Persistent Organic Contaminants Research Articles

Characteristics and pollution indices of leachates from municipal solid waste landfills in Iranian metropolises and their implications for MSW management

Leachate from municipal solid waste landfills poses a significant threat to aquatic ecosystems due to poor management practices. This study evaluated thirty leachate samples from Iranian metropolises using the Leachate Pollution Index (LPI). Various parameters, including BOD₅, COD, TDS, pH, EC, heavy metals, turbidity, PAHs, phthalates, and humic acid, were analysed. The BOD₅ levels ranged from 350 to 20,000 mg/L, and the COD levels ranged from 2,000 to 90,000 mg/L. The TDS content varied between 14.7 and 67 g/L, while the turbidity ranged from 15 to 186 NTU. Heavy metals were present but within standard limits. The phthalate concentrations ranged from 6 to 150.8 mg/L, and the humic acid concentrations ranged from 135 to 2,200 mg/L. Naphthalene was the most frequent hydrocarbon detected. The LPIs were less than 30 for all the samples, with the highest in Ahvaz and the lowest in the treated samples from Tehran. This study highlights the presence of persistent organic and hazardous contaminants in Iran’s municipal landfills, emphasizing the need for effective leachate treatment and improved waste management practices. Enhanced final disposal methods, increased waste recovery, and improved solid residue separation are crucial for preventing further leachate production and environmental contamination.

PFAS, PCBs, PCDD/Fs, PAHs and extractable organic fluorine in bio-based fertilizers, amended soils and plants: Exposure assessment and temporal trends

Bio-based fertilizers (BBFs) produced from organic waste contribute to closed-loop nutrient cycles and circular agriculture. However, persistent organic contaminants, such as per- and poly-fluoroalkyl substances (PFAS), polychlorobiphenyls (PCBs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), as well as polyaromatic hydrocarbons (PAHs) can be present in organic waste or be formed during valorization processes. Consequently, these hazardous substances may be introduced into agricultural soils and the food chain via BBFs. This study assessed the exposure of 84 target substances and extractable organic fluorine (EOF) in 19 BBFs produced from different types of waste, including agricultural and food industrial waste, sewage sludge, and biowaste, and through various types of valorization methods, including hygienization at low temperatures (<150 °C) as well as pyrolysis and incineration at elevated temperatures (150–900 °C). The concentrations in BBFs (ΣPFOS & PFOA: <30 μg kg−1, Σ6PCBs: <15 μg kg−1, Σ11PAHs: <3 mg kg−1, Σ17PCDD/Fs: <4 ng TEQ kg−1) were found to be below the strictest thresholds used in individual EU countries, with only one exception (pyrolyzed sewage sludge, Σ11PAHs: 5.9 mg kg−1). Five BBFs produced from sewage sludge or chicken manure contained high concentrations of EOF (>140 μg kg−1), so monitoring of more PFAS is recommended. The calculated expected concentrations in soils after one BBF application (e.g. PFOS: <0.05 μg kg−1) fell below background contamination levels (PFOS: 2.7 μg kg−1) elsewhere in the literature. This was confirmed by the analysis of BBF-amended soils from field experiments (Finland and Austria). Studies on target legacy contaminants in sewage sludge were reviewed, indicating a general decreasing trend in concentration with an apparent half-life ranging from 4 (PFOS) to 9 (PCDD/Fs) years. Modelled cumulative concentrations of the target contaminants in agricultural soils indicated low long-term risks. Concentrations estimated and analyzed in edible plant part were low, indicating that exposure by plant consumption is well below tolerable daily intakes.

