Comparative assessment of microplastics in water and sediment of a large European river

The Impact of Microplastics on Adsorption of Chlorophenols by River-Suspended Sediments

Although microplastics (MPs) are widely recognized as carriers of environmental pollutants, their impact on the adsorption behavior of chlorophenols (CPs) by river-suspended sediments (SS) remains poorly understood. This study systematically investigated the effects of three common MPs (PVC, PS, and PE) on the adsorption of 4-chlorophenol (MCP), 2,4-dichlorophenol (2,4-DCP), and 2,4,6-trichlorophenol (2,4,6-TCP) by SS from the Yellow River. Adsorption isotherms revealed that PVC significantly promoted CP adsorption, fitting well with the Langmuir model (R² > 0.95), whereas PS and PE showed better agreement with the Freundlich model (R² > 0.96). The enhancement effect varied with MP type and CP species, with PVC demonstrating the most pronounced promotion (65% increase for 2,4,6-TCP). Conversely, PS and PE hindered 2,4-DCP adsorption due to its higher partition coefficient in SS (36.83 ± 6.3 L/kg) compared to MPs (1.85 ± 0.01 L/kg for PS and 2.03 ± 0.05 L/kg for PE). Environmental factor analysis revealed that ionic strength exerted dual effects by initially enhancing CP adsorption through reduced solubility and later inhibiting it via electrostatic repulsion. Humic acid (HA) promoted TCP adsorption but inhibited DCP adsorption through aggregation and dispersal mechanisms on SS surfaces. Acidic conditions (pH 2-6) significantly enhanced CP adsorption by maintaining their molecular states, while alkaline conditions reduced adsorption due to electrostatic repulsion. Mechanistically, MPs altered SS surface properties and formed aggregates that either facilitated or competed for CP adsorption sites. This study provides a theoretical basis for ecological risk assessment of combined microplastic-pollutant contamination in sediment-laden rivers.

Downsizing plastics, upsizing impact: How microplastic particle size affects Chironomus riparius bioturbation activity

Microplastic contamination in freshwater systems poses serious ecological risks, yet the role of particle size in shaping these impacts remains underexplored. This study investigates the influence of microplastic size on bioturbation activities of Chironomus riparius larvae, a process essential for sediment dynamics and nutrient cycling. Employing luminophore sediment profile imaging (LSPI), we tracked the vertical distribution of polyethylene particles within sediment layers, focusing on two distinct size ranges: small (53-63 μm) and large (250-300 μm) spherical particles. Microplastics (MPs) were introduced at a 0.076% sediment ratio to reflect natural exposure scenarios. Initial findings reveal that both particle sizes undergo downward transport, though with different patterns. Notably, smaller particles demonstrated a more pronounced effect on larval behaviour, appearing frequently in digestive tracts and suggesting increased bioavailability. Temporal analysis showed distinct reworking dynamics for each particle size, with larger particles exhibiting a delayed reworking time compared to the smaller particles. This highlights the critical influence of particle size on the fate and behaviour of MPs in freshwater systems, with smaller particles potentially posing a greater ecological risk due to their quicker and more active incorporation into sedimentary processes. This study provides critical insights into size-specific interactions between MPs and freshwater organisms, enhancing our understanding of their impacts on ecosystem health and sedimentary processes.

Plastic debris exposure and effects in rivers: Boundaries for efficient ecological risk assessment

Until recently, plastic pollution research was focused on the marine environments, and attention was given to terrestrial and freshwater environments latter. This discussion paper aims to put forward crucial questions on issues that limit our ability to conduct reliable plastic ecological risk assessments in rivers. Previous studies highlighted the widespread presence of plastics in rivers, but the sources and levels of exposure remained matters of debate. Field measurements have been carried out on the concentration and composition of plastics in rivers, but greater homogeneity in the choice of plastic sizes, particularly for microplastics by following the recent ISO international standard nomenclature, is needed for better comparison between studies. The development of additional relevant sampling strategies that are suited to the specific characteristics of riverine environments is also needed. Similarly, we encourage the systematic real-time monitoring of environmental conditions (e.g., topology of the sampling section of the river, hydrology, volumetric flux and velocity, suspended matters concentration) to better understand the origin of variability in plastic concentrations in rivers. Furthermore, ingestion of microplastics by freshwater organisms has been demonstrated under laboratory conditions, but the long-term effects of continuous microplastic exposure in organisms are less well understood. This discussion paper encourages an integrative view of the issues involved in assessing plastic exposure and its effects on biota, in order to improve our ability to carry out relevant ecological risk assessments in river environments.

Small microplastics have much higher mass concentrations than large microplastics at the surface of nine major European rivers

Understanding the fates and impacts of microplastics requires information on their sizes, polymer types, concentrations, and spatial and temporal distributions. Here, we focused on large (LMPs, 500 µm to 5 mm) and small (SMPs, 25 to 500 µm) microplastics sampled with the exact same protocol in nine of the major European rivers during the seven months of the Tara Microplastic Expedition. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC-MS) analyses were used to determine the microplastics contents by number and mass. The median LMP concentration was 6.7 particles m-3, which was lower than those in other regions of the world (America and Asia). The SMP mass concentration was much higher to the LMP concentrations, with SMP/LMP ratios up to 1000 in some rivers. We did not observe a systematic positive effect of urban areas for the two size classes or polymers; this could be explained by the fact that the transport of microplastic is highly heterogeneous in rivers. We believe that this study has important implications for predictive models of plastics distribution and fate in aquatic environments.

Microplastics in freshwater and marine ecosystems: Occurrence, characterization, sources, distribution dynamics, fate, transport processes, potential mitigation strategies, and policy interventions

Most of the literature on microplastics (MPs) focuses on freshwater or terrestrial ecosystems, frequently overlooking their interconnections with the marine environments. This oversight is worrying given that both ecosystems serve as primary pathways for the introduction of MPs into marine environments. This review synthesizes existing literature on MPs in both freshwater and marine ecosystems across all six continents. The most commonly produced plastic polymers in industry are polyethylene (36 %) and polypropylene (21 %), and studies revealed that these two materials are the most abundant in aquatic ecosystems. Primary and secondary MPs originate from a range of sources including land-based disposal, the ocean, airborne deposition, wastewater treatment facilities, automobiles, pharmaceuticals and personal care products, synthetic textiles, and insect repellents. Notably, secondary MPs, which are formed from the breakdown of larger plastic items comprise approximately 69-81% of marine debris, especially in urbanized, densely populated areas. The inconsistencies of the methodologies (sampling, extraction, and quantification) and the units employed for result presentations are part of the major limitations in MPs research. Environmental phenomena such as heteroaggregation, weathering, adsorption, leaching, and fragmentation are the major factors influencing the behavior, fate, and degradation process of plastic particles. The physicochemical properties of plastic polymers, such as density, crystallinity, as well as bioturbation, meteorological forces, and wind actions, including currents, waves, and tides, are responsible for biofouling, aggregation, sinking into the bottom sediment, resuspension, and the vertical, horizontal, and spatiotemporal distributions and transport of MPs. The potential solutions to mitigate plastic pollution are grounded in the 3Rs framework, which includes reducing production and consumption, advancing the biotechnological, chemical and microbial development of degradable polymers, promoting reusable plastic products with lower environmental impacts over their lifetimes, and recycling waste into new products. The regulatory policies on single-use plastics commonly involve permanent bans and financial penalties for violators. In addition, nations such as the United States, the Netherlands, and northern Europe have introduced economic incentives to encourage the return of reusable materials to reduce plastic waste and the resulting envrionmental pollution.

Unveiling microplastic pollution: Evaluating the role of Sinotaia quadrata (Caenogastropoda, Viviparidae) as a monitoring tool in freshwater ecosystems

Freshwater species play a key role in monitoring microplastics (MPs) pollution, providing insights into its distribution, accumulation, and potential ecological and human health risks in aquatic ecosystems. This study evaluates the invasive snail Sinotaia quadrata as a potential tool for monitoring MPs pollution in freshwater ecosystems heavily impacted by human activities. Specifically, we examined whether the characteristics of MPs (i.e., shape, color, and chemical composition) found in water and sediment were reflected in those accumulated by S. quadrata, and whether MPs accumulation varied across different snail size classes. MPs were detected in all environmental matrices and snail samples, with fragments and filaments as the dominant shapes, blue, white, and black as the most common colors, and polypropylene, polyethylene, and polyethylene terephthalate as the primary polymers. A significant difference in MPs concentration per gram was found across snail size classes, with smaller snails accumulating more MPs than larger individuals, likely due to higher feeding rates during growth. A positive correlation was observed between snail shell length and weight, while MPs concentration per gram showed significant negative correlations with both parameters. These findings suggest that S. quadrata accumulates MPs from the environment, reflecting local contamination levels. While S. quadrata is an invasive species, this study demonstrates its potential utility in MPs monitoring, particularly in the context of eradication efforts. This approach integrates pollution assessment with invasive species management, offering a broader perspective on the role of biological invasions in environmental monitoring.

