Sources of microplastics pollution in the marine environment: Importance of wastewater treatment plant and coastal landfill

Assessment of microplastic contamination in compost leachate: insights from a municipal compost plant in Isfahan, Iran

The increasing production of waste has become one of the major environmental challenges of our time, particularly in waste management. While the composting process can transform municipal waste into a valuable product, the presence of plastics and microplastics (MPs) (< 5 mm) in the waste and their integration into the final compost and leachate pose significant environmental concerns. This is the first study to analyze the abundance of MP in the compost leachate from one of the Isfahan compost plant (S1), located in one of Iran's major cities with high population density, during the summer season. MPs were counted using a stereomicroscope, and fourier transform infrared spectroscopy (FTIR) was utilized to identify polymer types. The results revealed an average abundance of MPs in the S1 leachate during the summer of 992.66 ± 100.85 items/L. Over 62% of the MPs identified in this study fell within the 1000-5000 μm size range, with a concentration of 610.28 ± 59.26 items/L. Polystyrene and polyamide emerged as the most frequently identified polymers (18.46% and 16.8%), and fragments were the most commonly observed shape among the MPs. This study underscores that compost leachate contains high concentrations of MPs that can disseminate into various environmental compartments such as groundwater, surface water, soil, and even air. Consequently, compost leachate should be recognized as a significant source of MPs entering the environment.

Key adsorbents and influencing factors in the adsorption of micro- and nanoplastics: A review

Microplastics and nanoplastics (MNPs) are emerging contaminants in drinking water sources that pose serious risks to human health and ecosystems. Several removal strategies, such as adsorption, exist but present challenges for their industrial scalability. This review provides a concise overview of MNP adsorption mechanisms and highlights the limited but critical exploration of column adsorption in the literature, emphasizing its importance for large-scale applications. Special attention is given to carbon-based materials due to their cost-effectiveness, environmental friendliness and sustainability. Other adsorbents (e.g., metal-organic frameworks, clays) are also discussed for their promising performance in realistic water matrixes. To predict and optimize the efficiency of adsorbents, leading simulation models are reviewed. Taken together, this work provides a comprehensive overview of the fundamental factors, such as adsorption mechanisms, adsorbent selection and experimental conditions, to optimize MNP adsorption. By highlighting the underexplored area of column-based processes, it provides valuable information to advance adsorption as a viable industrial-scale solution for MNP contamination.

Machine learning outperforms humans in microplastic characterization and reveals human labelling errors in FTIR data

Microplastics are ubiquitous and appear to be harmful, however, the full extent to which these inflict harm has not been fully elucidated. Analysing environmental sample data is challenging, as the complexity in real data makes both automated and manual analysis either unreliable or time-consuming. To address challenges, we explored a dense feed-forward neural network (DNN) for classifying Fourier transform infrared (FTIR) spectroscopic data. The DNN provides conditional class distributions over 16 microplastic categories given an FTIR spectrum, exceeding number of categories in other works. Our results indicate that this DNN, which is significantly smaller than contemporary models, outperforms other models and even human classification performance. Specifically, while the model broadly reproduces the decisions of human annotators, in cases of disagreement either both were incorrect or the human annotation was incorrect. The errors not being reproduced indicate that the DNN is making informed generalisable decisions. Additionally, this work indicates that there exists an upper limit on metrics measuring performance, where metrics measure agreement between human and model predictions. This work indicates that a small and efficient DNN can making high throughput analysis of difficult FTIR data possible, where predictions match or exceed the reliability typical to low-throughput methods.

Microplastic pollution in surface waters of urban canals in a highly urbanized city (Dunkirk, Northern France): influence of dry and wet periods on discharge to the sea

Microplastic (MP) pollution is a growing environmental concern, with urban waterways constituting critical pathways for transporting MPs into marine ecosystems. This study investigated the distribution, abundance, diversity, and flux of MPs in six urban canals influenced by urban and industrial activities in the city of Dunkirk, during dry and wet (rainy) periods. Plastic abundance was higher during the wet period (18.25 ± 22.16 particles/m3) compared to the dry period (8.14 ± 7.76 particles/m3), reflecting increased inputs from surface runoff and stormwater discharge. Spatial trends revealed distinct site-specific patterns, with the most urbanized sites (S1 and S6) exhibiting the highest abundances. Fibers were the dominant type accounting for over 75% of particles at all sites. PET was the main polymer in urban sites, while PE and PP were more prevalent in industrial zones. The estimated annual flux of MP at the outlet ranged from 19.21 × 106 ± 26.12 × 105 particles/year/m3 (dry period) to 23.97 × 107 ± 19.41 × 106 particles/year/m3 (wet period), revealing the significant contributions of urban canals to coastal pollution. These results highlight the need for improved source control and stormwater management to better assess and mitigate MP pollution in urban aquatic systems.

Micro- and nano-plastics pollution in the marine environment: Progresses, drawbacks and future guidelines

Marine pollution by micro/nanoplastics (M/NPs) has emerged as a critical global issue, with widespread ecological and economic consequences. Numerous studies have investigated M/NPs pollution in marine environments, but there remains a need to assess progress, identify challenges, and propose future strategies. This review provides updated insights into marine M/NPs, including their sources, detection methods, global data from diverse marine ecosystems, and the challenges in mitigating pollution. The review reveals that the ocean harbors approximately 5.25 trillion plastic debris pieces, with a total of 50-75 trillion plastic and microplastic particles, with deep-sea regions containing up to 4 billion plastic microfibers per square kilometer. Human activities, including industrial practices and aquaculture, are major contributors to M/NPs pollution, which threatens 17% of marine species and incurs an economic loss of 6-9 billion USD. M/NPs are found across various marine habitats, including shorelines, sea floors, water columns, biota, and floating debris. Analyzing nanoplastics is particularly challenging due to their heterogeneous aggregation with other contaminants and their much lower concentrations than natural particles. Key drawbacks in addressing M/NPs pollution include inadequate funding, insufficient regulations, and a lack of policy frameworks on the prevalence, distribution, and sources of M/NPs. There is an increasing focus on utilizing innovative technologies such as artificial intelligence (AI) to monitor, assess risks, and predict the spread of M/NPs. Therefore, urgent global cooperation, involving all stakeholders and the general public, is essential. Additionally, integrating scientific and engineering methods, along with AI technologies, is crucial for monitoring and controlling M/NPs pollution and developing sustainable solutions.

Remediation of Micro- and Nanoplastics by Membrane Technologies

Micro- and nanoplastics (NPs) cannot be completely removed from water/wastewater in conventional wastewater treatment plants (WWTPs) and drinking water treatment plants (DWTPs). According to the literature analysis, membrane processes, one of the advanced treatment technologies, are the most effective and promising technologies for the removal of microplastics (MPs) from water and wastewater. In this article, firstly, the properties of MPs commonly found in water and wastewater treatment and their removal efficiencies are briefly reviewed. In addition, research on the use of microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), and membrane bioreactors (MBR) for the remediation of MPs and NPs from water/wastewater is reviewed, and the advantages/disadvantages of each removal method are discussed. Membrane filtration is also compared with other methods used to remove MPs. Furthermore, the problem of membrane fouling by MPs during filtration and the potential for MPs to be released from the polymeric membrane structure are discussed. Finally, based on the literature survey, the current status and gaps in research on MPs removal by membrane technologies are identified, and recommendations for further research are made.

Zebrafish and Drosophila as Model Systems for Studying the Impact of Microplastics and Nanoplastics ‐ A Systematic Review

Microplastics and nanoplastics (MNPs) are byproducts of plastics created to benefit humanity, but improper disposal and inadequate recycling have turned them into a global menace that we can no longer conceal. As they interact with all living organisms, including humans, their mechanism of interaction and their perilous impact must be meticulously investigated. To uncover the secrets of MNPs, there must be model systems that exist to interlink the two major scenarios: they must represent the environmental impact and be relevant to humans. Therefore, zebrafish and Drosophila are perfect to describe these two cases, as they are well studied and relatable to humans. In this review, 39% zebrafish studies reported higher mortality and hatching rates at greater MNP concentrations, severe oxidative stress as seen by raised malondialdehyde (MDA) levels, and reduced superoxide dismutase (SOD) activity. About 50% of studies showed severe neurotoxic behavior with drop of locomotor activity, suggesting neurotoxicity. MNPs have a significant impact on fertility rate of Drosophila. More than half of the studies revealed genotoxicity in Drosophila as observed by wing spot assays and modified genomic expressions associated with stress and detoxification processes. These findings emphasize the potential of MNPs to bioaccumulate, impair physiological systems, and cause oxidative and neurobehavioral damage. This study underscores the importance for thorough risk evaluations of MNPs and their environmental and health consequences.