Trimetallic MOF–derived Fe–Mn–Sn oxide heterostructure enabling exceptional catalytic degradation of organic pollutants

Developing efficient and environmentally benign heterogeneous catalysts that activate peroxymonosulfate (PMS) for the degradation of persistent organic contaminants remains a challenge. Metal–organic frameworks (MOFs)–derived metal oxide catalysts in advanced oxidation processes (AOPs) have received considerable attention research fraternity. Herein, we report an innovative magnetic trimetallic MOF-derived Fe-Mn-Sn oxide heterostructure (FeMnO@Sn) with adjustable morphology, size and Sn content, prepared through an impregnation–calcination strategy. The formation of a novel magnetic Fe2O3/Fe3O4/Mn3O4 heterostructure induces the generation of abundant Fe2+ and Mn2+ sites on the FeMnO@Sn surface. Meanwhile, the introduction of SnO2 into the Fe2O3/Fe3O4/Mn3O4 heterostructure facilitates the cleavage of the OO bond in adsorbed PMS. The synergy among the different functionalities of each metal oxide plays a vital role in the swift and effective degradation of pollutants. In addition, the uniquely designed catalyst exhibits magnetic properties that facilitate easy recycling and repeated use, thereby meeting environmental protection requirements. Overall, this research highlights the design of heterogeneous catalysts for the effective activation of PMS and provides valuable insights for the advancement of future environmental catalysts.

Regulation mechanism of exogenous nitric oxide on phenanthrene uptake by ryegrass roots

Polycyclic aromatic hydrocarbons (PAHs) constitute a category of persistent organic contaminants that possess the potential to induce carcinogenic, teratogenic, and mutagenic consequences. Our previous findings have revealed that plant roots actively take up PAHs through co-transport with protons, and auxin can promote PAHs uptake by wheat roots. It remains unclear whether nitric oxide (NO), a signaling molecule involved in numerous physiological processes in plants and downstream of auxin, can affect PAHs uptake by plant roots. In our study, 50 μmol/L sodium nitroprusside (SNP) significantly enhanced phenanthrene uptake after 4 h of exposure. After the addition of SNP (50 μmol/L), the H+ flux on root surface increased, and H+-ATPase activity was activated, indicating that exogenous NO promotes phenanthrene uptake by plant roots via activating H+-ATPase. By studying the effects of 50 μmol/L cyclic guanosine monophosphate (cGMP), 5 mmol/L Ca2+, and 50 μmol/L adenosine monophosphate (AMP) on phenanthrene uptake by ryegrass roots and measuring root calcium-dependent protein kinases (CDPK) activity, we demonstrated that exogenous NO promotes phenanthrene uptake through the signaling pathway of NO, cGMP, Ca2+, CDPK, 14-3-3 protein and H+-ATPase. The results contribute significant insights into elucidating the underlying mechanisms of NO modulating PAHs absorption by plant roots, thereby offering crucial strategies for advancing food safety measures and enhancing the phytoremediation potential of soils and waters contaminated with PAHs.

Legacy and emergent contaminants in glaucous-winged gull eggs from Canada's Pacific coast: Spatial distribution, temporal trends, and risks for human consumers

Using glaucous-winged gull (Larus glaucescens) eggs from Canada's Pacific coast, we investigated spatial and temporal trends (2008–2022) of a suite of legacy and emergent contaminants, including 16 perfluoroalkyl substances (PFAS), 15 polybrominated diphenyl ethers (PBDEs), 7 alternative halogenated flame retardants (AHFRs), total mercury (THg), as well as stable isotopes of carbon (δ13C) and nitrogen (δ15N) to control for diet. Legacy organochlorines (OCs) were also measured in eggs in 2020 for a preliminary human health risk assessment (HHRA). Between 2008 and 2022, glaucous-winged gull eggs from more urban-influenced colonies (Mandarte Island) were up to ∼2x more contaminated with PFAS, PBDEs, AHFRs, and THg than eggs from the offshore colony (Cleland Island), suggesting different source regions and dietary exposures. Concentrations of Σ15PBDEs declined linearly among colonies (p < 0.001), consistent with several North American phase-outs and regulatory restrictions dating back to the early/mid 2000s. Conversely, temporal trends for PFOS, Σ12PFCAs, Σ7AHFRs, and THg were characterized by a combination of second-order declines and non-linear increases in recent years. After correcting THg for dietary shifts using δ15N, THg concentrations followed a U-shaped trend at Mandarte and Cleland Islands, while those at Mitlenatch Island remained relatively constant over time. Increasing trends for some contaminants coincided with both an increase in δ13C and δ15N. For the HHRA, all gull eggs collected in 2020 had hazard quotients (HQs) < 0.2, indicating no foreseeable risk or harm for First Nations consumers for certain contaminants. Our findings indicate that spatio-temporal trends of persistent organic contaminants and THg in Pacific glaucous-winged gull eggs are influenced by a combination of factors, including the impact of regulations on anthropogenic emissions, accompanied by changes in foraging behaviour and food-web structure.