Making waves: Unraveling microplastic deposition in rivers through the lens of sedimentary processes

River networks are the major pathways for microplastic (MP) transport from terrestrial environments to oceans. It is essential to understand where MPs reside and how they move along river networks because of their potential to negatively impact ecosystems. However, the ability to quantify the water-sediment exchange of MPs, locations of deposition, and the time scales over which burial occurs is limited. To fill this gap, previous work on processes that control MP deposition are briefly reviewed in this Perspective paper, with the aim of enhancing our understanding of the dynamic interplay between flow, sediment transport, and MP movement through river networks. Detailed studies on MP deposition onto surficial sediment show that MP transport can be explained by the shear stress theory, hyporheic exchange, and bioturbation. Nevertheless, these processes cannot fully explain the observed distribution of MPs in deeper river sediments. It is proposed that bedform movement, channel reworking, bar formation, and aggradation/degradation at the river network scale should be included when estimating MP deposition. It is argued that incorporating data on MP distribution in riverbeds with fluvial geomorphological and particle transport models will improve the current evaluation of MP transport in river networks and their burial residence time distribution.

Molecular mechanisms by which polyethylene terephthalate (PET) microplastic and PET leachate promote the growth of benthic cyanobacteria

Toxic blooms of benthic cyanobacteria greatly threaten freshwater ecological health and drinking water safety. Meanwhile, microplastic pollution is becoming increasingly severe and microplastics accumulate in large quantities at the bottom of lakes and rivers, widely coexisting with algae. However, impacts of microplastics on benthic cyanobacteria are still unknown. This study investigated effects of microplastic polyethylene terephthalate (PET) - which is commonly found at the bottom of lakes and rivers - and its leachate at environmentally relevant concentration (0.3 mg/L) and high exposure concentration (3.0 mg/L) on typical benthic cyanobacteria (Oscillatoria sp. and Pseudanabaena sp.), and clarified the related molecular mechanisms through transcriptomic analysis. Results show that PET or PET leachate (PET-L) can promote benthic cyanobacterial growth and promotive effect of PET-L is more obvious than that of PET system. Promotion effect of PET or PET-L is more significant at environmentally relevant concentration (39-63 % increase compared with the control) compared with high exposure concentration (21-58 % increase compared with the control). In the presence of PET or PET-L, due to an increase in the number of cyanobacterial cells, concentrations of harmful metabolites (cylindrospermopsin, geosmin, and 2-methylisoborneol) in water also increased. Although PET particles may not be conducive to benthic cyanobacterial growth due to shading effect and mechanical damage, photosynthetic efficiency of algae was improved and dysregulated genes related to photosynthesis and extracellular transport of glycolipid were upregulated according to transcriptome analysis. Moreover, PET decomposition components, such as terephthalic acid and ethylene glycol, may be able to serve as carbon sources for cyanobacterial growth. Upregulation of genes associated with glycolysis, oxidative phosphorylation, and translation revealed that PET can promote the growth of benthic cyanobacteria. This study has important value in evaluating the impact of benthic cyanobacteria on aquatic ecological health and drinking water safety with the coexistence of microplastics.

Assessment of microplastics and associated ecological risk in the longest river (Godavari) of peninsular India: A comprehensive source-to-sink analysis in water, sediment and fish

Persistent microplastics (MPs) accumulation in the aqueous environments is considered a threat to the ecosystem, potentially harming aquatic species and human health. In view of the escalating problem of MPs pollution in India, a comprehensive investigation of MPs accumulation in major riverine systems is necessary. The current study aims to estimate MPs abundance in surface water, sediment, and fish samples along the entire stretch of Godavari, the largest river in peninsular India. Average MPs concentrations in water lie in the range of 311-939 MPs/m3 and 2-144 MPs/kg d.w. for sediment. Urban regions and dam reservoirs showed elevated MPs abundance, emphasizing the impact of anthropogenic activities. The μ-Raman analysis revealed PE and PP were the abundantly occurring polymers in all matrices. Polymer and ecological risk index identify most sampling sites as extremely high-risk zones, posing a potential threat to aquatic ecosystems and human health. Plotted t-SNE (t-distributed Stochastic Neighbour Embedding) revealed similarities in MPs morphology and compositions among water, sediment and fish samples. Examined MPs in edible (flesh+skin) and inedible parts (GIT and gills) of seven different fish species showed a higher average MPs abundance in edible parts (10.7 ± 14.9 MPs/fish) than gills (7 ± 8.1 MPs/fish) and GIT (6.6 ± 5.5 MPs/fish). This suggests that removing gills and GIT from fish doesn't eliminate the consumer's risk of MPs intake. Overall, our work highlights the significant MPs pollution in the Godavari River, further providing essential data on the ecological risk of MPs to guide municipal action plans, improve waste management, target high-risk areas, and raise awareness to mitigate impacts.

Microplastics in the Hamburg port area-an analysis of sediment depth profiles along the upper Elbe river, Germany

Harbours pose a unique environment of increased anthropogenic pressure and artificial river morphology that are of specific interest concerning microplastic release and accumulation. To address the specific situation in the Hamburg port area, a study in cooperation with the Hamburg Port Authority (HPA) was conducted. Sediment samples at different depth levels were taken at seven sites with similar flow velocity and underlying morphology. Two sites are located upstream and downstream of the port of Hamburg, while four sites are located in the centre area of the port. One additional site takes into account an estuary of a receiving stream flowing into the upper river Elbe. For the analysis of microplastic concentrations in the samples, the biogenic organic matter was removed by oxidative digestion followed by wet sieving and density separation. For identification, the Nile red staining method in combination with fluorescence microscopy was applied. A subset of identified synthetic polymers was investigated for polymer composition via µRaman spectroscopy. In addition, sediment parameters such as grain size distribution, organic matter and water content were analysed. In total, a number of 31 sediment samples divided into different depths below riverbed level were examined. In brief, 11,280 microplastic particles could be identified. Both the highest and lowest number of particles were detected at centre port sites ranging from 60 to 21,799 microplastics per kilogramme dry weight. Fragments are the dominating particle morphology throughout all locations, except for one centre harbour site where microbeads are most common. Frequently appearing synthetic polymers were detected to be polyvinyl chloride (34%) and polyethylene terephthalate (28%). Within this study, a significant correlation between microbead concentrations and the percentage of sand fractions (coarse, middle and fine sand) was detected.

Multigenerational effects of virgin and sampled plastics on the benthic macroinvertebrate Chironomus riparius

Although sediments are important reservoirs of plastics, most of the ecotoxicological studies on these contaminants are focused on the organisms living in the water column, while only a smaller number of evidence concerns the plastic impact on benthic species. Therefore, this study compared the multigenerational effects on the sediment-dwelling midge Chironomus riparius exposed to both virgin polystyrene microbeads (22,400-224,000 plastics/kg sediments dry weight), and plastic mixtures (40-420 plastics/kg dry weight) collected from four of the main tributaries of Po River (Ticino, Adda, Oglio and Mincio Rivers, Northern Italy) to evaluate the role played by other characteristics related to these physical contaminants in determining their toxicity as opposed to concentration alone. The modified Chironomid Life-Cycle Toxicity Test (OECD 233) was used to evaluate the multigenerational effects on the Emergence and Development Rates, Fecundity and Fertility. In addition, a biomarkers' suite of cellular stress, neurotoxicity, and energetic metabolism was applied in the 2nd generation (2nd/3rd instar of larvae) to investigate the potential mechanisms associated to the apical effects. Our results showed no significant (p > 0.05) multigenerational effect for any of the endpoints tested for the virgin plastics' exposures. Coherently, no significant effects on biomarkers were measured. Concerning the sampled plastics, the particles collected in Adda River instead induced a significant decrease (p < 0.05) of the Emergence Rate in the 2nd generation, suggesting that this parameter was the most susceptible among those measured. These results highlight that the different plethora of polymers, sizes and shapes of plastics sampled in natural ecosystems, compared to homogeneous characteristics of virgin polystyrene microbeads, appears to have considerable importance over concentration alone in determining the toxicity of these emerging contaminants.

Effects of microplastics on Daphnia-associated microbiomes in situ and in vitro

Microplastic pollution in aquatic environments is a growing global concern. Microplastics, defined as plastic fragments smaller than 5 mm, accumulate in freshwater reservoirs, especially in urban areas, impacting resident biota. This study examined the effects of microplastics (MP) on the performance and microbiome of Daphnia, a keystone organism in freshwater ecosystems, through both in situ sampling of freshwater ponds and a controlled 23-day in vitro exposure experiment. Using bacterial 16S ribosomal RNA gene amplicon sequencing and whole-genome shotgun sequencing, we analyzed the microbiome's composition and functional capacity in relation to microplastic pollution levels. Urban ponds contained higher microplastic concentrations in water and sediment than natural ponds, with distinct differences in plastic composition. Bacterioplankton communities, defined as bacterial assemblages in the water column, were more diverse and richer than Daphnia-associated microbiomes. Overall, the in situ study showed that the composition of the Daphnia-associated community was influenced by many factors including microplastic levels but also temperature and redox potential. Functional analysis showed increased relative abundances of polyethylene terephthalate degradation enzymes and antibiotic resistance genes in microbiomes from high-microplastic ponds. In the in vitro experiment, the bacterioplankton inoculum source significantly influenced Daphnia survival and microbiome composition. Network analysis identified specific taxa associated with MP within the Daphnia microbiome. Our findings highlight that urbanization leads to higher microplastic and antibiotic resistance gene burdens, influencing host-associated microbiomes through taxonomic shifts, functional enrichment, and survival outcomes, with potential implications for the resilience of aquatic ecosystems.

