Methods for separating microplastics from complex solid matrices: Comparative analysis

Microplastics monitoring in freshwater systems: A review of global efforts, knowledge gaps, and research priorities

The escalating production of synthetic plastics and inadequate waste management have led to pervasive microplastic (MP) contamination in aquatic ecosystems. MPs, typically defined as particles smaller than 5 mm, have become an emerging pollutant in freshwater environments. While significant concern about MPs has risen since 2014, research has predominantly concentrated on marine settings, there is an urgent need for a more in-depth critical review to systematically summarize the current global efforts, knowledge gaps, and research priorities for MP monitoring in freshwater systems. This review evaluates the current understanding of MP monitoring in freshwater environments by examining the distribution, characteristics, and sources of MPs, alongside the progression of analytical methods with quantitative evidence. Our findings suggest that MPs are widely distributed in global freshwater systems, with higher abundances found in areas with intense human economic activities, such as the United States, Europe, and China. MP abundance distributions vary across different water bodies (e.g., rivers, lakes, estuaries, and wetlands), with sampling methods and size range selections significantly influencing reported MP abundances. Despite great global efforts, there is still a lack of harmonized analyzing framework and understanding of MP pollution in specific regions and facilities. Future research should prioritize the development of standardized analysis protocols and open-source MP datasets to facilitate data comparison. Additionally, exploring the potential of state-of-the-art artificial intelligence for rapid, accurate, and large-scale modeling and characterization of MPs is crucial to inform effective strategies for managing MP pollution in freshwater ecosystems.

Distribution of microplastics in (sub)urban soils of Serbia and Cd, As, and Pb uptake by Capsella bursa-pastoris (L.) Medik

Omnipresent in terrestrial ecosystems, microplastics (MPs) represent a hazard to soil biota and human health, while their relationship with other environmental contaminants remains poorly acknowledged. This study investigated MPs prevalence in (sub)urban soils of Serbia and its impact on Cd, As, and Pb mobility in the soil-medicinal plant Capsella bursa-pastoris (L.) Medik system. Soil physicochemical parameters (pH, Eh, SOM, and texture) were analyzed alongside the Cd, As, and Pb pseudo-total (aqua regia) and phytoavailable (EDTA) contents. Toxic elements' concentrations in soil fractions and C. bursa-pastoris roots and shoots were determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). Pseudo-total Cd, As, and Pb contents in soils ranged from 0.16 to 2.23 μg g-1, 2.00-36.92 μg g-1, and 0.18-65.54 μg g-1, respectively. Using an optimized density separation method with 30% H2O2 and 5% NaClO, we found an average abundance of 489 MPs per kg of soil. ATR-FTIR spectroscopy confirmed the presence of seven polymer types, whereby the main contributors were polystyrene (PS) - 28.57% and cardanol prepolymer (PCP) - 23.81%. The dominant associated pollution sources were road networks and industrial activities. Spearman correlation analysis revealed the interconnection among soil MPs, physicochemical variables, and Cd, As, and Pb mobility. We identified significant positive correlations between MPs' abundance and phytoavailable concentrations of Cd, As, and Pb (ρ = 0.82, 0.95, and 0.63). Moreover, soil MPs strongly positively correlated with Cd contents in roots (ρ = 0.61) and shoots of C. bursa-pastoris (ρ = 0.65). These findings underscore the synergistic effects of MPs and toxic metals in urban environmental pollution, with possible implications for human health. Further research is required to deepen our understanding of the impact of MPs on element mobility in complex plant-soil systems and to elucidate the broader consequences of induced alterations.