Urban Groundwater in the cities of Europe: hidden challenges in a changing climate

In European cities, groundwater remains an issue of significant concern, largely because it is “out of sight and out of mind.” The general public, and even decision-makers, possess only a limited understanding of the state and characteristics of this vital resource. As a consequence, problems related to groundwater quality or changing water tables/piezometric surfaces may persist for years, or even decades, without being adequately addressed-or worse, without being noticed at all before resulting in land subsidence,saltwater intrusion, deep migration of persistent organic contaminants like PFAS (Le monde, 2023) or other irreversible consequences. The urban water cycle is central to ensuring the supply of clean, safe drinking water, effective sanitation, and wellfunctioning drainage systems for millions of residents. The impacts of human activities, such as land use change, excessive water abstraction and mismanagement, and the discharge of wastewater can exert a far greater influence on groundwater systems and hydrogeology than climate change. These activities alter the quantity and quality of both surface and groundwater, raising complex scientific, technical, socio-economic, cultural, and ethical challenges in urban water management. It is important to address the many challenges associated with ensuring water security and safety in cities (Quevauviller et al., 2024), as well as for development of effective climate change mitigation and adaptation strategies for urban areas (IPCC, 2024). Groundwater plays a critical role in the green transition and is an integral component of most climate change mitigation and adaptation strategies (Ingemarsson et al., 2022), and for meeting the increasing demand for freshwater in cities due to accelerating urbanization (United Nations, 2022). Many urbanized areas in Europe already face poor chemical and quantitative status (EEA, 2024; Sentek et al., 2024), and global change including increasing populations and sea level rise pose a tremendous challenge for safe and secure water supply especially in coastal European cities. Open access to digital subsurface data e.g. through the European Geological Data Infrastructure supports societal needs and UN sustainable development goals (Hinsby et al., 2024). This special issue demonstrates some of the important issues that the water supply of European cities are facing in times of increasing competing use of the subsurface (Volckko et al., 2020), projected climate change impacts on the hydrological cycle (Henriksen et al., 2023) and with freshwater now being among the transgressed planetary boundaries (Richardsson et al., 2023). [...]

Opportunity and Challenge of Advanced Porous Sorbents for PFAS Removal.

Per- and polyfluoroalkyl substances (PFASs), comprising over 9,000 persistent synthetic organic contaminants, are extensively found in the environment and pose significant risks to both human and ecological health. Among the strategies for addressing PFAS contamination, adsorption processes have proven to be cost-effective. Traditional sorbents such as ion-exchange resins and activated carbon have been found to exhibit low adsorption capacities and slow equilibration times. Recent innovations in porous materials, including metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and porous organic polymers (POPs), however, offer significant improvements in the efficiency of PFAS adsorption. This review thoroughly examines the latest advancements in these materials, analyzing their mechanisms of adsorption, and concludes by suggesting directions for future research that could further enhance their effectiveness in PFAS management.