Emerging investigator series: open dumping and burning: an overlooked source of terrestrial microplastics in underserved communities

Open dumping and burning of solid waste are widely practiced in underserved communities lacking access to solid waste management facilities; however, the generation of microplastics from these sites has been overlooked. We report elevated concentrations of microplastics (MPs) in soil of three solid waste open dump and burn sites: a single-family site in Tuttle, Oklahoma, USA, and two community-wide sites in Crow Agency and Lodge Grass, Montana, USA. We extracted, quantified, and characterized MPs from two soil depths (0-9 cm and 9-18 cm). The average of abundance of particles found at community-wide sites three sites (18, 460 particles kg-1 soil) equals or exceeds reported concentrations from currently understood sources of MPs including biosolids application and other agricultural practices. Attenuated total reflectance Fourier transformed infrared (ATR-FTIR) identified polyethylene as the dominant polymer across all sites (46.2-84.8%). We also detected rayon (≤11.5%), polystyrene (up to 11.5%), polyethylene terephthalate (≤5.1), polyvinyl chloride (≤4.4%), polyester (≤3.1), and acrylic (≤2.2%). Burned MPs accounted for 76.3 to 96.9% of the MPs found in both community wide dumping sites. These results indicate that solid waste dumping and burning activities are a major source of thermally oxidized MPs for the surrounding terrestrial environment with potential to negatively affect underserved communities.

Emerging contaminants in the Mediterranean Sea endangering Lebanon's Palm Islands Natural Reserve

The Mediterranean Sea is an intercontinental marine environment renowned for its biodiversity and ecological significance. However, it is also one of the most polluted seas globally with significant levels of microplastics and heavy metals among other emerging contaminants. In Lebanon, inadequate waste management infrastructure and unregulated industrial discharges have exacerbated water quality deterioration by introducing these complex contaminants into surface and seawater. The Palm Islands Natural Reserve in Lebanon is a UNESCO-designated marine protected area and home to endangered species. However, the reserve faces significant threats from pollution, including heavy metals and microplastics, exacerbated by nearby Tripoli's escalating contamination. Plasticisers, particularly phthalates, are recognized for their hormone-disrupting effects, and heavy metals like cadmium, lead, and arsenic pose severe eco-toxicological risks. This study investigates the levels of heavy metals and phthalates in water and sediments from the Palm Islands. Samples were collected from different locations within the reserve, and heavy metals and phthalates were detected, including chromium (13.58 to 19.28 μg L-1), arsenic (2.05 to 5.04 μg L-1), cadmium (1.27 to 3.04 μg L-1), and lead (0.92 to 2.88 μg L-1). Cadmium levels exceeded the permissible limits set by environmental regulatory bodies, highlighting an urgent pollution problem. Phthalates, including DEP and DEHP, were also detected in concentrations of 7.12-10.25 μg L-1 for DEP and 38.47-56.12 μg L-1 for DEHP raising concerns over their potential eco-toxicological impact on marine species. Our research underscores the need for comprehensive environmental monitoring, better waste management infrastructure, and stricter regulatory measures to address pollution in Lebanon's coastal ecosystems.

A review of liquid crystal monomers (LCMs) as emerging contaminants: Environmental occurrences, emissions, exposure routes and toxicity

The widespread occurrence of liquid crystal monomers (LCMs) in the environment has raised concerns about their persistence, bioaccumulation, and toxicity (PBT). Here we review the lifecycle of environmental LCMs, focusing on their occurrences, emission sources, human exposure routes, and toxicity. Industrial emissions from Liquid Crystal Display (LCD) manufacturing and e-waste recycling are the primary point sources of LCMs. In addition, emissions from LCD products, air conditioning units, wastewater treatment plants, and landfills contribute to environmental occurrence of LCMs as secondary sources. Dietary routes were identified as the primary exposure pathways to humans. E-waste dismantling workers and infants/children are vulnerable populations to LCMs exposure. Exposure to LCMs has been shown to potentially induce oxidative stress, metabolic disorders, and endocrine disruption. Accumulation of LCMs in the brain and liver tissues of exposed animals highlights the need for toxicokinetic studies.

Microplastics and per- and polyfluoroalkyl substances (PFAS) in landfill-wastewater treatment systems: A field study

Landfills and wastewater treatment plants (WWTP) are point sources for many emerging contaminants, including microplastics and per- and polyfluoroalkyl substances (PFAS). Previous studies have estimated the abundance and transport of microplastics and PFAS separately in landfills and WWTPs. In addition, previous studies typically report concentrations of microplastics as particle count/L or count/g sediment, which do not provide the information needed to calculate mass balances. We measured microplastics and PFAS in four landfill-WWTP systems in Illinois, USA, and quantified mass of both contaminants in landfill leachate, WWTP influent, effluent, and biosolids. Microplastic concentrations in WWTP influent were similar in magnitude to landfill leachates, in the order of 102 μg plastic/L (parts-per-billion). In contrast, PFAS concentrations were higher in leachates (parts-per-billion range) than WWTP influent (parts-per-trillion range). After treatment, both contaminants had lower concentrations in WWTP effluent, although were abundant in biosolids. We concluded that WWTPs reduce PFAS and microplastics, lowering concentrations in the effluent that is discharged to nearby surface waters. However, partitioning of both contaminants to biosolids may reintroduce them as pollutants when biosolids are landfilled or used as fertilizer.

Microplastic migration from landfill-mined soil through earth filling operations and ecological risk assessment: a case study in New Delhi, India

Microplastics (MPs), plastic pieces smaller than 5 mm, are emerging as a critical ecological threat, potentially disrupting ecosystems and complicating waste management practices. Landfill-Mined Soil-Like Material (LMSLM), a byproduct of landfill reclamation, is gaining global traction for rehabilitating degraded land and repurposing it for geotechnical applications. While studies have examined contaminants like heavy metals and salts, MPs contamination has been largely overlooked, raising environmental concerns. The widespread use of LMSLM in earth-filling increases the risk of MP pollution. Additionally, significant gaps remain in understanding how MPs are distributed across different size fractions during sieving, which is critical for developing effective remediation strategies and informing future policies. This study aims to fill the existing knowledge gap by investigating the presence of microplastics in LMSLM collected from three aged waste dumpsites in New Delhi, India, and evaluating the ecological risks associated with its reuse. The results revealed the presence of MPs in all LMSLM samples with concentrations ranging from 25950 to 41110 items/kg. Fibers and fragments were the dominant shapes, with 60 % of particles measuring less than 425 µm. The color characteristics revealed the dominance of white, transparent, and black color. Polyethylene and polypropylene were the most common polymers, with smaller amounts of polyamide, polyethylene terephthalate, and polyester. SEM-EDX analysis revealed weathering effects and the presence of heavy metals, including Lead (Pb), Cadmium (Cd), and Arsenic (As), adsorbed on the MP surface. Ecological risk assessment using the Polymer Hazard Index and Pollution Load Index identified hazard levels of V and II, respectively, while the Potential Ecological Risk Index indicated a medium risk. Furthermore, the dimensional analysis demonstrates that MP width, particularly in fiber-shaped MPs, plays a crucial role in determining retention and migration during sieving, while MPs with uniform shapes, like spheres and fragments, exhibit limited movement. These findings underscore the need for protective measures when using LMSLM in geotechnical applications to prevent MP migration and contamination of surrounding environments. The study highlights the importance of further research on MP contamination in reclaimed landfill materials and its implications for sustainable land use and waste management.

Biodegradation of poly(butylene adipate terephthalate) and poly(vinyl alcohol) within aquatic pathway

Understanding the environmental fate of biodegradable plastics in aquatic systems is crucial, given the alarming amount of plastic waste and microplastic particles transported through aquatic pathways. In particular, there is a need to analyze the biodegradation of commercialized biodegradable plastics upon release from wastewater treatment plants into natural aquatic systems. This study investigates the biodegradation behaviors of poly(butylene adipate terephthalate) (PBAT) and poly(vinyl alcohol) (PVA) in wastewater, freshwater, and seawater. Biodegradation of PBAT and PVA assessed through biochemical oxygen demand (BOD) experiments and microcosm tests revealed that the type of aquatic system governs the biodegradation behaviors of each plastic, with the highest biodegradation rate achieved in wastewater for both PBAT and PVA (25.6 and 32.2 % in 30 d, respectively). Plastic release pathway from wastewater into other aquatic systems simulated by sequential incubation in different microcosms suggested that PBAT exposed to wastewater and freshwater before reaching seawater was more prone to degradation than when directly exposed to seawater. On the other hand, PVA displayed comparable biodegradation rate regardless of whether it was directly exposed to seawater or had passed through other environments beforehand. Metagenome amplicon sequencing of 16S rRNA genes revealed distinct community shifts dependent on the type of plastics in changing environments along the simulated aquatic pathway. Several bacterial species putatively implicated in the biodegradation of PBAT and PVA are discussed. Our findings underscore the significant influence of pollution routes on the biodegradation of PBAT and PVA, highlighting the potential for wastewater treatment to facilitate rapid degradation compared to direct exposure to pristine aquatic environments.

