complex environments is of great concern. Here the strain Stenotrophomonas maltophilia SJTH1 was found with great and stable estrogen-degradation efficiency even under stress environments. The strain could utilize 17β-estradiol (E2) as a carbon source and degrade 90% of 10 mg/L E2 in a week; estrone (E1) was the first degrading intermediate of E2. Notably, diverse pH conditions (3.0-11.0) and supplements of 4% salinity, 6.25 mg/L of heavy metal (Cd²⁺ or Cu²⁺), or 1 CMC of surfactant (Tween 80/ Triton X-100) had little effect on its cell growth and estrogen degradation. The addition of low concentrations of copper and Tween 80 even promoted its E2 degradation. Bioaugmentation of strain SJTH1 into solid clay soil achieved over 80% removal of E2 contamination (10 mg/kg) within two weeks. Further, the whole genome sequence of S. maltophilia SJTH1 was obtained, and a series of potential genes participating in stress-tolerance and estrogen-degradation were predicted. Four dehydrogenases similar to 17β-hydroxysteroid dehydrogenases (17β-HSDs) were found to be induced by E2, and the four heterogenous-expressed enzymes could oxidize E2 into E1 efficiently. This work could promote bioremediation appliance potential with microorganisms and biodegradation mechanism study of estrogens in complex real environments.

Predicting the fate of eDNA in the environment and implications for studying biodiversity

Environmental DNA (eDNA) applications are transforming the standard of characterizing aquatic biodiversity via the presence, location and abundance of DNA collected from environmental samples. As eDNA studies use DNA fragments as a proxy for the presence of organisms, the ecological properties of the complex and dynamic environments from which eDNA is sampled need to be considered for accurate biological interpretation. In this review, we discuss the role that differing environments play on the major processes that eDNA undergoes between organism and collection, including shedding, decay and transport. We focus on a mechanistic understanding of these processes and highlight how decay and transport models are being developed towards more accurate and robust predictions of the fate of eDNA. We conclude with five recommendations for eDNA researchers and practitioners, to advance current best practices, as well as to support a future model of eDNA spatio-temporal persistence.

Occurrence, fate and risk assessment of BPA and its substituents in wastewater treatment plant: A review

Several bisphenol analogues (BPs) are gradually replacing bisphenol A (BPA) in many fields, following strict restrictions on the production and use of BPA. The presence of micropollutants in wastewater treatment plants (WWTPs) may pose risks to the aquatic ecosystem and human health. In this review, we outlined the occurrence and fate of BPs in WWTPs, and estimated their potential risks to the aquatic ecosystem. BPA is still the most predominant bisphenol analogue in WWTPs with high detection rate and concentration, followed by bisphenol S (BPS) and F (BPF). Biodegradation and adsorption are the main removal pathways for removal of BPs in WWTPs. The secondary (activated sludge process, biological aerated filter, and membrane bioreactor) and advanced (membrane technique, ultraviolet disinfection, adsorption process, and ozonation) treatment processes show high removal efficiency for BPs, which are influenced by many factors such as sludge retention time and redox conditions. BPs other than BPA (assessed in this review) in effluent of WWTPs have low risks to Daphnia magna and early life stages on medaka, while BPA shows a medium or high risk under certain conditions. Knowledge gaps have been identified and future line of research on this class of chemicals in WWTPs is recommended. More data are needed to illustrate the occurrence and fate of BPs in WWTPs. Environmental risks of BPs other than BPA initiating from wastewater discharge to aquatic organisms remain largely unknown.

A critical review on organic micropollutants contamination in wastewater and removal through carbon nanotubes

The prevalence of organic micropollutants (OMPs) in various environmental compartments is posing a serious health risks to all kinds of lives on the planet. The levels of OMPs such as polyaromatic hydrocarbons, antibiotics, pesticides, contraceptive medicines, and personal care products in water bodies are increasing with each passing day. It is an urgent need of time to limit the release of OMPs into the environment, and to remove the prevailing OMPs for sustainable environmental management. The majority of the conventional means of water decontamination are either inefficient or expensive. However, due to nanosize, high surface area, and hollow and layered structure, carbon nanotubes (CNTs) serve as excellent sorbents for the removal of a diverse range of OMPs. The occurrence of emerging OMPs and their detrimental effects on human and animal health are collected and discussed in this review. The characteristics and efficacy of various CNTs (pristine and modified) for the efficient removal of different OMPs, and the removal mechanisms have been reviewed and discussed. The literature demonstrated that adsorption of OMPs onto CNTs is very complicated and rely on multiple factors including the properties of adsorbent and the adsorbate as well as solution chemistry. It was found that H-bonding, electrostatic interactions, van der Waals forces, hydrophobic interactions, H-π bongs, and π-π interactions were the major mechanisms responsible for the adsorption of OMPs onto various kinds of CNTs. Despite of higher affinities for OMPs, hydrophobicity and higher costs restrain the practical application of CNTs for wastewater treatment on large scale. However, continuous production may lead to the development of cost-effective, efficient and eco-friendly CTNs technology for wastewater treatments in future.