Versatile injector for inline renewable solid-phase extraction: Application to cyclodextrin-based bioaccessibility assessment in environmental solids

BackgroundSolid phase extraction (SPE) is a standard sample preparation technique in HPLC workflows. Inline cartridges are high-performance alternatives to manual or robotic systems but at long term, they suffer from irreversible sorption of matrix components and sorbent compaction. Bead injection (BI) is a niche fluidic technique that allows renewing a sorbent bed through the manipulation of its suspension. However, there is a need for a versatile and reliable tool in HPLC that can exchange the inline sorbent automatically, resorting to inexpensive and assorted bulk sorbents. ResultsWe present a new flow path for a liquid chromatographic injector to perform inline micro-solid phase extraction. The sample is processed at real time, trapping the analytes and discarding the matrix. Cleaning the matrix and injecting 10 μL of sample takes 70 s, comparable with the injection in commercial HPLC systems. If the aim is to preconcentrate the analytes, average enrichment factors of 250 have been obtained after processing sample volumes of 3200 μL in 16 min (interleavable with the chromatographic step), keeping the peak position and width independent of the injected volume (compared to large volume direct injection).The desired bed mass is automatically and pressure-driven manipulated in the valve, retained by an inline frit, and optionally, after the analysis, removed by forward flow.The chromatographic performance of the new design is compared to the standard 6-port, 2-position HPLC injector. As a case study, we have monitored the extraction kinetics of a cyclodextrin-based bioaccessibility extraction test of persistent organic contaminants in soil, by extracting several fractions in valve, process them with inline SPE with a balanced hydrophilic-hydrophobic reversed-phase sorbent, and inject the bioaccessible compounds into HPLC. Aiming at avoiding carryover, the sorbent bed (ca. 3 mg) is exchanged before every run. It should be noted that this contribution focuses on HPLC, but other non-separative techniques, such as Flow Injection Analysis, can equally benefit from this injection platform. SignificanceThis contribution reports the first use of inline BI-solid phase extraction in HPLC workflows, without heart-cut eluate injection, in which the sorbent can be exchanged automatically by forward flow. This performance is enabled by prototyping a valve that can autonomously swap sorbents in real-time for diverse samples, as a cartridge exchanger, but using cost-effective and environmentally friendlier bulk sorbents (bed masses from sub-mg to 5 mg) without requiring additional hardware.

Surface hydroxyl-riched ultrasmall monodispersed CuO nanoparticles for rapid degradation of tetracycline by peroxymonosulfate activation

The activation of peroxymonosulfate (PMS) is viewed as a highly prospective strategy to address antibiotic abuse issues. In this work, surface hydroxyl-riched ultrasmall (3–5 nm) monodispersed CuO nanoparticles (NPs) are firstly applied in the degradation of tetracycline (TC) by PMS activation. The ultrasmall CuO NPs facilitate rapid degradation of TC, achieving approximately 90 % degradation within 1 min and 97 % degradation within 15 min. Furthermore, the degradation efficiency of TC remains 90 % after five cycles. The CuO/PMS system not only exhibits outstanding anti-interference properties toward various anions and organics, and high catalytic activity in a wide pH range, but also could efficiently degrade other common organic pollutants, possessing higher practical application value. Mechanistic experiments elucidated that singlet oxygen (1O2) is the main active substance for TC degradation. This work provides a newly developed and highly effective catalyst for rapid removal of persistent organic contaminants from wastewater by the activation of PMS.

The emerging and legacy persistent organic contaminants in corals of the South China Sea

Seawater warming, ocean acidification and chemical pollution are the main threats to coral growth and even survival. The legacy persistent organic contaminants (POCs), such as polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), and the emerging contaminants, including polybrominated diphenyl ethers (PBDEs), dechlorane plus (DPs) and novel brominated flame retardants (NBFRs) were studied in corals from Luhuitou fringing reef in Sanya Bay and Yongle atoll in Xisha Islands, the South China Sea (SCS). Total average concentrations of ∑16PAHs, ∑23OCPs, ∑34PCBs, ∑8PBDEs, ∑2DPs and ∑5NBFRs in 20 coral species (43 samples) from the SCS were 40.7 ± 34.6, 5.20 ± 5.10, 0.197 ± 0.159, 3.30 ± 3.70, 0.041 ± 0.042 and 36.4 ± 112 ng g−1 dw, respectively. PAHs and NBFRs were the most abundant compounds and they are likely to be dangerous pollutants for future coral growth. Compared to those found in other coral reef regions, these pollutants concentrations in corals were at low to median levels. Except for PBDEs, POCs in massive Porites were significantly higher than those in branch Acropora and Pocillopora (p < 0.01), as large, closely packed corals may be beneficial for retaining more pollutant. The current study contributes valuable data on POCs, particularly for halogenated flame retardants (HFRs, including PBDEs, DPs and NBFRs), in corals from the SCS, and will improve our knowledge of the occurrence and fate of these pollutants in coral reef ecosystems.

