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

Combined effects of pH and dissolved organic matter on the availability of pharmaceuticals and personal care products in aqueous environment

The interaction between pharmaceuticals and personal care products (PPCPs) with dissolved organic matter (DOM) can alter their bioavailability and toxicity. Nevertheless, little is known about how pH and DOM work together to affect the availability of PPCPs. This study investigated the impact of pH and DOM on the availability of seven PPCPs, namely Carbamazepine, Estrone, Bisphenol A, Testosterone Propionate, Triclocarban, 4-tert-Octylphenol and 4-n-Nonylphenol, using negligible depletion solid-phase microextraction (nd-SPME). The uptake kinetics of PPCPs by the nd-SPME fibers increased proportionally with DOM concentrations, likely due to enhanced diffusive conductivity in the unstirred water layer. At neutral pH, the partitioning coefficients of PPCPs for Humic Acid (log KDOC 3.87-5.25) were marginally higher than those for Fulvic Acid (log KDOC 3.64-5.11). Also, the log KDOC values correlated linearly with the log DOW (pH 7.0) values of PPCPs, indicating a predominant role for hydrophobic interactions in the binding of DOM and PPCPs. Additionally, specific interactions like hydrogen bonding, π-π, and electrostatic interactions occur for certain compounds, influenced by the polarity and spatial conformation of the compounds. For these ionizable PPCPs, the log DDOC values exhibit a strong dependence on pH due to the dual influence of pH on both DOM and PPCPs. The log DDOC values rose from pH 1.0 to 3.0, peaked at pH 5.0 to 9.0, and then (sharply) declined from 11.0 to 13.0. The reasons are that in strong acidic circumstances, the coiled and compressed shape of DOM inhibits the hydrophobic interaction, whereas in strong alkaline conditions, significant electrostatic repulsion reduces the sorption. This study reveals that the effects of DOM on the bioavailability of PPCPs are dependent on both pH and the specific compound involved.

Association of tetrabromobisphenol A (TBBPA) with micro/nano-plastics: A review of recent findings on ecotoxicological and health impacts

Despite the diverse research into the environmental impact of plastics, several stones have yet to be unraveled in terms of their ecotoxicological potential. Moreover, their detrimental impacts have become terrifying in recent years as the understanding of their tendency to associate and form cohorts with other emerging contaminants grew. Despite the hypothesis that microplastics may potentially adsorb organic pollutants, sequestering and making them not bioavailable for enhanced toxicity, evidence with pollutants such as Tetrabromobisphenol A (TBBPA) defers this assertion. TBBPA, one of the most widely used brominated flame retardants, has been enlisted as an emerging contaminant of serious environmental and human health concerns. Being also an additive to plasticware, it is not far to suspect that TBBPA could be found in association with micro/nanoplastics in our environment. Several pieces of evidence from recent studies have confirmed the micro/nanoplastics-TBBPA association and have exposed their compounded detrimental impacts on the environment and human health. This study, therefore, presents a comprehensive and up-to-date review of recent findings regarding their occurrence, factors that foster their association, including their sorption kinetics and isotherms, and their impacts on aquatic/agroecosystem and human health. The way forward and prospects for future studies were presented. This research is believed to be of significant interest to the readership due to its relevance to current environmental challenges posed by plastics and TBBPA. The study not only contributes valuable insights into the specific interaction between micro/nanoplastics and TBBPA but also suggests the way forward and prospects for future studies in this field.

Mechanistic explanation and influence of molecular structure on chemical degradation and toxicity reduction by hydroxyl radicals

This study explored the influence of structural characteristics of organic contaminants on the degradation during an advanced oxidation process (AOP). The target contaminants were acetaminophen (ACT), bisphenol A (BPA), and tetracycline (TC). The Fenton process was selected as the model process in which major reactive species of hydroxyl radicals in most AOPs are generated for target compound degradation. The optimal reagent concentration ratio was [Fe2+]/[H2O2] = 0.5 mM/0.5 mM in an acidic condition, resulting in 83.49%, 79.01%, and 91.37% removals of ACT, BPA, and TC, respectively. Contrarily, the mineralization rates were apparently lower compared to their respective removal efficiencies. Experimental observation also suggested that the aromatic structure was rather difficult to degrade since their unsaturated electron clouds would hinder the attack of hydroxyl radicals due to electric repulsion. The preferred attacking sites of an aromatic ring differ due to the functional groups and structure symmetry. However, the electrophilic attack of the hydroxyl radical is the major reaction for decomposing aliphatic structures of cyclic or branched organics, resulting in the highest removal and mineralization of TC among these three tested chemicals. In addition, an apparent removal of a contaminant may not necessarily reduce its toxic impact on the environment.

A critical and comprehensive review of the current status of 17β-estradiol hormone remediation through adsorption technology

Even at low concentrations, steroid hormones pose a significant threat to ecosystem health and are classified as micropollutants. Among these, 17β-estradiol (molecular formula: C18H24O2; pKa = 10.46; Log Kow = 4.01; solubility in water = 3.90 mg L-1 at 27 °C; molecular weight: 272.4 g mol-1) is extensively studied as an endocrine disruptor due to its release through natural pathways and widespread use in conventional medicine. 17β-estradiol (E2) is emitted by various sources, such as animal and human excretions, hospital and veterinary clinic effluents, and treatment plants. In aquatic biota, it can cause issues ranging from the feminization of males to inhibiting plant growth. This review aims to identify technologies for remediating E2 in water, revealing that materials like graphene oxides, nanocomposites, and carbonaceous materials are commonly used for adsorption. The pH of the medium, especially in acidic to neutral conditions, affects efficiency, and ambient temperature (298 K) supports the process. The Langmuir and Freundlich models aptly describe isothermal studies, with interactions being of a low-energy, physical nature. Adsorption faces limitations when other ions coexist in the solution. Hybrid treatments exhibit high removal efficiency. To mitigate global E2 pollution, establishing national and international standards with detailed guidelines for advanced treatment systems is crucial. Despite significant advancements in optimizing technologies by the scientific community, there remains a considerable gap in their societal application, primarily due to economic and sustainable factors. Therefore, further studies are necessary, including conducting batch experiments with these adsorbents for large-scale treatment along with economic analyses of the production process.

Characterization and low-temperature biodegradation mechanism of 17β-estradiol-degrading bacterial strain Rhodococcus sp. RCBS9

Steroidal estrogens residues in the environment can be a serious hazard to humans and animals and has been listed as group 1 carcinogens by World Health Organization (WHO). Microbial degradation is one of the effective strategies for the removal of such contaminants. In this study, a low-temperature degrading bacterial strain (Rhodococcus sp. RCBS9) was isolated from the soil of a dairy farm for 17β-estradiol (E2) degradation. The strain RCBS9 exhibited an efficient degradation potential at low temperatures. To lean how different factors influence E2 degradation, we have found a major role of intracellular enzymes in E2 degradation. Genomic and metabolomic analyses have suggested potential degradation genes and four metabolic pathways. These findings provide valuable strain resources for the low temperature bioremediation of E2 contamination and insights into E2 biodegradation mechanism.

The microbial oxidation of pharmaceuticals in an anaerobic aqueous environment: Effect of dissolved organic matter fractions from different sources

Previous studies have demonstrated the importance of dissolved organic matter (DOM) on the biodegradation of trace organic contaminants occurred in the hyporheic zone. However, the role of diverse DOM fractions with distinct physicochemical properties on the biodegradation of pharmaceuticals under reducing conditions is scarcely known. To address this knowledge gap, DOMs derived from road-deposited sediment, soil, and active sludge (namely allochthonous DOM) and algae (namely autochthonous DOM) were collected and isolated into different fractions. Thereafter, the effect of DOM fractions on the anaerobic microbial oxidation of two typical pharmaceuticals, i.e., ritonavir (RTV) and tetracycline (TC) was explored by using simulated anaerobic microcosms. Mechanistic insights into how DOM fractions from different sources influence pharmaceutical biodegradation processes were provided by optical and electrochemical analyses. Results showed that humic acid and fulvic acid fractions from allochthonous DOM could enhance the biodegradation of TC (12.2 % per mgC/L) and RTV (14.5 % per mgC/L), while no significant impact was observed for that of hydrophilic fractions. However, autochthonous DOM promoted the biodegradation of TC (4.17 % per mgC/L) and inhibited that of RTV. Mechanistic analysis showed that the higher of humification and aromatization level of DOM components, the stronger their promotive effect on the biodegradation of TC and RTV. Further, the promotive mechanism could be attributed to the response of quinone moieties in DOM as extracellular electron acceptors that yields more energy to support microbial metabolism. These results provide a more comprehensive understanding of diverse DOM fractions mediating microbial anaerobic oxidation of trace organic pollutants, and extend our insights into contamination control and remediation technologies.