Review of mayflies (Insecta Ephemeroptera) as a bioindicator of heavy metals and microplastics in freshwater

Heavy metal and microplastic pollutions are prevalent in freshwater ecosystems, with many freshwater bodies being contaminated by one or both of these pollutants. Recent studies reported extreme detections of Cd, Pb and Zn, high concentrations of Cr, Pb and Cu and microplastics acting as vectors of pollutants, including heavy metals. Mayflies can serve as bioindicators of heavy metal contamination in freshwater ecosystems because changes in their community structure, physiology, and behaviour can reflect and help predict the concentrations of metals in these environments. This review discusses the ecological alterations induced by tissue metal concentration in mayflies and other macroinvertebrates. As sensitive taxa to heavy metal contamination, mayflies can reflect the impacts of this pollution through their ethology and relationship to the substrate, highlighting issues such as eutrophication, alterations in community structure, inhibitory effects and sediment toxicity. Mayflies are also highly affected by microplastic exposure, which leads to ingestion, bioaccumulation, biomagnification, habitat and community alteration, behavioural changes, physiology alteration and toxicity. Mayflies bioindication metrics for assessing the impact of heavy metals and microplastics include the examination of community alteration, functional feeding behaviour, molecular structure, dietary and toxicity impacts, bioaccumulation and biomagnification and biomarkers. Current challenges for the utilization of mayflies as bioindicators include temporal variations in sensitivity, lack of universally recognised protocols and need for standardised protocols for microplastic analysis. Additionally, the applicability of mayflies as bioindicators may vary across different ecosystems, emphasising the need for selecting suitable indicators that align with the unique characteristics of the ecosystem.

Priorities to inform research on tire particles and their chemical leachates: A collective perspective

Concerns over the ecological impacts of urban road runoff have increased, partly due to recent research into the harmful impacts of tire particles and their chemical leachates. This study aimed to help the community of researchers, regulators and policy advisers in scoping out the priority areas for further study. To improve our understanding of these issues an interdisciplinary, international network consisting of experts (United Kingdom, Norway, United States, Australia, South Korea, Finland, Austria, China and Canada) was formed. We synthesised the current state of the knowledge and highlighted priority research areas for tire particles (in their different forms) and their leachates. Ten priority research questions with high importance were identified under four themes (environmental presence and detection; chemicals of concern; biotic impacts; mitigation and regulation). The priority research questions include the importance of increasing the understanding of the fate and transport of these contaminants; better alignment of toxicity studies; obtaining the holistic understanding of the impacts; and risks they pose across different ecosystem services. These issues have to be addressed globally for a sustainable solution. We highlight how the establishment of the intergovernmental science-policy panel on chemicals, waste, and pollution prevention could further address these issues on a global level through coordinated knowledge transfer of car tire research and regulation. We hope that the outputs from this research paper will reduce scientific uncertainty in assessing and managing environmental risks from TP and their leachates and aid any potential future policy and regulatory development.

A multiple biomarker approach to understand the effects of microplastics on the health status of European seabass farmed in earthen ponds on the NE Atlantic coast

The occurrence of microplastics (MPs) in aquaculture environments is a growing concern due to their potential negative effects on fish health and, ultimately, on seafood safety. Earthen pond aquaculture, a prevalent aquaculture system worldwide, is typically located in coastal and estuarine areas thus vulnerable to MP contamination. The present study investigated the possible relation between MP levels of European seabass (Dicentrarchus labrax) farmed in an earthen pond and its health status. More precisely, two groups of fish were established based on the lowest and highest number of MPs found collectively in their gastrointestinal tract (GIT), liver, and dorsal muscle: fish with ≤2 MP/g and fish with ≥4 MP/g. The intestinal integrity and oxidative stress biomarkers in the liver and dorsal muscle were evaluated in the established groups. No significant differences in the biometric and organosomatic parameters between groups were observed. The results indicated a significant increase in the number of acid goblet cells (GC) in the rectum of fish with higher MP levels (p = 0.016). Increased acid GC number may constitute a first defence strategy against foreign particles to protect the intestinal epithelium. No significant differences in oxidative stress biomarkers between the two fish groups were observed, namely in the activity of superoxide dismutase, catalase, glutathione reductase, and glutathione S-transferase in the liver, or in lipid peroxidation levels in the liver and dorsal muscle. The overall results suggest that MP levels were possibly related to an intestinal response but its potential implications on the health status of pond-farmed seabass warrant further investigation. Monitoring MP occurrence across stages of aquaculture production could help to elucidate the potential threats of MPs to fish health.

The dual role of coastal mangroves: Sinks and sources of microplastics in rapidly urbanizing areas

Mangrove ecosystems are vital for coastal protection, biodiversity, and pollution interception, yet their interactions with microplastics in rapidly urbanizing regions remain underexplored. This study investigated the microplastic dynamics in the Maozhou River and Dasha River, along with the coastal Xiwan Mangrove Park in the Pearl River Estuary, the second largest estuary in China. Samples were collected from mangrove and surrounding areas, identifying microplastics using Fourier-transform infrared spectroscopy (FTIR) and Laser Direct Infrared (LDIR) techniques. Microplastic concentrations ranged from 245.8 to 1562.4 n/m³ in water and 374.3 to 7475.3 n/kg in sediments. The Maozhou River exhibited consistent microplastic levels across varying hydrological conditions, while the Dasha River and Xiwan Mangrove showed greater sensitivity to water flow changes influenced by urban land use. During high-flow periods, urban river microplastic concentrations decreased due to dilution, whereas mangrove areas experienced elevated levels in water from urban runoff, upstream retention, and sediment resuspension, suggesting a potential for outward release. Weaker water dynamics led to increased microplastic accumulation in mangrove sediments. The distribution of microplastic types was influenced by multiple urban pollution sources, with synthetic rubbers linked to urban transportation comprising over 50 % of some samples, peaking at 79 %. These findings underscore the dual role of mangroves as microplastic sinks and potential sources, highlighting the significant impact of hydrological conditions on their function. This study offers new insights into microplastic pollution in urban mangrove ecosystems and emphasizes the urgent need for improved management strategies in coastal areas facing rapid urbanization.

Beach wrack as a potential microplastic hot spot in the South-Eastern Baltic Sea environment

Beach wrack is considered as a major source of nutrients to the sandy coast ecosystems in the South-East Baltic Sea, and it serves as the natural beach sediment storage and habitat formation material. However, it also could be a hot spot for microplastic and other types of marine litter accumulation. We carried out the recovery rate experiments to determine the most reliable method for a rapid and cost-effective application to extract microplastics from the beach wrack. The aeration of media in a saturated solution of sodium chloride revealed to be statistically significant and reliable, therefore was selected as a most suitable to extract the microplastics from the beach wrack. This study shows that the concentration of microplastics is significantly different between the four analyzed compartments in the coastal zone. The microplastic concentration in a beach wrack, with a mean value of 0.47 ± 0.17 items/cm3, contained 4.7 times more microplastics than observed in the surface sand samples. This study estimated that on average over 450 million microplastic items could be found during the castaway event in the South-East Baltic Sea coast.

Sand bed river dynamics controlling microplastic flux

Microplastic contamination of river sediments has been found to be pervasive at the global scale and responsive to plastic and sediment bed properties, the flow regime and the river morphology. The physical controls governing the storage, remobilization and pathways of transfer in sand bed rivers remain unquantified. This means it is not currently possible to determine the risks posed by microplastic contamination within these globally significant river systems. Using controlled flume experiments we show that sand bed rivers can store up to 40% of their microplastic load within the sediment bed indicating that these environments can act as resilient sinks of microplastics. By linking bedform dynamics with microplastic transport characteristics we show that similarities exist between granular transport phenomena and the behavior, and hence predictability, of microplastic flux. Specifically, we demonstrate the inverse relationship between bedform celerity and microplastic retention within the bed can be used to predict microplastic flux. Further, we show that, in these environments, microplastic shape is more important than previously thought in controlling the fate of microplastics. Together, these findings are significant since they have important implications for the prediction and hence management of microplastic contamination in sand bed environments.