Development and application of relevance and reliability criteria for water treatment removal efficiencies of chemicals of emerging concern

With the growth in production and use of chemicals and the fact that many end up in the aquatic environment, there is an increasing need for advanced water treatment technologies that can remove chemicals of emerging concern (CECs) from water. The current lack of a homogenous approach for testing advanced water treatment technologies hampers the interpretation and evaluation of CEC removal efficiency data, and hinders informed decision making by stakeholders with regard to which treatment technology could satisfy their specific needs. Here a data evaluation framework is proposed to improve the use of current knowledge in the field of advanced water treatment technologies for drinking water and wastewater, consisting of a set of 9 relevance criteria and 51 reliability criteria. The two criteria sets underpin a thorough, unbiased and standardised method to select studies to evaluate and compare CEC removal efficiency of advanced water treatment technologies in a scientifically sound way. The relevance criteria set was applied to 244 papers on removal efficiency, of which only 20% fulfilled the criteria. The reliability criteria were applied to the remaining papers. In general these criteria were fulfilled with regards to information on the target compound, the water matrix and the treatment process conditions. However, there was a lack of information on data interpretation and statistics. In conclusion, a minority of the evaluated papers are suited for comparison across techniques, compounds and water matrixes. There is a clear need for more uniform reporting of water treatment studies for CEC removal. In the future this will benefit the selection of appropriate technologies.

Attenuation, transport, and management of estrogens: A review

Overabundance of endocrine disruptors (EDs), such as steroid estrogens, in the natural environment disrupts hormone synthesis in aquatic organisms. Livestock and wastewater outflows contribute measurable quantities of steroid estrogens into the environment where they are picked up and transported via surface runoff and feedlot effluents into water matrices. E1, E2β, E2α, E3 and EE2 are the most prevalent estrogens in these environmental systems. Estrogens in soils and water undergo several concurrent attenuation processes including sorption to particles, biotransformation, photo-transformation, and plant uptake. This review summarizes current studies on the attenuation and transport of steroid estrogens with a focus on estrogen attenuation and transport modeling. The authors use this information to synthesize appropriate strategies for reducing estrogenicity in the environment.

Assessment of endocrine disruptor effects of levonorgestrel and its photoproducts: Environmental implications of released fractions after their photocatalytic removal

The presence of levonorgestrel (LNG) in water bodies via direct discharge and human excretion has been reported worldwide, but its effects on the reproduction of aquatic species and humans are still unknown. Owing to its recalcitrant properties, LNG is not completely removed during wastewater treatment plants, and many species may be exposed to low traces of this compound from discharged effluents. Thus, in this study, a photocatalytic process for removing LNG along with screening of endocrine disruptor effects for risk assessment was applied. Although the removal rate of LNG by ultraviolet C (UV-C) radiation was >90%, reproductive toxicity testing using the BeWo cell line exposed to LNG and its degraded fraction showed the reduced production of basal human chorionic gonadotropin hormone (β-hCG) by more than 73%, from 8.90 mIU mL^-1 to <2.39 mIU mL^-1, with both LNG and the degraded fraction. β-hCG hormone has been implicated in the viability of trophoblastic cells during the first trimester of pregnancy; therefore, degraded fractions and waterborne LNG may affect reproduction in some aquatic species and humans with low level of exposure.

Microbially reduced humic acid promotes the anaerobic photodegradation of 17α--ethinylestradiol

Photolysis and microbial activity are relatively obvious in shallow, eutrophic waters with low dissolved oxygen content. Ubiquitous humic acid (HA) can act as electron acceptor and be reduced by bacterial under such conditions, and the reduced form of humic acid (RHA) plays an important role in the photolysis contaminants. In this study, anaerobic 17α-ethinylestradiol (EE2) photodegradation was performed along with biodegradation by Shewanella putrefaciens mediated by HA. The mechanism of such coupled photolysis and biodegradation of EE2 was thus elucidated. The removal rate in such coupled degradation in the presence of 10 mgC L^-1 of HA at pH 8.0 was greater than that of either photolysis or biodegradation alone. HA which had been reduced in a double-chamber microbial fuel cell showed better promotion to EE2 photodegradation than fresh HA. Reactive species scavenging experiments indicated that hydroxyl radical and excited triplet states of HA were primary contributors to EE2 photodegradation in anaerobic conditions. More of them were produced from RHA than from pristine HA. Besides, the degraded EE2 solutions inhibited the proliferation of MCF-7 human cancer Cells. These findings improve our understanding of the environmental transformation of EE2 in the shallow, anoxic waters.