Microplastics in aquatic systems: An in-depth review of current and potential water treatment processes

Plastic products, despite their undeniable utility in modern life, pose significant environmental challenges, particularly when it comes to recycling. A crucial concern is the pervasive introduction of microplastics (MPs) into aquatic ecosystems, with deleterious effects on marine organisms. This review presents a detailed examination of the methodologies developed for MPs removal in water treatment systems. Initially, investigating the most common types of MPs in wastewater, subsequently presenting methodologies for their precise identification and quantification in aquatic environments. Instruments such as scanning electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, Raman spectroscopy, surface-enhanced Raman spectroscopy, and Raman tweezers stand out as powerful tools for studying MPs. The discussion then transitions to the exploration of both existing and emergent techniques for MPs removal in wastewater treatment plants and drinking water treatment plants. This includes a description of the core mechanisms that drive these techniques, with an emphasis on the latest research developments in MPs degradation. Present MPs removal methodologies, ranging from physical separation to chemical and biological adsorption and degradation, offer varied advantages and constraints. Addressing the MPs contamination problem in its entirety remains a significant challenge. In conclusion, the review offers a succinct overview of each technique and forwards recommendations for future research, highlighting the pressing nature of this environmental dilemma.

Seasonal dynamics, tidal influences, and anthropogenic impacts on microplastic distribution in the Yangtze River estuary: A comprehensive characterization and comparative analysis

Microplastics (MPs) are emerging contaminants with significant ecological and human health implications. This study examines the abundance, characteristics, and distribution of MPs in the Yangtze River estuary, focusing on seasonal variations, tidal cycles, and anthropogenic influences. Surface samples were collected using the Manta trawl method to ensure consistency with previous marine MP research. The study found an average MP concentration of 1.01 (± 0.65) n m-3, predominantly comprising low-density polymers such as polystyrene (38 %), polypropylene (33 %), and polyethylene (29 %). MPs were mainly fragments (34.9 %) and foam (30.7 %), with a prevalence of white particles. Seasonal analysis indicated significantly higher MP concentrations during flood seasons (1.32 ± 1.09 n m-3), nearly 1.9 times higher than during non-flood seasons (0.70 ± 0.28 n m-3). Tidal cycles also impacted MP distribution, with ebb tides showing increased concentrations (2.44 ± 1.30 n m-3) compared to flood tides (1.48 ± 2.07 n m-3). Furthermore, MP abundance showed a decreasing trend with increasing distance from urban centers, with significant correlations (0.52 < R2 < 0.65, P < 0.001). These findings underscore the necessity for seasonally adjusted monitoring and robust management strategies to combat MP pollution. The study advocates for the integration of diverse sampling methods and the consideration of environmental factors in future MP assessments, laying the groundwork for understanding the MP transport mechanism in the Yangtze River estuary and similar estuarine systems worldwide.

Development and application of a novel extraction protocol for the monitoring of microplastic contamination in widely consumed ruminant feeds

Plastics and, in particular, microplastics (MPs) (< 5 mm) are emerging environmental pollutants responsible for interconnected risks to environmental, human, and animal health. The livestock sector is highly affected by these contaminants, with 50-60 % of the foreign bodies found in slaughtered domestic cattle being recognized as plastic-based materials. Additionally, microplastics were recently detected inside ruminant bodies and in their feces. MPs presence in ruminants could be explained by the intensive usage of plastic materials on farms, in particular to store feeds (i.e. to cover horizontal silos and to wrap hay bales). Although feed could be one of the main sources of plastics, especially of microplastics, a specific protocol to detect them in ruminant feeds is not actually present. Hence, the aim of this study was to optimize a specific protocol for the extraction, quantification, and identification of five microplastic polymers (high-density polyethylene, low-density polyethylene, polyamide fibers/particles, polyethylene terephthalate and polystyrene) from feeds typically used in ruminant diets (corn silage, hay, high protein feedstuff and total mixed ration). Several combinations of Fenton reactions and KOH digestion were tested. The final extraction protocol involved a KOH digestion (60 °C for 24 h), followed by two/three cycles of Fenton reactions. The extraction recoveries were of 100 % for high-density, low-density polyethylene, polyamide particles, and polystyrene and higher than 85 % for polyethylene terephthalate and polyamide fibers. Finally, the optimized protocol was successfully applied in the extraction of microplastics from real feed samples. All the feeds contained microplastics, particularly polyethylene, thus confirming the exposure of ruminants to MPs.

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.