Heterogenous bioluminescence patterns, cell viability, and biofilm formation of Photobacterium leiognathi strains exposed to ground microplastics

Microplastics (MPs) have been detected in various aquatic environments and negatively affect organisms, including marine luminous bacteria. This study investigated the differences in bioluminescence patterns, cell viability, and biofilm formation of Photobacterium leiognathi strains (LB01 and LB09) when exposed to various concentrations of ground microplastics (GMPs; 0.25%, 0.50%, 1%, or 2% [w/v] per mL) at 22°C or 30°C for 3.1 days (75 h) and 7 days. The strains exhibited heterogenous responses, including variable bioluminescence patterns, cell viability, and biofilm formation, due to the GMPs having effects such as hormesis and bioluminescence quenching. Moreover, the bioluminescence and cell viability differed between the two strains, possibly involving distinct cellular mechanisms, suggesting that GMPs affect factors that influence quorum sensing. Furthermore, the biofilm formation of LB01 and LB09 was observed following exposure to GMPs. Both strains showed increased biofilm formation at higher GMP concentrations (1% and 2%) after 3.1 days at 30°C and 22°C. However, in the 7-day experiment, LB01 significantly (p < 0.05) increased biofilms at 22°C, while LB09 significantly (p < 0.05) produced biofilms at 30°C. These findings highlight the strain-specific responses of Phb. leiognathi to MP pollutants. Therefore, this study underscores the importance of evaluating MPs as environmental stressors on marine microorganisms and their role in the ecophysiological repercussions of plastic pollution in aquatic environments.

Fate and effects of an environmentally relevant mixture of microplastics in simple freshwater microcosms

Most studies assessing the effects of microplastics (MPs) on freshwater ecosystems use reference materials of a certain size, shape, and polymer type. However, in the environment, aquatic organisms are exposed to a mixture of different polymers with different sizes and shapes, resulting in different bioaccessible fractions and effects. This study assesses the fate and effects of an environmentally relevant mixture of high-density polyethylene (HDPE) fragments, polypropylene (PP) fragments, and polyester (PES) fibres in indoor freshwater microcosms over 28 days. The MP mixture contained common polymers found in freshwater ecosystems, had a size range between 50 and 3887 µm, and was artificially aged using a mercury lamp. The invertebrate species included in the microcosms, Lymnea stagnalis (snail) and Lumbriculus variegatus (worm), were exposed to four MP concentrations: 0.01, 0.05, 0.1 and 1 % of sediment dry weight. MPs fate was assessed by performing a balance of the MPs in the surface water, water column, and sediment after a stabilization period and at the end of the experiment. Sedimentation rates per day were calculated (2.13 % for PES, 1.46 % for HDPE, 1.87 % for PP). The maximum size of MPs taken up by the two species was determined and compared to the added mixture and their mouth size. The size range taken up by L. variegatus was smaller than L. stagnalis and significantly different from the size range in the added mixture. The No Observed Effect Concentrations (NOECs) for the reproduction factor of L. variegatus and the number of egg clutches produced by L. stagnalis were 0.01 % and 0.1 % sediment dry weight, respectively. The EC10 and EC50 for the same endpoint for L. stagnalis were 0.25 % and 0.52 %, respectively. This study shows that current MP exposure levels in freshwater sediments can result in sub-lethal effects on aquatic organisms, highlighting the importance of testing MP mixtures.

Microplastics and silver nanoparticles compromise detrital food chains in streams through effects on microbial decomposers and invertebrate detritivores

Abundance of microplastics (MPs) in freshwater ecosystems has become an emerging concern due to their persistence, toxicity and potential interactions with other contaminants. Silver nanoparticles (Ag-NPs), which share common sources with MPs (e.g., personal care products), are also a subject of concern. Thus, the high probability of co-occurrence of both contaminants raises additional apprehensions. This study assessed, for the first time, the impacts of MPs and Ag-NPs, alone or in mixtures, on stream detritus food webs. Physiological and ecological responses of aquatic fungal communities, invertebrate shredders (Allogamus sp.) and collectors (Chironomus riparius) were examined. Additionally, antioxidant enzymatic responses of microbes and shredders were analyzed to unravel the mechanisms of toxicity; also, neuronal stress responses of Allogamus sp. were assessed based on the activities of cholinesterases. Organisms were exposed to environmentally realistic concentrations of polyethylene MPs, extracted from a personal care product (0.1, 0.5 and 10 mg L-1), for 7 days, in the absence or presence of Ag-NPs (0.1 mg L-1 and 1 mg L-1). The exposure to both contaminants reduced the growth rates of all tested organisms. MPs, Ag-NPs, and their mixtures led to a decrease in leaf litter decomposition by fungi and shredders. The availability of fine particulate organic matter, released by the shredders, increased when exposed to these contaminants. The negative effects of these contaminants were further strengthened by the responses of antioxidant enzymes that revealed high level of oxidative stress in both fungi and Allogamus sp. Moreover, the activities of cholinesterases showed that Allogamus sp. were under neuronal stress upon exposure to both contaminants. The impacts in mixtures were stronger than those of individual contaminants suggesting interactive effects. Overall, our study showed adverse effects of MPs and Ag-NPs across trophic levels and indicated that they may compromise key processes, such as organic matter decomposition in streams.

Impacts of microplastics on ecosystem services and their microbial degradation: a systematic review of the recent state of the art and future prospects

Microplastics are tiny plastic particles with a usual diameter ranging from ~ 1 μ to 5 µm. Recently, microplastic pollution has raised the attention of the worldwide environmental and human concerns. In human beings, digestive system illness, respiratory system disorders, sleep disturbances, obesity, diabetes, and even cancer have been reported after microplastic exposure either through food, air, or skin. Similarly, microplastics are also having negative impacts on the plant health, soil microorganisms, aquatic lives, and other animals. Policies and initiatives have already been in the pipeline to address this problem to deal with microplastic pollution. However, many obstacles are also being observed such as lack of knowledge, lack of research, and also absence of regulatory frameworks. This article has covered the distribution of microplastics in water, soil, food and air. Application of multimodel strategies including fewer plastic item consumption, developing low-cost novel technologies using microorganisms, biofilm, and genetic modified microorganisms has been used to reduce microplastics from the environment. Researchers, academician, policy-makers, and environmentalists should work jointly to cope up with microplastic contamination and their effect on the ecosystem as a whole which can be reduced in the coming years and also to make earth clean.

Microplastics in riverine systems: Recommendations for standardized sampling, separation, digestion and characterization

Microplastic (MP) pollution has emerged as a global concern, prompting numerous studies on MP detection. Due to the remaining methodological challenges, it affects the accuracy and reliability of MP's impact assessment on river systems. To address this, the establishment of standardized operating protocols is crucial, encompassing sampling, separation, digestion, and characterization methods. This study evaluates the current tools used for identifying and quantifying MPs in riverine ecosystems, aiming to offer harmonized guidelines for future protocols. Recommendations include adopting a consistent format for reporting MP concentrations and providing improved information on sampling, separation, and digestion for enhanced cross-study comparisons. The importance of quality assurance and quality control is also discussed. Furthermore, we highlight unresolved issues, proposing avenues for further investigation. Suggestions encompass standardizing river sampling methods, optimizing technical steps and analysis processes, and enhancing the accuracy, reliability, and comparability of detection data to advance our understanding of MPs in river environments.

Spatio-temporal trends in microplastic presence in the sediments of the River Thames catchment (UK)

This study investigated the spatio-temporal variability of microplastics (MPs) in the sediments of the River Thames (UK) catchment over 30 months (July 2019 - Dec 2021). The average MP concentration was 61 items kg-1 d.w., with fragments <1 mm being dominant and polyethylene (PE) the most common polymer. Adjacent land use influenced MP concentrations and types, with industrial sites showing particularly high levels and a prevalence of small beads and industrial polymers. MP concentrations generally decreased after higher winter flows, likely due to sediment rearrangement or winnowing. This study describes the seasonal concentrations and characteristics of MPs present in sediment from the River Thames catchment, and attempts to identify their likely origin. Further, the study provides new insights into the mobility and fate of MPs in riverine settings under varying flow conditions, which is vital given the predicted increases in flooding under various global heating scenarios.

Distribution, flux, and risk assessment of microplastics at the Anzali Wetland, Iran, and its tributaries

Microplastic pollution has raised significant concerns among scientific communities and society in recent years due to its increase and lesser-known effects on the environment. To improve the knowledge of microplastic pollution in freshwater, we investigated microplastics in Anzali Wetland, a Ramsar site in northern Iran, as well as its nine main entering rivers. The extracted microplastics were characterized via visual identification, SEM-EDX, and μ-Raman methods. Microplastics (size range: 50-5000 μm) were found in all water and sediment samples with concentration of fibrous particles as well as polypropylene and polyethylene polymers. The mean concentration of microplastics in bottom sediment and surface water samples of the wetland was 301 ± 222 particles∙kg-1 d.w. and 235 ± 115 particles∙m-3 (0.23 particles∙L-1), respectively. The microplastic concentration in the central and eastern parts of the wetland was higher than in other areas; however, the mean concentrations revealed homogeneity across the wetland area. Water properties (dissolved oxygen, pH, temperature, electrical conductivity, and salinity in water) did not affect the concentration of microplastic particles, though correlational analysis revealed a strong positive association between microplastic quantity and turbidity. There was a significant positive relationship between microplastic concentration and the percentage of clay in sediment samples. The quantity of microplastics in river water was higher than in wetland water, but the difference between the results was not significant. However, the quantity of microplastics in the river's littoral sediment was higher than in the bottom sediment of the wetland where the difference between the results was significant. Microplastic ecological risk assessment showed high potential ecological risk. The findings underscore the importance of effective management strategies and the implementation of policies to mitigate the negative impact of MP pollution on ecosystems and human health.