Insight into the effect of microplastics on the adsorption and degradation behavior of thiamethoxam in agricultural soils

Thiamethoxam and microplastics are both common pollutants in farmland soil; however, few studies have focused on the interaction between thiamethoxam and microplastics in soil. Here, a batch experiment and soil incubation experiment were performed to explore the mechanism and effects of microplastics on the adsorption and degradation behaviors of thiamethoxam in soil, respectively. First, the batch experimental results indicated that the adsorption process of thiamethoxam on the microplastic/soil mixtures and soil-only systems mainly relies on chemical interactions. All sorption processes had moderate intensities of adsorption, and the sorption process occurred on the heterogeneous surface. In addition, the particle size and dose of microplastics could both affect the adsorption behavior of thiamethoxam onto microplastics/soil systems. The sorption capacity of thiamethoxam in soil decreases as the particle size of microplastics increases, but the sorption capacity increases as the dose of microplastics increases. Second, the results of the soil incubation experiment showed that the half-lives of thiamethoxam ranged from 57.7 d to 86.6 d, from 86.6 d to 173.3 d, and 115 d in the biodegradable microplastic/soil systems, nondegradable microplastic/soil systems, soil-only systems, respectively. These results indicate that biodegradable microplastics promoted the degradation of thiamethoxam, while nondegradable microplastics delayed the degradation process of thiamethoxam in soil. Overall, microplastics could change the degradation behaviors, sorption capacity and adsorption efficiency, and then affect the mobility and persistence of thiamethoxam in the soil environment. These findings contribute to understanding the influence of microplastics on the environmental fate of pesticides in the soil environment.

Sorption and desorption of epiandrosterone and cortisol on sewage sludge: Comparison to aquatic sediment

Steroids have aroused global concern due to their potent endocrine-disrupting effects. Androgens and glucocorticoids are the most abundant species in sewage; however, our understanding of their fate and risks from the source to environmental sinks remains elusive. This study compared the sorption-desorption characteristics of epiandrosterone (EADR) and cortisol (CRL) in sewage sludge and aquatic sediment, and the surface and molecular interactions were tentatively investigated through infrared spectroscopy and the fluorescence excitation-emission matrix. The results showed that the sorption capacities of EADR and CRL in the sludge were 4015 L/kg and 81.17 L/kg, respectively, which are much larger than those in the sediment (EADR: 78.77 L/kg, CRL: 6.39 L/kg); 0.02%-1.2% of EADR and 0.2%-14.5% of CRL could be desorbed from sludge, while the desorption ratios were even lower in the sediment. The high organic content in the sludge might contribute to the larger sorption capacities, while the weak interaction between steroids and organic matter could lead to larger desorption potential. The sediment contained more mineral content and featured a larger specific surface area, which could be responsible for the greater desorption hysteresis for EADR and CRL. These results will help to better understand the potential risk of sewage sludge-associated steroids and their distribution in sediment-water systems.

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.

Effects of dissolved organic matter derived from chicken manure on the biotransformation of roxarsone in soil

Roxarsone (3-nitro-4-hydroxyphenylarsonic acid, ROX), widely used as a livestock feed additive, is excreted untransformed in large concentrations. Accumulation of this manure in the open environment increases dissolved organic matter (DOM) and ROX in soil within the aeration zone. And microbial action plays a dominant role in the transformation of ROX. However, the specific effect of DOM on the biotransformation of ROX is not known. In this paper, we investigated the transformation rate, metabolite content, and microbial community response of ROX in soils with different DOM concentrations (71.61, 100, 200, 500, and 800 mg L-1). The transformation of ROX was consistent with first-order transformation kinetics. DOM promoted the transformation of ROX, and with high DOM (DOM ≥200 mg L-1), ROX was transformed almost completely within two days. In this case, DOM provided nutrients to microorganisms and promoted their growth, accelerating the transformation of ROX. Also, the solubility of ROX was enhanced by DOM to increase its bioavailability. The microbial diversity was negatively correlated with DOM concentration and ROX transformation time; during the transformation of ROX, Bacillus, Arthrobacter, Enterococcus, Acinetobacter, and Pseudomonas became dominant in the soil with anomalously high levels of DOM. This study demonstrates the transformation process of ROX under actual environmental conditions where organic matter coexists with ROX, and this understanding is important for the prevention and control of arsenic pollution in soil within the aeration zone with anomalously high levels of DOM.

(Anti)estrogenic activity impacted by complex environmental matrices: A DOM and multiphase distribution approach

The presence of estrogenic endocrine disruptors in aquatic environments has been a concern and bioassays are recommended tools for their monitoring. However, the physicochemical properties of contaminants and the environmental matrix features may influence the resultant response. This study aimed to assess this influence on the Yeast Estrogen Screen (YES) assay. Mixtures of 17β-estradiol (E2) and humic acid (HA) were evaluated through the Schild approach aiming to investigate the interactions between estrogens and dissolved organic matter (DOM). Moreover, environmental samples from municipal landfill leachate and wastewater treatment plant (WWTP) influents and effluents were screened for (anti)estrogenic activity at both dissolved and particulate phases. Finally, results were statistically confronted with physicochemical parameters through principal component analysis (PCA). The HA test concentrations strongly reduced the E2 response, even at low levels. Humic substances may not only reduce estrogen bioavailability, but also interfere with the assay mechanism through enzymatic inhibition thus masking the sample estrogenic potential. Landfill leachate had total E2-Eq in the range 1282-2591 ng L^-1, while WWTP influent and effluent were in the range 12.1-41.4 and <DL-2.3 ng L^-1, so estrogenicity was reduced 92% in average. Particulate phase was responsible for 33-100% of measured E2-Eq between matrices, though cytotoxicity occurred in some extracts. Antiestrogenic activity was observed in both phases and might also have masked the estrogenicity of samples. PCA did not resulted in positive correlations supporting a multiphase distribution pattern of estrogenic compounds. Nevertheless, the solids and organic matter characteristics supported the data interpretation. In conclusion, the in vitro YES assay is subjected to factors intrinsic to the environmental sample that can influence on the measured estrogenic response. Therefore, results interpretation should be performed together with organic matter characterization parameters, cytotoxicity and antiestrogenic activity evaluation.

Characterization of dissolved black carbon and its binding behaviors to ceftazidime and diclofenac pharmaceuticals: Employing the molecular weight fractionation

As the ubiquitous component of the aquatic environment, dissolved organic matter (DOM) readily bind with residual pharmaceutical contaminants (PCs) and influence their environmental behaviors. However, the binding mechanisms between dissolved black carbon (DBC), a vital part of the natural DOM pool, and PCs were poorly researched. In this study, the bulk DBC was divided into four fractions in molecular weight (MW) via an ultrafiltration system, and the properties of DBC and their binding interaction with two kinds of typical PCs (ceftazidime (CAZ) and diclofenac (DCF)) were explored concretely. The results showed that low MW component was the main contributor to bulk DBC, and the aromaticity increased with the increase of MW. The categories of chemical structures and fluorescent substances in different MW DBC were similar. Multispectral techniques showed that the oxygen-enriched compounds in DBC had the higher affinity to CAZ/DCF. The -NH-, -COOH, -NH₂ groups in CAZ molecules appeared to form the hydrogen bond with DBC. Fluorescence quenching experiments were analyzed, and the binding mechanisms were specifically expounded from the thermodynamic perspective. The fluorophore of fulvic acid-like compounds (FA) were quenched by both static and dynamic quenching mechanisms, while only static quenching occurred for humic acid-like compounds (HA). For bulk DBC, the hydrogen bond and van der Waals force were the major forces in the HA-CAZ system, while the hydrophobic force made the primary contribution to the HA-DCF system, which might be ascribed to the higher hydrophobic nature of DCF. Notably, with the increase of HA MW, the main binding mode of HA-CAZ/DCF changed from hydrophobic force to hydrogen bond and van der Waals force gradually, which also directly proved that various noncovalent interactions co-driven the binding processes. Our findings are beneficial to better assess the fate of DBC and PCs and the corresponding complexes in the aquatic environment.