Photodegradation of 17β-estradiol on silica gel and natural soil by UV treatment

This paper evaluates the UV photodegradation of 17β-estradiol (E2) on silica gel and in natural soil with different soil components. Silica gel was chosen as a stable and pure support to simulate the photochemical behavior of E2 on the surface of natural soil. Ultraviolet light, rather than visible light, was confirmed to play a decisive role in the photodegradation of E2 on silica gel. The effect of three soil components, including humic acid (HA), inorganic salts, and relative humidity (RH), on the photochemical behavior of E2 on silica gel or soil under UV irradiation was then evaluated. Two HA concentrations (10 and 20 mg g^-1) and three salts (ferric sulfate, copper sulfate and sodium carbonate) were observed to obviously inhibit the degradation of E2 on silica gel. Interestingly, nitrate was found to obviously improve the removal efficiency of E2. Both too-dry and too-wet conditions obviously reduced the removal rate of E2, and the optimum relative humidity (RH) value was found to be approximately about 35% (30 °C). Furthermore, twenty intermediate products and two major pathways were proposed to describe the transformation processes of E2 treated by UV irradiation, among which oligomers were found to be the major intermediate products before complete mineralization. The efficient UV removal of E2 on silica gel and natural soil suggested a feasible strategy to remediate E2 contaminated soil.

Dissolved organic matter and estrogen interactions regulate estrogen removal in the aqueous environment: A review

This review summarizes the characterization and quantification of interactions between dissolved organic matter (DOM) and estrogens as well as the effects of DOM on aquatic estrogen removal. DOM interacts with estrogens via binding or sorption mechanisms like π-π interaction and hydrogen bonding. The binding affinity is evaluated in terms of organic-carbon-normalized sorption coefficient (Log K_OC) which varies with types and composition of DOM. DOM has been suggested to be a more efficient sorbent compared with other matrices, such as suspended particulate matter, sediment and soil; likely associated with its large surface area and concentrated carbon content. As a photosensitizer, DOM enhanced estrogen photodegradation when the concentration of DOM was below a threshold value, and when above, the acceleration effect was not observed. DOM played a dual role in affecting biodegradation of estrogens depending on the recalcitrance of the DOM and the nutrition status of the degraders. DOM also acted as an electron shuttle (redox mediator) mediating the degradation of estrogens. DOM hindered enzyme-catalyzed removal of estrogens while enhanced their transformation during the simultaneous photo-enzymatic process. Membrane rejection of estrogens was pronounced for hydrophobic DOM with high aromaticity and phenolic moiety content. Elimination of estrogens via photolysis, biodegradation, enzymolysis and membrane rejection in the presence of DOM is initiated by sorption, accentuating the role of DOM as a mediator in regulating aquatic estrogen removal.

Photochemical degradation of halogenated estrogens under natural solar irradiance

Halogenated estrogens are thought to be moderately potent endocrine-disrupting compounds that are formed during chlorine-based wastewater disinfection processes and may represent a significant fraction of the total amount of estrogen delivered from wastewater treatment plants to receiving waters. Yet we lack key information about the photochemical degradation of halogenated estrogens, a process that has important implications for UV-based wastewater treatment and environmental fate modeling. To better understand halogenated estrogen degradation in aquatic environments, we studied the direct photolysis of 17β-estradiol (E2), 2-bromo-17β-estradiol (monoBrE2), 2,4-dibromo-17β-estradiol (diBrE2), and 2,4-dichloro-17β-estradiol (diClE2) as well as the indirect photolysis of diBrE2 under natural solar irradiance. We found that direct photolysis rate constants increased with halogenation as pKa values decreased and molar absorptivity spectra shifted toward higher wavelengths. Compared to E2, quantum yields were threefold larger for monoBrE2, but 15-32% smaller for the dihalogenated forms. The rate of diBrE2 (pKa ∼ 7.5) photolysis was strongly influenced by pH. At pH 7, diBrE2 degraded on minute time scales due to the large red-shifted molar absorptivity values and greater quantum yields of the phenolate form. Degradation rates were only slightly different in the presence of Suwannee River Humic Acid (5 mg L-1), and quenching experiments pointed to excited triplet state dissolved organic matter (3DOM*) as the dominant reactive intermediate responsible for the indirect photolysis of diBrE2. Overall, our data suggest that halogenated estrogens are particularly susceptible to photochemical degradation at environmentally relevant pH values.

