Environmental context Thiolated arsenic(V) compounds widely occur in natural environments. Their physicochemical properties, including pH-dependent charging, control their behaviour in terrestrial and aquatic environments. We show that the first thiolation of inorganic and methylated arsenic(V) compounds forming an arsinothioyl (As═S) moderately increases pKa values, whereas a second thiolation forming a thiol (–SH) strongly decreases pKa. In contrast to thiolation, consecutive methylations of arsenic(V) steadily increase pKa values. Abstract Thiolated arsenic compounds have been detected in an increasing number of environmental compartments. Experimental evidence on the effect of thiolation on the pH-dependent speciation (i.e. charging) of thiolated arsenic compounds is, however, very limited, or for some toxicologically highly relevant compounds, absent to date. Based on acid–base titration data recorded in 0.01 and 0.1 M of sodium chloride (NaCl) background electrolytes, we derive proton dissociation constants (pKa values) for some major environmentally relevant arsenic compounds, including dimethylmonothioarsinic acid (DMMTAV: pKa = 6.44). We further show that the calculated pKa estimates used so far to assess and predict the behaviour of thiolated arsenic compounds considerably deviate from experimental evidence.
Rationale. Cobwebs (spider webs) were used as a proxy for monitoring the concentrations, sources and risks of polycyclic aromatic hydrocarbons (PAHs) in indoor environments. The results demonstrated that spider webs are an effective and useful bioindicator for monitoring PAH depositions from different sources in indoor environments. Methodology. PAHs were monitored in different indoor settings, including electronic workshops (EWs), public buildings (PBs) and residential buildings (RBs), using cobwebs as a proxy. PAH concentrations in cobwebs obtained from different indoor environments were analysed by gas chromatography-mass spectrometry. Results. The PAH concentrations in the cobwebs ranged from 100 to 3610, 10 to 8830 and 400 to 6750 & micro;g kg-1 for EWs, PBs and RBs respectively. Discussion. The homologue compositions suggested prevalence of 3-and 4-ring PAHs in the cobwebs. The risk evaluation of PAHs in the cobwebs suggested no adverse non-carcinogenic risk, but an adverse carcinogenic risk for adults and children. The preliminary source apportionment results indicated that PAHs in the cobwebs originated mainly from combustion processes.
Environmental context This study provides a simple and sensitive method for measuring trace amounts of antimony. This measurement is needed as antimony is known as a toxic element in environmental samples. Antimony is widely distributed in the environment and can come into contact with humans. Here the ultraviolet-visible spectrophotometry is combined with dispersive liquid-liquid microextraction. The approach can help monitor antimony pollution and protect environmental and human health.Rationale Trace antimony (Sb) has environmental and health risks, so sensitive and selective analytical methods for its determination in diverse samples is a necessity. Existing techniques often require complex procedures or expensive instrumentation, highlighting the need for a simple, efficient and cost-effective method.Methodology A novel ion pair-dispersive liquid-liquid microextraction (IP-DLLME) procedure was developed. SbIII was oxidised to SbV in hydrochloric acid (HCl) using potassium permanganate (KMnO4) to form the extractable hexachloroantimonate ion (SbCl6-). The ion-pair with methyl violet was subsequently extracted into chlorobenzene. Key parameters, including solvent type and volume, methyl violet concentration, acid concentration, extraction time and ionic strength, were systematically optimised.Results Under optimised conditions, the method exhibited a linear calibration range of 5-300 ng mL-1, with a limit of detection of 4.1 ng mL-1, a limit of quantification of 12.3 ng mL-1 and an enrichment factor of 270. Recovery studies demonstrated good tolerance toward common coexisting ions. The method was successfully applied to natural water, bottled orange juice, kohl and safety match samples.Discussion The proposed IP-DLLME method provides a practical, selective and sensitive approach for routine determination of trace Sb in environmental and consumer products. Its simplicity, high enrichment factor and minimal reagent consumption make it suitable for widespread application. Future studies may focus on extending this approach to detect other toxic metal ions and coupling with alternative detection techniques such as ion pair chromatography and ion selective electrodes.
