ABSTRACT Heavy metal contamination of aquatic ecosystems is a pathway of risk to human health. This study measured cadmium (Cd) and lead (Pb) concentrations in the water, muscles and gills of Epinephelus chlorostigma from Saudi Arabian Dammam and Jubail regions. It also examined DNA and RNA concentrations and their ratio in these tissues to evaluate the associated genetic effect. Cd and Pb were slightly higher in Jubail. Cadmium was significantly lower in gill for Dammam (p<0.01) compared to Jubail. Jubail samples showed insignificant increase in DNA concentration and the RNA/DNA ratios in gill with decreased RNA level compared to Dammam. Conversely, muscles showed higher DNA, RNA contents and RNA/DNA ratio (p<0.05) for Dammam compared to Jubail. Histopathological changes were shown in tissues due to heavy metal exposure. In general, heavy metals concentrations, compared to the permissible edible limits set by FAO/WHO, suggest that some health concerns should be taken into consideration.

ABSTRACT This research reports the biosynthesis and application of a novel AgNP–curdlan nanocomposite using Priestia aryabhattai BMS3 for the effective removal of the endocrine-disrupting pharmaceutical pollutant, dydrogesterone, in water. The biosynthesis of silver nanoparticles (AgNPs) was validated through a distinct surface plasmon resonance peak at 432 nm, with a yield of 1.42 g/L. Concurrently, P. aryabhattai produced the exopolysaccharide curdlan at 96 h fermentation with a yield of 3.04 g/L. The nanocomposite was fabricated by integrating AgNPs into the curdlan matrix in a 1:5 ratio using ultrasonication and formed a stable reddish-brown film. The nanocomposite showed effective adsorption against dydrogesterone, attaining 92.45% and 91.13% removal as validated by UV-visible spectroscopy and HPLC, respectively. Experiments were carried out in synthetic wastewater at relatively high spiking levels. Results exhibit proof-of-concept, not the field evaluation.

Plastics are a major source of anthropogenic pollution in coastal waters and can modify dissolved organic matter (DOM) depending on polymer type. A 21-day microcosm experiment incubating polypropylene (PP), low-density polyethylene (LDPE), high-density polyethylene (HDPE), and nylon (Nyl) in autoclaved seawater under natural light was conducted to assess DOM release and transformation. FTIR spectroscopy indicated oxidative and hydrolytic degradation. Dissolved organic carbon (DOC) release followed the order PP, LDPE > Nyl > HDPE, reflecting differences in polymer structure and crystallinity. PARAFAC analysis of excitation–emission matrix (EEM) spectra identified humic-like (C, M) and protein-like (T, B) fluorophores. Blueshifts in C and M and a redshift in T fluorescence indicated the release of labile, less aromatic DOM. A strong positive correlation between DOC and the B fluorophore, along with elevated T:B and M:C ratios, confirmed enhanced bioavailable DOM, highlighting the role of polymer heterogeneity in altering coastal carbon cycling.

Microplastics are plastic particles less than 5 mm in size that have been identified as important pollutants in the environment today. In this study, the results from 84 studies published between 2019 and 2025 were reviewed and important findings regarding microplastics, which include abundance, composition, routes of human exposure and health hazards were addressed. Microplastics have been identified in all environments, including indoor, outdoor, urban and even the natural environment in remote areas such as Antarctica, demonstrating the importance of the atmospheric transport of microplastics and their subsequent movement in the air over long distances. The results of these studies show that fibers, among the microplastic forms identified, were the most predominant type, particularly particulates less than 100 µm in size. Additionally, regarding polymer compositions, PET, PE, PP and PS were reported at higher abundances in the results. Various analytical assays have been performed to identify and analyze microplastics, including Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy, which have been used throughout the studies. Health studies provide evidence that these particles are associated with respiratory inflammation, oxidative stress and metabolic conditions, necessitating further epidemiological studies to assess both short- and long-term exposures. Furthermore, microplastics pose significant environmental concerns.

ABSTRACT Nanoplastics (NPs) and tetrabromobisphenol A (TBBPA) are emerging contaminants in the aquatic system. However, their combined effects on primary producers remain poorly understood. Therefore, this study aimed to investigate the effects of NPs, TBBPA, and their combination on the freshwater microalgae Scenedesmus obliquus. This study employed field emission scanning electron microscopy, liquid chromatography‒mass spectrometry, Fourier Transform Infrared Spectroscopy, dynamic light scattering, and zeta potential analysis to characterize the materials and assess their interactions. The mixture of NPs with TBBPA showed enhanced growth inhibition, oxidative stress, and antioxidant activity while reducing photosynthetic pigment levels compared to pristine TBBPA. Collectively, these findings provide critical insights into the co-exposure of NPs and TBBPA, highlighting the ecotoxicological risk to primary producers in freshwater ecosystems.