Distribution and effects of microplastics as carriers of heavy metals in river surface sediments

There are few studies on microplastics (MPs) in urban river sediments compared to oceans, soils, and even rivers. In this study, the seasonal abundance of MPs, as well as their influencing factors on heavy metal adsorption in river sediments of the Ancient Canal of Zhenjiang City, China, were investigated for the first time. Through on-site sampling, microscopic observation, Raman spectroscopy, scanning electron microscopy, and high-temperature digestion, the abundance, shape, color, particle size, type, and surface characteristics of MPs in Ancient Canal sediments in different seasons, as well as the influencing factors of MPs as heavy metal carriers in different seasons, were analyzed. The results showed that the average abundance of MPs is 2049.09 ± 883.78 and 2216.36 ± 826.21 items kg-1 dry sediments in summer and winter, respectively, and different sites change significantly. In addition, particle sizes, types, colors, and shapes of MPs exhibited seasonal variations. Four MPs shapes were mainly observed: fibers, fragments, particles, and films. Among them, MPs in summer sediments are mainly fiber, and MPs in winter sediments are mainly particles. In the sediment in summer and winter, transparent MPs and small-size (<0.5 mm) MPs are the main ones, where the abundance of MPs decreased with increasing MPs size. The main MPs species are polyvinyl chloride (PVC), polystyrene (PS), polypropylene (PP), polyethylene terephthalate (PET), polycarbonate (PC), and polyethylene (PE), with PP being the predominant MPs in the sediments in different seasons. Scanning electron microscopy-energy dispersive spectrometer (SEM-EDS) revealed that the surfaces of the MPs were characterized by rough, porous, cracked, and torn, with the attachment of various heavy metal elements, and all of the heavy metal elements accumulated to different degrees on the MPs. There was a significant positive correlation (p < 0.05) between the Mn content in the MPs and the Mn content in the sediments in winter, suggesting that the Mn in the MPs in winter may be derived from the sediments. In addition, the type, shape, size, and color of MPs affect the adsorption capacity of heavy metals. Most of the adsorption of MPs on Pb showed a significant negative correlation, and the adsorption of MPs on Cr, Zn, Cu, Cd, and Mn showed a significant positive correlation. MPs can be used as carriers of heavy metals, which will further enhance the hazards of living organisms and pose a potential threat to the safety of the urban river environment.

Unveiling the ecotoxicological impact of microplastics on organisms - the persistent organic pollutant (POP): A comprehensive review

Microplastics have been ubiquitous in our environment for decades, and numerous studies have revealed their extensive dispersion, reaching far beyond the surface of the land, soil, aquatic ecosystems. They have infiltrated the food-chain, the food web, even the air we breathe, as well as the water we drink. Microplastics have been detected in the food we consume, acting as vectors for hazardous chemicals that adhere to their hydrophobic surfaces. This can result in the transfer of these chemicals to the aquatic life, posing a threat to their well-being. The release of microplastics into different environmental settings can give rise to various eco-toxicological implications. The substantial body of literature has led scientists to the consensus that microplastic pollution is a global problem with the potential to impact virtually any type of ecosystem. This paper aims to discuss crucial information regarding the occurrence, accumulation, and ecological effects of microplastics on organisms. It also highlights the new and emerging disease named "Plasticosis" that is directly linked to microplastics and its toxicological effects like permanent scarring and long-term inflammation in the digestive system of the seabirds. By comprehending the behaviour of these microplastic pollutants in diverse habitats and evaluating their ecological consequences, it becomes possible to facilitate a better understanding of this toxicological issue.

Fauna - Microplastics interactions: Empirical insights from benthos community exposure to marine plastic waste

Microplastic deposition in soft marine sediments raises concerns on their role in sediment habitats and unknown effects on resident macrobenthic communities. To assess the reciprocal influence that MPs and macrobenthos might have on each other, we performed a mesocosm experiment with ambient concentrations of environmental Polyethylene (PE) and a non-manipulated, natural macrobenthic community from the Belgian part of the North Sea (BPNS). Our results show that PE fragments increase mortality of abundant bivalves (specifically Abra alba) after 30 days of exposure but not for the most abundant polychaete Owenia fusiformis, possibly due to its predominant suspension feeding behavior. Fast burial of surface MPs exposes deep-dwelling burrowers to the pollutant, however reducing the amount of MPs interacting with (sub) surface living fauna. We conclude that macrobenthos promotes the sequestration of deposited MPs, counteracting resuspension, and can have cascading effects on biodiversity due to their effect on abundant and functionally important species.

Contamination by microplastics and sorbed organic pollutants in the surface waters of the Tietê River, São Paulo-SP, Brazil

Microplastics (MPs) are particles between 1 μm and 5 mm in size, originating mainly from poor solid waste and effluent management, that can reach water bodies from various sources. In freshwater environments, the occurrence, distribution, and characterization of this new class of pollutants are still little explored, especially in Brazil. The aim of this study was to assess the occurrence of MPs, as well as the presence and concentration of polychlorinated biphenyls (PCBs) sorbed to these particles in the surface waters of the Tietê River - SP. Surface water samples were collected in duplicate during the dry and wet seasons. The identification and characterization of the MPs was carried out through visual inspection and the chemical identity of the particles was verified using Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR). For the analysis of PCBs adsorbed to the MPs, the sample extracts were analyzed by gas chromatography coupled with mass spectrometry (GC-MS). The MPs were found in concentrations ranging from 6.67 to 1530 particles m-3, with a predominance of the polymers polyethylene (PE, with 58.17 %) and polypropylene (PP, with 23.53 %). The main morphological categories identified were fragments (56.63 %), fibers (28.42 %), and transparent films (13.06 %). Higher abundances of PCBs were observed in the lower size range, between 0.106 and 0.35 mm. The total concentrations of PCBs in MPs ranged from 20.53 to 133.12 ng g-1. The results obtained here are relevant for understanding the dynamics and level of contamination of MPs and organic pollutants sorbed to these particles in the Tietê River, as well as helping with mitigation measures for the restoration and preservation of this ecosystem.

Unseen riverine risk: Spatio-temporal shifts of microplastic pollution and its bioavailability in freshwater fish within the Ikopa River urban system

Growing concern over microplastic pollution, driven by their widespread accumulation in the environment, stresses the need for comprehensive assessments. This study investigates the spatial and temporal distribution of microplastics in the Ikopa River (Antananarivo - Madagascar), which flows through a densely populated area, and examines their correlation with contamination levels in local fish species. By analyzing upstream and downstream stations across wet and dry seasons, only a notable increase in microplastic concentration downstream during the wet season was observed, ranging from 138.6 ± 9.0 to 222.0 ± 24.5 particles m-3, with polyethylene-co-vinyl acetate being the predominant polymer at 62.3 ± 5.13% of the total sampled polymers. This distribution underlines the impact of urban activities on pollution levels. Fish species, gambusia and Nile tilapia, were assessed for microplastic occurrence in gills and gastrointestinal tracts. Higher contamination rates were found in gambusia, enlightening the influence of feeding behaviour and fish habitat on microplastics contamination. Ingestion of microplastics directly from the water column was evident in both species, with the detection of high-density plastics such as polytetrafluoroethylene and polyvinyl chloride suggesting likely sediment contamination. This research highlights the widespread contamination of aquatic environments and its direct impact on local wildlife, pointing to a clear requirement for effective pollution management strategies.

Combined effect and mechanism of microplastic with different particle sizes and levofloxacin on developing Rana nigromaculata: Insights from thyroid axis regulation and immune system

Microplastics (MPs) usually appear in the aquatic environment as complex pollutants with other environmental pollutants, such as levofloxacin (LVFX). After 45-day exposure to LVFX and MPs with different particle sizes at environmental levels, we measured the weight, snout-to-vent length (SVL), and development stages of Rana nigromaculata. Furthermore, we analyzed proteins and genes related to immune system and thyroid axis regulation, intestinal histological, and bioaccumulation of LVFX and MPs in the intestine and brain to further explore the toxic mechanism of co-exposure. We found MPs exacerbated the effect of LVFX on growth and development, and the order of inhibitory effects is as follows: LVFX-MP3>LVFX-MP1>LVFX-MP2. 0.1 and 1 μm MP could penetrate the blood-brain barrier, interact with LVFX in the brain, and affect growth and development by regulating thyroid axis. Besides, LVFX with MPs caused severer interference on thyroid axis compared with LVFX alone. However, 10 μm MP was prone to accumulating in the intestine, causing severe histopathological changes, interfering with the intestinal immune system and influencing growth and development through immune enzyme activity. Thus, we concluded that MPs could regulate the thyroid axis by interfering with the intestinal immune system.

Occurrence, potential sources, and ecological risk assessment of microplastics in the inland river basins in Northern China

Microplastics (MPs) are the pollutants, found widely across various environmental media. However, studies on the MP pollution in urban rivers and the necessary risk assessments remain limited. In this study, the abundance and characteristics of microplastics in a typical urban river were examined to evaluate their distribution, sources, and ecological risks. It was observed that the abundance of MPs in sediments (220-2840 items·kg-1 dry weight (DW)) was much higher than that in surface water (2.9-10.3 items·L-1), indicating that the sediment is the "sink" of river MPs. Surface water and sediment were dominated by small particle size MPs (< 0.5 mm). Fiber and debris were common shapes of MPs in rivers and sediments. The microplastics in river water and sediments were primarily white and transparent, respectively. Polypropylene (PP) and polyethylene (PE) were the major polymers found.