Mechanisms of Polyethylene Terephthalate Pellet Fragmentation into Nanoplastics and Assimilable Carbons by Wastewater Comamonas

Comamonadaceae bacteria are enriched on poly(ethylene terephthalate) (PET) microplastics in wastewaters and urban rivers, but the PET-degrading mechanisms remain unclear. Here, we investigated these mechanisms with Comamonas testosteroniKF-1, a wastewater isolate, by combining microscopy, spectroscopy, proteomics, protein modeling, and genetic engineering. Compared to minor dents on PET films, scanning electron microscopy revealed significant fragmentation of PET pellets, resulting in a 3.5-fold increase in the abundance of small nanoparticles (<100 nm) during 30-day cultivation. Infrared spectroscopy captured primarily hydrolytic cleavage in the fragmented pellet particles. Solution analysis further demonstrated double hydrolysis of a PET oligomer, bis(2-hydroxyethyl) terephthalate, to the bioavailable monomer terephthalate. Supplementation with acetate, a common wastewater co-substrate, promoted cell growth and PET fragmentation. Of the multiple hydrolases encoded in the genome, intracellular proteomics detected only one, which was found in both acetate-only and PET-only conditions. Homology modeling of this hydrolase structure illustrated substrate binding analogous to reported PET hydrolases, despite dissimilar sequences. Mutants lacking this hydrolase gene were incapable of PET oligomer hydrolysis and had a 21% decrease in PET fragmentation; re-insertion of the gene restored both functions. Thus, we have identified constitutive production of a key PET-degrading hydrolase in wastewater Comamonas, which could be exploited for plastic bioconversion.

Deciphering morphology patterns of environmental microfibers: Insights into source apportionment

Microfibers, a prevalent form of microplastics, undergo diverse environmental interactions resulting in varied morphological changes. These changes can offer insights into their environmental trajectories. Despite its importance, comprehensive studies on microfiber morphology are scarce. This study collected 233 microfibers from the East China Sea and South China Sea. Based on morphological features observed in microscopic images of microfibers, such as curvature, cross-sectional shapes, diameter variations, and crack shapes, we identified a general morphological pattern, classifying the environmental microfibers into three distinct morphological types. Our findings highlight noticeable differences in morphological metrics (e.g., length, diameter, and surface roughness) across three types, especially the diameter. Microfibers of Type I had an average diameter of 19.45 ± 4.93 μm, significantly smaller than Type II (263.00 ± 75.15 μm) and Type III (299.68 ± 85.62 μm). Within the three-dimensional (3D) space fully defined by these quantitative parameters, the clustering results of microfibers are also consistent with the proposed morphology pattern, with each category showing a potential correlation with specific chemical compositions. Type I microfibers correspond to synthetic cellulose, while 94.79 % of Types II and III are composed of polymers. Notably, we also validated the great applicability of the morphology categories to microfibers in diverse environmental compartments, including water and sediments in nearshore and offshore areas. This classification aids in the efficient determination of microfiber sources and the assessment of their ecological risks, marking a significant advancement in microfiber environmental studies.

Characterization and removal of microplastics in the Guheshwori Wastewater Treatment Plant, Nepal

Contamination of river water systems by microplastic particles (MPPs) is one of the emerging global environmental concerns with potentially widespread ecological, socioeconomic, and health implications. A wastewater treatment plant (WWTP) processes and treats wastewater to remove pollutants and release safe water into the environment. There has been limited research on the characterization of microplastics and their removal in WWTP in South Asia. In this work, we report on the characterization of microplastics in wastewater and sludge samples (n = 300) from Guheshwori WWTP located on the bank of the Bagmati River in Kathmandu city, Nepal representing inlet, secondary aeration tank (SAT), outlet, and sludge from November 2021 to November 2022. On average, we detected 31.2 ± 17.3 MPPs/L, 11.2 ± 9.4 MPPs/L, 8.5 ± 5.6 MPPs/L, and 6.6 ± 4.8 MPPs/g in the samples collected from inlet, SAT, outlet, and sludge, respectively. Commonly found MPPs were in the form of fiber, fragments, foam, and pellets. Largely, MPPs were red, yellow, white, blue, and black. Among the 44 μm - 150 μm, 150 μm - 500 μm and 500 μm - 5 mm categories of size fractions, the most dominant fractions were 500 μm - 150 μm in inlet, SAT, and sludge, and 150 μm - 44 μm in the outlet sampling unit. The Guheshwori WWTP was able to remove 72.5 % of MPPs on average, that mostly occurred in the inlet. The effluent released into the river and the sludge still contained a significant number of MPPs.

Beyond surface: Unveiling ecological and economic ramifications of microplastic pollution in the oceans

Every year, the global production of plastic waste reaches a staggering 400 million metric tons (Mt), precipitating adverse consequences for the environment, food safety, and biodiversity as it degrades into microplastics (MPs). The multifaceted nature of MP pollution, coupled with its intricate physiological impacts, underscores the pressing need for comprehensive policies and legislative frameworks. Such measures, alongside advancements in technology, hold promise in averting ecological catastrophe in the oceans. Mandated legislation represents a pivotal step towards restoring oceanic health and securing the well-being of the planet. This work offers an overview of the policy hurdles, legislative initiatives, and prospective strategies for addressing global pollution due to MP. Additionally, this work explores innovative approaches that yield fresh insights into combating plastic pollution across various sectors. Emphasizing the importance of a global plastics treaty, the article underscores its potential to galvanize collaborative efforts in mitigating MP pollution's deleterious effects on marine ecosystems. Successful implementation of such a treaty could revolutionize the plastics economy, steering it towards a circular, less polluting model operating within planetary boundaries. Failure to act decisively risks exacerbating the scourge of MP pollution and its attendant repercussions on both humanity and the environment. Central to this endeavor are the formulation, content, and execution of the treaty itself, which demand careful consideration. While recognizing that a global plastics treaty is not a panacea, it serves as a mechanism for enhancing plastics governance and elevating global ambitions towards achieving zero plastic pollution by 2040. Adopting a life cycle approach to plastic management allows for a nuanced understanding of possible trade-offs between environmental impact and economic growth, guiding the selection of optimal solutions with socio-economic implications in mind. By embracing a comprehensive strategy that integrates legislative measures and technological innovations, we can substantially reduce the influx of marine plastic litter at its sources, safeguarding the oceans for future generations.

Pilot-scale performance of gravity-driven ultra-high flux fabric membrane systems for removing small-sized microplastics in wastewater treatment plant effluents

The ubiquitous nature and environmental impacts of microplastic particles and fibers demand effective solutions to remove such micropollutants from sizable point sources, including wastewater treatment plants and road runoff facilities. While advanced methods, e.g., microfiltration and ultrafiltration, have shown high removal efficiencies of small-sized microplastics (<150 μm), the low flux encountered in these systems implies high operation costs and makes them less effective in high-capacity wastewater facilities. The issue presents new opportunities for developing cheap high-flux membrane systems, deployable in low-to high-income economies, to remove small-sized microplastic and nanoplastics in wastewater. Here, we report on developing an ultra-high flux gravity-driven fabric membrane system, assessed through a laboratory-scale filtration and large-scale performance in an actual wastewater treatment plant (WWTP). The method followed a carefully designed water sampling, pre-treatment protocol, and analytical measurements involving Fourier transform infrared (FTIR) spectroscopy and laser direct infrared (LDIR) imaging. The result shows that the ultra-high flux (permeance = 550,000 L/m2h⋅bar) fabric membrane system can effectively remove small-sized microplastics (10-300 μm) in the secondary effluent of an actual WWTP at high efficiency greater than 96 %. The pilot system demonstrated a continuous treatment capacity of 300,000 L/day through a 1 m2 surface area disc, with steady removal rates of microplastics. These findings demonstrate the practical, cheap, and sustainable removal of small-sized microplastics in wastewater treatment plants, and their potential value for other large-scale point sources, e.g., stormwater treatment facilities.