Distribution, ecological fate, and risks of steroid estrogens in environmental matrices

Over the past two decades, steroidal estrogens (SEs) such as 17α-ethylestradiol (EE2), 17β-estradiol (E2),17α-estradiol (17α-E2), estriol (E3) and estrone (E1) have elicited worldwide attention due to their potentially harmful effects on human health and aquatic organisms even at low concentration ng/L. Natural steroidal estrogens exhibit greater endocrine disruption potency due to their high binding effect on nuclear estrogen receptors (ER). However, less has been explored regarding their associated environmental risks and fate. A comprehensive bibliometric study of the current research status of SEs was conducted using the Web of Science to assess the development trends and current knowledge of SEs in the last two decades, from 2001 to 2021 October. The number of publications has tremendously increased from 2003 to 2021. We summarized the contamination status and the associated ecological risks of SEs in different environmental compartments. The results revealed that SEs are ubiquitous in surface waters and natural SEs are most studied. We further carried out an in-depth evaluation and synthesis of major research hotspots and the dominant SEs in the matrices were E1, 17β-E2, 17α-E2, E3 and EE2. Nonetheless, investigations of SEs in soils, groundwater, and sediments remain scarce. This study elucidates SEs distribution, toxicological risks, ecological fate and mitigation measures, which will be beneficial for future monitoring, management, and risk assessment. Further studies are recommended to assess the toxicological risks of different SEs in complex environmental matrices to pursue a more precise and holistic quantitative estimation of estrogenic risk.

Environmental fate and toxicity of androgens: A critical review

Androgens are released by humans and livestock into the environment and which cause potent endocrine disruptions even at nanogram per liter levels. In this article, we reviewed updated research results on the structure, source, distribution characteristics and the fate of androgens in ecological systems; and emphasized the potential risk of androgens in aquatic organism. Androgens have moderately solubility in water (23.6-58.4 mg/L) and moderately hydrophobic (log Kow 2.75-4.40). The concentration of androgens in surface waters were mostly in ng/L ranges. The removal efficiencies of main wastewater treatment processes were about 70-100%, except oxidation ditch and stabilization ponds. Sludge adsorption and microbial degradation play important role in the androgens remove. The conjugated androgens were transformed into free androgens in environmental matrices. Global efforts to provide more toxicity data and establish standard monitoring methods need a revisit. Of the day available, there is an urgent need for comprehensive consideration of the impact of androgens on the environment and ecology.

Fate, occurrence, and removal of estrogens in livestock wastewaters

During the last decades, livestock and animal feeding operations have been expanded. In parallel, these activities are among the major sources of estrogens in the environment. Thus, considering the environmental and health risks associated with estrogenic compounds, this work reviews the fate, occurrence, and removal of free and conjugated E1, E2, and E3 in livestock wastewaters. A systematic literature review was carried out, and after applying the eligibility criteria, 66 peer-reviewed papers were selected. Results suggest high estrogen concentrations and, consequently, high estrogenic activity, especially in samples from swine farming. E1 and E2 are frequently found in wastewaters from bovine, swine, and other livestock effluents. Aerobic treatment processes were more efficient for estrogen removal, whereas anaerobic systems seem poorly effective. Removal efficiencies of estrogens and estrogenic activity of up to 90% were reported for constructed wetlands, advanced pond systems, trickling filters, membrane bioreactors, aerated and nitrifying reactors, combined air flotation, and vegetable oil capture processes. High concentrations found in wastewaters from livestock allied to the removal efficiencies reported for anaerobic processes (usually used to treat livestock wastewaters) evidence the importance of monitoring these compounds in environmental matrices.

Insight into the effect of wastewater-derived dissolved organic matter composition on norgestrel degradation in activated sludge: Coupled bacterial community and molecular characteristics

Dissolved organic matter (DOM) mediates the microbial transformation of micropollutants, including norgestrel (NGT) in natural waters. However, little is known of the effect of complex and variable wastewater-derived DOM composition on NGT degradation during wastewater treatment. In this study, the relationship between the compositions of initial DOM and NGT removal efficiencies of 17 wastewater treatment plants (WWTPs) in spring and summer were analyzed. The different molecular composition of DOM was selected in the lab to further explore its effect on NGT degradation by activated sludge. Results indicated that the DOM composition was a substantial driver of NGT removal in WWTPs. The discrepancies in the initial DOM composition contributed to the differences in the kinetics of NGT degradation by activated sludge. The larger rapid decay phase rates of NGT are usually accompanied by a large proportion of labile substances in DOM. High-throughput sequencing and ultrahigh-resolution mass spectrometry were used to further analyze the evolution of bacterial communities and DOM molecular composition were combined with network analysis to reveal the intrinsic relationship that how DOM composition affected NGT degradation by regulating core microbes. Eighty-nine core OTUs were significantly associated with NGT degradation, and 73 occurred in the rapid decay phase, implying that NGT degradation was mainly regulated by the initial composition of DOM. Nine major transformation products were identified in different groups with widely varying concentrations or relative abundances of these transformation products. This work provides valuable insights into the effects of wastewater-derived DOM composition on NGT degradation by activated sludge and innovatively explores the influence mechanisms from the bacterial community and molecular characterization perspectives.

Interactions between dissolved organic matter and perfluoroalkyl acids in natural rivers and lakes: A case study of the northwest of Taihu Lake Basin, China

Understanding the interactions between dissolved organic matter (DOM) and perfluoroalkyl acids (PFAAs) is essential for predicting the distribution, transport, and fate of PFAAs in aquatic environments. Based on field investigations in the northwest of Taihu Lake Basin combined with laboratory experiments, we obtained DOM and PFAA concentrations as well as compositions and investigated key factors of DOM affecting PFAA variability and capture of PFAAs by DOM. Results indicated that the total concentrations of PFAAs were 73.4-689 ng/L in surface water and that PFAAs were dominated by C3-7 perfluoroalkyl carboxylic acids and perfluorooctane sulfonic acid. The main components of DOM included tyrosine-, fulvic-, and tryptophan-like substances. The Mantel test revealed a significant positive correlation between DOM and PFAAs (P = 0.0001). Fulvic-like substances were identified as the most crucial factors affecting PFAA variability. The laboratory experiments revealed that DOM can spontaneously aggregate into a microgel. Furthermore, 19.1-50.9% of PFAAs, DOM characteristic peaks, and several metals (Ca, Mg, Cu, and Fe) can be removed during aggregation, indicating the capacity of DOM binding organic/inorganic substances. The fulvic-like substances were more effectively removed than the protein-like substances. The distribution coefficients of all PFAAs except perfluorohexanoic acid significantly correlated with their perfluorinated carbon numbers (r = 0.975, p<0.001). Our results provided insights into the interactions between DOM and PFAAs, improving the understanding of the distribution, transport, and fate of PFAAs in aquatic environments.

Straw return in paddy field alters photodegradation of organic contaminants by changing the quantity rather than the quality of water-soluble soil organic matter

Straw return, an important agricultural management practice, is worldwide adopted to enhance soil carbon sequestration and soil fertility. Although water-soluble soil organic matter (WSOM) in paddy field is known to affect the photodegradation of organic contaminants, how straw return regulates the photosensitization of WSOM by changing its properties remain unclear. Here, we determined the temporal variations in the content, chemical characteristics, and photosensitizing ability of WSOM after wheat straw return in a wheat-rice rotation system using optical spectroscopy and steady-state photodegradation tests. After straw return, the WSOM content first increased to a maximum and then gradually decreased to pre-return level at day 90. Nevertheless, the relative abundance of humic-like components in WSOM was not shifted by straw return, and protein-like component in WSOM just showed a slight decrease at day 45. All the WSOM samples inhibited sulfamethoxazole (SMX) photodegradation by light filtering, reactive species quenching and other mechanisms, while promoted diuron (DIU) degradation via reacting with •OH, ¹O₂ and excited triplet WSOM. The photodegradation of SMX and DIU was little affected by straw return changing WSOM composition and photochemical activity. However, straw return could decelerate SMX and DIU photodegradation by elevating WSOM content in a relatively short-term. This study emphasizes that straw return may reduce the photodegradation of organic contaminants by increasing WSOM concentration instead of altering WSOM chemical characteristics.