Exploring the Potential of Endophytic Microorganisms and Nanoparticles for Enhanced Water Remediation

Endophytic microorganisms contribute significantly to water bioremediation by enhancing pollutant degradation and supporting aquatic plant health and resilience by releasing bioactive compounds and enzymes. These microorganisms inhabit plant tissues without causing disease or any noticeable symptoms. Endophytes effectively aid in eliminating contaminants from water systems. Nanoparticles serve as potent enhancers in bioremediation processes, augmenting the efficiency of pollutant degradation by increasing surface area and bioavailability, thereby improving the efficacy and rate of remediation. Their controlled nutrient release and ability to stabilize endophytic colonization further contribute to the enhanced and sustainable elimination of contaminated environments. The synergistic effect of endophytes and nanoparticles in water remediation has been widely explored in recent studies, revealing compelling outcomes. Water pollution poses significant threats to human health, ecosystems, and economies; hence, the sixth global goal of the Sustainable Development Agenda 2030 of the United Nations aims to ensure the availability and sustainable management of water resources, recognizing their crucial importance for current and future generations. Conventional methods for addressing water pollution exhibit several limitations, including high costs, energy-intensive processes, the production of hazardous by-products, and insufficient effectiveness in mitigating emerging pollutants such as pharmaceuticals and microplastics. Noticeably, there is an inability to effectively remove various types of pollutants, thus resulting in incomplete purification cycles. Nanoparticle-enhanced water bioremediation offers an innovative, eco-friendly alternative for degrading contaminants. A growing body of research has shown that integrating endophytic microorganisms with nanoparticles for water bioremediation is a potent and viable alternative. This review examines the potential of using endophytic microorganisms and nanoparticles to enhance water remediation, exploring their combined effects and applications in water purification. The paper also provides an overview of synthetic methods for producing endophyte-nanoparticle composites to optimize their remediation capabilities in aqueous environments. The final section of the review highlights the constraints related to integrating endophytes with nanoparticles.

Occurrence and abundance of microplastics and plasticizers in landfill leachate from open dumpsites in Sri Lanka

This is the first attempt that investigate the abundance of plasticizers in leachate sediment in the scientific literature, alongside the debut effort to explore the abundance of microplastics and plasticizers in landfill leachate and sediment in Sri Lanka. Microplastics in sizes ranging from ≥2.0-5.0, ≥1.0-2.0, and ≥ 0.5-1.0 mm were extracted from the leachate draining from ten municipal solid waste open dump sites and sediment samples covering seven districts. Microplastics were extracted by density separation (Saturated ZnCl2) followed by wet peroxide digestion and the chemical identification was conducted by Fourier Transform Infrared spectroscopy. Plasticizers were extracted to hexane and analyzed by high-performance liquid chromatography. The total mean microplastic abundance in leachate was 2.06 ± 0.62 mg/L whereas it was 363 ± 111 mg/kg for leachate sediments. The most frequently found polymer type was polyethylene (>50%), and white color was dominant. The average concentration of bisphenol A (BPA), benzophenone (BP) and diethyl-hydrogen phthalate (DHEP) in leachate was 158 ± 84.4, 0.75 ± 0.16 and 170 ± 85.8 μg/L respectively. Furthermore, BP and DHEP in leachate sediment was 100 ± 68.3 and 1034 ± 455 μg/kg respectively. As landfill leachate is directly discharged into nearby surface and groundwater bodies that serve as sources of drinking water, the study highlights the potential concerns of microplastic and plasticizer exposure to the surrounding Sri Lankan community through consumption of contaminated drinking water. Therefore, there is a timely need of develop the effective waste management and pollution control measures to minimize the possible threats to both the environment and human health.

The impact of arbuscular mycorrhizal fungi and endophytic bacteria on peanuts under the combined pollution of cadmium and microplastics