Nano-based remediation strategies for micro and nanoplastic pollution

Due to rapid urbanization, there have been continuous environmental threats from different pollutants, especially from microplastics. Plastic products rapidly proliferate significantly contributing to the occurrence of micro-plastics, which poses a significant environmental risk. These microplastics originated from diverse sources and are characterized by their persistent and widespread occurrence; human health and the entire ecosystem are adversely affected by them. The removal of microplastics not only requires innovative technologies but also efficient materials capable of effectively eliminating them from our environment. The progress made so far has highlighted the advantages of utilizing the dimensional and structural properties of nanomaterials to increase the effectiveness of existing methods for micro-plastic treatment, aiming for a more sustainable approach to their removal. In the current review, we demonstrate a thorough overview of the sources, occurrences, and potential harmful effects of microplastics, followed by a further discussion of promising technologies used for their removal. An in-depth examination of both advantages and a few limitations of all these given technologies, including physical, chemical, and biological approaches, has been discussed. Additionally, the review explores the use of nanomaterials as an effective means to overcome obstacles and improve the efficiency of microplastic elimination methods. n conclusion, this review addresses, current challenges in this field and outlines the future perspectives for further research in this domain.

Optimization and application of pretreatment method of microplastics detection in municipal solid waste landfills

The landfill is one of the most important sources of microplastics (MPs). The pretreatment method is a precondition of microplastics study for the presence of complex substances in landfills. Therefore, it is essential to examine the impact of different pretreatment methods on the microplastics detection. A literature review and a comparison experiment on digestion solutions were performed to establish a comprehensive identification method for MPs in landfills. When exposed to of 30 % H2O2, minimal mass reduction of PE, PP and PET were 4.00 %, 3.00 % and 3.00 % respectively, and the least surface damage was observed in MPs, while exhibiting the most optimal peak value for infrared spectral characteristics. It is demonstrated that the effect of 30 % H2O2 dissolution was superior compared to 10 % KOH and 65 % HNO3. The method was subsequently utilized to investigate the distribution of MPs in a landfill. The dominant MPs were polyethylene (PE, 18.56-23.91 %), polyethylene terephthalate (PET, 8.80-18.66 %), polystyrene (PS, 10.31-18.09 %), and polypropylene (PP, 11.60-14.91 %). The comprehensive identification method of "NaCl density separation + 30 % H2O2 digestion + NaI density separation + sampling microscope + Mirco-FTIR" is suitable for the detection of MPs in landfills.

Dynamics of microplastic abundance under tidal fluctuation in Musi estuary, Indonesia

Tidal dynamics contribute to fluctuations in microplastic abundance (MPs). This is the first study to characterize MPs under the influence of tidal fluctuations in the Musi River Estuary. MPs samples were collected during flood and ebb tides at 10 research stations representing the inner, middle and outer parts of the Musi River Estuary. MPs were extracted to identify the shape, color and size. MP abundances were 467.67 ± 127.84 particles/m3 during flood tide and 723.67 ± 112.05 particles/m3 during ebb tide. The concentration of MPs in the outer zone of the estuary (ocean) was detected to be higher than in the inner zone of the estuary (river). The MPs found were dominated by black color, film shape and size 101-250 μm. A greater abundance of MPs at ebb tide than at flood tide implies that the Musi Estuary's largest source of emissions is discharge from the river.

Snow dumping station - A considerable source of tyre wear, microplastics, and heavy metal pollution

Snow dumping stations can be a hotspots for pollutants to water resources. However, little is known about the amount of microplastics including tyre wear particles transported this way. This study investigated microplastics and metals in snow from four snow dumping stations in Riga, Latvia, a remote site (Gauja National Park), and a roof top in Riga. Microplastics other than tyre wear particles were identified with Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) (>500 µm) and focal plane array based micro-Fourier Transform Infrared (FPA-µFTIR) imaging (10-500 µm), tyre wear particles by Pyrolysis Gas Chromatography-Mass Spectroscopy (Py-GC-MS), and total metals by Inductively Coupled Plasma with Optical Emission Spectroscopy (ICP-OES). Microplastics detected by FTIR were quantified by particle counts and their mass estimated, while tyre wear particles were quantified by mass. The concentrations varied substantially, with the highest levels in the urban areas. Microplastic concentrations measured by FTIR ranged between 26 and 2549 counts L-1 of melted snow with a corresponding estimated mass of 19-573 µg/L. Tyre wear particles were not detected at the two reference sites, while other sites held 44-3026 µg/L. Metal concentrations varied several orders of magnitude with for example sodium in the range 0.45-819.54 mg/L and cadmium in the range 0.05-0.94 µg/L. Correlating microplastic measured by FTIR to metal content showed a weak to moderate correlation. Tyre wear particles, however, correlated strongly to many of the metals. The study showed that snow can hold considerable amounts of these pollutants, which upon melting and release of the meltwater to the aquatic environment could impact receiving waters.

Influencing factors of microplastic generation and microplastic contamination in urban freshwater

This research analyzes data on the microplastic (MP) contamination in the environmental systems (atmosphere, lithosphere, hydrosphere) and the levels of MPs in freshwater of cities with different levels of national income. This study investigates the influencing factors of MP generation, i.e., mismanaged plastic waste, untreated wastewater, number of registered motor vehicles, and stormwater runoff. The statistical correlations between the MP contamination in urban freshwater and the four influencing factors of MP generation are determined by linear regression. The results indicate that MPs are most abundant in aquatic systems (i.e., hydrosphere) and pose a serious threat to the human food chain. The regression analysis shows a strong correlation between mismanaged plastic waste and microfragment smaller than 300 μm in particle size in urban freshwater with high goodness-of-fit (R2 = 0.8091). A strong relationship with high goodness-of-fit also exists between untreated wastewater and microfragment of 1000-5000 μm in particle size (R2 = 0.9522). The key to mitigate the MP contamination in urban freshwater is to replace improper plastic waste management and wastewater treatment with proper management practices.

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.

Plastic pollution in Moreton Bay sediments, Southeast Queensland, Australia

The mounting issue of plastic waste in the aquatic ecosystem is a growing source of concern. Most plastic waste originates on land and a significant proportion of this eventually finds its way into the marine environment, which is widely regarded as a major repository for plastic debris. Currently, there exists a substantial gap in our understanding of how much plastic, the main polymer types, and the distribution of plastic in the marine environment. This study aimed to provide information on mass concentrations of a range of plastics in the surface sediments in the semi-enclosed Moreton Bay, just offshore the large city of Brisbane, Southeast Queensland, Australia. Surface sediment samples were quantitatively analysed for a suite of 7 common plastic polymer types (i.e., polystyrene (PS), polycarbonate (PC), poly-(methyl methacrylate) (PMMA), polypropylene (PP), polyethylene terephthalate (PET), polyethylene (PE) and polyvinyl chloride (PVC)) using a pressurized liquid extraction (PLE) followed by double-shot microfurnace pyrolysis coupled to gas chromatography mass spectrometry (Pyr-GC/MS). The advantage of this approach is that it can measure plastics below the limit of visual detection. The study revealed that Σ7plastics were consistently present in the samples, although the concentrations displayed a wide range of concentrations from 3.3 to 2194.2 μg/g across different sites. Among the polymers analysed, PE and PVC were found at the highest concentrations, ranging from 2.3 to 1885.9 μg/g and 3.0-979.5 μg/g, respectively. Based on the average concentrations of plastics measured, the dry bulk density and volume of sediments within the top 10 cm of the bay, it was estimated that there is a minimum of 7000 t of plastics stored in the surface sediments of the bay. This study is the first to report the mass concentrations of identified plastics and identify the main polymer types in Moreton Bay. This is important information to develop management plans to reduce the plastic waste entering the coastal marine environment.

Microplastic contamination in wastewater: Sources, distribution, detection and remediation through physical and chemical-biological methods

Microplastics are tiny plastic particles smaller than 5 mm. that have been widely detected in the environment, including in wastewater. They originate from various sources including breakdown of larger plastic debris, release of plastic fibres from textiles, and microbeads commonly used in personal care products. In wastewater, microplastics can pass through the treatment process and enter the environment, causing harm to biodiversity by potentially entering the food chain. Additionally, microplastics can act as a vector for harmful pollutants, increasing their transport and distribution in the environment. To address this issue, there is a growing need for effective wastewater treatment methods that can effectively remove microplastics. Currently, several physical and chemical methods are available, including filtration, sedimentation, and chemical degradation. However, these methods are costly, low efficiency and generate secondary pollutants. Furthermore, lack of standardization in the measurement and reporting of microplastics in wastewater, makes it difficult to accurately assess microplastic impact on the environment. In order to effectively manage these issues, further research and development of effective and efficient methods for removing microplastics from wastewater, as well as standardization in measurement and reporting, are necessary to effectively manage these detrimental contaminants.