Short-term microplastic effects on marine meiofauna abundance, diversity and community composition

Background

Due to the copious disposal of plastics, marine ecosystems receive a large part of this waste. Microplastics (MPs) are solid particles smaller than 5 millimeters in size. Among the plastic polymers, polystyrene (PS) is one of the most commonly used and discarded. Due to its density being greater than that of water, it accumulates in marine sediments, potentially affecting benthic communities. This study investigated the ingestion of MP and their effect on the meiofauna community of a sandy beach. Meiofauna are an important trophic link between the basal and higher trophic levels of sedimentary food webs and may therefore be substantially involved in trophic transfer of MP and their associated compounds.

Methods

We incubated microcosms without addition of MP (controls) and treatments contaminated with PS MP (1-µm) in marine sediments at three nominal concentrations (103, 105, 107particles/mL), for nine days, and sampled for meiofauna with collections every three days. At each sampling time, meiofauna were collected, quantified and identified to higher-taxon level, and ingestion of MP was quantified under an epifluorescence microscope.

Results

Except for Tardigrada, all meiofauna taxa (Nematoda, turbellarians, Copepoda, Nauplii, Acari and Gastrotricha) ingested MP. Absorption was strongly dose dependent, being highest at 107 particles/mL, very low at 105 particles/mL and non-demonstrable at 103 particles/mL. Nematodes accumulated MP mainly in the intestine; MP abundance in the intestine increased with increasing incubation time. The total meiofauna density and species richness were significantly lower at the lowest MP concentration, while at the highest concentration these parameters were very similar to the control. In contrast, Shannon-Wiener diversity and evenness were greater in treatments with low MP concentration. However, these results should be interpreted with caution because of the low meiofauna abundances at the lower two MP concentrations.

Conclusion

At the highest MP concentration, abundance, taxonomic diversity and community structure of a beach meiofauna community were not significantly affected, suggesting that MP effects on meiofauna are at most subtle. However, lower MP concentrations did cause substantial declines in abundance and diversity, in line with previous studies at the population and community level. While we can only speculate on the underlying mechanism(s) of this counterintuitive response, results suggest that further research is needed to better understand MP effects on marine benthic communities.

Beneath the surface: Exploring microplastic intricacies in Anadara granosa

Anadara granosa or blood cockles have been reported to be a candidate for biomonitoring agents due to their sedimentary nature and their nutrient uptake mechanisms. Yet, this bivalve is still regarded as a delicacy in Asian cuisine. Malaysia is the largest exporter of this sea product that contaminated cockles may also be experienced by the importing countries. However, the bioaccumulation of microplastics in A. granosa cultivated in Malaysia has not been extensively studied. It is crucial to comprehend the risk posed to humans by consuming A. granosa in their diet. Therefore, the purpose of this research is to investigate the levels of microplastic accumulation in A. granosa from major exporters in Peninsular Malaysia, to evaluate the associated risk of microplastics on the species, and to estimate daily human consumption of microplastics through the consumption of A. granosa. The abundance of microplastics was quantified through the use of a stereo microscope, and the polymer type was determined using FTIR and micro-FTIR. Findings from this investigation revealed that all samples of A. granosa were contaminated with microplastics, with the highest levels of accumulation found in bivalves collected from the west coast (0.26 ± 0.15 particles/g) of Peninsular Malaysia. Fragment and fiber microplastics, measuring between 0.05 and 0.1 mm in size, were found to be the most prevalent in A. granosa, with blue being the dominant identified colour and rayon being the most common polymer type. Microplastic risk assessment due to the presence of polyacrylate, polycarbonate (PC), and polymethyl methacrylate (PMMA) resulted in a high risk of contamination for A. granosa. It was further determined that the current estimated dietary intake (EDI) suggests that consumers of A. granosa uptake approximately 21.8-93.5 particles/person/year of microplastics. This study highlights that A. granosa accumulates microplastics, which could potentially result in bioaccumulation and biomagnification in humans through consumption.

Assessment and accumulation of microplastics in the Indian riverine systems: Risk assessment and implications of translocation across the water-to-fish continuum

Microplastic (MP) pollution has engulfed global aquatic systems, and the concerns about microplastic translocation and bioaccumulation in fish and other aquatic organisms are now an unpleasant truth. In the past few years, MP pollution in freshwater systems, particularly rivers and subsequently in freshwater organisms, especially in fish, has caught the attention of researchers. Rivers provide livelihood to approximately 40 % of the global population through food and potable water. Hence, assessment of emerging contaminants like microplastics in rivers and the associated fauna is crucial. This study assessed microplastics (MPs) in fish, sediment and freshwater samples across the third largest riverine system of peninsular India, the Mahanadi River. The number concentrations of MPs measured in water, sediment and fish ranged from 337.5 ± 54.4-1333.3 ± 557.2 MPs/m3, 14.7 ± 3.7-69.3 ± 10.1 MPs/kg. Dry weight and 0.4-3.2 MPs/Fish, respectively. Surprisingly, MPs were found in every second fish sample, with a higher MP number in the gut than in the gills. Black and blue coloured filaments with <0.5 mm size were the dominant MPs with polypropylene and polyethylene polymers in abundance. The Polymer Hazard Index (PHI) and the Potential Ecological Risk Index (PERI) studies revealed that the majority of the sampling sites fell in Risk category V (dangerous category). An irregular trend in the MP concentration was observed downstream of the river, though relatively elevated MP concentrations in water and fish samples were observed downstream of the river. t-Distributed Stochastic Neighbour Embedding (t-SNE) unveiled distinct patterns in MP distribution with a higher similarity exhibited in the MPs found in fish gill and gut samples, unlike water and sediment, which shared certain characteristics. The findings in the current study contribute to filling the knowledge gap of MP assessment and accumulation in global freshwater systems and highlight the microplastic contamination and accumulation in fish with its potential implications on human health.

Microplastic analysis in sediments of the Elbe River by electrostatic separation and differential scanning calorimetry

This study presents the most extensive investigation of microplastic (MP) contents in sediment from the Elbe River. We employed electrostatic separation (ES) and differential scanning calorimetry (DSC) to overcome limitations of sample throughput and time-consuming analysis. In total 43 sediment samples were collected using a Van-Veen grab. Subsequently, coarse materials (d10 > 100 μm) and fine materials (d10 ≤ 100 μm) were enriched using ES and density separation. DSC was utilized for MP identification and quantification, based on the phase-transition signals of eight different polymers. MP presence was detected in 25 samples, with successful quantification in 12 samples. The MP content in coarse material samples from shoreline areas ranged from 0.52 to 1.30 mg/kg, while in fine material samples from harbor basins, it ranged from 5.0 to 44.6 mg/kg. The most prevalent polymers identified were LD-PE, HD-PE, PP, and PCL. These findings confirmed the suitability of DSC for analyzing MP in complex environmental samples. MP hotspots were identified in harbor basins, where natural sedimentation processes and increased anthropogenic activities contribute to MP accumulation. Additionally, industrial sewage potentially contributed to MP content in sediment samples. The highest pollution levels were observed in the middle Elbe, between the confluences of Mulde and Havel. Lowest MP contents were found in the lower Elbe, potentially influenced by tides. Future studies should focus on holistic investigations of selected river sections, encompassing sediment, water, and biota samples, rather than the entire catchment area. This approach would facilitate the generation of spatiotemporal data on MP distribution in freshwater streams. In addition, more research is needed to explore potential interactions between different MP and sediment types during DSC measurements.

Comparative microplastic analysis in urban waters using μ-FTIR and Py-GC-MS: A case study in Amsterdam

The contamination of freshwater with microplastics (MPs) has been established globally. While the analysis of MPs has predominantly involved spectroscopic methods for revealing particle numbers, the potential of employing spectroscopy for mass estimation has been underutilized. Consequently, there is a need to enhance our understanding of the mass loads of MPs and ensure the complementarity and comparability of various techniques for accurate quantification. This study presents the first comparative results on urban water samples using micro Fourier-transform infrared (μ-FTIR) imaging and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) to identify and quantify MPs in both particle numbers and mass concentration. Two sampling campaigns in summer and winter were conducted at 11 locations within the Amsterdam canal network. An advanced in-situ volume-reducing sampling pump was employed to collect MPs from the surface water within the size fraction of 10-300 μm. The analysis revealed MP concentrations within the range of 16-107 MP/m3, estimated to be 2.0-789 μg/m3 by μ-FTIR imaging and 8.5-754 μg/m3 by Py-GC-MS. The results of the two analysis techniques showed good comparability in terms of the general trends of MP abundances, with variations in polymer compositions due to the inherent inter-methodological differences. Elevated MP concentrations were observed in the city center compared to the suburban areas. In addition, seasonal differences in MP abundances were noted at the locations with high human activity.