Alps at risk: High-mountain lakes as reservoirs of persistent and emerging contaminants

Despite their remote locations, high-mountain lakes located in the Alps are vulnerable to chemical pollution. This discussion explores the important aspects of these lakes as repositories of Persistent Organic Pollutants (POPs) and Contaminants of Emerging Concern (CECs), elucidating their sources and implications for both the environment and human health. In terms of the presence of POPs in high-altitude lakes of the Alps, 14 studies have been identified examining the occurrence of polychlorinated biphenyls, dichlorodiphenyltrichloroethane an its metabolites, polybrominated diphenyl ethers, and polycyclic aromatic hydrocarbons. The bulk of research on POPs in high-mountain lakes is concentrated in the Italian Alps (63%), followed by Switzerland (22%), Austria (12%), and France (3%), respectively. Sediment is predominantly investigated (65%), followed by fish (33%) and water (2%). Similarly, in relation to the presence of CECs in high-mountain lakes of the Alps, six studies have been identified investigating the occurrence of musks, perfluorinated compounds, and microplastics. Investigations into CECs predominantly occur in Switzerland (42%), France (33%), and Italy (25%), with fish samples (muscle and liver) being the primary focus (46%), followed by sediment (17%) and water (17%). Other compartments like zooplankton, frog/tadpoles, and snow remain less explored. The discussion also shed light on various pathways through which pollutants reach these remote landscapes, including atmospheric transport, glacial meltwater, and human activities. Protecting these pristine peaks demands concerted efforts encompassing ongoing research, vigilant monitoring, and dedicated conservation initiatives.

Organic pollutants degradation by a superb MXene-based Z-scheme heterojunction Photocatalyst: Synthesize, delamination process, mechanism and toxicity assessment

In this study, a new CeO2/MXene-TiO2 photocatalyst was created using a simple and economical approach and thoroughly characterized by different techniques, including TEM, XPS, BET, XRD, Raman, and SEM. The focus of this research was to improve the degradation of tetracycline (TC), a commonly used antibiotic with known environmental and health risks. To optimize the degradation process, RSM- CCD method was used to systematically vary key parameters including initial TC concentration, photocatalyst dosage, pH and irradiation time. The trapping experiments were revealed that the hydroxyl (•OH) and superoxide anion (•O2-) radicals played a crucial role in this process. An impressive degradation efficiency of 96.60 % was achieved under optimal conditions, attributed to the Z-scheme electron transfer heterojunction, which enhances the generation and separation of oxidant species. LC-MS analysis was employed to elucidate the photodegradation pathway of TC by identifying the reaction intermediates. This analysis facilitated the proposal of a plausible mechanism for TC degradation. The demonstrated efficacy of the CeO₂/MXene-TiO₂ photocatalyst suggests its potential application in wastewater treatment for the significant degradation of persistent organic contaminants.