Are we underestimating stormwater? Stormwater as a significant source of microplastics in surface waters

Stormwater represent a critical pathway for transporting microplastics (MPs) to surface waters. Due to complex dynamics of MPs in stormwater, its dispersion, weathering, risk, and transport are poorly understood. This review bridges those gaps by summarizing the latest findings on sources, abundance, characteristics, and dynamics involved in stormwater MP pollution. Weathering starts before or after MPs enter stormwater and is more pronounced on land due to continuous heat and mechanical stress. Land use patterns, rainfall intensity, MPs size and density, and drainage characteristics influence the transport of MPs in stormwater. Tire and road wear particles (TRWPs), littering, and road dust are major sources of MPs in stormwater. The concentrations of MPs varies from 0.38-197,000 particles/L globally. Further MP concentrations showed regional variations, highlighting the importance of local monitoring efforts needed to understand local pollution sources. We observed unique signatures associated with the shape and color of MPs. Fibers and fragments were widely reported, with transparent and black being the predominant colors. We conclude that the contribution of stormwater to MP pollution in surface waters is significantly greater than wastewater treatment plant effluents and demands immediate attention. Field and lab scale studies are needed to understand its behavior in stormwater and the risk posed to the downstream water bodies.

Leachate from municipal solid waste landfills: A neglected source of microplastics in the environment

Over the past decade or so, microplastics (MPs) have received increasing attention due to their ubiquity and potential risk to the environment. Waste plastics usually end up in landfills. These plastics in landfills undergo physical compression, chemical oxidation, and biological decomposition, breaking down into MPs. As a result, landfill leachate stores large amounts of MPs, which can negatively impact the surrounding soil and water environment. However, not enough attention has been given to the occurrence and removal of MPs in landfill leachate. This lack of knowledge has led to landfills being an underestimated source of microplastics. In order to fill this knowledge gap, this paper collects relevant literature on MPs in landfill leachate from domestic and international sources, systematically summarizes their presence within Asia and Europe, assesses the impacts of landfill leachate on MPs in the adjacent environment, and particularly discusses the possible ecotoxicological effects of MPs in leachate. We found high levels of MPs in the soil and water around informal landfills, and the MPs themselves and the toxic substances they carry can have toxic effects on organisms. In addition, this paper summarizes the potential impact of MPs on the biochemical treatment stage of leachate, finds that the effects of MPs on the biochemical treatment stage and membrane filtration are more significant, and proposes some novel processes for MPs removal from leachate. This analysis contributes to the removal of MPs from leachate. This study is the first comprehensive review of the occurrence, environmental impact, and removal of MPs in leachate from landfills in Asia and Europe. It offers a comprehensive theoretical reference for the field, providing invaluable insights.

Organic pollutants adsorbed on microplastics: Potential indicators for source appointment of microplastics

Pollution by microplastics (MPs) has caused potential threats to the environment. Understanding the sources of MPs in the environment can help control their emissions and reduce environmental risks. Source apportionment of MPs has been conducted according to the characteristics of MPs themselves (such as types of polymers and morphological characteristics). However, the specificity and resolution of the appointments of sources need to be improved. Organic pollutants adsorbed on MPs can be used as a novel and reliable indicator to identify the source of MPs in the environment. In the present work, the analytical methods of MPs and organic pollutants adsorbed on MPs were critically reviewed, and the occurrence of organic pollutants and factors influencing their adsorption on MPs were discussed. Furthermore, the potential applications of organic pollutants adsorbed on MPs as indicators for determining the sources of MPs were highlighted. The study would help recognize the sources of MPs, which will support efforts aimed at reducing their emissions and further pollution of the ecosystem.

Current patterns and trends of microplastic pollution in the marine environment: A bibliometric analysis

Microplastics are pervasive in the natural environment and pose a growing concern for global health. Plastic waste in marine environments has emerged as a global issue, threatening not only marine biota but also human health due to its implications for the food chain. This study aims to discern the patterns and trends of research, specifically on Marine Microplastic Pollution (MMP), based on a bibliometric analysis of scientific publications from 2011 to 2022. The methodology utilized in this study comprises three stages: (a) creating a bibliographical dataset from Scopus by Elsevier and the Web of Science Core Collection by Clarivate Analytics, (b) analyzing current research (trends and patterns) using bibliometric analysis through Biblioshiny tool, and (c) examining themes and subthemes in MMP research (wastewater treatment, plastic ingestion, the Mediterranean Sea, microplastics pollution, microplastics in freshwater, microplastic ingestion, plastic pollution, and microplastic pollution in the marine environment). The findings reveal that during the studied period, the number of MMP publications amounted to 1377 articles, with an average citation per publication of 59.23 and a total citation count of 81,553. The most cited article was published in 2011, and since then, the number of publications on this topic has been increasing steadily. The author count stood at 5478, with 22 trending topics identified from the 1377 published titles. Between 2019 and 2022, the countries contributing most to the publication of MMP articles were China, the United States of America (USA), and the United Kingdom (UK). However, a noticeable shift in the origin of author countries was observed in the 2019-2022 timeframe, transitioning from a dominance by the USA and the UK to a predominance by China. In 2019, there was a substantial increase in the volume of publications addressing the topic of microplastics. The results show that the most prevalent themes and subthemes pertained to MMP in the Mediterranean Sea. The journals with the highest number of MMP articles published were the Marine Pollution Bulletin (253 articles) and Science of the Total Environment (190 articles). The analysis concludes that research on MMP remains prominent and appears to be increasing each year.

Identification of microplastics in raw and treated municipal solid waste landfill leachates in Hong Kong, China

Plastics are indispensable in modern society but also pose a persistent threat to the environment. In particular, microplastics (MPs) have a substantial environmental impact on ecosystems. Municipal solid waste landfill leachates are a source of MPs, but leakage of MPs from leachates has only been reported in a few studies. As a modern city, Hong Kong has a remarkably high population density and a massive plastic waste generation. However, it depends on conventional landfilling for plastic waste management and traditional thermal ammonia stripping for leachate treatment. Yet, the MP leakage from landfill leachates in Hong Kong has not been disclosed. This is the first study that aimed to identify, quantify, and characterise MPs in raw and treated leachates, respectively, from major landfill sites in Hong Kong. The concentrations of MPs varied from 49.0 ± 24.3 to 507.6 ± 37.3 items/L among the raw leachate samples, and a potential correlation was found between the concentration of MPs in the raw leachate sample from a given landfill site and the annual leachate generation of the site. Most MPs were 100-500 μm fragments or filaments and were transparent or yellow. Regarding the polymeric materials among the identified MPs, poly(ethylene terephthalate) and polyethylene were the most abundant types, comprising 45.30% and 21.37% of MPs, respectively. Interestingly, leachates treated by ammonia stripping contained higher concentrations of MPs than raw leachate samples, which demonstrated that the traditional treatment process may not be sufficient regarding the removal of emerging pollutants, such as MPs. Overall, our findings provide a more comprehensive picture of the pollution of MPs in landfill leachates in Hong Kong and highlight the urgent need for adopting the consideration of MPs into the conventional mindset of waste management systems in Hong Kong.

To what extent is blue mussels caging representative of microplastics in the natural environment?

Bivalves have gained prominence in active biomonitoring of microplastics (MPs) pollution. Nevertheless, critical questions persist regarding blue mussels' selectivity and representativeness of the presence of microplastics in the natural environments. In this current study, we explored short- and long-term exposure durations for caged mussels, aiming to establish the minimum period required for them to attain a steady-state in microplastics retention and investigate their selectivity in a real-world context. Various deployment periods (1, 2, and 5 weeks) were tested, with concurrent collection of MPs from the surrounding water each week. The results revealed a significant increase in ingested MPs, reaching a threshold of approximately 1.4 MPs per gram of wet weight during the fifth week of caging. The characteristics of MPs found in mussels exhibited some differences from those collected in the surrounding waters and were less temporally variable. Notably, the collected caged mussels demonstrated a tendency to retain smaller particles (<80 μm). This study underscores complex processes governing MPs selection in natural environments and the need for further research to gain a more comprehensive understanding of the conditions and suitability of mussels as bioindicators for assessing MPs pollution.