A Study of High-Frequency Noise for Microplastics Classification Using Raman Spectroscopy and Machine Learning

Given the growing urge for plastic management and regulation in the world, recent studies have investigated the problem of plastic material identification for correct classification and disposal. Recent works have shown the potential of machine learning techniques for successful microplastics classification using Raman signals. Classification techniques from the machine learning area allow the identification of the type of microplastic from optical signals based on Raman spectroscopy. In this paper, we investigate the impact of high-frequency noise on the performance of related classification tasks. It is well-known that classification based on Raman is highly dependent on peak visibility, but it is also known that signal smoothing is a common step in the pre-processing of the measured signals. This raises a potential trade-off between high-frequency noise and peak preservation that depends on user-defined parameters. The results obtained in this work suggest that a linear discriminant analysis model cannot generalize properly in the presence of noisy signals, whereas an error-correcting output codes model is better suited to account for inherent noise. Moreover, principal components analysis (PCA) can become a must-do step for robust classification models, given its simplicity and natural smoothing capabilities. Our study on the high-frequency noise, the possible trade-off between pre-processing the high-frequency noise and the peak visibility, and the use of PCA as a noise reduction technique in addition to its dimensionality reduction functionality are the fundamental aspects of this work.

New insights into changes in phosphorus profile at sediment-water interface by microplastics: Role of benthic bioturbation

Microplastics (MPs) have attracted increasing attention due to their ubiquitous occurrence in freshwater sediments and the detrimental effects on benthic invertebrates. However, a clear understanding of their downstream impacts on ecosystem services is still lacking. This study examines the effects of bio-based polylactic acid (PLA), fuel-based polyethylene terephthalate (PET), and biofilm-covered PET (BPET) MPs on the bioturbator chironomid larvae (Tanypus chinensis), and the influence on phosphorus (P) profiles in microcosms. The changes in biochemical responses and metabolic pathways indicated that MPs disrupted energy synthesis by causing intestinal blockage and oxidative stress in T. chinensis, leading to energy depletion and impaired bioturbation activity. The impairment further resulted in enhanced sedimentary P immobilization. For larval treatments, the internal-P loadings were respectively 11.4%, 8.6%, and 9.0% higher in the PLA, PET, and BPET groups compared to the non-MP control. Furthermore, the influence of bioturbation on P profiles was MP-type dependent. Both BPET and PLA treatments displayed more obvious impacts on P profiles compared to PET due to the changes in MP bioavailability or sediment microenvironment. This study connects individual physiological responses to broader ecosystem services, showing that MPs alter P biogeochemical processes by disrupting the bioturbation activities of chironomid larvae.

A comprehensive assessment of macro and microplastics from Rivers Ganga and Yamuna: Unveiling the seasonal, spatial and risk factors

There have been growing apprehensions and concerns regarding the increasing presence of plastic pollutants in the holiest river of India, the Ganga, and its major tributary, Yamuna. In response to this issue, the current study aimed to conduct a comprehensive investigation of the seasonal and spatial distribution of macro to microplastics (MPs) in the surface water, water column, and sediments from the River Ganga and Yamuna. MP samples were collected from various points of these Rivers, including upstream, downstream, and drainage points around the vicinity of Haridwar, Agra, Prayagraj, and Patna cities. With a significant seasonal variation, the estimated MPs and plastic flux were higher during the wet season than during the dry season. MPs sized 300 µm-1 mm and fibre-shaped blue and black colored MPs were pre-dominant in both rivers. Polyacrylamide, polyamide, and polyvinyl chloride were the most ascertained polymers. MPs including hazardous polymers (hazard score >1000) may pose a risk to the population of Indo-Gangetic Plain via direct and indirect exposure to MPs. The information provided in this study could serve as a starting point for the action plan required by municipal corporations to mitigate plastic pollution and target the possible sources at each location.

Microplastics in a small river: Occurrence and influencing factors along the river Oker, Northern Germany

Much attention regarding the environmental pollution by plastics had focused on the Oceans. More recently, contamination of freshwater ecosystems has been addressed but information from smaller rivers in moderately populated catchments is still comparatively scarce. This study explored the microplastic (MP) occurrence in the small regional river Oker, Northern Germany (catchment area 1822 km2, population of ca. 500,000, discharge approx. 12 m3 s-1). MPs (fibers and fragments in the size range 0.3-5 mm, identification by microscopy) were found in all 10 in-stream samples collected along the course of the river, ranging between 28 and 134 particles m-3 with an overall average of 63 particles m-3. This MP concentration found in the small river Oker is similar to, or higher than, that reported for larger rivers in similar environments in Central Europe. On average, higher MP concentration was found at urban (71 particles m-3) compared to rural sampling sites (51 particles m-3). Within the Oker catchment, in-stream MP concentration showed no or low correlation to the catchment-scale factors of catchment size and population. Additional samples taken from three locations directly influenced by discharges of potential MP point sources confirmed wastewater treatment plants of different capacities and an urban rainwater sewer as sources. Our results support findings that MP concentrations in small rivers are crucially influenced by local sources, superimposing linear relationships to factors of catchment size and -population. They show that even small rivers draining moderately populated catchments may exhibit comparatively high concentrations of MPs, and thereby represent underestimated pathways of MP in the environment.

Regression analysis for the determination of microplastics in sediments using differential scanning calorimetry

This research addresses the growing need for fast and cost-efficient methods for microplastic (MP) analysis. We present a thermo-analytical method that enables the identification and quantification of different polymer types in sediment and sand composite samples based on their phase transition behavior. Differential scanning calorimetry (DSC) was performed, and the results were evaluated by using different regression models. The melting and crystallization enthalpies or the change in heat capacity at the glass transition point were measured as regression analysis data. Ten milligrams of sea sand was spiked with 0.05 to 1.5 mg of microplastic particles (size: 100 to 200 µm) of the semi-crystalline polymers LD-PE, HD-PE, PP, PA6, and PET, and the amorphous polymers PS and PVC. The results showed that a two-factorial regression enabled the unambiguous identification and robust quantification of different polymer types. The limits of quantification were 0.13 to 0.33 mg and 0.40 to 1.84 mg per measurement for semi-crystalline and amorphous polymers, respectively. Moreover, DSC is robust with regard to natural organic matrices and allows the fast and non-destructive analysis of microplastic within the analytical limits. Hence, DSC could expand the range of analytical methods for microplastics and compete with perturbation-prone chemical analyses such as thermal extraction-desorption gas chromatography-mass spectrometry or spectroscopic methods. Further work should focus on potential changes in phase transition behavior in more complex matrices and the application of DSC for MP analysis in environmental samples.

Spatial and temporal trends of microplastic contamination in surface sediment of Benoa Bay: An urban estuary in Bali-Indonesia

This study aims to explore microplastic contamination in the sediments of Benoa Bay. Eight locations were sampled, with four duplications denoting the rainy and dry seasons. Based on observations, the microplastic concentration varied from 9.51 to 90.60 particles/kg with an average of 31.08 ± 21.53 particles/kg. The area near the landfill had the highest abundance, while the inlet and center of Benoa Bay and the Sama River had the lowest concentration. The fragments (52.2 %) and large microplastic sizes (64.7 %) were the most documented particles. We also identified 17 polymers, which dominated (37.5 %) by polyethylene, polypropylene, and polystyrene. There were no appreciable variations in abundance between seasons, although there were substantial variations in shape and size. Comprehensive investigation, adequate policies, continuous monitoring, and reducing waste from land- and sea-based sources that engage various stakeholders must be implemented urgently to prevent the release of microplastic into the aquatic ecosystem.

Time-varying microplastic contributions of a large urban and industrial area to river sediments

The quantification of microplastic (MP) pollution in rivers is often constrained by a lack of historical data on a multi-decadal scale, which hinders the evaluation of public policies. In this study, MP contents and trends were analyzed in dated sediment cores sampled upstream and downstream of a large metropolis, in environmental deposits that exhibited consistent sedimentation patterns from the 1980s to 2021. After a thorough sedimentological analysis, MPs were quantified in samples by micro Fourier Transform InfraRed spectroscopy (μFTIR imaging) and a density separation and organic matter digestion procedure. Microplastics recorded in the upstream core are relatively ubiquitous all along the dated sequence. The results also confirmed a sever increase of microplastics levels in the downstream core, by one order of magnitude, and an increase of polymer types. Polypropylene, polyethylene, and polystyrene represent ubiquitous contamination and were predominant at the two stations, whereas polyvinyl chloride and polytetrafluoroethylene were suspected to be abundant at the downstream station, but were not detected at the upstream station. Their presence could be linked to local contamination from specific industrial sources that manufactured and utilized these polymers. Surprisingly, in the downstream station sediment has recorded a relative improvement in polymers associated with industrial sources since the 2000s and, to a lesser extent, for ubiquitous ones since the 2010s. This trend of mitigation diverges from that of global assessments, that assume uncontrolled MP pollution, and suggest that European Union wastewater policy and regulation on industrial discharges have positively influenced water quality, and certainly also on MPs. However, the accumulation of microplastics remains high in recent deposits and raises the emerging concern of the long-term management of these reservoirs.