Environmental context Single particle-inductively coupled plasma-time-of-flight mass-spectrometry (SP-ICP-ToF-MS) is a powerful technique for characterizing nanoparticles, colloidal particles and fine and ultrafine particles in waters, soil, air and biota. However, this technology generates massive datasets that can take days to process, severely bottlenecking large scale environmental measurements. To address this shortcoming, this paper introduces a streamlined, automated workflow that drastically reduces analysis time of SP-ICP-ToF-MS, allowing researchers to quickly and efficiently extract crucial insights from complex heterogenous environmental systems.Rationale Existing data processing applications for single particle-inductively coupled plasma-time-of-flight-mass spectrometry (SP-ICP-ToF-MS), while valuable, have some limitations including restricted multi-sample analysis capabilities, vendor-specific constraints and the lack of efficient visualization approaches. Researchers need flexible, interactive visualization tools that can reveal compositional patterns and enable side-by-side sample comparisons for rapid trend identification and comprehensive data exploration across large datasets.Methodology we developed IsotopeTrack, an open-source Python-based platform designed specifically for SP-ICP-ToF-MS data processing with cross-platform compatibility (Windows and MacOS). The application implements complete calibration methodologies including transport rate and sensitivity calibrations, three distinct peak detection algorithms (Currie method, Formula C and compound Poisson log-normal) and element specific parameter optimization. Performance was validated using diverse engineered nanoparticles (NPs) including titanium dixoide (TiO2), cerium oxide (CeO2), metallic alloys (nickel-iron-cobalt, Ni-Fe-Co; nickel-iron-chromium-manganese, Ni-Fe-Cr-Mn; nickel-iron-molybdenum, Ni-Fe-Mo) and gold/silver (Au/Ag) core-shell particles. The platform features an interactive results canvas with drag and drop capabilities for constructing customized analysis pipelines and it supports multiple file formats.Results IsotopeTrack successfully analyzed multi-element alloy compositions with a high accuracy. For Ni-Fe-Co alloys, measured mass compositions of 60Ni (29.3%), 57Fe (55.1%) and 59Co (17.7%) closely matched known values of 28% Ni, 55% Fe and 17% Co. Ultra-uniform gold NPs yielded mean diameters of 52.0 +/- 5.0 nm, 29.5 +/- 4.4 nm and 21.1 +/- 4.3 nm for nominal 50-, 30 and 20-nm particles. The platform generated comprehensive visualizations including elemental correlations, isotopic ratio distributions, ternary diagrams and composition heatmaps. Processing time was reduced from hours to minutes through parallel processing. The comparison of environmental samples consisting of hundreds of thousands of particles was greatly facilitated.Discussion IsotopeTrack addressed critical limitations in SP-ICP-ToF-MS data analysis by providing batch processing and interactive visualization tools. Element specific optimization ensured analytical rigor, while dramatically reducing processing time. This open-source framework represents a significant advance in single particle analysis, enabling efficient processing of large datasets essential for NP characterization in complex systems.
Environmental context Polycyclic aromatic hydrocarbons (PAHs) are toxic, persistent organic pollutants widely introduced into marine environments through oil spills, industrial effluents and incomplete combustion processes. Owing to their hydrophobic nature, PAHs readily accumulate in sediments and biota, posing serious ecological risks associated with their carcinogenic and mutagenic properties. In this study, we show that indigenous microbial assemblages contribute directly to PAH transformation in marine systems and underscore their relevance to intrinsic biogeochemical attenuation and environmentally compatible remediation approaches.Rationale Polycyclic aromatic hydrocarbons (PAHs) are persistent organic contaminants whose chemical stability and toxicity pose risks in marine environments. Phenanthrene (Phe) is used as a model PAH to elucidate transformation mechanisms relevant to more complex and carcinogenic compounds. Although microbial degradation of PAHs is recognised as a key attenuation process, chemically resolved evidence linking enzymatic activity to transformation intermediates in marine systems remains limited. This study investigates Phe degradation by a marine Pseudomonas oleovorans strain, integrating proteomic and metabolite analyses to resolve dominant degradation pathways.Methodology Pseudomonas oleovorans strain NIOSV8 was incubated in Luria-Bertani broth (LB) amended with Phe (100 mg L-1) for 48 h. Phe removal was quantified over time. Protein expression profiles under control and Phe-amended conditions were analysed using liquid chromatography-mass spectrometry (LC-MS) quadrupole time of flight (QToF)-based shotgun proteomics. Differentially expressed proteins were used to infer active metabolic pathways. Degradation intermediates were identified using gas chromatography-mass spectrometry (GC-MS) to validate proteomic interpretations.Results Approximately 55% of Phe was degraded within 48 h. Proteomic analysis identified 5902 proteins across all conditions, with 2486 proteins detected exclusively in Phe-amended cultures, indicating metabolic reprogramming. Enzymes associated with aromatic hydrocarbon transformation were enriched, particularly salicylate hydroxylase and catechol 2,3-dioxygenase-related proteins, consistent with a salicylate-catechol degradation sequence. Multiple oxidoreductases and dehydrogenases involved in xenobiotic metabolism were also upregulated. GC-MS analysis detected intermediates such as 1-naphthol and 8-methyl-1-naphthoic acid, which support the oxidative transformation of Phe to salicylate-related compounds.Discussion The combined proteomic and metabolite evidence demonstrates that Phe degradation proceeds by a salicylate-mediated pathway. The induction of oxidoreductases highlights oxidative reactions in PAH transformation and the maintenance of redox balance. Changes in energy metabolism indicate that Phe degradation is a metabolically demanding process. These findings provide mechanistic insight into microbial PAH transformation and contaminant fate in marine environments and sediments.