Ultraviolet photosensitized transformation mechanism of microcystin-LR by natural organic matter in raw water

Microcystins (MCs), produced by cyanobacterial blooms in eutrophic water, are common toxic metabolites and a potential threat to human health. However, the mechanism of MC photodegradation by photosensitizers in raw water remains unclear. In photodegradation and quenching experiments, this study investigates the photosensitized degradation of microcystin-LR (MC-LR) by fulvic acid (FA, a kind of dissolved organic matter with natural photosensitizing properties) under ultraviolet (UV) light irradiation. The photodegradation mechanisms of FA are also explored. The photodegradation process of MC-LR by FA was consistent with second-order reaction kinetics. The degradation rate of MC-LR in FA decreased from 80% to 55% as the pH increased from 3 to 9, because the binding ability of FA to MC-LR reduces as the pH increases. Given that FA can both inhibit and promote MC-LR degradation depending on its concentration, the optimum initial FA concentration for degrading MC-LR was determined as 9.86 mgC·L^-1. The excited triplet state of FA (³FA^∗) accounted for 50.12% of the MC-LR loss; the remaining loss (49.88%) was contributed by reactive oxygen species and direct photolysis. This implies that the main pathway of MC-LR degradation is reaction with ³FA^∗. The MC-LR degradation rate is 36% higher under UV irradiation than that under simulated sunlight irradiation.

Phthalates removal efficiency in different wastewater treatment technology in the Eastern Cape, South Africa

The removal capacity of different wastewater treatment plant (WWTP) technologies adopted in rural areas for phthalate was investigated in the Eastern Cape, South Africa. Wastewater samples collected from three selected WWTPs which use activated sludge (AS), trickling filter (TF), and oxidation pond (OP) technology were extracted using the solid-phase extraction method followed by gas chromatography-mass spectrometry (GC-MS) analysis. The six selected phthalate esters (PAEs) dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP), benzyl butyl phthalate (BBP), di(2-ethyl hexyl) phthalate (DEHP), and di-n-octyl phthalate (DOP) were detected in all the samples collected from the WWTPs. DBP was the most abundant compound in the influent, effluent, and sludge samples with a maximum detection of 2497 μgL^-1, 24.2 μgL^-1, and 1249 μg/g dW, respectively, followed by DEHP and BBP. There was a relatively high removal capacity achieved by AS in Alice, TF in Berlin, and OP in Bedford with a removal efficiency that varied between 77 and 99%, 76 and 98%, and 61 and 98%, respectively. A high significant correlation of PAE removal with total suspended solids (TSS) and turbidity suggests that the removal performance proceeded more through adsorption on settling particles and sludge than on biodegradation. However, the concentrations of PAEs detected in the final effluent and sludge samples exceeded acceptable levels allowed internationally for a safe aquatic environment. AS may have exhibited a more stable and better performance across the different seasons; however, pollution source control still deserves a special attention to prevent the risk posed by these micropollutants.

Contamination and Risk Assessment of Estrogens in Livestock Manure: A Case Study in Jiangsu Province, China

This study investigated the occurrence and contamination risk of estrogens in livestock manure in Jiangsu Province, China. Four estrogens-estriol (E3), 17β-estradiol (17β-E2), bisphenol A (BPA), and 17α-ethinyloestradiol (EE2)-were detected in livestock manure from hens, ducks, swine, and cows. The respective mean concentrations of each estrogen found in these manures were 289.8, 334.1, 330.3, and 33.7 μg/kg for E3; 38.6, 10.9, 52.9, and 38.8 μg/kg for 17β-E2; 63.6, 48.7, 51.9, and 11.7 μg/kg for BPA; and 14.3, 11.3, 25.1, and 21.8 μg/kg for EE2. Estrogens were most frequently detected at high concentrations in the manure of finishing pigs, followed by the manure of growing pigs and piglets. Estrogens can be partially degraded after banking up for seven days; yet, great quantities of estrogens remain in livestock manure. The total estradiol equivalent quantity (EEQt) estimated to be present in aquatic environments but originating from livestock waste was 10.5 ng/L, which was greater than the hazard baseline value (1 ng/L) and also higher than the proposed lowest observable effect concentration (10 ng/L) of E2 in aquatic environments. The results of our study demonstrate that livestock waste is an important source of estrogens, which may potentially affect the hormonal metabolism of aquatic organisms.