It remains unclear how symbiotic microbes impact the growth of peanuts when they are exposed to the pollutants cadmium (Cd) and microplastics (MPs) simultaneously. This study aimed to investigate the effects of endophytic bacteria Bacillus velezens SC60 and arbuscular mycorrhizal fungus Rhizophagus irregularis on peanut growth and rhizosphere microbial communities in the presence of Cd at 40 (Cd40) or 80 (Cd80) mg kg-1 combined without MP or the presence of low-density polyethylene (LDPE) and poly butyleneadipate-co-terephthalate (PBAT). This study assessed soil indicators, plant parameters, and Cd accumulation indicators. Results showed that the application of R. irregularis and B. velezens significantly enhanced soil organic carbon and increased Cd content under the conditions of Cd80 and MPs co-pollution. R. irregularis and B. velezens treatment increased peanut absorption and the enrichment coefficient for Cd, with predominate concentrations localized in the peanut roots, especially under combined pollution by Cd and MPs. Under treatments with Cd40 and Cd80 combined with PBAT pollution, soil microbes Proteobacteria exhibited a higher relative abundance, while Actinobacteria showed a higher relative abundance under treatments with Cd40 and Cd80 combined with LDPE pollution. In conclusion, under the combined pollution conditions of MPs and Cd, the co-treatment of R. irregularis and B. velezens effectively immobilized Cd in peanut roots, impeding its translocation to the shoot.

Identification of microplastics extracted from field soils amended with municipal biosolids

Microplastic particles in arable soil are expected to impact the environment and potentially human health. The application of municipal biosolids (MBs) to agricultural land presents a further dilemma in that biosolids act as a fertilizer for crop growth, and a disposal pathway for wastewater treatment plants. They are also a direct path for emerging contaminants, such as microplastics to enter the terrestrial environment. Reliable methods are needed to identify and quantify microplastics, found in agricultural soils to determine how microplastics are being cycled in the terrestrial environment. In this study, we developed a method for extracting microplastics from soil, and characterized their composition and identity for particles sized 5 μm to 2 mm. Method development was initially completed using natural soils spiked with microplastics and MBs, followed by the analyses of soil sampled from an agricultural field where MBs were recently applied at a rate of 13 tons dw/ha. The procedures that used the spiked samples showed that microplastics can be reliably extracted from soil in a laboratory setting, and identified and semi-quantified by thermogravimetric analysis combined with Fourier-transform infrared spectroscopy (TGA-FTIR). However, when the same methods were applied to the soil samples collected from the agricultural field, reproducibility became a challenge, as the number and type of microplastics changed even within the same soils (i.e., collected the same day from the same exact location). The variation in reproducibility observed between laboratory and field samples underscores the significant heterogeneity present in the environment. This heterogeneity, in turn, affects the identification and quantity of microplastics detected, a phenomenon observed even when comparing different fields within a single treatment regimen.

Iron plaque formation and its influences on the properties of polyethylene plastic surfaces in coastal wetlands: Abiotic factors and bacterial community

Iron (Fe) plaques in coastal wetlands are widely recognized because of their strong adsorption affinity for natural particles, but their interaction behaviors and mechanisms with plastics remain unknown. Through laboratory incubation experiments, paired with multiple characterization methods and microbial analysis, this work focused on the characteristics of Fe plaques on low-density polyethylene plastic surfaces and their relationship with environmental factors in coastal wetlands (Mangrove and Spartina alterniflora soil). The results showed that iron plaques increased the adhesive force of the plastic surface from 65.25 to 300 nN and promoted the oxidation of the plastic surface. Fe plaque formation was stimulated by salinity, anaerobic conditions, natural organic matter, and a weak alkaline scenario (pH 8.0-8.3). The Fe content showed a stable positive correlation with heavy metals loading (i.e., As, Mn, Co, Cr, Pb, and Zn). Furthermore, we revealed that Fe plaque was positively regulated by Nitrospirae through 16S rRNA high-throughput sequencing analysis. Meanwhile, Verrucomicrobia and Kiritimatiellaeota. may act as depressants by consuming salt. This work illustrated that iron plaques could enhance the role of plastics in contaminant migration by altering their adsorption performance, providing new insights into plastic interface behavior and potential ecological effects in coastal wetlands.