Enhanced degradation of tetracycline by TiO2@MXene with peroxydisulfate under visible light irradiation

Photocatalysis and peroxydisulfate (PS) based advanced oxidation techniques are promising technologies in the field of water treatment that can be used to destroy increasingly persistent organic contaminants. The current work used a simple hydrothermal approach to synthesize a catalyst made of composites of TiO2 nanospheres and multi-layer Ti3C2Tx sheets (TiO2@MXene). Tetracycline (TC) was then effectively degraded by the TiO2@MXene material integrated with PS activation (300 mg/L). Under simulated sunlight (AM 1.5G, P = 2.8 W) irradiation, the combination method dramatically increases TC degradation. Following a 30-min treatment with 300 mg/L TiO2@MXene (wt.10 %), the optimal efficiency can reach 100 %. As the reactive functional species, holes (h+), SO4-•, •OH, and •O2− dominate the catalytic process. Furthermore, investigation was conducted into significant factors such as catalyst dosage, PS dosage, common anions, and TiO2 loading dosage. The TiO2@MXene material was demonstrated to be a feasible and sustainable strategy worth taking into consideration in the mitigation of emerging water contaminants due to its ease of recovery, stability of surface properties, and recyclability. Furthermore, the proposed degradation mechanism further demonstrated the viability of TiO2@MXene with PS in TC degradation. This, this study provides insights into the design of effective photocatalyst coupling PS activation for the efficient degradation of organic pollutants.

Ecotoxicity of perfluorooctanoic acid and perfluorooctane sulfonate on aquatic plant Vallisneria natans.

Perfluorinated compounds (PFCs) are persistent organic contaminants that are highly toxic to the environment and bioaccumulate, but their ecotoxic effects on aquatic plants remain unclear. In this study, the submerged plant Vallisneria natans was treated with short-term (7 days) and long-term (21 days) exposures to perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) at concentrations of 0, 0.01, 0.1, 1.0, 5.0, and 10 mg/L, respectively. The results showed that both high concentrations of PFOA and PFOS inhibited the growth of V. natans and triggered the increase in photosynthetic pigment content in leaves. The oxidative damage occurred mainly in leaves, but both leaves and roots gradually built up tolerance during the stress process without serious membrane damage. Both leaves and roots replied to short-term stress by activating superoxide dismutase (SOD), catalase (CAT) and polyphenol oxidase (PPO), while peroxidase (POD) was involved under high concentration stress with increasing exposure time. Leaves showed a dose-effect relationship in integrated biomarker response (IBR) values under short-term exposure, and the sensitivity of roots and leaves to PFOS was higher than that of PFOA. Our findings help to increase knowledge of the toxic effects of PFCs and have important reference value for risk assessment and environmental remediation of PFCs in the aquatic ecosystem.

Characterization of persistent organic contaminants in the atmosphere of Gadani's ship breaking yards and its surrounding: Implications for sustainable ship recycling practices

Gadani is internationally renowned for its extensive ship-breaking operations, positioning it as one of the globe's primary ship-breaking hubs. A comprehensive study was conducted to evaluate the presence of organic contaminants in the air within Gadani, encompassing the areas surrounding ship-breaking facilities, proximate residential settlements, and adjacent roadways. Passive air samplers were employed to collect a total of 30 air samples. The analytical results unveiled a notably elevated concentration of specific organic compounds, with a pronounced prevalence of polycyclic aromatic hydrocarbons (PAHs), short-chain chlorinated paraffins (SCCPs), and polychlorinated biphenyls (PCBs) at the ship-breaking yard. Notably, dichlorodiphenyltrichloroethanes (DDTs) and DDE were detected at substantially lower levels. In particular, sites in close proximity to ship-breaking activities exhibited elevated concentrations of PCBs (Σ7PCB 0.065429 to 7.345714 ng/sample), PAHs (Σ8PAH 2.44 to 134.23 ng/sample), and SCCPs (0.18 to 25.6 ng/sample). Conversely, DDTs and DDE demonstrated higher concentrations near residential settlements. The evaluation of Molecular Diagnostic Ratios for PAHs revealed anthracene/anthracene + phenanthrene ratios of 0.88, 0.69, and 0.5 for ship-breaking areas, roadside locations, and community surroundings, respectively. Furthermore, the benz[a]anthracene/benz-[a]anthracene + chrysene molecular ratios were measured at 0.77 (ship-breaking sites), 0.82 (roadside), and 0.83 (community), respectively. The molecular ratio of fluoranthene/fluoranthene + pyrene at ship-breaking sites was 0.23, while roadside and community ratios were 0.36 and 0.89, respectively. These findings underscore the significant contribution of ship-recycling activities to the atmospheric release of SCCPs, PCBs, and PAHs, emphasizing the global imperative for responsible ship recycling practices.