Modeling the fate and transport of 17β-estradiol in the South River watershed in Virginia

Hormones excreted by livestock metabolisms often enter surface water through feces and urine and can potentially cause adverse impacts to aquatic biota. This study involved a modeling analysis of 17β-estradiol (E2), a prevalent estrogen, in the South River watershed located in Augusta County, Virginia from 2013 to 2015. Cattle manure, poultry litter, biosolids, septic systems, and wastewater treatment plants (WWTPs) were considered as sources of E2 in this study. The EPA's BASINS modeling framework was configured to track the fate and transport of E2. The first-order kinetics and the wash-off model were adopted to characterize the attenuation and the transport of E2. The modeling results indicated that the flow rate was a major input affecting the simulated E2 levels in the water. During storm events, E2 on the land surface was transported into the rivers by the surface runoff and the E2 released into streams was diluted by the high water flow. Variations of the simulated E2 concentrations in the South River depended on the relative magnitudes of the loads from point and nonpoint sources. Modeling results showed that E2 levels in the South River were below the lowest observable effect level (LOEL) for fish. However, the practices of storing manure before land application and fencing off rivers to keep cattle out of the water are encouraged to prevent the potential for high E2 levels in streams receiving feedlot runoff.

Role of humic substances in the photodegradation of naproxen under simulated sunlight

Humic substances (HS) including humic acid (HA) and fulvic acid (FA) are ubiquitous in the natural waters. Although numerous studies documented their role in photodegradation of organic pollutants, the competitive effects of photosensitization and light-screening of HS on the photodegradation of pollutants are not yet clear. In this work, the role of HS in the photodegradation of the pharmaceutical naproxen (NP) was studied under simulated sunlight. The direct photodegradation quantum yield of NP in deionized water was 2.1 × 10^-2, and the apparent quantum yields for photosensitized degradation of NP in the presence of FA and HA were 2.3 × 10^-4 and 2.6 × 10^-5, respectively. Both direct and photosensitized photodegradation decreased with increasing pH, consistent with the trend of singlet oxygen (¹O₂) reaction rate constants of NP. HA inhibited the photodegradation of naproxen thoroughly. In contrast, FA accelerated the photodegradation of NP at lower substrate concentration and light intensity, and vice versa. Direct photodegradation of NP declined sharply with spectral radiation attenuation of UV region, when HS-mediated photosensitization predominantly accounted for the photodegradation. The direct photodegradation was ascribed to decomposition of excited triplet state of naproxen (³NP^∗) and self-sensitization effect involving ¹O₂. The FA-mediated photodegradation was mainly attributed to ¹O₂ oxidation in aerated solution. These findings are important for assessing the competitive effects of humic substances on the photodegradation of pollutants under various conditions in natural waters.

Quantitative proteomic analyses of the microbial degradation of estrone under various background nitrogen and carbon conditions

Microbial degradation of estrogenic compounds can be affected by the nitrogen source and background carbon in the environment. However, the underlying mechanisms are not well understood. The objective of this study was to elucidate the molecular mechanisms of estrone (E1) biodegradation at the protein level under various background nitrogen (nitrate or ammonium) and carbon conditions (no background carbon, acetic acid, or humic acid as background carbon) by a newly isolated bacterial strain. The E1 degrading bacterial strain, Hydrogenophaga atypica ZD1, was isolated from river sediments and its proteome was characterized under various experimental conditions using quantitative proteomics. Results show that the E1 degradation rate was faster when ammonium was used as the nitrogen source than with nitrate. The degradation rate was also faster when either acetic acid or humic acid was present in the background. Proteomics analyses suggested that the E1 biodegradation products enter the tyrosine metabolism pathway. Compared to nitrate, ammonium likely promoted E1 degradation by increasing the activities of the branched-chain-amino-acid aminotransferase (IlvE) and enzymes involved in the glutamine synthetase-glutamine oxoglutarate aminotransferase (GS-GOGAT) pathway. The increased E1 degradation rate with acetic acid or humic acid in the background can also be attributed to the up-regulation of IlvE. Results from this study can help predict and explain E1 biodegradation kinetics under various environmental conditions.