Environmental context Tunnel wash water contains high concentrations of tyre-road wear particles, tyre-derived chemicals, and metals, which can threaten aquatic ecosystems if untreated. This study applies a multi-analytical approach to assess pollutant retention and transformation during sedimentation, revealing treatment limitations and emphasising the need for advanced strategies to reduce pollution from enclosed road infrastructures. Rationale Tunnel wash water (TWW) accumulates tyre-road wear particles (TRWPs), tyre-derived chemicals (TDCs) and metals at high concentrations, posing risks to aquatic ecosystems if untreated. Understanding pollutant retention and transformation during treatment is essential for effective mitigation. Methodology We investigated TWW from the V & aring;lereng tunnel (Oslo, Norway) using a multi-analytical approach. TRWPs were quantified by pyrolysis-gas chromatography-mass spectrometry (PYR-GC/MS) with a marker mix (M4), a single marker (4-vinylcyclohexene, 4-VCH), and automated scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) single particle analysis with machine-learning classification (automated single particle analysis, ASPA, MC2). Metals were analysed by inductively coupled plasma-mass spectrometry (ICP-MS) and TDCs by ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Samples were collected before, during and after sedimentation treatment over 21 days. Results Zinc (Zn) was the most abundant metal (274-2300 mu g L-1), reduced by up to 93% post-treatment. TRWP concentrations ranged from 15-160 mg L-1 (M4), 13-122 mg L-1 (4-VCH) and 13-240 mg L-1 (ASPA MC2), with treatment efficiencies of 95-99.7%. Despite reductions, fine particles (<20 m) dominated both untreated and treated water (up to 85%). For TDCs, N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine (6PPD) showed 85% reduction, whereas 6PPD-quinone (6PPD-Q) (-26%) and N,N-diphenylguanidine (DPG) (-3.7%) exhibited negative retention, likely due to leaching and transformation. 1-hydroxybenzotriazole hydrate (OHBT) increased by up to 167% during sedimentation. Discussion Sedimentation effectively removed particles and metals but was insufficient for several dissolved TDCs, releasing them at ecotoxicologically relevant concentrations (e.g. 6PPD-Q exceeded Environment Protection Authority freshwater limits). This first cross-validation of three TRWP quantification methods highlights the need for advanced treatment technologies and regulatory thresholds for tyre-derived pollutants.
Environmental context Each year, tonnes of tyre wear particles enter the terrestrial environment and undergo natural aging. This study investigates the effect of artificial weathering, particle concentration and preparation method on the reproduction of Caenorhabditis elegans, a soil- and water-dwelling nematode, using the standardised toxicology assay ISO 10872.Rationale Tyre abrasion is one of the largest sources of microplastic (MP) in aquatic and terrestrial environments. Despite this fact, research on tyre wear particles (TWP) and its effects on soil ecosystems is scarce, especially regarding natural weathering processes. This leaves a large knowledge gap on the interactions of TWP with soil biota.Methodology Cryo-milled tyre tread (CMTT) and diamond-ground tyre tread (DGTT) were artificially weathered through dry ozone treatment and heat exposure. Particles were analysed by scanning electron microscopy, particle size distribution and shape characterisation. TWP leachate composition was examined using liquid chromatography-mass spectrometry. The impact on the reproduction of the nematode Caenorhabditis elegans, a widely used toxicological model, was tested for leachate concentration, exposure duration and TWP aging status, using offspring per adult as the endpoint.Results The comminution method significantly influenced TWP particle size distribution, with diamond grinding yielding smaller particles and a more structured surface morphology than cryo-milling. Aging with ozone (180 min) and heat (20 min at 100 degrees C) reduced DGTT particle sizes by 27-58%, but not in CMTT. Additionally, aging increased carboxylic functional groups and led to a brittle structure in both TWP types. Leachate composition varied with comminution method and aging. Benzothiazole, N-Cyclo-N-phenylurea and aniline were more abundant in pristine and aged CMTT and aged DGTT. Diphenylguanidine had the highest concentration in all leachates. Aged TWP leachates, regardless of comminution, had significant toxic effects on C. elegans. Leachate from pristine CMTT was more toxic than from pristine DGTT. Nematode offspring correlated negatively with ozone exposure duration in aged DGTT. Tests with aged CMTT leachate showed even short-term exposure reduced offspring numbers.Discussion The results underscore the importance of oxidative and mechanical weathering in TWP toxicity and challenge the use of pristine particles in toxicological assays for risk assessment in the natural environment.