Carbon feasibility of terminating plastic waste leakage by landfill mining: A case study based on practical projects in China

Over 900 million tons (Mt) of plastic waste (PW) are disposed in Chinese landfills, posing a permanent risk of migration through environmental media. Landfill mining has emerged as a promising solution to this problem but requires incineration and a substantial energy supply for the excavation, sorting and recycling processes, which themselves exert environmental impacts, particularly on climate change. Based on the life cycle assessment of pilot-scale demonstration projects, this study investigates the carbon feasibility of landfill mining followed by several PW treatments to quantify whether terminating PW leakage from landfills will produce unaffordable greenhouse gas emissions in the drive towards carbon neutrality. The changing trend of the carbon feasibility was deduced considering the decarbonization scenarios of electricity sector and petrochemical industries. When all the sorted PW is treated by incineration with power generation, the climate-change impact of mining is 134.10 kg CO2-eq per ton of aged refuse, projected to increase by 100.47 % in 2050. To completely eliminate the PW in Chinese landfills, the incineration pathway would generate a minimum of 2457.66 Mt CO2-eq emissions, equivalent to 17.69 % of the 2020 emissions in China by carbon flow analysis. In all scenarios, the most carbon-feasible solution was mechanical recycling of high-quality PW combined with chemical recycling of low-quality PW, although the industrial application of chemical recycling technologies remains uncertain. This study provides stakeholders with systematic guidance for balancing the trade-off between PW management and climate action.

Forecasting global plastic production and microplastic emission using advanced optimised discrete grey model

Plastic pollution has become a prominent and pressing environmental concern within the realm of pollution. In recent times, microplastics have entered our ecosystem, especially in freshwater. In the contemporary global landscape, there exists a mounting apprehension surrounding the manifold environmental and public health issues that have emerged as a result of the substantial accumulation of microplastics. The objective of the current study is to employ an enhanced grey prediction model in order to forecast global plastic production and microplastic emissions. This study compared the accuracy level of the four grey prediction models, namely, EGM (1,1, α, θ), DGM (1,1), EGM (1,1), and DGM (1,1, α) models, to evaluate the accuracy levels. As per the estimation of the study, DGM (1,1, α) was found to be more suitable with higher accuracy levels to predict microplastic emission. The EGM (1,1, α, θ) model has slightly better accuracy than the DGM (1,1, α) model in predicting global plastic production. Various accuracy measurement tools (MAPE and RMSE) were used to determine the model's efficiency. There has been a gradual growth in both plastic production and microplastic emission. The current study using the DGM (1,1, α) model predicted that microplastic emission would be 1,084,018 by 2030. The present study aims to provide valuable insights for policymakers in formulating effective strategies to address the complex issues arising from the release of microplastics into the environment and the continuous production of plastic materials.

Incidence and exposure to microplastics in table salt present in the Iran market

Plastics and microplastics (MPs) are toxic, pervasive and threatening the biotic and abiotic components of the earth, and they threaten food safety and food security by moving in the food chain. In this study, the amounts and characteristics of 40 table salt samples with different brands, including sea salt (No = 13), rock (No = 13), bulk (No = 8) and non-standard (No = 6), were investigated with a combination of sieving, filtration, observation and FTIR, Micro-Raman and SEM techniques. The results showed that all the salts were contaminated with MPs. In general, the abundance range of detected particles was 700-5470 MPs/kg. The abundance of MPs was higher in counterfeit and non-standard salts (1825 ± 1808 MPs/kg). Investigating the relationship between the effect of the purification process (Kruskal-Wallis Test, P = 0.841), the type of packaging (Kruskal-Wallis Test, P = 0.609), and the type of salt (Kruskal-Wallis Test, P = 0.942), on the abundance of MPs using a comparison test Kruskal-Wallis was not significant. However, the numerical difference was recognizable. The most identified polymer in the salts was cellulose acetate, which probably causes by unmanaged plastic litter in the environment (especially cigarette butts). The dominant form of particles was fragment-shaped, which is the most abundant form of identified MPs in the environment. Both environmental pollution and secondary pollution (during production and packaging), respectively, contribute to the contamination of salts with MPs. The estimated human dietary intake (EDI) and the amount of estimated annual intake (EAI) for different ages in Iran were obtained EDI = 5-59 MPs/capita/day and EAI = 1967-21563 MPs/capita/year. The surface morphology of the particles showed that the MPs were affected by continuous weathering, mechanical fracture and oxidation. MPs are a threat to human health due to the absorption and transmission of dangerous pollutants and their inherent toxicity. Therefore, a solution must be thought of to prevent the contamination of the food chain through salts by MPs, (with protective measures at the salt source, and by improving its production processes.

Characteristics and removal efficiency of microplastics at secondary wastewater treatment plant in Lithuania

Wastewater treatment plants (WWTPs) are the most significant barrier between anthropogenic microplastics and environmental ecosystems. The distribution and characteristics of microplastics in WWTPs remain uncertain and incompletely understood, particularly in northeastern Europe (Baltic States), where there is a lack of data on microplastic pollution and distribution. This study presents the removal efficiency and variation in characteristics of microplastics in different stages of the secondary WWTP during a 3-month sampling campaign in Lithuania. The abundance, size, shape, color, and chemical composition of microplastics in the wastewater at different treatment stages were thoroughly examined, in a size range from 20 to 1000 μm. On average, 2962 ± 25 particles/L of microplastic enter the studied WWTP. The obtained microplastic removal efficiency was 55.4% ± 3.9%, highlighting the necessity to enhance wastewater treatment strategies focusing on microplastic removal. Fragment-type microplastics smaller than 100 μm were removed from wastewater samples with the highest removal efficiency. Furthermore, our study includes recommendations to improve microplastic removal efficiency and contribute to mitigating microplastic pollution. PRACTITIONER POINTS: A large number of MPs in the size range of 20-1000 μm enter Lithuanian WWTP. Small-sized MPs within a range of 20-50 μm and 50-100 μm were removed with the highest efficiency of 54.07 ± 1.68% and 56.4 ± 2.43%, respectively. The shape and size of MPs have a major impact on the efficiency of their removal. Future research should prioritize the development of economical and energy-efficient systems, specifically designed for the removal of MPs in WWTPs.

Tackling microplastics pollution in global environment through integration of applied technology, policy instruments, and legislation

Microplastic pollution is a serious environmental problem that affects both aquatic and terrestrial ecosystems. Small particles with size of less than 5 mm, known as microplastics (MPs), persist in the environment and pose serious threats to various species from micro-organisms to humans. However, terrestrial environment has received less attention than the aquatic environment, despite being a major source of MPs that eventually reaches water body. To reflect its novelty, this work aims at providing a comprehensive overview of the current state of MPs pollution in the global environment and various solutions to address MP pollution by integrating applied technology, policy instruments, and legislation. This review critically evaluates and compares the existing technologies for MPs detection, removal, and degradation, and a variety of policy instruments and legislation that can support the prevention and management of MPs pollution scientifically. Furthermore, this review identifies the gaps and challenges in addressing the complex and diverse nature of MPs and calls for joint actions and collaboration from stakeholders to contain MPs. As water pollution by MPs is complex, managing it effectively requires their responses through the utilization of technology, policy instruments, and legislation. It is evident from a literature survey of 228 published articles (1961-2023) that existing water technologies are promising to remove MPs pollution. Membrane bioreactors and ultrafiltration achieved 90% of MPs removal, while magnetic separation was effective at extracting 88% of target MPs from wastewater. In biological process, one kg of wax worms could consume about 80 g of plastic/day. This means that 100 kg of wax worms can eat about 8 kg of plastic daily, or about 2.9 tons of plastic annually. Overall, the integration of technology, policy instrument, and legislation is crucial to deal with the MPs issues.

A standard analytical approach and establishing criteria for microplastic concentrations in wastewater, drinking water and tap water

The ubiquitous presence of microplastics (MPs) in natural water bodies reflects the global issue regarding these micropollutants. The main problem of MPs lies on the difficulty of removing these particles from water during wastewater and drinking water treatments. The release of MPs to the environment in treated wastewater contributed to the dispersion of these micropollutants, which enhances the harmful effect of MPs on fauna and flora. In addition, their presence in tap water entails a potential risk to human health since MPs can be directly consumed. The first step is being able to quantify and characterise these microparticles accurately. In this work, a comprehensive analysis on the presence of MPs in wastewater, drinking water and tap water has been conducted with emphasis on sampling methods, pre-treatment, MP size and analytical methods. Based on literature data, a standard experimental procedure has been proposed with the objective of recommending a methodology that allows the homogenisation of MP analysis in water samples. Finally, reported MP concentrations for influents and effluents of drinking and wastewater treatment plants and tap water have been analysed, in terms of abundance, ranges and average values, and a tentative classification of different waters based on their MP concentrations is proposed.