A comprehensive evaluation of factors affecting the reactivity of FeS towards hexabromocyclododecane diastereoisomers

Reactivity of iron sulfide (FeS) towards hexabromocyclododecane (HBCD) was explored under conditions of varying temperature, pH, inorganic ion and dissolved organic matter (DOM) in this study. Results show that the reduction of HBCD by FeS has an activation energy of 29.2 kJ mol^-1, suggesting that the rate-limiting step in the reduction was a surface-mediated reaction. The reduction of HBCD by FeS was a highly pH-dependent process. The optimal rate for HBCD reduction by FeS was observed at a pH of 6.2. All the tested inorganic ions suppressed the reduction of HBCD by FeS. XPS analysis confirmed that both Fe(II)-S and bulk S(-II) on FeS surface could be impacted by solution pH and inorganic ions and were responsible for the regulation of HBCD reduction. Some DOMs (i.e., fulvic acid, humic acid, salicylic acid, catechol and sodium dodecyl sulfate) were found to hinder the reduction via competing with HBCD for active sites on FeS surface. However, the presence of 2,2'-bipyridine, triton X-100 and cetyltrimethyl ammonium bromide was able to significantly enhance the rate of HBCD reduction by 5.8, 9.0 and 20 times, respectively. Different factors could influence the reduction efficiency of HBCD diastereoisomers to different extent, but not the reaction orders of HBCD diastereoisomers (α-HBCD < γ-HBCD < β-HBCD). Moreover, FeS could completely remove HBCD diastereoisomers in sediments with multiple factors within 9 d reaction. Our results contribute to give a better understanding on the performance of FeS towards HBCD under real and complex conditions and facilitate the application of FeS in remediation sites.

Estradiol and Estrogen-like Alternative Therapies in Use: The Importance of the Selective and Non-Classical Actions

Estrogen is one of the most important female sex hormones, and is indispensable for reproduction. However, its role is much wider. Among others, due to its neuroprotective effects, estrogen protects the brain against dementia and complications of traumatic injury. Previously, it was used mainly as a therapeutic option for influencing the menstrual cycle and treating menopausal symptoms. Unfortunately, hormone replacement therapy might be associated with detrimental side effects, such as increased risk of stroke and breast cancer, raising concerns about its safety. Thus, tissue-selective and non-classical estrogen analogues have become the focus of interest. Here, we review the current knowledge about estrogen effects in a broader sense, and the possibility of using selective estrogen-receptor modulators (SERMs), selective estrogen-receptor downregulators (SERDs), phytoestrogens, and activators of non-genomic estrogen-like signaling (ANGELS) molecules as treatment.

The binding characteristics of sediment-derived dissolved organic matter with ceftazidime: a microstructural and spectroscopic correlation study

This research focused on the characterization of sediment-derived dissolved organic matter (SDOM) extracted from sediment of Yellow River and the binding behaviors of ceftazidime (CAZ) with the presence of SDOM. The morphology, surface composition and structure of SDOM and the complexation between SDOM and CAZ in terms of component features, binding capacity and sequence were studied by multiple approaches. Results showed that SDOM was in situ autochthonous-dominated with a low weight-average molecular weight and aromaticity (the value of S_R was 2.523). The multiple morphological characteristics, high surface oxygen contents (53.49%) and more aliphatic (H/C = 1.91) of SDOM were further confirmed. Studies on SDOM-CAZ interaction suggested that the functional groups and chemical compositions of SDOM were susceptible to CAZ. In more detail, the aromatic protons and aliphatic protons of CAZ impacted significantly, and the binding between CAZ and SDOM might relate to noncovalent. The protein-like fractions were considered to be the primary participant with 49% fractions lost and the aromatics and amides as mainly active site interaction with CAZ. These findings have significant implications on the environmental fate of cephalosporin antibiotics and that of sediment-derived DOM.

Suppression mechanism of model humic constituents on laccase-enabled 17β-estradiol oxidation and oligomerization

Humic constituents (HCs) are ubiquitous in the aquatic ecosystems, and contain various functional groups that seriously impact the conversion of 17β-estradiol (17β-E2) by fungal laccase. The purpose of this study was to explore the influencing mechanism of HCs on Trametes versicolor laccase-enabled 17β-E2 oxidation and oligomerization. Herein, T. versicolor-secreted laccase could rapidly convert 99.2% of 17β-E2 (rate constant = 3.7 × 10^-2 min^-1, half-life = 18.7 min) into multifarious oligomers at 25 °C and pH 5.0, by phenolic radical-caused C-C and/or C-O self-linking routes, whereas HCs with O-phenolic hydroxyl groups (O-p-OH, i.e., catechol, pyrogallol, gallic acid, and caffeic acid) dramatically suppressed 17β-E2 oligomerization. Compared with HC-free, 17β-E2 rate constants weakened 6.3-15.8 fold in the presence of HCs containing O-p-OH. It is largely because the O-p-OH was preferentially oxidized by T. versicolor laccase to create the electrophilic O-quinone monomers/oligomers. These unstable reactive O-quinone intermediates strongly reversed 17β-E2 phenolic radicals to their monomeric molecules via two proton-transfer versus two electron-transfer channels, thus intercepting 17β-E2 oxidation and oligomerization. These findings highlight new insights into the effect of HCs containing O-p-OH on T. versicolor laccase-started 17β-E2 conversion, which is beneficial to re-understanding the fate and geochemical behavior of 17β-E2 in water.

Migration and abiotic transformation of estrone (E1) and estrone-3-sulfate (E1-3S) during soil column transport

Steroid estrogens have received worldwide attention and given rise to great challenges of aquatic ecosystems security, posing potential adverse effects on aquatic organisms and human health even at low levels (ng/L). The present study focused on understanding the mobility and abiotic transformation of estrone (E1) and estrone-3-sulfate (E1-3S) over spatial and time scales during soil transport. Column transport experiments showed that the migration capacity of E1-3S was far stronger than E1 in soil. The calculated groundwater ubiquity score and leachability index values also indicated the high leaching mobility of E1-3S. The hydrolysis of E1-3S and abiotic transformation into estradiol and estriol was observed in the sterilized soil. Furthermore, possible transformation products (e.g., SE₂₃₉, E2₃₇₈, E1 dimer₅₃₈, E1-E2 dimer₅₄₁) of E1 and E1-3S in soil were analyzed and identified after the column transport experiments. The estrogenic activity was estimated by 17β-estradiol equivalency values during the transport process in aqueous and soil phases. Additionally, the potential leaching transport to groundwater of E1-3S requires further critical concern.

Surface functional groups determine adsorption of pharmaceuticals and personal care products on polypropylene microplastics

The pervasiveness of microplastics (MPs), which can absorb pharmaceuticals and personal care products (PPCPs), has a certain impact on pollutant migration in natural waters. The adsorption behaviors of PPCPs on the aged polypropylene (PP) followed the pseudo-second-order kinetics and Langmuir isotherm, and the adsorption capacity (q_e) on the aged PP was much higher than that on the fresh PP. The Weber-Morris and Boyd models confirmed that the liquid-film and intra-particle diffusion affected the adsorption of PPCPs on the aged PP while the surface diffusion was a rate-limiting step for the fresh PP. The analysis of SEM-EDS, BET, FT-IR, and XPS further showed that changes in the type and content of the surface functional groups of PP led to differences in adsorption capacity and adsorption interactions. The Dragon-descriptor-based LFER and the quantum-chemical-descriptor-based QSAR models reflected the difference in adsorption interaction mechanisms. The examined models showed that the adsorption of the fresh PP toward PPCPs relied on hydrophobic and hydrogen bonding interaction, while for the aged PP electrostatic interaction and hydrogen bonding controlled the adsorption. The findings clarified interactions between PPCPs and MPs and provided a theoretical basis for the assessment of environmental behavior and ecological risk when MPs and PPCPs coexist.

Using a fugacity model to determine the degradation rate of typical polycyclic musks in the field: A case study in the North Canal River watershed of Beijing, China

To quantitate the degradation rate of 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-[g]-2-benzopyran (HHCB) and 7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene (AHTN) under field conditions, a level III fugacity model combined with a least-squares method was used to determine the degradation rate of HHCB and AHTN in the North Canal River watershed of Beijing, China. Model fitting, validation, sensitivity, and uncertainty analyses revealed that the established model was stable and robust. The degradation rates of HHCB and AHTN were 4.16 × 10^-3 h^-1 (t_1/2 = 167 h) and 1.68 × 10^-2 h^-1 (t_1/2 = 41.3 h), respectively. The calculated degradation rates were extrapolated to the Liangshui River, and indicated that the differences between the measured and predicted concentrations were less than 0.32 and 0.34 log units for HHCB and AHTN, respectively. The attenuation rates of HHCB and AHTN were calculated, and the results indicated that degradation was an important yet not the sole contributor to the degradation of the polycyclic musks. Results of uncertainty analyses indicated that the inflow and outflow concentrations of the polycyclic musks in the surface water of each segment strongly influenced the model outputs, followed by environmental factors (water depth and flow rate). It is essential to measure the degradation rate in the field because of the influence of the surrounding environment. The present study reveals the utility of fugacity models to quantify the degradation rate of organic micropollutants in the field.

