Microcystins (MCs) are a class of toxic secondary metabolites produced by some cyanobacteria strains that endanger aquatic and terrestrial organisms in various freshwater systems. Although patterns in MC occurrence are being recognized, divergences in the global data still hamper our ability to predict the toxicity of cyanobacterial blooms. This study aimed (i) to determine the dynamics of MCs and other cyanopeptides in a tropical reservoir, (ii) to investigate the correlation between peptides and potential cyanotoxin producers (iii) identifying the possible abiotic factors that influence the peptides. We analyzed, monthly, eight MC variants (MC-RR, -LA, -LF, -LR, -LW, -YR, [D-Asp3]-RR and [D-Asp3]-LR) and other peptides in 47 water samples collected monthly, all season long, from two sampling sites in a tropical eutrophic freshwater reservoir, in southeastern Brazil. The cyanopeptides were assessed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The biomass of potential cyanobacterial producers and water quality variables were measured. MCs were detected in both sampling sites year-round; the total MC concentration varied from 0.21 to 4.04 μg L−1, and three MC variants were identified and quantified (MC-RR, [D-Asp3]-RR, -LR). Additionally, we identified 28 compounds belonging to three other cyanopeptide classes: aeruginosin, microginin, and cyanopeptolin. As potential MC producers, Microcystis spp. and Dolichospermum circinalis were dominant during the study, representing up to 75% of the total phytoplankton. Correlational and redundancy analysis suggested positive effects of dissolved oxygen, nitrate, and total phosphorus on MC and microginins concentration, while water temperature appeared to favor aeruginosins. A comparison between our results and historical data showed a reduction in total phosphorus and cyanobacteria, suggesting increased water quality in the reservoir. However, the current MC concentrations indicate a rise in cyanobacterial toxicity over the last eight years. Moreover, our study underscores the pressing need to explore cyanopeptides other than MCs in tropical aquatic systems.

Nanoplastics (NPs) can adversely affect living organisms. However, the uptake of NPs by plants and the physiological and molecular mechanisms underlying NP-mediated plant growth remain unclear, particularly in the presence of iron minerals and humic acid (HA). In this study, we investigated NP accumulation in rice (Oryza sativa L.) and the physiological effects of exposure to polystyrene NPs (0, 20, and 100 mg L−1) in the presence of iron plaque (IP) and HA. NPs were absorbed on the root surface and entered cells, and confocal laser scanning microscopy confirmed NP uptake by the roots. NP treatments decreased root superoxide dismutase (SOD) activity (28.9–44.0%) and protein contents (31.2–38.6%). IP and HA (5 and 20 mg L−1) decreased the root protein content (20.44–58.3% and 44.2–45.2%, respectively) and increased the root lignin content (22.3–27.5% and 19.2–29.6%, respectively) under NP stress. IP inhibited the NP-induced decreasing trend of SOD activity (19.2–29.5%), while HA promoted this trend (48.7–50.3%). Transcriptomic and metabolomic analysis (Control, 100NPs, and IP-100NPs-20HA) showed that NPs inhibited arginine biosynthesis, and alanine, aspartate, and glutamate metabolism and activated phenylpropanoid biosynthesis related to lignin. The coexistence of IP and HA had positive effects on the amino acid metabolism and phenylpropanoid biosynthesis induced by NPs. Regulation of genes and metabolites involved in nitrogen metabolism and secondary metabolism significantly altered the levels of protein and lignin in rice roots. These findings provide a scientific basis for understanding the environmental risk of NPs under real environmental conditions.

Rivers are main conduits for the delivery of plastics to the sea, while also functioning as reservoirs for plastic retention. In tropical regions, rivers are exposed to both high levels of plastic pollution and invasion of water hyacinths. This aquatic plant forms dense patches at the river surface that drift due to winds and currents. Recent work suggests that water hyacinths play a crucial role in influencing plastic transport, by efficiently trapping the majority of surface plastic within their patches. However, a comprehensive understanding of the interaction between water hyacinths and plastics is still lacking. We hypothesize that the properties relevant to plastic transport change due to their trapping in water hyacinth patches. In particular, the length scale, defined as the characteristic size of the transported material, is a key property in understanding how materials move within rivers. Here, we show that water hyacinth patches trap on average 54%–77% of all observed surface plastics at the measurement site (Saigon river, Vietnam). Both temporally and spatially, we found that plastic and water hyacinth presence co-occur. The formation of plastic-plant aggregates carries significant implications for both clean-up and monitoring purposes, as these aggregates can be detected from space and need to be jointly removed. In addition, the length scale of trapped plastics (4.0 m) was found to be forty times larger than that of open water plastics (0.1 m). The implications of this increased length scale for plastic transport dynamics are yet to be fully understood, calling for further investigation into travel distances and trajectories. The effects of plastic trapping likely extend to other key properties of plastic-plant aggregates, such as effective buoyancy and mass. Given the prevalence of plant invasion and plastic pollution in rivers worldwide, this research offers valuable insights into the complex environmental challenges faced by numerous rivers.