Spatial distribution of anthropogenic particles and microplastics in a meso-tidal lagoon (Arcachon Bay, France): A multi-compartment approach

Assessment of microplastic (MP) contamination is still needed to evaluate this threat correctly and tackle this issue. Here, MP contamination was assessed for a meso-tidal lagoon of the Atlantic coast (Arcachon Bay, France). Sea surface, water column, intertidal sediments and wild oysters were sampled. Five different stations were studied to assess the spatial distribution of the contamination. Two were outside of the bay and three were inside the bay (from the inlet to the back). A distinction was made between all anthropogenic particles (AP, i.e. visually sorted) and MP (i.e. plastic polymer confirmed by ATR-FTIR spectroscopy). The length of particles recovered in this study ranged between 17 μm and 5 mm. Concentration and composition in sea surface and water column samples showed spatial variations while sediment and oyster samples did not. At outside stations, the sea surface and the water column presented a blended composition regarding shapes and polymers and low to high concentrations (e.g. 0.16 ± 0.08 MP.m-3 and 561.7 ± 68.5 MP.m-3, respectively for sea surface and water column), which can be due to coastal processes and nearby input sources. The inlet station displayed a well-marked pattern only at the sea surface. High AP and MP concentrations were recorded, and fragments along with polyethylene overwhelmed (respectively 76.0 % and 73.2 %). Higher surface currents could explain this pattern. At the bay back, AP and MP concentrations were lower and fibers were mainly recorded. Weaker hydrodynamics in this area was suspected to drive this contamination profile. Overall, fragments and buoyant particles were mainly detected at the sea surface while fibers and negatively buoyant particles prevailed in other compartments. Most of the studied samples presented an important contribution of fiber-shaped particles (from 31.5 % to 94.2 %). Finally, contamination was ubiquitous as AP and MP were found at all stations in all sample types.

Microplastics in landfill leachate: Sources, detection, occurrence, and removal

Due to the accumulation of an enormous amount of plastic waste from municipal and industrial sources in landfills, landfill leachate is becoming a significant reservoir of microplastics. The release of microplastics from landfill leachate into the environment can have undesirable effects on humans and biota. This study provides the state of the science regarding the source, detection, occurrence, and remediation of microplastics in landfill leachate based on a comprehensive review of the scientific literature, mostly in the recent decade. Solid waste and wastewater treatment residue are the primary sources of microplastics in landfill leachate. Microplastic concentration in raw and treated landfill leachate varied between 0-382 and 0-2.7 items L-1. Microplastics in raw landfill leachate are largely attributable to local plastic waste production and solid waste management practices. Polyethylene, polystyrene, and polypropylene are the most prevalent microplastic polymers in landfill leachate. Even though the colors of microplastics are primarily determined by their parent plastic waste, the predominance of light-colored microplastics in landfill leachate indicates long-term degradation. The identified morphologies of microplastics in leachate from all published sources contain fiber and fragments the most. Depending on the treatment method, leachate treatment processes can achieve microplastic removal rates between 3% and 100%. The review also provides unique perspectives on microplastics in landfill leachate in terms of remediation, final disposal, fate and transport among engineering systems, and source reduction, etc. The landfill-wastewater treatment plant loop and bioreactor landfills present unique difficulties and opportunities for managing microplastics induced by landfill leachate.

From oceans to dinner plates: The impact of microplastics on human health

Microplastics, measuring less than 5 mm in diameter, are now found in various environmental media, including soil, water, and air, and have infiltrated the food chain, ultimately becoming a part of the human diet. This study offers a comprehensive examination of the intricate nexus between microplastics and human health, thereby contributing to the existing knowledge on the subject. Sources of microplastics, including microfibers from textiles, personal care products, and wastewater treatment plants, among others, were assessed. The study meticulously examined the diverse routes of microplastic exposure-ingestion, inhalation, and dermal contact-offering insights into the associated health risks. Notably, ingestion of microplastics has been linked to gastrointestinal disturbances, endocrine disruption, and the potential transmission of pathogenic bacteria. Inhalation of airborne microplastics emerges as a critical concern, with possible implications for respiratory and cardiovascular health. Dermal contact, although less explored, raises the prospect of skin irritation and allergic reactions. The impacts of COVID-19 on microplastic pollution were also highlighted. Throughout the manuscript, the need for a deeper mechanistic understanding of microplastic interactions with human systems is emphasized, underscoring the urgency for further research and public awareness.

Tracing the fate of microplastic in wastewater treatment plant: A multi-stage analysis of treatment units and sludge

Microplastic (MP) pollution is ubiquitous in the environment presenting a global problem for both scientists and the general public. One of the major pathways of MPs entering the natural environment is through wastewater treatment plants (WWTPs). Once MPs reach the natural environment, they are posing threat to aquatic ecosystems and public health. The aim of this study is to investigate the concentration, morphology, and composition of MPs in different treatment units of a WWTP. Sampling included different points across WWTP in the water and sludge lines. Pre-treatment of the samples consists of advanced Fenton oxidation, and alkaline and enzymatic digestion followed by density separation. Once the particles were isolated, their morphology and size were studied using a stereoscopic and optical microscope followed by final confirmation with ATR-FTIR and micro-FTIR spectroscopy. Microplastic particle concentrations exhibit significant reductions as water undergoes treatment in the WWTP. For summer sampling, concentrations decreased from 351 MP/L (influent) to 35 MP/L (primary clarifier), 32 MP/L (biological reactor), and 13 MP/L (2.3 MP/L) (secondary clarifier). Similarly, winter sampling showed reductions from 403 MP/L (influent) to 159 MP/L (primary clarifier), 178 MP/L (biological reactor), and 26 MP/L (5.6 MP/L) (secondary clarifier). Removal efficiency of WWTP is high and exceeds 96%. The most abundant morphology is fibers followed by fragments and films. Polymers such as PE, synthetic cellulose, PP, PVC, PE-PP, PEEA, PA, acrylamide, and PES are widely detected in different units of WWTP. The number of MPs that are avoided from being emitted into the environment through direct water discharge was estimated to be 9.1 × 1012 MP/year. Removed MPs tend to accumulate in the sludge that is used for agricultural purposes although it should be managed as waste properly, avoiding the transition of MPs pollutants to terrestrial ecosystems adding to the number of MPs that will inevitably end up in receiving water bodies through direct WWTP effluent discharge that was set in 5.1 × 1010 MP/year in the studied WWTP.

Tire wear particles in different water environments: occurrence, behavior, and biological effects-a review and perspectives

As an important source of microplastics, the water ecological risk of tire wear particles (TWPs) has attracted widespread attention worldwide. However, the occurrence and behavior of TWPs and their biological effects in water environments have not been clearly analyzed. For example, most contemporary studies have focused on the evaluation of the aquatic toxicity of TWPs leachate, and little attention has been paid to the behavior process and potential risks of its surface properties in water environments. In addition, most studies rely on preparing TWPs under laboratory conditions or purchasing commercial TWPs for studying their water environmental behavior or exposure. These obviously cannot meet the requirements of accurate assessment of water ecological risks of TWPs. As thus, in addition to describing the occurrence, distribution, and (aging) transformation of TWPs in different water environments, we further tried to explain the potential water environment behavior process and multiple pathways leading to potential adverse impacts of TWPs on aquatic organisms from the perspectives of particle self-toxicity and release toxicity, as well as synergistic effects of TWPs and other substances are also discussed. The existing data, such as studies on the self-characteristics of TWPs, environmental factors, and subjects, are insufficient to comprehensively evaluate the recent changes in essential water ecosystem services and multifunctions caused by TWPs, implying that the impact of TWPs on water environmental health needs to be further evaluated, and the corresponding countermeasures should be recommended. In this context, the current review provides an outlook on future research on TWPs in aquatic environments.