A model of natural degradation of 17-α-ethinylestradiol in surface water and identification of degradation products by GC-MS

Over the past decade, the environment has been polluted by a wide spectrum of exogenous chemicals and environmental analysis has become one of the most progressive parts of analytical research. The aim of this work was to determine the kinetics of natural degradation, and to identify the degradation products of the massively used estrogenic drug, 17-α-ethinylestradiol. The photodegradation, oxidation and thermostability conditions were selected according to ICH requirements for pharmaceutical stability testing. A simple 72-h photodegradation study in purified water exhibited significant first-order kinetics with the kinetic constant k = 0.0303 h^-1, and degradation halftime 22.8 h. The basic halftime could be reduced to 17.1 h by the addition of sea salt, and increase in temperature. Monohydroxy, dihydroxy and dehydrogenated derivatives of ethinylestradiol with intact steroidal structure were identified as major degradation products resulting from simple photodegradation. The addition of an oxidative agent significantly accelerated the degradation rate; combined with higher temperature, the degradation halftime was reduced to 1.1 h with the first-order kinetic constant k = 0.632 h^-1. TOC analysis showed a notable decrease of organic mass (18% in 3 days) during oxidation experiments, and confirmed the degradation of steroidal structure.

Degradation of organic pollutants mediated by extracellular peroxidase in simulated sunlit humic waters: A case study with 17β-estradiol

A growing body of research indicated that natural processes such as photolysis, biotransformation and sorption contribute to natural attenuation of organic compounds in natural waters. Here we report another potential natural reaction involving induction by extracellular peroxidase (POD) in sunlit humic waters. The degradation behavior of a natural estrogen 17β-estradiol (E2) in waters containing both horseradish peroxidase (HRP) and Suwannee River humic acid (SRHA) were studied under simulated sunlight. Significant enhancement of E2 degradation was observed in the presence of HRP as compared to direct and SRHA-inducted photolysis, resulting from the efficient degradation of E2 induced by HRP using photoproduced H₂O₂. The contribution of direct photolysis, indirect photolysis and enzymatic degradation to E2 degradation was calculated as 36.6, 31.7 and 31.7%, respectively. Lower yields of hydroxylation products and several new dimer products in E2+SRHA+HRP system relative to E2+SRHA system indicated that E2 degradation was primarily mediated by HRP, revealing the presence of HRP strongly affected the degradation pathway of E2. Take naturally occurring POD into consideration, enzymatic degradation may be an important attenuation pathway of E2 and other contaminants that are sensitive to peroxidases in certain waters such as humic rich freshwater system.

Mitigating 17α-ethynylestradiol water contamination through binding and photosensitization by dissolved humic substances

Photodegradation is an important abiotic pathway transforming organic pollutants in natural waters. Humic substances (HS), including humic and fulvic acids, are capable of accelerating the photodegradation of steroid estrogens. However, how the photodegradtion of the emerging pollutants influenced by HS is not clear. Thus, we studied the roles and mechanisms of HS in inducing the photodegradation of 17α-ethynylestradiol (EE2). HS generally induces EE2 photodegradation through binding and reactive species generation. Apart from hydroxyl radical (HO), the excited triplets of humic substances (³HS*) are other key reactive species degrading EE2 by abstracting electrons. HO and ³HS* were responsible for about 60% of the overall EE2 photodegradation at 250μmol HS L^-1. Most of EE2 molecules bound to the HS via H-bonding, π-π and hydrophobic interactions. The binding role of HS in promoting EE2 photodegradation was rationalized by 17β-estradiol competitive binding with EE2 to the humic and fulvic acids. Furthermore, HS-promoted photodegradation can alter EE2 toxicity to wheat, rice and Ormosia plants. This study extends our knowledge on the photochemical behaviors and ecological risks of steroid estrogens in natural waters.

Photodegradation of 17α-ethynylestradiol in dissolved humic substances solution: Kinetics, mechanism and estrogenicity variation

17α-Ethynylestradiol (EE2) in natural waters may cause adverse effects on organisms due to its high estrogenic potency. Laboratory studies were performed to study the effects of a local humic acid (LHA), fulvic acid (LFA) and Aldrich humic acid (AHA) on the photochemical behavior and estrogenic potency of EE2. Here photolytic experiments demonstrated that pure aqueous EE2 could undergo direct and self-sensitized photodegradation at a global rate of 0.0068hr^-1. Photodegradation rate of EE2 in 5.0mg/L dissolved humic substances (DHS) was determined to be 0.0274, 0.0296 and 0.0254hr^-1 for LHA, LFA and AHA, respectively. Reactive oxygen species (ROS) and triplet dissolved humic substances (³DHS*) scavenging experiments indicated that the promotion effect of DHS on EE2 photodegradation was mainly aroused by the reactions of HO (35%-50%), ¹O₂ (<10%) and ³DHS* (22%-34%). However, the photodegradation of EE2 could also be inhibited when DHS exceeded the threshold of 10mg/L. Three hydroxylation products of EE2 were identified using GC-MS and their formation pathways were also proposed. In vitro estrogenicity tests showed that EE2 was transformed into chemicals without estrogenic potency. These findings could extend our knowledge on the photochemical behaviors of steroid estrogens in sunlit natural waters.