Microplastics in packaged water, community stored water, groundwater, and surface water in rivers of Tamil Nadu after the COVID-19 pandemic outbreak

The increased load of plastic in waste streams after the COVID-19 pandemic outbreak has increased the possibility of microplastics (MPs) contamination channelling through the rivers and infiltrating the aquatic ecosystems. MPs in packaged water, community-stored water, groundwater, and surface water of Kaveri River (KR), Thamirabarani River (TR), Adyar River (AR), and Cooum River (CR) in Tamil Nadu were therefore investigated about 2 years after the COVID-19 pandemic outbreak. Using μFTIR and μRaman spectroscopy, polyamide, polypropylene, polyethylene, ethylene vinyl alcohol copolymer resin, and polyvinyl chloride were identified as the primary polymer types. The average number of MPs was 2.15 ± 1.9 MP/L, 1.1 ± 0.99 MP/L, 5.25 ± 1.15 MP/L, and 4 ± 2.65 MP/L in KR, TR, AR, and CR, respectively, and 1.75 ± 1.26 MP/L in groundwater, and 2.33 ± 1.52 MP/L in community stored water. Only LDPE was detected in recycled plastic-made drinking water bottles. More than 50% of MPs were found to be of size less than 1 mm, with fibrous MPs being the prevalent type, and a notable prevalence of blue-coloured microplastics in all the sample types. The Pollution Load Index (PLI) was >1 in all the rivers. Toxicity rating based on the polymer risk index (PORI) categorized AR and TR at medium risk (category II), compared to KR and CR at considerable risk (category III). Overall pollution risk index (PRI) followed a decreasing trend with CR > AR > KR > TR of considerable to low-risk category. Ecological risk assessment indicates a negligible risk to freshwater biota, except for four sites in the middle and lower stretches of Adyar River (AR - 2, AR - 4) and upper and lower stretches of Cooum River (CR - 1, CR - 3), located adjacent to direct sewer outlets, and one location in the lower stretch of Kaveri River (KR - 9), known for fishing and tourist activities.

From pollution to solutions: Insights into the sources, transport and management of plastic debris in pristine and urban rivers

River systems are important recipients of environmental plastic pollution and have become key pathways for the transfer of mismanaged waste from the land to the ocean. Understanding the sources and fate of plastic debris, including plastic litter (>5 mm) and microplastics (MPs) (<5 mm), entering different riverine systems is essential to mitigate the ongoing environmental plastic pollution crisis. We comprehensively investigated the plastic pollution in the catchments of two rivers in the Yangtze River basin: an urban river, the Suzhou section of the Beijing-Hangzhou Grand Canal (SZ); and a pristine rural river, the Jingmen section of the Hanjiang River (JM). The abundance of plastic pollutants in SZ was significantly higher than in JM: 0.430 ± 0.450 items/m3 and 0.003 ± 0.003 items/m3 of plastic litter in the water; 23.47 ± 25.53 n/m3 and 2.78 ± 1.55 n/m3 MPs in the water; and 218.82 ± 77.40 items/kg and 5.30 ± 1.99 items/kg of MPs in the sediment, respectively. Plastic litter and MPs were closely correlated in abundance and polymer composition. Overall, the polymer type, shape and color of MPs were dominant by polypropylene (42.5%), fragment (60.4%) and transparent (40.0%), respectively. Source tracing analysis revealed that packaging, shipping, and wastewater were the primary sources of plastic pollutants. The mantel analysis indicated that socio-economic and geospatial factors play crucial roles in driving the hotspot formation of plastic pollution in river networks. The composition of the MP communities differed significantly between the sediments and the overlying water. The urban riverbed sediments had a more pronounced pollutant 'sink' effect compared with the pristine rivers. These findings suggested that the modification of natural streams during urbanization may influence the transport and fate of plastic pollutants in them. Our results offer pivotal insights into effective preventive measures.

Optimization of microplastic removal based on the complementarity of constructed wetland and microalgal-based system

As one of the emblematic emerging contaminants, microplastics (MPs) have aroused great public concern. Nevertheless, the global community still insufficiently acknowledges the ecological health risks and resolution strategies of MP pollution. As the nature-based biotechnologies, the constructed wetland (CW) and microalgal-based system (MBS) have been applied in exploring the removal of MPs recently. This review separately presents the removal research (mechanism, interactions, implications, and technical defects) of MPs by a single method of CWs or MBS. But one thing with certitude is that the exclusive usage of these techniques to combat MPs has non-negligible and formidable challenges. The negative impacts of MP accumulation on CWs involve toxicity to macrophytes, substrates blocking, and nitrogen-removing performance inhibition. While MPs restrict MBS practical application by making troubles for separation difficulties of microalgal-based aggregations from effluent. Hence the combined strategy of microalgal-assisted CWs is proposed based on the complementarity of biotechnologies, in an attempt to expand the removing size range of MPs, create more biodegradable conditions and improve the effluent quality. Our work evaluates and forecasts the potential of integrating combination for strengthening micro-polluted wastewater treatment, completing the synergistic removal of MP-based co-pollutants and achieving long-term stability and sustainability, which is expected to provide new insights into MP pollution regulation and control.

Comparison of plastic pollution between waters and sediments in four Po River tributaries (Northern Italy)

The monitoring of plastic contamination in freshwaters is still pioneering in comparison with marine environments, and few studies analyzed the distribution of these pollutants in both aqueous and bottom compartments of continental waters. Therefore, the aim of this study was the comparison of plastic pollution in both waters and sediments of four Po River tributaries (Ticino, Adda, Oglio and Mincio Rivers), which outflow from the main Italian sub-alpine Lakes, in order to establish the strengths and weaknesses of both matrices. The main results pointed out a heterogeneous plastic contamination, with the lowest values in Ticino (0.9 ± 0.5 plastics/m3 in waters and 6.8 ± 4.5 plastics/kg dry weight - d.w. - in sediments) and the highest in Mincio (62.9 ± 53.9 plastics/m3 in waters and 26.5 ± 13.3 plastics/kg d.w in sediments), highlighting a plastic amount in sediments four times higher than waters. Plastic pollution, mainly due to microplastics, was associated principally to a domestic input in both waters and sediments of Ticino and Adda Rivers, as well as in sediments of Oglio, while an industrial pollution was found in waters and sediments of Mincio and Oglio waters. Our data clearly highlighted as the monitoring of both matrices provide complementary information for a holistic risk assessment of these emerging contaminants in freshwaters: the aqueous matrix provides an instantaneous picture of contamination, while sediments the history of pollution.

Modeling the transport of microplastics along river networks

The excessive use of plastics in modern life has led to a significant increase in production and a corresponding rise in plastic waste generation. The slow degradation of plastics results in the introduction and accumulation of microplastics (MP) in the environment, posing environmental and health risks. River networks, acting as conduits between terrestrial and marine environments, play a crucial role in controlling the transport of MP. Predicting the complex processes of MP pathways in these environments is an ongoing challenge. To address this issue, we propose a model that integrates the advection-dispersion equation with anthropogenic MP loads and hydraulic river network characteristics. The validity of the model was assessed using literature data from three river networks worldwide. Model results show a good agreement between predictions and field observations (R2=0.72). Consequently, predicted MP data was used to perform a potential pollution assessment through the pollution load index, revealing in most cases higher MP contamination in headwaters stream and a dilution effect along the river network. The structure of the proposed model allows its further implementation to account for other transport mechanisms, interactions with other emerging contaminants (i.e., pharmaceuticals), and connections with other riverine environments, making it a valuable tool for understanding and mitigating MP pollution.

Gene expression analysis of Chironomus riparius in response to acute exposure to tire rubber microparticles and leachates

Tire rubber microparticles (TRPs) entering aquatic ecosystems through stormwater runoffs is a significant challenge. TRPs are formed by the abrasion of tires with the road surface and include chemical additives that are an additional cause for concern. Currently, information on the molecular effects of TRPs, or especially its additives, in freshwater organisms is scarce. To address this problem, an array covering different cellular processes has been designed for the freshwater midge Chironomus riparius. Fourth-instar larvae were exposed to two concentrations of TRPs (1 mg L-1, 10 mg L-1) and tire rubber leachates (TRLs) (0,0125 %, 5 %) to evaluate the transcriptional activity by Real-Time PCR. To assess acute toxicity, larvae were exposed for 24 h and genes related to the endocrine system, stress response, DNA repair mechanisms, immune system, oxidative stress, and detoxification mechanisms were evaluated. The activity of the enzymes: glutathione S-transferase (GST) and catalase was also examined. The main pathway affected was the stress response showing overexpression of HSPs (HSC70.3, HSC70.4, HSC70.5, HSP60). Moreover, there was a reduction of the GSTd3 and catalase disrupting the antioxidant system. The upregulation of InR indicates a potential disturbance in the insulin pathway and ABCB6 activation only in TRPs exposure suggests its potential implication in their transport. However, most of these alterations are caused by TRLs, showing higher toxicity than TRPs. The results obtained in this work provide the first approach at the molecular and cellular levels to elucidate the impact of TRLs in freshwater organisms. To perform a realistic evaluation of the TR effects, additional research is required to assess the TR's long-term effects at the molecular level.