Rationale The objective was to describe the mechanisms behind an increase in zinc (Zn) uptake by wheat roots due to the presence of citrate and histidine. Methodology The hypothetical mechanisms of Zn uptake in the presence of metal ligands were formalised in numerical models. The simulated Zn and ligand uptakes were compared to those measured in three hydroponic experiments with two bread wheat cultivars. Results Transpiration-driven apoplastic flux and solution-mediated dissociation of complexes resulting from limited Zn2+ diffusion could not explain the strong increase in Zn uptake by wheat roots in the presence of citrate or histidine. Transpiration-driven flux was also insufficient to cause the high histidine uptake, whereas this proved an adequate explanation for the low citrate uptake. Discussion Wheat roots likely absorb histidine and the undissociated Zn-histidine complex through membrane transporters according to a chemical potential gradient generated by plant energy conversion. Histidine and Zn-histidine could use different transport systems, or a common one with lower affinity for the complex. Zn-citrate complexes appear not be absorbed directly, but rapidly dissociated after the formation of a ternary complex of Zn-citrate with a biotic ligand at the root cell membrane. The metal ion released is internalised and the ligand recycled into the rhizosphere solution. According to the Michaelis-Menten parameters of the root uptake kinetics, the affinity of the transport systems was ranked in the order: histidine > Zn2+ > Zn-histidine > Zn-citrate. These results encourage research to identify transporters of histidine, and of complexes of Zn with histidine and citrate.
Environmental context Maintaining sufficient dissolved oxygen in rivers and lakes is crucial for the health of fish, the quality of drinking water, and the overall well-being of ecosystems. This study presents an intelligent, interpretable machine learning-based prediction framework to predict dissolved oxygen variation and accurately identify multiple driving factors. The breakthrough provides water managers with a powerful tool to anticipate water quality changes and protect vital water resources more effectively.Rationale Dissolved oxygen (DO) is a critical indicator of water quality, but accurately predicting DO fluctuations under the combined influence of various environmental factors remains challenging.Methodology This study presents an intelligent prediction framework that integrates interpretable machine learning methods with stacking generalisation techniques to forecast dynamic changes in water quality effectively. Using daily data (2020-2022) from seven stations in the Danjiangkou Reservoir, China, environmental factors were categorised into water quality, streamflow, meteorology and air pollution. A stacked model, combining support vector machine (SVM), multilayer perceptron (MLP), random forest (RF) and K-nearest neighbours (KNN) base learners with a LightGBM meta-learner, was constructed and interpreted using Shapley additive interpretation (SHAP) analysis. The contribution of each feature is accurately determined, and the mode of action of the main factors and the key threshold points are identified.Results The stacked model provides efficient and accurate DO forecasts, outperforming single base models with an average improvement in R2 of 5.22% on the test set, and achieving a 2.29% increase in R2 and a 4.81% reduction in root mean squared error (RMSE) compared to the unstacked LightGBM model. Global interpretation reveals that the water quality parameter category has the most significant impact (up to 70% of total feature importance), with water temperature (WT) being the most crucial factor. Other key contributors include conductivity (EC), ammonia nitrogen (NH3-N), turbidity, surface runoff, atmospheric pressure (AP) and sulfur dioxide (SO2).Discussion The proposed framework effectively captures the synergistic effects of multiple environmental factors on DO. It offers a robust method for forecasting their dynamics, demonstrating the value of categorised environmental analysis for water quality management.
To investigate the pollution status, sources, and ecological risks of polycyclic aromatic hydrocarbons ( PAHs ) in surface waters of low-latitude plateau lakes in China, monthly sampling and analysis of surface water 16 PAHs mass concentrations, composition characteristics, and spatiotemporal distribution were conducted in Qilu Lake in the central region of Yunnan Province from January to December 2024. The study quantitatively analyzed the pollution sources and relative contributions of PAHs detected and assessed their ecological risks in Qilu Lake. The findings revealed that 13 PAHs were detected in varying degrees in the surface water of Qilu Lake during both the rainy and dry seasons, with a predominance of three-ring structures. During the rainy season, the total mass concentrations of 16PAHs ranged from undetected ( below the method detection limit, same below ) to 198.42 ngL-1( average 49.11 ngL-1), while during the dry season, it ranged from undetected to 213.38 ngL-1( average 63.79 ngL-1). The highest individual mass concentrations were found for Phe ( 49.94 ngL-1) and Ace ( 43.63 ngL-1). The average mass concentration of PAHs at all sampling points was higher in the dry season ( 63.79 ngL-1) compared to the rainy season ( 49.11 ngL-1). Spatial distribution showed that during the rainy season, PAHs mass concentrations were highest at Lake Management Station S2 ( 55.39 ngL-1), followed by Majiawan S3 ( 41.19 ngL-1), and then Lake Center S1 ( 34.60 ngL-1). In contrast, during the dry season, the order was Majiawan S3 ( 61.00 ngL-1) > Lake Management Station S2 ( 57.26 ngL-1) > Lake Center S1 ( 51.85 ngL-1). Positive Matrix Factorization ( PMF ) results indicate that during the rainy season, the surface water of Qilu Lake mainly sources PAHs from industrial sources ( contributing 31.9% ) and the volatilization leakage and combustion emissions of crude oil products ( contributing 29.5% ). In contrast, during the dry season, the primary sources are a mixture of coal and biomass combustion ( contributing 55.0% ) and biomass combustion alone ( contributing 25.2% ). Additionally, based on ecological risk assessment using the Risk Quotient ( RQ ), Ace, Flu, and Ant are identified as the main ecological risk factors for Qilu Lake. During the dry season, all sampling points and a specific points during the rainy season exhibit occasional moderate ecological risks. Overall, PAHs in the water body are at low to moderate ecological risk levels and require attention. In the context of heightened national focus on new pollutant management, traditional persistent organic pollutants such as PAHs still warrant continuous monitoring.