Unveiling the oxidation mechanism of persistent organic contaminants via visible light-induced dye-sensitized reaction by red mud suspension with peroxymonosulfate

A dye-sensitized photocatalysis system was developed for degrading persistent organic contaminants using solid waste (i.e., red mud, RM) and peroxymonosulfate (PMS) under visible light. Complete degradation of acid orange 7 (AO7) was achieved in RM suspension with PMS, where the co-existence of amorphous FeO(OH)/α-Fe2O3 was the key factor for PMS activation. The experimental results obtained from photochemical and electrochemical observations confirmed the enhanced PMS activation due to the Fe-OH phase in RM. DFT calculations verified the acceleration of PMS activation due to the high adsorption energy of PMS on FeO(OH) and low energy barrier for generating reactive radicals. Compared to the control experiment without AO7 showing almost no degradation of other organic contaminants (phenol, bisphenol A, 4-chlorophenol, 4-nitrophenol, and benzoic acid), photo-sensitized AO7* enhanced electron transfer in the FeIII/FeII cycle, dramatically enhancing the degradation of organic contaminants via radical (•OH, SO4•−, and O2•−) and non-radical (dye*+ and 1O2) pathways. Therefore, the novel finding of this study can provide new insights for unique PMS activation by heterogeneous Fe(III) containing solid wastes and highlight the importance of sensitized dye on the interaction of PMS with Fe charge carrier for the photo-oxidation of organic contaminants under visible light.

Ozonation of dioxolanes in water: Kinetics, transformation mechanism, and toxicity

Dioxolanes, which are structural analogs to dioxane, are emerging persistent mobile organic contaminants. These compounds are frequently detected in water and wastewater, but their removal has been rarely addressed in the literature. This work systematically investigated the ozonation of two representative dioxolanes, i.e., 1,3-dioxolane (1,3-D) and 2-methyl-1,3-dioxolane (2-M-1,3-D). The degradation rates of two dioxolanes exhibited a positive correlation with both ozone dosage and solution pH increment. Specifically, direct ozone oxidation dominates the degradation of dioxolanes at slightly acidic pH, while hydroxyl radical (•OH) becomes the primary oxidant under weak alkaline condition. The second-order reaction rate constants of ozone with 1,3-D and 2-M-1,3-D were determined to be 5.48 and 8.00 M−1s−1, respectively. The reaction rate constants with •OH were 9 orders of magnitude higher, reaching (3.75-8.18) × 109 and (2.65-5.78) × 109 M−1s−1 for 1,3-D and 2-M-1,3-D, respectively. A kinetic model involving 112 reactions well simulated the degradation of 1,3-D and 2-M-1,3-D under various conditions accordingly. Eight transformation products were identified totally, and seven of them (i.e., formic acid, acetic acid, oxalic acid, formaldehyde, acetaldehyde, glyoxylic acid, and 1,2-ethanediol monoacetate) were quantified. The observed evolution of these identified degradation products concludes that the degradation of 1,3-D and 2-M-1,3-D during ozonation mainly involves H-abstraction, dimerization, ring opening, disproportionation, and hydrolysis. This work not only provides essential kinetic data of dioxolanes, but also sheds light on their potential transformation mechanisms and aquatic environment risks during ozonation process.