Parent and conjugated estrogens and progestagens in surface water of the Santa Ana River: Determination, occurrence, and risk assessment

The present study investigated the occurrence of 13 parent and conjugated estrogens and progestagens in surface water of the Santa Ana River. With the exception of the synthetic hormones 17α-ethynylestradiol and mestranol, other compounds were detected at least twice at 10 representative sites, with the ubiquitous estrone (E1) and 17β-estradiol-3-sulfate as the dominant compounds quantified (0.24-6.37 ng/L and 0.49-9.25 ng/L, respectively). Sites near dairy farms exhibited high levels of conjugates, whereas those close to a sewage treatment plant (STP) effluent outlet displayed relatively high concentrations of E1. Principle component analysis coupled with multiple linear regression revealed dairy farms and the STP as the 2 significant contamination sources, accounting for 69.9% and 31.1% of the total hormone burden, respectively. Risk assessment results suggested E1 and 17β-estradiol (E2) as the 2 hormones with the largest risks to aquatic organisms, and which combined, contributed >90% of the total estrogenicity. Most of the sites investigated showed that E1 and E2 posed a medium risk (0.1 < risk quotient < 1), whereas each induced a high risk (risk quotient >1) at sites severely impacted by the STP and dairy farms. These results suggest that river health would benefit from effective treatment of waste at the STP and dairy farms prior to discharge. Environ Toxicol Chem 2016;35:2657-2664. © 2016 SETAC.

Factors Affecting Behavior of Phenolic Endocrine Disruptors, Estrone and Estradiol, in Constructed Wetlands for Domestic Sewage Treatment

This study investigated the efficiency of 12 pilot-scale constructed wetlands (CWs) with different configurations on the removal of estrone and estradiol from raw domestic sewage. An orthogonal design was employed to evaluate the impact of four principal design parameters of CWs, including four wetland types, three substrates, three plant conditions, and three hydraulic loading rates, in summer and winter. A bench-scale anoxic simulation test was performed in the laboratory to clarify the photolysis, sorption, and degradation of estrogens. Estrogens were more effectively removed by the 12 CWs during summer. The experiment showed that target estrogens were efficiently removed by wetland substrate under anoxic conditions through exothermic sorption and degradation even in winter. This suggests that the inefficient removal in CWs in winter likely resulted from subsequent cleavage of a considerable amount of estrogen conjugates in influent due to insufficient decomposition at low temperatures. The transformation from estradiol to estrone could be driven by residual microbial activities not inhibited by azide, and the reversible process was then driven by active microorganisms but not solely abiotic redox reactions. Among the four design parameters, wetland-type was the most important and downward-vertical flow CWs performed best.

Photodegradation of estrogenic endocrine disrupting steroidal hormones in aqueous systems: Progress and future challenges

This article reviews different photodegradation technologies used for the removal of four endocrine disrupting chemicals (EDCs): estrone (E1), 17β-estradiol (E2), estriol (E3) and 17α-ethinylestradiol (EE2). The degradation efficiency is greater under UV than visible light; and increases with light intensity up to when mass transfer becomes the rate limiting step. Substantial rates are observed in the environmentally relevant range of pH7-8, though higher rates are obtained for pH above the pKa (~10.4) of the EDCs. The effects of dissolved organic matter (DOM) on EDC photodegradation are complex with both positive and negative impacts being reported. TiO2 remains the best catalyst due to its superior activity, chemical and photo stability, cheap commercial availability, capacity to function at ambient conditions and low toxicity. The optimum TiO2 loading is 0.05-1gl(-1), while higher loadings have negative impact on EDC removal. The suspended catalysts prove to be more efficient in photocatalysis compared to the immobilised catalysts, while the latter are considered more suitable for commercial scale applications. Photodegradation mostly follows 1st or pseudo 1st order kinetics. Photodegradation typically eradicates or moderates estrogenic activity, though some intermediates are found to exhibit higher estrogenicity than the parent EDCs; the persistence of estrogenic activity is mainly attributed to the presence of the phenolic moiety in intermediates.