Extracellular laccase-activated humification of phenolic pollutants and its application in plant growth

Humification processes of phenolic pollutants may play a profound role in environment purification and plant growth. However, little literature is performed to explore exoenzyme-driven humification to polymerize 17β-estradiol (E2) and humic constituents (HCs), and the effects of their polymeric precipitates on plant growth are usually overlooked. Herein, E2 conversion and radish (Raphanus sativus L.) growth were systematically investigated under humification mediated by extracellular laccase (EL) of Trametes versicolor. Results disclosed that EL-assisted humification achieved a wonderful E2 conversion efficiency (>99%) within 2-h, but the presence of HCs such as humic acid (HA), vanillic acid (VA), and ferulic acid (FA) impeded E2 elimination significantly. Compared with HC-free, the kinetics constants declined by 2.84-, 5.72-, and 5.22-fold with HA, VA, and FA present, respectively. Intriguingly, three close-knit self/cross-linked precipitates (i.e., E2-HA, E2-VA, and E2-FA hybrid precipitates) in dark gray, dark brown, and deep yellow were created after a continuous humification by phenolic radical-initiated polymerization mechanisms. The formation of these humified precipitates was extremely effective on circumventing phytotoxicity caused by monomeric E2, VA, or FA. Furthermore, they acted as humic-like organic fertilizers, accelerating seed germination, root elongation, and enhancing NaCl-tolerance of radish through the combination of oxygen-contained functional components and auxin structural analogues with unstable and stubborn carbon skeletons. This is the first study reporting the pollution purification and plant growth promotion in EL-activated humification. Our findings frame valuable perspectives regarding the natural detoxification and carbon sequestration of phenolic pollutants and the application of their polymeric precipitates in global crop production.

Effect of colloidal fluorescence properties on the complexation of chloramphenicol and carbamazepine to the natural aquatic colloids

The complexation mechanism between pharmaceuticals and natural colloids is still uncertain due to the complexity, heterogeneity, and polydispersity of colloids. Therefore, this study investigated the effect of fluorescence properties on the complexation of chloramphenicol (CAP) and carbamazepine (CBZ) to the colloids from Poyang Lake Basin based on the multiple spectroscopic techniques and methods. Three-dimensional excitation-emission matrix fluorescence spectroscopy-parallel factor analysis results illustrated that two humic-like components and two protein-like components of colloids from the rivers and lakes were identified, with the much higher fluorescence intensity of the protein-like substance observed in lake samples. The protein-like substance decreased dramatically with the addition of CAP and CBZ, suggesting its higher binding capacity towards these drugs, especially for CBZ. In addition, the fluorescence quenching titration was proceeded to explore the binding mechanism between the colloids and the pharmaceuticals. Results of synchronous fluorescence spectra and two-dimensional correlation spectroscopy demonstrated that the fluorescence quenching effect occurred preferentially between the protein-like substances and the pharmaceuticals, with the stronger complexation for CBZ. Ryan-Weber model fitting results showed that the stability constant ranged from 4.02 to 5.04 with the higher binding capacity observed for the tryptophan-like substance. Combined, the fluorescence components in aquatic colloids could be significantly impacted the complexation of the pharmaceuticals. This study provides deep insights into the fate and pollution protection of pharmaceuticals.

Critical assessment of an equilibrium-based method to study the binding of waterborne organic contaminants to natural dissolved organic matter (DOM)

Dissolved organic matter (DOM) can play a major role in determining availability of pollutants to aquatic biota. Equilibrium dialysis is the most commonly used method to assess the interaction between DOM and organic contaminants. However, results obtained through this method can be affected by confounding factors linked to the diffusion of DOM through the membrane or the interaction of DOM and/or the compounds with the membrane itself. In this study, we propose an improved experimental approach, where highly hydrophilic cellulose-ester membranes with small molecular cut-off (100-500 Da) were used to overcome some of these hindrances. The performance of the method to determine the binding of a commonly used moderately hydrophobic herbicide (Isoproturon - ISU) with natural DOM was critically evaluated through a set of quality assurance criteria, across a range of DOM concentrations and pH conditions. DOM trans-membrane diffusion was prevented by the smaller pore size of the dialysis membrane. Good measurement reproducibility, mass balance closure, and successful trans-membrane equilibrium of ISU were obtained. ISU showed relatively low affinity with DOM (log K_DOC 1-2 L g^-1), which was significantly influenced by varying pH and DOM concentration. An alternative membrane may be needed for higher pH conditions as the greater adsorption effect blurred the observation of trans-membrane equilibrium and confounding mass balance closure. The paper makes recommendations on how to avoid measurement artefacts, while considering criteria for the expected mass distribution of compounds at equilibrium and for sorption onto the membrane and surfaces of the experimental units.

Adsorption behaviour and interaction of organic micropollutants with nano and microplastics - A review

Nano/microplastics (NPs/MPs) and organic micropollutants are contaminants exerting serious threats to aquatic ecosystems, which are further aggravated through their interactions. Organic micropollutants can adsorb on the surface of NPs/MPs, enter to the digestive systems of aquatic organisms with NPs/MPs, and desorb from the surface inside the organism. Consequently, the migration behaviour of organic micropollutants is significantly affected increasing their risk to accumulate in the food chain. Therefore, understanding the adsorption interactions between NPs/MPs and organic micropollutants is critical for evaluating the fate and impact of NPs/MPs in the environment. This review article provides an overview about the role of NPs/MPs as (temporary) sinks for organic micropollutants but also as primary sources of organic micropollutants through the leaching of plastic additives. Specifically, the following aspects are discussed: adsorption/desorption mechanisms (e.g., hydrophobic partitioning interaction, surface adsorption by van der Waals forces or hydrogen bonding, and pore filling), influencing environmental factors (e.g., pH, salinity, and dissolved organic matter), leaching of plastic additives from NPs/MPs, and potential ecotoxicological effects arising from the interactions of NPs/MPs and organic micropollutants.

Experimental and theoretical studies into the hydroxyl radical mediated transformation of propylparaben to methylparaben in the presence of dissolved organic matter surrogate

Dissolved humic and biogenic substances might be present in the aphotic zone and contribute to the fate of parabens in natural aquatic ecosystem under the fluctuation of water multi-parameters. Through the combination of batch tests with quantum chemical calculation, hydroxyl radical (•OH) mediated degradation of propylparaben (PP) to methylparaben (MP) has been confirmed in the present study. The interaction of dissolved oxygen with environmental relevant concentration of humic acid (HA), algal and bacterial cell lysis leads to a slow production of •OH. Aqueous PP undergoes a mild removal process with the pseudo-first order rate constant (10^-7, s^-1) higher at 7.43 in HA than at 3.30-4.89 in biogenic cell lysis. PP removal is correlated with the aromaticity of DOM surrogate and the produced •OH concentration, which could be enhanced by the increase of light intensity and DO other than HA. The •OH mediated process on PP removal has been confirmed by the linearly inhibited effect of tert-butanol while totally inhibited effects of higher concentration of sodium azide and co-existent chemical (17β-estradiol). Based on the detection of byproduct MP, two possible reaction pathways, •OH attacking at β-carbon (path-β) and terminal γ-carbon (path-γ) of the propyl side chain of PP, are proposed. Through the analysis of thermal and kinetics parameters, the •OH initiated H-abstraction and the resulting C-C bond cleavage leading to the formation of MP and acetaldehyde in path-β is confirmed to be the dominant reaction mechanism. Considering the universal occurrence of parabens and these DOM surrogates, this mild removal process has special implications for the self-purification of organic pollutants in natural aquatic ecosystems, especially in DOM-rich matrices in the aphotic zone.

Characterization and biogeochemical implications of dissolved organic matter in aquatic environments

Dissolved organic matter (DOM) is viewed as one of the most chemically active organic substances on earth. It plays vital roles in the fate, bioavailability and toxicity of aquatic exogenous chemical species (e.g., heavy metals, organic pollutants, and nanomaterials). The characteristics of DOM such low concentrations, salt interference and complexity in aquatic environments and limitations of pretreatment for sample preparation and application of characterization techniques severely limit understanding of its nature and environmental roles. This review provides a characterization continuum of aquatic DOM, and demonstrate its biogeochemical implications, enabling in-depth insight into its nature and environmental roles. A synthesis of the effective DOM pretreatment strategies, comprising extraction and fractionation methods, and characterization techniques is presented. Additionally, the biogeochemical dynamics of aquatic DOM and its environmental implications are discussed. The findings indicate the collection of representative DOM samples from water as the first and critical step for characterizing its properties, dynamics, and environmental implications. However, various pretreatment procedures may alter DOM composition and structure, producing highly variable recoveries and even influencing its subsequent characterization. Therefore, complimentary use of various characterization techniques is highly recommended to obtain as much information on DOM as possible, as each characterization technique exhibits various advantages and limitations. Moreover, DOM could markedly change the physical and chemical properties of exogenous chemical species, influencing their transformation and mobility, and finally altering their potential bioavailability and toxicity. Several research gaps to be addressed include the impact of pretreatment on the composition and structure of aquatic DOM, molecular-level structural elucidation for DOM, and assessment of the effects of DOM dynamics on the fate, bioavailability and toxicity of exogenous chemical species.