Macrolitter, especially macroplastics, (> 0.5 cm) negatively impact freshwater ecosystems, where they can be retained along lake shores, riverbanks, floodplains or bed sediments. Long-term and large-scale assessments of macrolitter on riverbanks and lake shores provide an understanding of litter abundance, composition, and origin in freshwater systems. Combining macrolitter quantification with hydrometeorological variables allows further study of leakage, transport, and accumulation characteristics. Several studies have explored the role of hydrometeorological factors in influencing macrolitter distribution and found that river discharge, runoff, and wind only partially explains its distribution. Other factors, such as land-use features, have not yet been thoroughly investigated. In this study, we provide a country-scale assessment of land-use influence on macrolitter abundance in freshwater systems. We analyzed the composition of the most commonly found macrolitter items (referred to as ‘top items’, n = 42,565) sampled across lake shores and riverbanks in Switzerland between April 2020 and May 2021. We explored the relationship between eleven land-use features and macrolitter abundance at survey locations (n = 143). The land-use features included buildings, city centers, public infrastructure, recreational areas, forests, marshlands, vineyards, orchards, other land, and rivers and canals. The majority of top items are significantly and positively correlated with land-use features related to urban coverage, notably roads and buildings. Over 60% of top items were found to be correlated with either roads or buildings. Notably, tobacco, food and beverage-related products, as well as packaging and sanitary products, showed strong associations with these urban land-use features. Other types of items, however, did not exhibit a relationship with land-use features, such as industry and construction-related items. Ultimately, this highlights the need to combine measures at the local and regional/national scales for effective litter reduction.

Recent research has highlighted the potential of honeybees and bee products as biological samplers for monitoring xenobiotic pollutants. However, the effectiveness of these biological samplers in tracking microplastics (MPs) has not yet been explored. This study evaluates several methods of sampling MPs, using honeybees, pollen, and a novel in-hive passive sampler named the APITrap. The collected samples were characterized using a stereomicroscopy to count and categorise MPs by morphology, colour, and type. To chemical identification, a micro-Fourier transform-infrared (FTIR) spectroscopy was employed to determine the polymer types. The study was conducted across four consecutive surveillance programmes, in five different apiaries in Denmark. Our findings indicated that APITrap demonstrated better reproducibility, with a lower variation in results of 39%, compared to 111% for honeybee samples and 97% for pollen samples. Furthermore, the use of APITrap has no negative impact on bees and can be easily applied in successive samplings. The average number of MPs detected in the four monitoring studies ranged from 39 to 67 in the APITrap, 6 to 9 in honeybee samples, and 6 to 11 in pollen samples. Fibres were the most frequently found, accounting for an average of 91% of the total MPs detected in the APITrap, and similar values for fragments (5%) and films (4%). The MPs were predominantly coloured black, blue, green and red. Spectroscopy analysis confirmed the presence of up to five different synthetic polymers. Polyethylene terephthalate (PET) was the most common in case of fibres and similarly to polypropylene (PP), polyethylene (PE), polyacrylonitrile (PAN) and polyamide (PA) in non fibrous MPs. This study, based on citizen science and supported by beekeepers, highlights the potential of MPs to accumulate in beehives. It also shows that the APITrap provides a highly reliable and comprehensive approach for sampling in large-scale monitoring studies.