Characterization of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD)-induced cardiotoxicity in larval zebrafish (Danio rerio)

N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) is a type of p-phenylenediamine (PPD), which is widely used in the manufacture of rubber tires owing to its excellent antiozonant properties. In this study, the developmental cardiotoxicity of 6PPD was evaluated in zebrafish larvae, and the LC50 was approximately 737 μg/L for the larvae at 96 h post fertilization (hpf). In the 6PPD treatment of 100 μg/L, the accumulation concentrations of 6PPD were up to 2658 ng/g in zebrafish larvae, and 6PPD induced significant oxidative stress and cell apoptosis in the early developmental stages of zebrafish. Transcriptome analysis showed that 6PPD exposure could potentially cause cardiotoxicity in larval zebrafish by affecting the transcription of the genes related to the calcium signal pathway and cardiac muscle contraction. The genes related to calcium signaling pathway (slc8a2b, cacna1ab, cacna1da, and pln) were verified by qRT-PCR, which were significantly downregulated in larval zebrafish after exposing to 100 μg/L of 6PPD. Simultaneously, the mRNA levels of the genes related to cardiac functions (myl7, sox9, bmp10, and myh71) also respond accordingly. H&E staining and heart morphology investigation indicated that cardiac malformation occurred in zebrafish larvae exposed to 100 μg/L of 6PPD. Furthermore, the phenotypic observation of transgenic Tg (myl7: EGFP) zebrafish also confirmed that 100 μg/L of 6PPD exposure could change the distance of atria and ventricles of the heart and inhibit some key genes (cacnb3a, ATP2a1l, ryr1b) related to cardiac function in larval zebrafish. These results revealed the toxic effects of 6PPD on the cardiac system of zebrafish larvae.

Abundance, characteristics, fate, and removal of microplastics during municipal wastewater treatment plant in the west of Iran: the case of Kermanshah city

The threat of microplastics (MPs) in aquatic systems is almost a new challenge in environmental management. The municipal wastewater treatment plants (WWTPs) act both as collectors of MPs from anthropic use and as a source to natural environments. This study is aimed to determine the abundance, characteristics, and removal of MPs in a municipal WWTP with conventional activated sludge process. Particle size/type, influent loads, and removal rate of MPs in bar screen, grit chamber, primary sedimentation, returned activated sludge, and secondary clarification units of this WWTP were studied by collecting composite samples from wastewater and sludge over a 3-month sampling campaign. Suspected MP particles were counted by light microscopy and characterized using SEM, EDS, FTIR, and TGA-DSC techniques. The mean total MPs, fibers, and fragment concentration after the grit chamber were 6608, 3594, and 3014 which were reduced to 1855, 802, and 1053 particles/L in the effluent, respectively. The sludge retention of total MPs, fibers, and fragments were 8001, 3277, and 4719 particles/L, respectively. The overall efficiency of WWTP with an activated sludge process to remove MPs was 64% and it removed 66.6% and 60% of fibers and fragments, respectively. Fibers were the dominant shape for the collected samples after the grit chamber and fragments were prevalent in the effluent. Polyethylene polymer was detected in most wastewater samples. Existing treatment processes are effective in the removal of MP particles but still act as a potential source to the aquatic ecosystem.

Microplastics as emergent contaminants in landfill leachate: Source, potential impact and remediation technologies

A significant amount of plastic waste is generated each year on a global scale, in which the maximum quantity of plastic waste is typically dumped in landfills in various parts of the world. Moreover, dumping plastic waste in landfills cannot address the issue of proper disposal; it simply delays the process. Exploiting waste resources entails environmental hazards because plastic wastes buried in landfills gradually break down into Microplastics (MPs) due to physical, chemical, and biological effects. The possibility of landfill leachate as a source of MPs in the environment has not received much attention. Without systematic treatment, MPs in leachate increase the risk to human health and environmental health since they contain dangerous and toxic pollutants and antibiotic resistance genes transmitted by leachate vectors. Due to their severe environmental risks, MPs are now widely recognized as emerging pollutants. Therefore, the composition of MPs in landfill leachate and the interaction of MPs with other hazardous contaminants are summarised in this review. The available potential mitigation or treatment methods of MPs in landfill leachate as of now, along with the drawbacks and challenges of the present leachate treatment for eliminating MPs, are described in this review. Since it is unclear how MPs will be removed from the current leachate facilities, it is crucial to develop innovative treatment facilities as quickly as possible. Finally, the areas that require more research to provide complete solutions to the persistent problem of plastic debris are discussed.

Mapping of heavy metal contamination associated to microplastics marine debris - A case study: Dubai, UAE

Microplastics (MPs) are ubiquitously detected in the environment. The adverse impact of microplastics on marine life is well documented. Previous research has shown that MPs can adsorb heavy metals, however, this fact has not been investigated along the coast of Dubai, UAE. Elemental composition of MPs debris was determined using X-ray fluorescence spectroscopic (XRF) analysis. The analyzed MPs were extracted from 80 sediment samples collected from the wrack lines of 16 Dubai, UAE beaches. A total of 480 MPs pieces extracted from the samples were analyzed in order to detect heavy metals. The polymer composition was previously confirmed by FTIR spectroscopy, showing that polyethylene (PE) and polypropylene (PP) were the most abundant MPs. 14 heavy metals were identified in the samples: Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Pb, Ce, Pr, Nd, Pd, and Co with different concentrations. Five of them (Cr, Ni, Cu, Zn, and Pb) are priority pollutants according to EPA. Their average concentrations in oxide form were Cr₂O₃ (2.96 %), NiO (0.32 %), CuO (0.45 %), ZnO (0.56 %), and PbO (1.49 %).

Abundance and characteristics of microplastics in drinking water treatment plants, distribution systems, water from refill kiosks, tap waters and bottled waters

Limited research studies have revealed the presence of microplastics (MPs) of different polymer types, shapes, and sizes in drinking water sources, influents of drinking water treatment plants (DWTPs), effluents of DWTPs, tap water, and bottled water. Reviewing the available information on MP pollution in waters, which is becoming more worrying in correlation with the increasing plastic production in the world every year, is noteworthy for understanding the current situation, identifying the deficiencies in the studies, and taking the necessary measures for public health as soon as possible. Therefore, this paper, in which the abundance, characteristics, and removal efficiencies of MPs in the processes from raw water to tap water and/or bottled water are reviewed is a guide for dealing with MP pollution in drinking water. In this paper, firstly, the sources of MPs in raw waters are briefly reviewed. In addition, the abundance, and characteristics (polymer type, shape, and size) of MPs in influents and effluents of DWTPs in different countries are reviewed and the effects of treatment stages (coagulation, flocculation, sedimentation, sand filtration, disinfection, and membrane filtration) of DWTPs on MP removal efficiency and the factors that are effective in removal are discussed. Moreover, studies on the factors affecting MP release from drinking water distribution systems (DWDSs) to treated water and the abundance and characteristics of MPs in tap water, bottled water and water from refill kiosks are reviewed. Finally, the deficiencies in the studies dealing with MPs in drinking water were identified and recommendations for future studies are presented.

Effects of irrigation on the fate of microplastics in typical agricultural soil and freshwater environments in the upper irrigation area of the Yellow River

Agricultural activities are among the most significant sources of microplastics (MPs) in water. However, few studies have explored the effect of irrigation on the fate of MPs in agricultural systems. This study investigated the distribution of MPs in agricultural soil, surface water, and sediment of adjacent rivers, as well as the "MP communities" in various environments before and after irrigation in a typical agricultural irrigation area of the Yellow River. MPs were detected in all of the examined sites. The number of MPs in surface water and sediment increased after irrigation, whereas those in the surface soil of croplands decreased. In the vertical direction, irrigation accelerated the migration of MPs (< 100 µm) deep into the soil. The vertical mobility of fibers in soil was faster than that of other types of MPs. Moreover, irrigation decreased the correlation between soil properties and MPs in soils. MP community analysis indicated that irrigation enhanced the differences between MP communities among adjacent environments. Collectively, our findings confirmed that river water irrigation caused secondary MP pollution in the soil environment and accelerated MP pollution in deep soil. Therefore, this study provides a theoretical basis for the development of strategies for MP pollution control in agricultural soil.

An assessment of the impact of structure and type of microplastics on ultrafiltration technology for microplastic remediation

Microplastic, which is of size less than 5 mm, is gaining a lot of attention as it has become a new arising contaminant because of its ecophysiology impact on the aquatic environment. These microplastics are found in freshwater or drinking water and are the major carriers of pollutants. Removal of this microplastic can be done through the primary treatment process, secondary treatment process, and tertiary treatment process. One approach for microplastic remediation is ultrafiltration technology, which involves passing water through a membrane with small pores to filter out the microplastics. However, the efficiency of this technology can be affected by the structure and type of microplastics present in the water. New strategies can be created to improve the technology and increase its efficacy in removing microplastics from water by knowing how various types and shapes of microplastics react during ultrafiltration. The filter-based technique, that is, ultrafiltration has achieved the best performance for the removal of microplastic. But with the ultrafiltration, too some microplastic that are of sizes less than of ultrafiltration membrane passes through the filter and enters the food chain. Accumulation of this microplastic on the membrane also leads to membrane fouling. Through this review article, we have assessed the impact of the structure, size, and type of MPs on ultrafiltration technology for microplastic remediation, with that how these factors affect the efficiency of the filtration process and challenges occur during filtration.