Organic matter interference with steroid hormone removal by single-walled carbon nanotubes - ultrafiltration composite membrane

Composite adsorbent-ultrafiltration membranes for micropollutant removal are an interesting concept, although water matrix compounds, such as organic matter (OM), may interfere with micropollutant adsorption. To prevent this interference, the adsorbents such as single-walled carbon nanotubes (SWCNTs) can be deposited on the permeate side of an ultrafiltration membrane (UF) that can retain OM. In this study, the 'shielding' effect by different UF MWCOs of such an SWCNT-UF composite was evaluated for nine different types of OM. All nine OM types competed with 17β-estradiol (E2) for adsorption to varying extents, and tannic acid (TA, 1.7 kDa) reduced E2 adsorption by SWCNT-UF most drastically. TA interference mechanisms included direct competition with hormones for adsorption sites, and indirect competition via TA-hormone interactions. TA was not fully retained by the composite membrane with an MWCO range of 3-100 kDa, resulting in ineffective shielding. In contrast, humic acid was mostly retained by the composite with low MWCO of 3-10 kDa and allowed high E2 adsorption. This study demonstrates that tailoring composite membranes by carefully choosing UF MWCO can prevent interference of OM types in micropollutant adsorption by permeate-side adsorbents.

Assessment of source and treated water quality in seven drinking water treatment plants by in vitro bioassays - Oxidative stress and antiandrogenic effects after artificial infiltration

Drinking water quality and treatment efficacy was investigated in seven drinking water treatment plants (DWTPs), using water from the river Göta Älv, which also is a recipient of treated sewage water. A panel of cell-based bioassays was used, including measurements of receptor activity of aryl hydrocarbon (AhR), estrogen (ER), androgen (AR), peroxisome proliferator-activated receptor alpha (PPARα) as well as induction of oxidative stress (Nrf2) and micronuclei formation. Grab water samples were concentrated by solid phase extraction (SPE) and water samples were analyzed at a relative enrichment factor of 50. High activities of AhR, ER and AR antagonism were present in WWTP outlets along the river. Inlet water from the river exhibited AhR and AR antagonistic activities. AhR activity was removed by DWTPs using granulated activated carbon (GAC) and artificial infiltration. AR antagonistic activity was removed by the treatment plants, except the artificial infiltration plant, which actually increased the activity. Furthermore, treated drinking water from the DWTP using artificial infiltration exhibited high Nrf2 activity, which was not found in any of the other water samples. Nrf2 activity was found in water from eight of the 13 abstraction wells, collecting water from the artificial infiltration. No genotoxic activity was detected at non-cytotoxic concentrations. No Nrf2 or AR antagonistic activities were detected in the inlet or outlet water after the DWTP had been replaced by a new plant, using membrane ultrafiltration and GAC. Neither target chemical analysis, nor chemical analysis according to the drinking water regulation, detected any presence of chemicals, which could be responsible of the prominent effects on oxidative stress and AR antagonistic activity in the drinking water samples. Thus, bioanalysis is a useful tool for detection of unknown hazards in drinking water and for assessment of drinking water treatments.

Evidence that watershed nutrient management practices effectively reduce estrogens in environmental waters

We evaluate the impacts of different nutrient management strategies on the potential for co-managing estrogens and nutrients in environmental waters of the Potomac watershed of the Chesapeake Bay. These potential co-management approaches represent agricultural and urban runoff, wastewater treatment plant effluent, and combined sewer overflow replacements. Twelve estrogenic compounds and their metabolites were analysed by gas chromatography-mass spectrometry. Estrogenic activity (E₂Eq) was measured by in vitro bioassay. We detected estrone E₁ (0.05-6.97 ng L^-1) and estriol E₃ (below detection-8.13 ng L^-1) and one conjugated estrogen (estrone-3-sulfate E₁-3S; below detection-8.13 ng L^-1). E₁ was widely distributed and positively correlated with E₂Eq, water temperature, and dissolved organic carbon (DOC). Among nonpoint sources, E₂Eq, and concentrations of E₁, soluble reactive phosphorus (SRP) and total dissolved nitrogen (TDN) decreased by 51-61%, 77-82%, 62-64%, 4-16% in restored urban and agricultural streams with best management practices (BMPs) relative to unrestored streams without BMPs. In a wastewater treatment plant (Blue Plains WWTP), >94% of E₁, E₁-3S, E₃, E₂Eq and TDN were removed while SRP increased by 305% during nitrification/denitrification as a part of advanced wastewater treatment. Consequently, E₁ and TDN concentrations in WWTP effluents were comparable or even lower than those observed in the receiving stream or river waters, and the effects of wastewater discharges on downstream E₁ and TDN concentrations were minor. Highest E₂Eq value and concentrations of E1, E3, and TDN were detected in combined sewer overflow (CSO). This study suggests that WWTP upgrades with biological nutrient removal, CSO management, and certain agricultural and urban BMPs for nutrient controls have the potential to remove estrogens from point and nonpoint sources along with other contaminants in streams and rivers.

Modified humic acids mediate efficient mineralization in a photo-bio-electro-Fenton process

Humic acids (HA) are common mediators in redox reactions in the aquatic environment. The structures and properties of HA are greatly influenced by environmental factors such as external electrons. In this study, qualitative changes in electron-modified HA and the underlying mechanisms were reported, which not only contribute to understanding the fate of HA and their impact on organic pollutants, but could facilitate their potential use for water purification. The photochemical activity and electron-donating capacity of HA were improved due to the increase of phenolic and carboxyl components via the reduction modification by electrons, creating a novel and efficient photo-bio-electro-Fenton system mediated by HA under neutral conditions without the use of hydrogen peroxide (H₂O₂). The in-situ continuous production of H₂O₂ ensured an adequate supply of hydroxyl radicals in this coupled system, achieving mineralization (92%) of HA and 17α-ethinylestradiol (EE2), a common synthetic estrogen with high estrogenic potency. Two degradation pathways with five degradation intermediates of EE2 were identified in our study. Effluents from the coupled system showed decreased endocrine-disrupting activity. Our findings demonstrated a new approach for the in-situ modification and potential use of HA for water treatment and particularly the concurrent degradation of HA and organic pollutants through a photo-bioelectrochemical system mediated by HA.

Insights into total estrogenic activity in a sewage-impacted urban stream assessed via ER transcriptional activation assay: Distribution between particulate and dissolved phases

Endocrine disrupting chemicals (EDC) are exogenous substances that can potentially mimic hormonal substances and cause adverse effects on the endocrine system of living beings. The behavior and fate of these compounds in the environment is directly related to their physical-chemical properties, which indicate great affinity for solid and organic particles and suggest an inherent mechanism of fractionation between dissolved and particulate phases of aqueous matrices. However, few studies have been considering this fact when quantifying these pollutants and their effects through bioassays. In this study, the fractionation of estrogenic substances between dissolved and particulate phases in an urban stream was investigated via estrogenic activity evaluation by the YES assay. Two fractions of suspended solids (< 0.7 µm and between 0.45 and 0.7 µm) and the dissolved phase were considered and two approaches of SPE percolations were applied. Total estradiol equivalent (E2-Eq) values were observed in the 29-65 ng L^-1 range, of which 35-62% were associated with the particulate phase. Most of the estrogenicity was associated with particles between 0.45 and 0.7 µm, whereas cytotoxicity was induced by extracts of particles greater than 0.7 µm. Results demonstrated the importance of solid fractions analysis towards the quantification of total estrogenic activity from aqueous environmental matrices and highlights the relevance of controlling fine suspended solids in sewage treatment plant effluents, regarding the control of endocrine disrupters in the environment.