International audience | Our study focused on the removal of pollutants from combined sewer overflow (CSO) using aerated vertical flow wetlands (VFW). Over a 7-months period, a pilot was fed with variable inlet concentrations and hydraulic loading rates of 0.5, 1.0, and 1.5 m3.m-2. Two aeration strategies were tested, intermittent aeration and continuous aeration, and their results were compared. Online measurement of NH4-N and NO3-N helps to balance nitrogen oxidation processes during a feeding event. The average removal rates of TSS, COD, dissolved COD (CODs), and NH4-N were always above 74%. Despite continuous aeration had showed higher oxygen concentration, the percentage of untreated NH4-N leaving the filter was similar in both aeration strategies. Additionally, higher NO3-N outflow loads during continuous aeration may be explained by temperature effect. Ongoing tests aim to reach a better comprehension on nitrogen conversion processes.

The role of economic factors is significant in the municipal waste management. The present descriptive-applied study aimed to present a new model of municipal waste management cost reduction priorities based on the Gray-TOPSIS model in Ahvaz City in 2022. Following the collection of data on the current municipal waste management, effective criteria influencing cost reduction in municipal waste management were determined through document analysis. Expert analysis was also utilized to identify factors impacting cost reduction in municipal waste management. The Gray-TOPSIS methodology was applied to prioritize solutions for cost reduction in municipal waste management. Through calculating the Kendall agreement index, 20 solutions for cost reduction in waste management were categorized and prioritized into educational, political, cultural, and executive groups. The findings revealed that while political measures such as approving laws related to municipal waste management and incentive and punitive policies with special weightings of 0.804 and 0.799, respectively, are the most effective solutions for reducing waste management costs, overall, educational process-related solutions with an average weighting of 0.686 have a higher priority than other processes. Government support and public education through various means, especially non-governmental media and social networks, are potential solutions for reducing municipal waste management costs in Ahvaz City under current conditions.

The exhibition industry serves as a huge platform for face-to-face participation and the formation of potential economic and business relationships in the current century. These gatherings cost greatly in terms of energy resources are responsible for the emission of greenhouse gases and other pollutants into the water, air, and soil. The present study seeks to investigate and identify the pollutant indices resulting from the activities of the exhibition industry, its respective services and preparing guide on the organization of exhibition sites. For this purpose, the most important environmental criteria influenced by the industry were first identified through the Delphi method and were then classified into nine main priority groups based on multi-criteria decision-making and the best/ worst method(BWM[1]) method. The environmental index of the region was thus selected as the most important criterion whereas the social and economic indices were determined to be the least important criteria. Moreover, 58 sub-indices of the main indices were also weighed and prioritized based on the pairwise comparison. As a result, the sub-criterion of environmentally sensitive region ranked first while the sub-criterion of impact on the local and regional identity was identified as the least important influential sub-criterion. Weighing and prioritization of the indices were eventually the main foundation for the compilation of the exhibition site construction and operation instructions, and persistent monitoring of some indices such as the indoor air quality and consumed energy can reduce the negative environmental consequences of exhibition activities significantly.

The use of copper (Cu) and silver (Ag) nanoparticles in coatings can eliminate surface microbial contamination. This study compared antibacterial activity of Cu- (Cu/CNTs) and Ag-coated carbon nanotubes (Ag/CNTs) synthesized by plasma-enhanced chemical vapor deposition (PECVD) against Escherichia coli and Staphylococcus aureus. Initially, the PECVD technique was applied to deposit the CNTs on high-resistivity silicon wafers previously decorated by nickel catalyst using an Electron Beam Gun. Then, the nanotubes were coated by Cu and Ag thin films in a vacuum evaporator using the Direct Current (DC) Magnetron Sputtering method. Finally, the antibacterial effects were determined by Standard Plate Count (SPC, with film thicknesses of 0, 10, 30 and 60 nm) and Disk Diffusion Test (based on zone of inhibition (ZOI) with nanoparticle concentrations of 5, 10 and 15 µg/mL). According to the SPC findings, the highest antibacterial activity of Cu/CNTs was found for the film thickness of 60 nm against E. coli (66%), and the lowest activity was related to the film thickness of 19 nm against S. aureus (28.8%). The antibacterial activity of Ag/CNTs was about 70% against E. coli with the highest thickness and about 34.12% against S. aureus. The lowest ZOI was measured for the bare CNTs at a concentration of 5 µg/mL (12 mm), and the highest ZOI was related to Ag/CNTs with a concentration of 15 µg/mL against S. aureus (18 mm). To conclude, the carbon nanotube composites coated with copper or silver nanoparticles can be used to control bacterial growth in aqueous solutions.