Advances in magnetic materials for microplastic separation and degradation

The widespread use of plastics in modern human society has led to severe environmental pollution with microplastics (MP/MPs). The rising consumption of plastics raises the omnipresence of microplastics in aquatic environments, which carry toxic organic matter, transport toxic chemicals, and spread through the food chain, seriously threatening marine life and human health. In this context, several advanced strategies for separating and degrading MPs from water have been developed recently, and magnetic materials and their nanostructures have emerged as promising materials for targeting, adsorbing, transporting, and degrading MPs. However, a comprehensive review of MP remediation using magnetic materials and their nanostructures is currently lacking. The present work provides a critical review of the recent advances in MP removal/degradation using magnetic materials. The focus is on the comparison and analysis of the MP's removal efficiencies of different magnetic materials, including iron/ferrite nanoparticles, magnetic nanocomposites, and micromotors, aiming to unravel the underlying roles of magnetic materials in different types of MP degradation and present the general strategies for designing them with optimal performance. Finally, the review outlines the forthcoming challenges and perspectives in the development of magnetic nanomaterials for MP remediation.

Nano-Iron Oxide (Fe3O4) Mitigates the Effects of Microplastics on a Ryegrass Soil-Microbe-Plant System

To understand microplastic-nanomaterial interactions in agricultural systems, a randomized block 90-day pot experiment was set up to cultivate ryegrass seedings in a typical red sandy soil amended with compost (1:9 ratio). Polyvinyl chloride (PVC) and polyethylene (PE) microplastic (MP) contaminants were added into pot soils at 0.1 and 10%, whereas nano-Fe3O4 (as nanoenabled agrochemicals) was added at 0.1% and 0.5% in comparison with chemical-free controls. The combination of nano-Fe3O4 and MPs significantly increased the soil pH (+3% to + 17%) but decreased the total nitrogen content (-9% to - 30%; P < 0.05). The treatment group with both nano-Fe3O4 and PE had the highest total soil C (29 g kg-1 vs 20 g kg-1 in control) and C/N ratio (13 vs 8 in control). Increased rhizosphere nano-Fe3O4 concentrations promoted ryegrass growth (+42% dry weight) by enhancing the chlorophyll (+20%) and carotenoid (+15%) activities. Plant leaf and root peroxidase enzyme activity was more significantly affected by nano-Fe3O4 with PVC (+15%) than with PE (+6%). Nano-Fe3O4 significantly changed the ryegrass bacterial community structure from belowground (the rhizoplane and root endosphere) to aboveground (the phylloplane). Under MP contamination, the addition of nano-Fe3O4 increased bacterial diversity (+0.35%) and abundance (+30%) in the phylloplane and further intensified the connectivity of ryegrass aboveground bacterial networks (positive association increased 17%). The structural equation model showed that the change in the plant microbiome was associated with the rhizosphere microbiome. Overall, these findings imply the positive influences of nano-Fe3O4 on the soil-microbe-plant system and establish a method to alleviate the harmful effects of MP accumulation in soils.

Naturally aged polylactic acid microplastics stunted pakchoi (Brassica rapa subsp. chinensis) growth with cadmium in soil

Biodegradable microplastics (BMPs) and cadmium (Cd) are posing threats to agro-systems especially to plants and current studies mostly used virgin BMPs to explore their ecological effects. However, effects of naturally aged BMPs and their combined effects with Cd on pakchoi are yet to be unraveled. Therefore, this study incubated naturally aged polylactic acid (PLA) MPs through soil aging process and investigated the single and combined effects of Cd and PLA MPs (virgin and aged) on pakchoi (Brassica rapa subsp. chinensis) morphology, antioxidant systems and soil microbial activities. Our results found that after being deposited in soil for six months, aged PLA (PLAa) MPs formed with a fractured surface, demonstrating more detrimental effects on pakchoi than virgin ones. PLA/PLAa MPs and Cd stunted pakchoi growth, caused oxidative stress and altered the biophysical environment in soil, separately. Moreover, co-existence of PLA/PLAa MPs and Cd caused greater damages to pakchoi than applied alone. The co-presence of PLAa MPs and Cd inhibited pakchoi biomass accumulation rate by 92.2 % compared with the no-addition group. The results unraveled here emphasized BMPs, especially aged BMPs, could trigger negative effects on agro-systems with heavy metals. These findings will give reference to future holistic assessments of BMPs' ecological effects.