Multi-Heteroatom Doped Fe@CN Activation Peroxomonosulfate for the Removal of Trace Organic Contaminants from Water: Optimizing Fabrication and Performance

Modification of catalysts by multi-heteroatom doping (S, P, B) is an effective way to improve the peroxomonosulfate activation performance of catalysts. In recent years, highly toxic and persistent trace organic contaminants have been frequently detected in water. Consequently, we proposed the advanced oxidation processes of peroxomonosulfate activated by multi-heteroatom doped Fe@CN (X-Fe@CN) to eliminate trace organic contaminants. The physical phases of X-Fe@CN and its precursors were characterized by X-ray diffraction and scanning electron microscopy. In evaluating the catalytic properties and iron ion leaching of X-Fe@CN-activated PMS for the removal of dicamba and atenolol, B-Fe@CN and PB-Fe@CN were selected and optimized. The active sites of the catalysts were characterized by X-ray photoelectron spectroscopy and Raman. The pathways of PMS activation by B-Fe@CN and PB-Fe@CN were identified in combination with electron paramagnetic resonance and electrochemical experiments. Defects, O-B-O and pyrrolic nitrogen on the surface of B-Fe@CN could adsorb and activate PMS to produce SO4•−, ·OH and 1O2. Further doping with P enhanced the electron transfer on the catalyst surface, thus accelerating the activation of peroxomonosulfate. This study compared the effects of multi-heteroatom modifications and further demonstrated the synergistic effect between P and B, which can provide a theoretical basis for the selection of multi-heteroatom doped catalysts in water treatment.

Effects of short and long-term thermal exposure on microbial compositions in soils contaminated with mixed benzene and benzo[a]pyrene: A short communication

Polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene, and xylene (BTEX) are the most persistent and toxic organic contaminants often found co-contaminated in anthropogenic and petrochemical industrial sites. Therefore, an experiment was performed for the safe biodegradation of benzene and benzo[a]pyrene (BaP) through thermally-enhanced biodegradation, and to explore the influence of elevated thermal treatments on microbial diversity and composition. The results revealed that elevated thermal treatments (15 to 45 °C) significantly enhanced the diversity of both bacteria and fungi. The composition analysis revealed that short-term and long-term elevated temperature conditions can directly enhance the specificity of microorganisms that play a crucial role in the biodegradation of benzene and BaP co-contaminated soil. Moreover, the indirect role of elevated temperature conditions on microbial compositions was through the fluctuations of soil properties, especially soil pH, moisture, TOC, potassium, phosphorous, total Fe, Fe(II), and Fe(III). In addition, the correlation analyses revealed that thermal exposure enhances the synergistic association (fungal-fungal, fungal-bacterial, bacterial-bacterial) of microbes to degrade the toxic contaminants and to cope with harsh environmental conditions. These results concluded that the biodegradation of benzene and BaP co-contamination was efficiently enhanced under the thermally-enhanced biodegradation approach and the elevation of temperature can affect the microbial compositions directly via microbial specificity or indirectly by influencing the soil properties.

Improved sea rice yield and accelerated di-2-ethylhexyl phthalate (DEHP) degradation by straw carbonization returning in coastal saline soils

Di-2-ethylhexyl phthalate, a persistent organic contaminant, is widely distributed in the environment and poses substantial threats to human health; however, there have been few investigations regarding the risks and remediation of DEHP in coastal saline soils. In this work, we studied the influences of straw carbonization returning on sea rice yield and DEHP degradation. Straw carbonization returning significantly increased soil nutrients and reduced salt stress to improve sea rice yield. DEHP degradation efficiency was enhanced to a maximum of 78.27% in straw carbonized return with 60% sea rice, mainly attributed to the high pH value, high soil organic matter and enriched potential DEHP degraders of Nocardioides, Mycobacterium and Bradyrhizobium. Some key genes related to metabolism (esterase and cytochrome P450) and DEHP-degradation (pht4, pht5, pcaG, dmpB, catA and fadA) were elevated and explained the accelerated DEHP degradation, shifting from the benzoic acid pathway to the protocatechuate pathway in straw carbonization returning. The results obtained in this study provide a deep and comprehensive understanding of sea rice yield improvement and DEHP degradation mechanisms in coastal paddy soil by a straw carbonization returning strategy.