The widespread use of the insecticide DDT has left a legacy of pollution that still threatens ecosystems today. This study presents a method to accurately measure the bioavailability of DDT and its breakdown products in contaminated soils. This will improve risk assessments and guide sustainable land management practices, helping to protect both the environment and human health. The insecticide dichlorodiphenyltrichloroethane (DDT) and its degradation products (collectively DDX) are persistent organic pollutants that pose significant environmental risks due to their persistence and bioaccumulation in ecosystems. Accurate quantification of DDX bioavailability in soil systems is crucial for effective land management and risk assessment. This study utilised equilibrium passive sampling with polyoxymethylene (POM) to determine the bioavailability of DDX in soil. The sorption dynamics of 10 DDX compounds were investigated (p,p′-DDT, o,p′-DDT, p,p′-dichlorodiphenyldichloroethane (p,p′-DDD), o,p′-DDD, p,p′-dichlorodiphenyldichloroethene (p,p′-DDE), o,p′-DDE, p,p′-dichlorodiphenylmethane (p,p′-DDM), p,p′-dichlorobenzophenone (p,p′-DBP), 1-chloro-2,2-bis(4-chlorophenyl)ethylene (p,p′-DDMU) and dicofol) and their POM–water partition coefficients (KPOM) were determined. The study involved interlaboratory comparisons, using soils from nine historically contaminated sites and ecotoxicology assessments (mortality, reproduction and bioaccumulation in earthworms, Eisenia fetida) to validate the POM method. K POM values for 9 of the 10 DDX compounds were successfully determined, allowing for accurate quantification of freely dissolved pore water concentrations of DDX in historically contaminated soils. The interlaboratory study highlighted important considerations in extraction and gas chromatography–mass spectrometry analysis, and the ecotoxicology study demonstrated the potential of POM passive sampling as a reliable tool for assessing DDX bioavailability (bioaccumulation in Eisenia fetida). The POM method proved to be a robust and reliable approach for quantifying freely dissolved DDX, with implications for improving the accuracy of risk assessments and guiding sustainable land management practices. The study also highlighted the need for careful consideration of analytical challenges, such as the potential degradation of DDX compounds during gas chromatography analysis, to ensure accurate quantification.
Arsenic (As) can be taken up by phytoplankton or adsorbed onto phytoplankton cell surfaces. Current studies typically overlook the effects of surface adsorption and the variability in As content among individual cells within a population. In this study, we combine citrate–TiIII–EDTA chemical washing, which effectively removes surface-adsorbed As, with single-cell analysis to accurately quantify both intracellular and extracellular As content in individual phytoplankton cells. Recent advancements in single-cell analytical techniques have enabled the quantification of total arsenic (As) content in individual phytoplankton cells. However, these measurements include As absorbed onto cell surfaces. Therefore, to accurately assess cellular uptake of As, methods for removing surface-bound As need to be developed. Incubation experiments were conducted to assess As uptake in Pediastrum duplex, Scenedesmus acutus and Staurastrum paradoxum. Surface-bound As was removed using a washing solution containing TiIII-citrate and ethylenediaminetetraacetic acid (EDTA). Intracellular As concentrations were measured using single cell inductively coupled plasma–mass spectrometry (single cell ICP-MS). Additionally, non-biological adsorption was quantified by measuring As levels in ‘dead’ phytoplankton cells pre-treated with sodium azide (NaN3). No significant changes in cell densities or intracellular As distribution patterns were observed following the chemical wash. Subsequent single cell ICP-MS analyses revealed significant variability in As accumulation among individual phytoplankton cells. S. paradoxum exhibited the highest As accumulation capacity, with cells containing between 300 and 5000 ag As, averaging 1650 ag of As per cell. S. acutus had the lowest accumulation, ranging from 300 to 2600 ag As, with an average of 800 ag of As per cell. ‘Dead’ phytoplankton cells pre-treated with NaN3 generally contained less than 1000 ag As, averaging 400 ag of As per cell. Average intracellular As concentrations measured using single cell ICP-MS were consistent with previous studies that used microwave digestion with ICP-MS (102–104 ag of As per cell). There was significant variability in As accumulation among individual cells of the same phytoplankton species. Notably, some S. paradoxum cells accumulated high levels of As, reaching up to 5000 ag cell–1. NaN3 was largely effective in inhibiting biological activity for assessing extracellular As adsorbed onto cell surfaces. However, some phytoplankton cells may have remained viable and continued to take up As from the culture medium.