Recent advances on microplastics pollution and removal from wastewater systems: A critical review

Microplastics (MPs) (plastic particles <5 mm) are globally acknowledged as a serious emerging micropollutant, which passes through various pathways in natural habitats and eventually ends up in our food chain. In this context, the present study critically reviews recent advances in MPs sampling and detection, occurrence, fate, and removal in wastewater treatment plants (WWTPs) by delineating their characteristics that manifest toxicity in the environment via effluent discharge. While there is currently no standard protocol in place, this work examined and compared the latest approaches adopted for improved sampling, sample processing, and characterization of MPs via fluorescence imaging and certified reference materials for method validation. MPs concentration from different sources in the WWTPs varies considerably ranging between 0.28 and 18285 MPs/L (raw wastewater), 0.004-750 MPs/L (effluent), and 0.00023-10380 MPs/kg (sludge). Assessment of MPs removal efficiency across different treatment stages in various in WWTPs has been performed and elucidated their removal mechanisms. The overall MPs removal efficiency in primary, secondary, and tertiary treatment stages in WWTPs reported to be around 57-99%, 78.1-99.4%, and 90-99.2%, respectively. Moreover, the review covers advanced treatment methods for removing MPs, including membrane bioreactors, coagulation/flocculation, ultrafiltration, rapid sand filtration, ozonation, disc filtration, and reverse osmosis, which have been found to be highly effective (>99%). Membrane bioreactors have been proclaimed to be the most reliable secondary treatment technique for MPs removal. Coagulation (92.2-95.7%) followed by ozonation (99.2%) as a tertiary treatment chain has been demonstrated to be the most efficient in removing MPs from secondary-treated wastewater effluent. Further, the review delineates the effect of different treatment stages on the physical and chemical characteristics of MPs, associated toxicity, and potential impact factors that can influence the MPs removal efficiency in WWTPs. Conclusively, the merits and demerits of advanced treatment techniques to mitigate MPs pollution from the wastewater system, research gaps, and future perspectives have been highlighted.

Pouring hot water through drip bags releases thousands of microplastics into coffee

Microplastics (MPs) released from food packaging have attracted widespread attention. In this study, drip bags made from polyethylene (PE), polypropylene (PP), polyester (PET), and rayon selected from eight brands were employed to investigate MPs releasing. Fourier-transform infrared microspectroscopy (μ-FTIR), optical microscope and scanning electron microscope (SEM) were used to study the effects of brewing time and temperature on the release of MPs. The results showed that a single plastic coffee bag steeped at 95 ℃ for 5 min could release more than 10,000 MPs particles into a cup of coffee. Irregular blocks, long strips, and size range of 10-500 μm MPs were easier to be released, implying that consuming 3-4 cups of coffee will lead to an intake of 50 thousand MPs particles daily. Rayon was the primary type of released MPs, accounting for over 80% of the total amount of the released MPs. Our results are hoped to provide evaluation standards of material selection for processing coffee bags.

Microplastic sources, formation, toxicity and remediation: a review

Microplastic pollution is becoming a major issue for human health due to the recent discovery of microplastics in most ecosystems. Here, we review the sources, formation, occurrence, toxicity and remediation methods of microplastics. We distinguish ocean-based and land-based sources of microplastics. Microplastics have been found in biological samples such as faeces, sputum, saliva, blood and placenta. Cancer, intestinal, pulmonary, cardiovascular, infectious and inflammatory diseases are induced or mediated by microplastics. Microplastic exposure during pregnancy and maternal period is also discussed. Remediation methods include coagulation, membrane bioreactors, sand filtration, adsorption, photocatalytic degradation, electrocoagulation and magnetic separation. Control strategies comprise reducing plastic usage, behavioural change, and using biodegradable plastics. Global plastic production has risen dramatically over the past 70 years to reach 359 million tonnes. China is the world's top producer, contributing 17.5% to global production, while Turkey generates the most plastic waste in the Mediterranean region, at 144 tonnes per day. Microplastics comprise 75% of marine waste, with land-based sources responsible for 80-90% of pollution, while ocean-based sources account for only 10-20%. Microplastics induce toxic effects on humans and animals, such as cytotoxicity, immune response, oxidative stress, barrier attributes, and genotoxicity, even at minimal dosages of 10 μg/mL. Ingestion of microplastics by marine animals results in alterations in gastrointestinal tract physiology, immune system depression, oxidative stress, cytotoxicity, differential gene expression, and growth inhibition. Furthermore, bioaccumulation of microplastics in the tissues of aquatic organisms can have adverse effects on the aquatic ecosystem, with potential transmission of microplastics to humans and birds. Changing individual behaviours and governmental actions, such as implementing bans, taxes, or pricing on plastic carrier bags, has significantly reduced plastic consumption to 8-85% in various countries worldwide. The microplastic minimisation approach follows an upside-down pyramid, starting with prevention, followed by reducing, reusing, recycling, recovering, and ending with disposal as the least preferable option.