Influence of microplastics occurrence on the adsorption of 17β-estradiol in soil

High levels of steroid estrogens are continuously detected in the soil environment, and even the concentration in vegetables and fruits has reached levels that have an impact on children's health, which has attracted growing attention. Moreover, microplastics (MPs) in the soil system are also of increasing concern worldwide. The effects of MPs on the adsorption of organic pollutants in soil systems, however, remain largely unexplored. In this study, MPs common in greenhouse vegetable soil (polyethylene, polyvinyl chloride and polystyrene) were selected to investigate the effect of MPs occurrence on the adsorption of 17β‑estradiol (E2) in soil under various conditions. The experimental results showed that the adsorption capacity of MPs to E2 is stronger than that of soil. Moreover, the occurrence of MPs in soil increased the adsorption capacity for E2, and the addition amount and aging of MPs enhanced the promotion effect. This enhancement indicated that the input of MPs into soil might reduce the mobility of E2 by improving the adsorption capacity of the soil. These results deepen the understanding of the adsorption behavior of E2 in the coexisting system of MPs and soil and provide a theoretical basis for E2 pollution control.

Occurrence and risk assessment of steroid estrogens in environmental water samples: A five-year worldwide perspective

The ubiquitous occurrence of steroid estrogens (SEs) in the aquatic environment has raised global concern for their potential environmental impacts. This paper extensively compiled and reviewed the available occurrence data of SEs, namely estrone (E1), 17α-estradiol (17α-E2), 17β-estradiol (17β-E2), estriol (E3), and 17α-ethinyl estradiol (EE2), based on 145 published articles in different regions all over the world including 51 countries and regions during January 2015-March 2020. The data regarding SEs concentrations and estimated 17β-estradiol equivalency (EEQ) values are then compared and analyzed in different environmental matrices, including natural water body, drinking and tap water, and wastewater treatment plants (WWTPs) effluent. The detection frequencies of E1, 17β-E2, and E3 between the ranges of 53%-83% in natural water and WWTPs effluent, and the concentration of SEs varied considerably in different countries and regions. The applicability for EEQ estimation via multiplying relative effect potency (REP_i) by chemical analytical data, as well as correlation between EEQ_bio and EEQ_cal was also discussed. The risk quotient (RQ) values were on the descending order of EE2 > 17β-E2 > E1 > 17α-E2 > E3 in the great majority of investigations. Furthermore, E1, 17β-E2, and EE2 exhibited high or medium risks in water environmental samples via optimized risk quotient (RQ_f) approach at the continental-scale. This overview provides the latest insights on the global occurrence and ecological impacts of SEs and may act as a supportive tool for future SEs investigation and monitoring.

Strong sorption of two fungicides onto biodegradable microplastics with emphasis on the negligible role of environmental factors

Microplastics have attracted much attention in recent years because they are able to interact with other pollutants including pesticides, with implications for the potential risks to biota. However, the sorption behavior of pesticides on microplastics, especially on biodegradable microplastics which are promising alternatives to conventional polymers, has been insufficiently studied. In this study, triadimefon and difenoconazole were selected as model triazole fungicides, and their sorption behavior on a typical biodegradable microplastics (PBS: polybutylene succinate) and two conventional polyethylene (PE) and polyvinyl chloride (PVC) microplastics was investigated with batch experiments in an aqueous solution. PBS presented the highest sorption capacity for triadimefon (104.2 ± 4.8 μg g^-1) and difenoconazole (192.8 ± 2.3 μg g^-1), which was 1.8- and 1.3-fold that on PE and 4.4- and 7.4-fold that of PVC, respectively. The results of sorption kinetic and isotherm modeling were better fit by a pseudo-second order model and linear model, respectively. More importantly, the effects of environmental factors (pH, salinity and dissolved organic matter) on the sorption behavior were investigated. Fungicide sorption on PBS was generally not affected by salinity, pH or dissolved organic matter. However, in contrast, salinity and dissolved organic matter both significantly decreased sorption on PE and PVC. The results showed that not only the sorption capacities of biodegradable microplastics but also their responses to environmental factors are quite different from those of conventional microplastics. This finding highlights the importance of the role played by biodegradable microplastics in the accumulation and transportation of organic pollutants.

Leachability of endocrine disrupting chemicals (EDCs) in municipal sewage sludge: Effects of EDCs interaction with dissolved organic matter

In this study, experiments were performed to assess the significance of dissolved organic matter (DOM) on the leachability of four common EDCs, i.e., bisphenol A (BPA), 17α-ethinylestradiol (EE2), progesterone (PGT) and testosterone (TST), in municipal sewage sludge (MSS) under landfill conditions. The DOM was derived from two sources: MSS (MDOM), and natural soil represented by organic matter obtained from the Suwannee River (NDOM). Fluorescence excitation-emission matrix quenching combined with parallel factor analysis was adopted to characterize the interaction properties between the EDCs and DOM. The accumulative leachability of the target EDCs ranged from 0.09% (PGT) to 3.8% (TST). In particular, the leaching of BPA, EE2 and TST followed S-shaped curves, while PGT exhibited continuous leaching potential in untreated MSS. With the introduction of DOM, (i) the leachability of BPA and EE2 increased to 13.4% and 61.6%, respectively, whereas those of PGT and TST declined by 61.3% and 45.8%, respectively, and (ii) BPA, EE2 and PGT no longer reached leaching equilibrium but the S-shaped leaching property of TST persisted. The differential effects of MDOM and NDOM at identical concentrations on the EDCs leachability increased with curing time. BPA, EE2 and PGT quenched the MDOM fluorophores attributed to aromatic protein-like components. The fluorescence quenching of NDOM by BPA, EE2 and PGT was centered on soluble microbial by-product-like and humic-like substances. Compared with PGT, EE2 and BPA had greater capability for binding with DOM components largely via hydrophobic interactions, whereas PGT preferentially interacted with the DOM hydrophilic functionalities through specific interactions. TST had no binding capability but displayed potentials competing for sorption sites with DOM moieties. Our findings suggested that the management of MSS increased the risk of environmental contamination by EDCs for a long duration and that DOM was a useful indicator to predict the migration and transport properties of EDCs.

Molecular Dynamics Simulation of the Structures, Dynamics, and Aggregation of Dissolved Organic Matter

Dissolved organic matter (DOM) plays a significant role in the transport and transformation of pollutants in the aquatic environment. However, the experimental characterization of DOM has been limited mainly to bulk properties, and the molecular-level interactions among various components of DOM remain to be fully characterized. Here, we use molecular dynamics (MD) simulations to probe the structural properties of model DOM systems at atomic detail. The 200 ns simulations, validated by available experimental data, reveal processes and mechanisms by which chemical species (cations, peptides, lipids, lignin, carbohydrates, and some low-molecular-weight aliphatic and aromatic compounds) aggregate to form complex DOM. The DOM aggregates are dynamic, consisting of a hydrophobic core and amphiphilic exterior. The lipid tails and other hydrophobic fragments form the core, with hydrophilic and amphiphilic groups exposed to water, making DOM accessible to both polar and nonpolar species. Thus, the lipid component acts as a nucleator, whereas cations (especially Ca²⁺) connect the molecular fragments on the surface by coordinating with the O-containing functional groups of DOM. The structural details revealed here provide new insights including surface accessible atoms, overall assemblage, and interactions among the molecules of DOM for understanding the kinetics and mechanisms through which DOM interacts with metal and other contaminants.

Influence of humic acids on fungal laccase-initiated 17α-ethynylestradiol oligomerization: Transformation kinetics and products distribution

Fungal laccase has aroused great concern in rapidly removing estrogens because of its ability to accelerate humification and oligomerization. Here, the effect of two humic acids (HAs) on the reaction kinetics and products distribution of 17α-ethynylestradiol (EE2) in laccase-initiated humification and coupling was systematically elucidated. Laccase from Trametes versicolor exhibited over 98.3% removal rate for EE2 at pH 5.0 within 120 min, while HAs invariably restrained EE2 transformation by competing with target-substrate for the enzymatic catalytic center. EE2 removal followed pseudo-first-order kinetics, and the rate constant was decreased markedly with increasing concentration of two HAs (0-60 mg L^-1). Additionally, laccase heightened the aromaticity and humification degrees (A_{250 nm}/A_{365 nm} ratio) of HAs probably due to the formation of new humic polymers such as (HA)_m and/or (HA)_m-(EE2)_n (m and n represent the number of HA and EE2 units, respectively). Three major EE2 oligomers were identified, in accordance with a mechanism involving the phenoxy radical-driven polymerization to yield a wide variety of self-coupling products. Notably, HAs diminished the extent of EE2 self-coupling but aggrandized the cross-coupling between EE2 and HAs, and the inhibition degree of EE2 self-coupling increased with the concentration of HAs. One major reason is EE2 could be covalently incorporated into humic molecules to produce (HA)_m-(EE2)_n cross-coupling products via radical-caused C-C, C-O-C, and/or C-O-C bonds, thereby reducing EE2 self-oligomerization. These findings highlight that HAs play a vital role in the fungal laccase-induced humification and oligomerization of EE2, which obviously alter the geochemical fate and transport of EE2 in natural aquatic ecosystems.