Photosensitized Degradation of 17β-estradiol and 17α-ethinylestradiol: Role of Humic Substances Fractions

Photodegradation of 17α-ethinylestradiol (EE2) and 17β-estradiol (E2) was investigated under simulated solar radiation. Photodegradation kinetics in the absence and presence of humic substances (HSs) fractions (humic acids [HAs], fulvic acids [FAs], and XAD-4), were compared. Although all three fractions were responsible for a noticeable increase on photodegradation rates, the effects were greater for FA and XAD-4. Half-life time decreased from 46 and 94 h (direct photodegradation) for EE2 and E2, respectively, to 6.4, 2.1, and 2.7 h (for EE2) and 5.7, 2.9, and 3.1 h (for E2) in the presence of HAs, FAs, and XAD-4, respectively. The XAD-4 fraction results were similar to those of FAs, which is considered the most photochemically active fraction of HSs. Studies were also conducted in organic matter-rich environmental water matrices. After 5 h, photodegradation ranged from 44 to 94% for EE2 and from 27 to 95% for E2, compared with 16% for EE2 and 6% for E2 in ultrapure water. The maximum photodegradation was obtained in an estuarine water sample, known to be rich in FAs and XAD-4 fractions and poor in HAs, showing that not only is the presence of organic matter an important factor for the photodegradation increase, as also the type of organic matter is determinant.

Effect of natural aquatic humic substances on the photodegradation of estrone

Photodegradation of estrone (E1) was investigated under simulated solar radiation in absence and presence of the different fractions of humic substances (HS), namely humic acids (HA), fulvic acids (FA) and XAD-4 fraction. The pseudo-first order photodegradation rate constants increased from 0.1137 h(-1), in ultrapure (MQ) water, to 0.1774, 0.1943 and 0.3109 h(-1), in presence of HA, FA and XAD-4, respectively. Half-life time decreased from 6.10 h in MQ water to 3.91, 3.57 and 2.23 h in presence of HA, FA and XAD-4, respectively. These results evidence the relevant photosensitizing effect of XAD-4 fraction of HS on the degradation of E1, which, to the best of our knowledge have never been studied. Photodegradation studies were also conducted in organic matter-rich environmental aquatic matrices, namely fresh, estuarine and waste water. After 2 h, photodegradation achieved values ranged between 35.6 and 57.1% in natural water samples, compared with 26.4% in ultrapure water. The higher photodegradation occurred in an estuarine water sample, known to be rich in XAD-4 fraction and poor in HA, indicating that not only the presence of organic matter, but also its type, are determinant in the E1 photodegradation rate. Finally, the use of sodium azide as singlet oxygen ((1)O2) scavenger during the phototransformation of E1 in ultrapure and in two wastewater samples allowed to conclude that (1)O2 has an important role in the E1 photodegradation.

Effects of pH and dissolved oxygen on the photodegradation of 17α-ethynylestradiol in dissolved humic acid solution

To probe the mechanisms responsible for pH and dissolved oxygen (DO) affecting the photodegradation of 17α-ethynylestradiol (EE2) in dissolved humic acid (HA) solution, EE2 aqueous solutions with pH values ranging from 3.0 to 11.0 and different DO conditions were irradiated by using a 300 W mercury lamp equipped with 290 nm light cutoff filters. In 5.0 mg L(-1) HA solutions (pH 8.0), EE2 was degraded at a rate of 0.0739 h(-1) which was about 4-fold faster than that in Milli-Q water. The degradation of EE2 was mainly caused by the oxidation of photogenerated reactive species (RS), and the contribution of direct photodegradation to EE2 degradation was always lower than 27%. Both the direct and indirect photodegradation of EE2 were closely dependent on the EE2 initial concentration, pH value and DO concentration. The photodegradation rate of EE2 decreased with increased initial concentration of EE2 due to the limitation of photon flux. With pH and DO increasing, the degradation rate of EE2 increased significantly due to the increase in the yields of excited EE2 and RS. Among the photogenerated RS, HO˙ and (3)HA* were determined to be the key contributors, and their global contribution to EE2 photodegradation was about 50%. Although HA could generate more (1)O2 than HO˙, the contribution of (1)O2 to EE2 degradation was lower than 13% due to its low reactivity towards EE2. This study could enlarge our knowledge on the photochemical behaviors of steroid estrogens in natural sunlit waters.