Red mud originating from Vietnam is used in the treatment of phosphorus-contaminated water. Suitability of a pseudo first order (PFO) model to describe the kinetics of phosphorus adsorption on O-RM was confirmed, with the adsorption process reaching an equilibrium after 20 min. Findings of this study will contribute to the industrial application of low-cost materials in wastewater treatment. Oxidised activated red mud (O-RM) materials have a high adsorption capacity for phosphorus, are easy to synthesise, are low-cost, have a short adsorption time and are readily applicable in practice. Morphological and compositional analysis of O-RM materials was performed by energy-dispersive X-ray (EDS), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). Surface area and porosity was examined by Brunauer, Emmett and Teller (BET) method as well as scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Phosphorus content was measured by a colourimetric method based on the ISO 6878:2004 standard. This study investigated the activation process of red mud using an oxidation method at a temperature of 373.15 K (100°C). The O-RM has a large surface area with preserved key components such as FeO(OH), Fe2O3, AlO(OH), and Al(OH)3. As a result, O-RM became an efficient adsorbent for phosphorus with high adsorption capacity (218.15 mg g−1) and short adsorption time (20 min). O-RM is inexpensive, easy to synthesise, stable, reusable and environmentally friendly material which makes it a highly promising option for treating phosphorus-contaminated wastewater. The morphology and chemical composition of O-RM including FeO(OH), Fe2O3, AlO(OH) and Al(OH)3 was confirmed. Factors affecting the phosphorus adsorption process onto the O-RM, such as pH, contact time, adsorption thermodynamics, stability, reusability of the material and the influence of other ions, were also studied and validated.
Plastic pollution is a growing crisis, with tiny microplastic (MP) particles spreading through our environment and potentially affecting ecosystems in ways we do not fully understand. This study found that thermoplastic-bead MPs and polyethylene terephthalate MPs can chemically interact with naturally occurring minerals like goethite, altering the surfaces of the MPs and potentially influencing how pollutants and microbes interact with the altered particles. Understanding these surface changes is crucial for predicting how MPs behave in nature and assessing their long-term environmental impact. This study investigated how goethite (GT) affects the surface of thermoplastic-bead microplastics (TPB-MPs) and polyethylene terephthalate MPs (PET-MPs) under simulated natural conditions. Chosen for its prevalence and roles in environmental geochemistry, GT interacts with MPs and influences their behavior and pollutant interactions. The hypothesis was that GT adsorption alters MP surface chemistry, affecting environmental biogeochemistry. MP surfaces were examined before and after GT treatment using X-ray photoelectron microscopy (XPS). Prior Fourier–transform infrared (FT-IR) analysis identified TPB-MPs as PET-based materials, indicating compositional similarity. XPS revealed the chemical compositions and electron binding energies in PET-MPs and TPB-MPs before and following GT adsorption. GT adsorption decreased surface carbon and increased oxygen content more in PET-MPs than TPB-MPs. PET-MPs showed stronger charge transfer and hydrogen bonding with GT, whereas TPB-MPs interactions were weaker and dominated by Van der Waals forces. Variations in peak intensity indicated enhanced C–O and O–C═O bonds and masking of C–C/C═C bonds in PET-MP. TPB-MP’s interactions with GT were weaker. Shifts in Fe2p doublet suggested chemical changes from GT adsorption. The results show that GT changes the surface chemistry of PET-MPs, enhancing their environmental transformation and reactivity. Binding energy shifts indicate surface hydrogen bonding and potential oxidation and charge transfer, highlighting GT’s role in mediating MP–mineral interactions. TPB-MPs exhibit weaker GT adsorption and fewer chemical changes, influencing their persistence and interactions with pollutants. Future research should explore oxidative transformation and microbial responses to MPs with mineral coatings. GT adsorption alters surface composition, electron scattering, and peak intensities mainly through physical interactions, with chemical effects needing further study.
Characterizing dissolved organic matter (DOM) is important for understanding its quality, which is highly linked to its reactivity. The DOM acts as a substrate for the abiotic production of hydrogen peroxide (H2O2). In southern Florida aquatic environments, we found that the origin of DOM has a profound effect on the H2O2 concentrations. Dissolved organic matter (DOM) is a complex mixture of compounds that is ubiquitous in aquatic ecosystems and is involved in multiple biogeochemical processes. The degradation of DOM due to exposure to solar radiation can produce reactive photoproducts. Among these, reactive oxygen species (ROS), particularly hydrogen peroxide (H2O2), are strong oxidizing agents. We aim to expand our understanding of the complex relationship between DOM and H2O2 in tropical and subtropical aquatic systems in Florida. Using absorbance and fluorescence-based methods, we characterized the DOM quality. Additionally, we measured H2O2 concentrations in 42 aquatic systems. Freshwater aquatic ecosystems showed a broad variation in DOM quantity and quality. Based on their origin, the water samples can be grouped int three categories: autochthonous, recently produced allochthonous and allochthonous DOM. Using parallel factor analysis modeling (PARAFAC), we validated five fluorescent components: three humic-like components, one fulvic-component and one protein-like component. Notably, the humic-like component C4 (A), autochthonous and fresh allochthonous DOM, showed a significant direct relationship with H2O2 concentrations. Conversely, in water bodies primarily characterized by allochthonous DOM origin, a significant direct linear relationship was observed between chlorophyll-a and H2O2 concentrations. Overall, our results support the idea that reactive humic compounds serve as a primary substrate for H2O2 production. However, in the absence of reactive compounds, the biological processes also play a crucial role in the H2O2 production.