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.

17 beta-estradiol biodegradation by anaerobic granular sludge: Effect of iron sources

Steroid estrogens, as typical endocrine disrupting chemicals (EDCs), have raised an increasing concern due to their endocrine disrupting effects on aquatic animals and potential hazards on human health. Batch experiments were conducted to study 17 beta-estradiol (E2) removal and Estradiol Equivalent Quantity (EEQ) elimination by anaerobic granular sludge (AnGS) combined with different valence iron sources. Results showed that E2 was effectively biodegraded and transformed into E1 by AnGS. The addition of different valence iron sources all promoted E2 degradation, reduced E2 Equivalent Quotient (EEQ) concentration, and increased methane production in the batch experiments. The enhancement effect of zero-valent iron (ZVI) on E2 removal and EEQ elimination was stronger than that of Fe²⁺ and Fe³⁺ in our experiments. The enhancement effect proportion of ZVI corrosion, Fe²⁺, and Fe³⁺ in the process of E2 degradation by AnGS combined with ZVI were 42.26%, 40.21% and 17.53%, respectively.

Recent Progress on Luminescent Metal-Organic Framework-Involved Hybrid Materials for Rapid Determination of Contaminants in Environment and Food

The high speed of contaminants growth needs the burgeoning of new analytical techniques to keep up with the continuous demand for monitoring and legislation on food safety and environmental pollution control. Metal-organic frameworks (MOFs) are a kind of advanced crystal porous materials with controllable apertures, which are self-assembled by organic ligands and inorganic metal nodes. They have the merits of large specific surface areas, high porosity and the diversity of structures and functions. Latterly, the utilization of metal-organic frameworks has attracted much attention in environmental protection and the food industry. MOFs have exhibited great value as sensing materials for many targets. Among many sensing methods, fluorometric sensing is one of the widely studied methods in the detection of harmful substances in food and environmental samples. Fluorometric detection based on MOFs and its functional materials is currently one of the most key research subjects in the food and environmental fields. It has gradually become a hot research direction to construct the highly sensitive rapid sensors to detect harmful substances in the food matrix based on metal-organic frameworks. In this paper, we introduced the synthesis and detection application characteristics (absorption, fluorescence, etc.) of metal-organic frameworks. We summarized their applications in the MOFs-based fluorometric detection of harmful substances in food and water over the past few years. The harmful substances mainly include heavy metals, organic pollutants and other small molecules, etc. On this basis, the future development and possible application of the MOFs have prospected in this review paper.

Interactions among low-molecular-weight organics, heavy metals, and Fe(III) during coagulation of landfill leachate nanofiltration concentrate

The generation of landfill leachate nanofiltration concentrate (LLNC) has been a dilemma for leachate treatment plants because it contains large amounts of refractory organics with low molecular weight (LMWO), as well as heavy metals (HMs), and is difficult to handle. The coagulation removal of LMWOs is a significant challenge, as is the removal of HMs bonded to LMWOs. In this study, coagulation through the dosing of FeCl₃ was used to remove LMWOs and HMs from LLNC. The results interestingly demonstrated that the removal rates of dissolved organic carbon (DOC), Cr, Ni, and As reached up to 84.1% ± 3.9%, 91.0 ± 1.1%, 73.1 ± 2.2%, and 96.9 ± 1.5%, respectively. The partition of LMWO components, as well as the interactions among the LMWOs, HMs, and Fe(III) were investigated to determine the mechanism behind the LMWO and HM removal. LMWOs with a high degree of humification, including humic and fulvic acid-like components, were preferentially removed through aggregation and electrostatic attraction originating from the specialistic adsorption of Fe₂(OH)₂⁴⁺ and Fe₃(OH)₄⁵⁺. In addition to being removed, a portion of these two components was dissociated into aromatic protein I, aromatic protein II, and soluble microbial by-product-like materials due to an acid effect and the formation of inner-sphere complexes. A redundancy analysis revealed that As, Cr, and Ni are mainly removed through the electrostatic attraction of Fe(III), bonding to humic substances and hydrophilic organics, respectively. The outcomes provide a new understanding on the coagulation removal of LMWOs and HMs.

Fungal laccase-mediated humification of estrogens in aquatic ecosystems

Estrogens are a category of non-degradable organic pollutants prevalent in aquatic environments with reported health risks in human and wildlife reproduction. A biotechnological approach is proposed for utilizing fungal laccase-mediated humification reactions (L-MHRs) to remove estrogens from water. Through a reactive radical-mediated C-C, C-O-C, or C-N-C covalent coupling mechanism, multifarious complex polymeric structures are generated having limited solubilities, which significantly reduces their estrogenic activity and ecotoxicity. This review highlights the available literature associated with the self/cross-coupling mechanism of fungal L-MHRs in catalyzing the single-electron oxidation of estrogens and humic acid (HA). Advances in identifying unknown estrogen-HA cross-coupling products using high-resolution mass spectrometry combined with ¹³C-isotope labeling and ¹³C NMR may provide key research directions beneficial to aquatic ecological restoration measures.

Recent Applications and Newly Developed Strategies of Solid-Phase Microextraction in Contaminant Analysis: Through the Environment to Humans

The present review aims to describe the recent and most impactful applications in pollutant analysis using solid-phase microextraction (SPME) technology in environmental, food, and bio-clinical analysis. The covered papers were published in the last 5 years (2014–2019) thus providing the reader with information about the current state-of-the-art and the future potential directions of the research in pollutant monitoring using SPME. To this end, we revised the studies focused on the investigation of persistent organic pollutants (POPs), pesticides, and emerging pollutants (EPs) including personal care products (PPCPs), in different environmental, food, and bio-clinical matrices. We especially emphasized the role that SPME is having in contaminant surveys following the path that goes from the environment to humans passing through the food web. Besides, this review covers the last technological developments encompassing the use of novel extraction coatings (e.g., metal-organic frameworks, covalent organic frameworks, PDMS-overcoated fiber), geometries (e.g., Arrow-SPME, multiple monolithic fiber-SPME), approaches (e.g., vacuum and cold fiber SPME), and on-site devices. The applications of SPME hyphenated with ambient mass spectrometry have also been described.

Predictive role of spectral slope ratio towards 17α-ethynylestradiol photodegradation sensitized by humic acids

Humic acids (HAs) have been shown to dominate the photodegradation of steroid estrogens in natural waters. Nevertheless, how the photosensitizing ability of HAs relates to their structural and optical characteristics remains largely unknown. In this study, 17α-ethynylestradiol (EE2) was selected as a model compound to study to what extent easily-measurable characteristics of HAs might be used to predict their photosensitization potency. HAs were extracted from sediments of two different sources, and then subjected to structural and optical properties characterization using elemental analyzer, UV-vis spectroscopy and fluorescence spectroscopy. Photochemical experiments show that the HAs from the two sources can effectively meditate EE2 photodegradation. Although with drastically different structural and optical properties, the photosensitizing ability of these HAs towards EE2 can be well described by simple linear regressions using a spectroscopic index, the spectral slope ratio (S_R). This optical indicator is correlated with various physicochemical properties of HAs, including the molecular weight, lignin content, charge-transfer interaction potential, photobleaching extent and sources. No universal prediction model could be established for predicting EE2 photodegradation kinetics on the basis of S_R, but in specific waters S_R could be a powerful indictor for predicting the EE2 photodegradation sensitized by HAs.

Adsorption of 17β-estradiol onto humic-mineral complexes and effects of temperature, pH, and bisphenol A on the adsorption process

The long-term use of animal manure in agriculture has resulted in estrogen pollution, which poses risks to facility vegetable soils. Owing to the complex soil composition, estrogen may exhibit a variety of behaviors at the water/soil interface. This study demonstrated the role of humic acid (HA) on the 17β-estradiol (E2) adsorption by clay minerals (montmorillonite, kaolinite, and hematite). The interfacial behaviors were investigated using adsorption kinetics and isotherms data. Then, the effects of temperature, pH, and bisphenol A (BPA) on the interactions between humic-mineral complexes and E2 were explored. The adsorption of E2 is an exothermic and spontaneous process, and the addition of HA to minerals significantly promoted their E2 adsorption capacities. Higher pH levels (>10) and the presence of BPA decreased the adsorption capacities of minerals and mineral complexes for E2. Moreover, intercalation, hydrophobic partitioning, π-π interactions and hydrogen bonding could dominate the E2 adsorption onto complexes. These results provided insight into the interfacial behaviors of E2 on the surfaces of humic-mineral complexes and promoted the understanding of the migration and transport of estrogens in soils.