Trapped microplastics within vertical redeposited sediment: Experimental study simulating lake and channeled river systems during resuspension events

Plastic waste and its fragments (microplastics; <5 mm) have been observed in almost all types of environments. However, the mechanisms underlying the flow and transport processes of plastics are unknown. This is particularly valid for river sediments, where complex interactions occur between particles and influence their vertical and horizontal distribution patterns. In this study, we investigated the vertical redistribution of 14 pristine microplastics (MPs) with different densities, sizes, and shapes within disturbed sediment without lateral transport (i.e., low-velocity flow). MPs were spiked into sediments (height: 8 cm) in a column with a height of 1 m (diameter: 6 cm) filled to the top with water. The sediment was perturbed by turning the column upside-down to simulate remobilization and the subsequent deposition of sediment. After the complete sedimentation of the particles, the water column was filtered and the sediment was cut into vertical sections. MPs were then extracted from the sediment using sieves and a density separation method, and were counted under a stereomicroscope. Low-density polymers were mainly recovered in the water column and at the surface of the sediment, whereas high-density polymers were found within all sediment sections. The vertical distribution of high-density polymers changes primarily with the sediment grain size. The distribution of each polymer type changes depending on the size and/or shape of the particles with complex interactions. The observed distributions were compared with the expected distributions based only on the vertical velocity formulas. Overall, the formulas used did not explain the sedimentation of a portion of low-density polymers and predicted a lower distribution in the sediment than those observed in the experiment. In conclusion, this study highlights the importance of considering MPs as multi-dimensional particles and provides clues to understand their fate in low-velocity flow systems, considering that they undergo scavenging in sediments.

Microplastics in plateau agricultural areas: Spatial changes reveal their source and distribution characteristics

The Huangshui catchment on the northeastern Qinghai-Tibet Plateau (QTP) was selected as the study area to investigate the abundance, distribution characteristics, and influencing factors of microplastics (MPs) in surface agricultural soils (0-20 cm). The MP levels ranged from 6 to 444 items/kg, with an average of 86 items/kg. The relative abundance of small-sized MPs (<2 mm) was higher than that of large-sized MPs (2-5 mm). Polyethylene was the most common, and residual mulching film in farmland was the main source of MPs. The spatial distribution characteristics of MPs were analyzed through inverse distance weight interpolation, and MP abundance in agricultural soils in neighboring urban areas was significantly higher than that in other areas. Further analysis found that population density was significantly positively correlated with MP abundance (R² = 0.9090, p < 0.01), indicating that human activities play a key role in MP pollution even in remote areas. In addition, the effects of irrigation, land use type, and soil physicochemical properties on the abundance of MPs were analyzed. Atmospheric transport and irrigation with surface water contribute to soil MP pollution. The direct effects of soil properties on MP abundance are still largely unclear, requiring further studies.

Effect of the first-flush phenomenon on the quantification of microplastics in rainwater

Precipitation of airborne microplastics (MPs) by rainfall is one of the major transport pathways of MPs from land-to-marine. While most studies examining wet precipitation of MPs collect surface runoffs, direct investigations of MPs in rainwater are hardly reported. In this study, high-frequency and direct rainwater sampling methodology considering the first-flush effect was demonstrated. The variations in MP abundance were evaluated by the inlet size of rainwater collector, time, and duration of sampling. As a result, a stable abundance of MPs was obtained when samplings were conducted at the same time and duration even with different collectors. On the other hand, the abundance increased as much as 4.5 times in samples collected at different times due to the first-flush effect of rainfall. Thus, our methodology that presents MPs concentration versus time curves based on high-frequency sampling would be helpful for easy comparison between similar rainfall studies.