Environmental context Understanding the ecotoxicity of tyre wear particles (TWPs), an increasing pollution source, is necessary for managing environmental risk. This study combines a tyre leachate ecotoxicity assessment and absorption and uptake of TWPs into plants. It was demonstrated that the risk of TWPs entering the food chain through the two studied aquatic plants is low, but managing the leachate levels in the local ecosystems is crucial.Rationale Tyre wear particles (TWPs) have been increasingly recognised as a major contributor of low size-range microplastics that are easily accessible to organisms. The present study aimed to expand on the limited ecotoxicity assessments of aquatic plants exposed to TWPs and understand the potential for TWP trophic transfer from the bottom of the food web.Methodology Here, the surface absorbance of TWPs was investigated using Lemna minor as a model organism for angiosperm plants. Growth inhibition caused by tyre leachate was investigated following the Organisation for Economic Cooperation and Development's protocol #221, with leachate characterised for 14 common tyre additive chemicals previously detected in Australia's environment. TWP environmental uptake was assessed using Persicaria sp. collected from a local creek affected by highway runoff in Brisbane.Results The results demonstrated that tyre leachate negatively affected L. minor growth and development at TWP concentrations above levels previously reported in the Australian environment (>1 mg mL-1 TWPs). A possible cause was nutrient deficiency due to stunted root development. TWP agglomerates absorbed to frond surfaces, but TWP uptake into plants could not be confirmed with the methods used. Analysis of TWP-exposed wild plants reported no detectable TWPs.Discussion Aquatic plants serve as food for fish, amphibians, and aquatic birds. This study observed TWP accumulation on L. minor surfaces, suggesting potential entry into the food web. However, the levels detected in lab-cultivated L. minor and wild Persicaria sp. suggest a low risk of trophic transfer in similar scenarios. Thus, although current environmental concentrations of TWPs may not threaten higher organisms from plants, high leachate levels can still harm aquatic vegetation.
Environmental context Anaerobic digestion (AD) is an important wastewater treatment technology. Quorum sensing (bacterial communication) regulates the interaction relationship between microorganisms, but the regulatory mechanism for methanogenic microorganisms in AD remains unclear. This study found that certain microbially produced chemicals (N-acyl homoserine lactones) can effectively regulate metabolic processes, encouraging mutualism and symbiosis between syntrophic bacteria and methanogens, making AD more efficient.Rationale This paper adopts an effective regulatory method for group social behaviour - quorum sensing - to achieve the regulation of syntrophic bacteria metabolism and increase methane production. The key focus is on the process in which the electronic carriers synthesised by the metabolism of syntrophic bacteria are used by methanogens. The results of this study will provide an effective regulatory means for enhancing the methanogenic efficiency during anaerobic digestion.Methodology A co-culture system of propionic acid co-oxidising bacteria and methanogens was constructed through anaerobic granular sludge acclimation. Different types of N-acyl homoserine lactones (AHLs, 2.0 mu g L-1) were added, including C4-HSL, C6-HSL, C8-HSL, C10-HSL and C12-HSL. The degradation rate of propionic acid, methane production, enzyme activity and microbial community structure were investigated.Results It was found that C4-HSL, C6-HSL and C12-HSL entered the rapid degradation period 1 day earlier than the blank group; methane production was enhanced by 28.3, 23.4 and 26.4% respectively; and the activities of formate dehydrogenase (FDH) enzymes were increased by 107.8, 86.2 and 90.0% respectively; and H2ase activity increased by 71.3, 90.1 and 69.1% respectively.Discussion Gene prediction indicated that AHLs promoted the process by regulating the FDH and H2ase genes. The AHLs enhanced the methanogenic process by enhancing enzyme activity. This was an important discovery that AHLs regulated the methanogenic production of methanogens' metabolism, and it provided a new strategy for the regulation of anaerobic digestion (AD).