ABSTRACT The study assessed the heavy metal distribution and ecological risk in marine sediments across three depths (10, 20 and 30 m) in Algoa Bay, South Africa. The concentration of heavy metals varied between depths, ranging from 0.8 to 124.5 mg/kg at 10 m depth contour, 0.5–96.7 mg/kg at 20 m depth contour and 0.7​​​​–113.3 mg/kg at 30 m depth contour determined using X-ray fluorescence (XRF). Higher concentrations were reported both at 10 and 30 m depths. The sediment quality was evaluated against the threshold effect concentration (TEC), probable effect concentration (PEC), effect range low (ERL) and effect range medium (ERM) guidelines. Pollution indices, including geoaccumulation (Igeo), the enrichment factor (EF), the pollution load index (PLI) and the potential risk index (PERI), consistently demonstrated anthropogenic accumulation of As, Ag, Cd and Hg. The PERI demonstrated the ecological risk from low to significantly high across all depths; 10, 20 and 30 m had PERI of 4013, 5391 and 5051, respectively.

ABSTRACT Silver nanoparticles (AgNPs) and microplastics (MPs) are the contaminants commonly found in wastewater and water resource recovery facilities. Here, we investigated the individual and combined effects of AgNPs and polyvinyl chloride (PVC) MPs on the activity and amoA gene abundance of ammonia-oxidizing microorganisms (AOMs). AgNPs exhibit concentration-dependent toxicity, with no inhibitory effect at 0.1 mg/L, partial inhibition at 0.5 and 1.0 mg/L (59.8 and 80.5% inhibition, respectively), and near-complete inhibition (≥ 90%) at higher concentrations. Interestingly, qPCR revealed that different AOM groups exhibited distinct tolerance levels: ammonia-oxidizing bacteria (AOB) tolerated AgNPs up to 1 mg/L, while ammonia-oxidizing archaea (AOA) exhibited better tolerance than the other AOMs at concentrations≥2.5 mg/L. Notably, complete ammonia oxidizers (comammox) showed the lowest tolerance, with inhibition at concentrations as low as 0.5 mg/L. PVC MPs alone (500 mg/L) had no discernible impact on both the activity and amoA gene numbers, but their interaction with AgNPs revealed that pre-settled MPs reduced AgNP toxicity, whereas freshly introduced MPs that remained afloat did not.

This study focuses on factors influencing adsorption thermodynamics, complex adsorption mechanism, conditions that promote material regeneration and the adsorption mechanisms of As3+ and As5+ on Fe3O4@mZrO2-Y/La/Ce. The estimated values of ∆G for As3+ and As5+ were consistently negative across all tested temperature conditions, indicating the spontaneity of the adsorption process. Moreover, the positive change in entropy (∆S) further suggests increased disorder in the solid‒liquid phases during adsorption. The most effective concentration for the regeneration solution was found between 0.15 and 0.2 mol/L, and the temperature was 40 °C. While there was a slight decrease in the adsorption of Fe3O4@mZrO2-Y/La/Ce with each cycle, the effectiveness of adsorption in later regeneration cycles showed a stabilization tendency. In last cycle, both As3+ and As5+ demonstrated stable adsorption abilities, highlighting the impressive regenerative capability of the materials. Overall, comprehensive thermodynamic and regeneration investigations revealed that chemisorption is the dominant adsorption process, likely involving ion exchange and/or surface complexation process.

This study investigates the release characteristics and influencing factors of volatile organic compounds (VOCs) in sludge drying exhaust gases from two urban sewage treatment plants and one sludge treatment plant in Zhengzhou, Henan Province. Through on-site sampling and dynamic simulation experiments, 99 VOC components were analyzed. Results show that aromatic hydrocarbons (28.2%–31.8%), particularly benzene-related compounds, dominate in sewage plants, while volatile oxygenated organic compounds (OVOCs) (22.9%–36.1%) are more prominent in sludge plants. Peak VOC concentrations of 780, 1220, and 1720 μg/m³ were observed 7−10 minutes after aeration, stabilizing thereafter. Higher drying temperatures and aeration intensities increase VOC release, with composting fermentation producing the highest emissions. These findings provide insights into selecting drying methods and exhaust gas treatment strategies for effective air pollution control.

ABSTRACT Iron contamination in potable water systems presents a persistent challenge, often exceeding regulatory thresholds and compromising public health. This review delineates the geogenic and anthropogenic drivers of iron mobilization in groundwater, followed by a comparative assessment of physicochemical methods; limited by cost, selectivity, and scalability. In contrast, iron-oxidizing bacteria (FeOB), notably from the Proteobacteria phylum, offer redox-mediated bioremediation pathways with enhanced sorption potential and biofilter adaptability. The review has emphasised on FeOB’s operational feasibility, integration with real-time monitoring, and alignment with BIS and CPCB standards. The review advocates for translational frameworks to deploy microbial technologies in decentralized water treatment systems.