Rationale. In the assessment of chemical contamination by heavy metals, it is difficult to distinguish the relative contributions of natural and anthropogenic sources, and to ascertain how they change over time. This study aimed at providing new information on the sources of lead (Pb) in the Antarctic coastal waters of Terra Nova Bay, in past and present times. Methodology. The samples were collected at Terra Nova Bay, during 1996-98 and in 2021, and analysed for their Pb mass fraction and isotopic composition. Samples included marine biota (Trematomus bernacchii fish and the Adamussium colbecki mollusc), suspended particulate matter (SPM) and surface sediment. The sediment was further fractionated both physically (fine fraction, <63 m, and coarse fraction, 63-2000 mu m) and chemically (labile and total Pb). Results. Pb mass fractions in organisms collected in 1996-98 (0.13-1.00 mu g g-1) were higher than those from 2021 (0.02-0.17 mu g g-1), with significant differences (P < 0.05) in specific tissues and organs: shell for the mollusc, gonads and spleen for the fish. The labile Pb mass fraction in the fine sediment averaged 3.27 g g-1, representing <10% of the total Pb. In seawater, the concentration of Pb associated to SPM was at the nanogram per litre level, peaking at 25-m depth. The Pb isotopic composition in biota revealed mixing of natural and anthropogenic inputs, with near-equal contributions. A similar pattern was also evident for Pb associated with SPM and the labile Pb in the fine sediment fraction, whereas labile Pb associated to the coarse fraction and total Pb were mostly composed of natural origin Pb. Discussion. The decrease in Pb mass fraction in biota from 1996-98 to 2021 suggests a general reduction of global Pb pollution, likely due to a decline in the use of leaded petrol. Nonetheless, isotopic data indicate that a significant fraction of Pb in Terra Nova Bay is still of anthropogenic origin, although the amount of bioavailable Pb is far from being of concern.
Rationale. Chemical aging of biological aerosols (bioaerosols) and their constituents in the atmosphere have not been well characterized so far. Thus, the goal of this research is to test the hypothesis that bioaerosol constituents undergo chemical transformations by simulated atmospheric oxidation by the hydroxyl radical (OH center dot). Methodology. In this work, an oxidation flow reactor (OFR) was used to expose pollen constituents and extracts of two pollen species (lodgepole pine and aspen) to OH center dot to simulate atmospheric pollen that is similar to 4.5 days old. Thermo-optical analysis and liquid and gas chromatography coupled to mass spectrometry were used to quantify changes in chemical composition upon oxidation. Results. The organic mass to organic carbon ratio (OM/5OC) of pollen extracts increased. Saccharides did not decrease appreciably upon oxidation in the OFR. By contrast, oxidation of the free amino acid proline resulted in hydroxyproline formation. Changes in the abundance of individual amino acids upon oxidation of the aerosolized pollen extracts were observed, notably an increase in hydroxyproline and otherwise general decreases in abundance of other free amino acids. Discussion. The results indicate that bioaerosol chemical composition can change significantly due to atmospheric photochemical transformations. Such transformations may lead to OM/OC ratios higher than those of other aerosol types and those generally assumed for bioaerosols. These findings provide new estimates for elemental signatures of aged bioaerosols for future atmospheric budgeting studies. The observed formation of photochemical oxidation products (e.g. hydroxyproline) suggests that such products could serve as chemical tracers for aged bioaerosols. The observed chemical changes imply that health effects of bioaerosols could also be modified in the atmosphere, necessitating further investigation.
Environmental context Per- and polyfluoroalkyl substances (PFASs), often called 'forever chemicals', have contaminated water sources worldwide and pose serious health risks. This study reviews how adsorption technologies - using materials such as activated carbon and advanced nanomaterials - can effectively capture and remove PFASs from water. These insights support the development of safer, more efficient treatment solutions and guide future policies to protect public health and the environment.Abstract Per- and polyfluoroalkyl substances (PFASs), a large and chemically diverse group of synthetic fluorinated compounds, have been extensively used in industrial processes and consumer products due to their remarkable thermal stability and resistance to degradation. However, their environmental persistence, bioaccumulation potential and associated health risks are of growing global concern, especially given that PFASs have been detected in over 98% of the US population and in ecosystems worldwide, with estimated environmental half-lives spanning decades to centuries. This review critically and comprehensively synthesises current knowledge on PFAS production, environmental dissemination and management strategies. It explores major contamination sources and pathways, highlights their global distribution and examines the evolving regulatory landscape. The review focuses on adsorption-based removal technologies, in-depth evaluating mechanisms of PFAS interactions with adsorbents such as activated carbon, biochar, metal-organic frameworks (MOFs) and ion-exchange resins. A comparative analysis of these materials considers their removal efficiencies, operational constraints and energy demands. Furthermore, the review also identifies challenges and knowledge gaps, including the need for improved mechanistic understanding, standardised testing and long-term performance data. Looking ahead, the article discusses future directions for PFAS remediation, including the development of advanced hybrid adsorbents, the integration of machine learning for material design and the alignment of scientific innovation with policy. The review concludes with recommendations for harmonised regulations and interdisciplinary collaboration to support sustainable and effective PFAS mitigation efforts.