Magnetic Extraction of Weathered Tire Wear Particles and Polyethylene Microplastics

Magnetic extraction offers a rapid and low-cost solution to microplastic (MP) separation, in which we magnetize the hydrophobic surface of MPs to separate them from complex environmental matrices using magnets. We synthesized a hydrophobic Fe-silane based nanocomposite (Fe@SiO₂/MDOS) to separate MPs from freshwater. Pristine and weathered, polyethylene (PE) and tire wear particles (TWP) of different sizes were used in the study. The weathering of MPs was performed in an accelerated weathering chamber according to ISO 4892-2:2013 standards that mimic natural weathering conditions. The chemical properties and morphology of the Fe@SiO₂/MDOS, PE and TWP were confirmed by Fourier transform infrared spectroscopy and Scanning electron microscopy, respectively. The thermal properties of PE and TWP were evaluated by Thermogravimetric analysis. Using 1.00 mg of Fe@SiO₂/MDOS nanocomposite, 2.00 mg of pristine and weathered PE were extracted from freshwater; whereas, using the same amount of the nanocomposite, 7.92 mg of pristine TWP and 6.87 mg of weathered TWP were extracted. The retrieval of weathered TWP was 13% less than that of pristine TWP, which can be attributed to the increasing hydrophilicity of weathered TWP. The results reveal that the effectiveness of the magnetic separation technique varies among different polymer types and their sizes; the weathering of MPs also influences the magnetic separation efficiency.

Changes in bacterial community structures in soil caused by migration and aging of microplastics

Microplastics (MPs) are classified as emerging pollutants and greatly threatens soil ecosystems. To determine the impact of microplastic migration on soil bacterial diversity, we conducted a 90-day indoor soil column simulation test. Soil and microplastic (granular polystyrene, polypropylene MPs) samples were collected from different soil layers on days 30, 60, and 90. The downward migration trend of MPs was obvious, and its surface functional groups, hydrophobic properties, and crystallinity changed. Bacterial diversity was significantly higher in the surrounding soil than on microplastic surfaces. Also, the topsoil has more bacterial diversity than the middle soil. A higher number of OTUs were detected on microplastic surfaces for the middle soil than in the topsoil. Proteobacteria abundance on microplastic surfaces in the topsoil gradually increased over the course of the experiment, while an opposite trend was observed for the middle soil. Nevertheless, Proteobacteria abundances in both layers were higher than in the surrounding soils. MPs alters the bacterial community composition of soils and provides unique substrates for colonization. The impacts of MPs on soil bacterial communities were better understood in this study. Our findings highlighted the relevance of MPs in soil ecosystems as well as the potential threats they pose.

Addition of polyvinyl pyrrolidone during density separation with sodium iodide solution improves recovery rate of small microplastics (20-150 μm) from soils and sediments

The purpose of this study was to identify a method to accurately separate small microplastics (<100 μm) from soil and sediment. We initially conducted spike-and-recovery tests using polyethylene microbeads and density separation and found that the recovery rate of microplastic particles smaller than 100 μm was less than 60%. This result suggested that previous reports have underestimated the concentrations of microplastics smaller than 100 μm in soil. When polyvinyl pyrrolidone was added and dispersed in a heavy liquid, the recovery rate exceeded 90%, regardless of the microplastic particle size. This improved recovery rate was independent of the type of polymer (polyethylene, polypropylene, polystyrene, polyethylene terephthalate, or nylon 6) and the physicochemical properties of the soil (Andisols, Entisols, or Ultisols), and the method was also effective for marine and lake sediments. Using this method, we measured microplastic concentrations in paddy soil. The results showed that the most common particle size, 20-100 μm, accounted for 64% of all microplastics. Accurate separation from the soil of fractions smaller than 100 μm, which account for the majority of microplastics in soil, will enable an accurate assessment of the impact of microplastics on the soil ecosystem. The method identified in this study can serve as the basic technique for achieving that goal.

Separation of false-positive microplastics and analysis of microplastics via a two-phase system combined with confocal Raman spectroscopy

In the field of microplastics research, more accurate standardised methods and analytical techniques still need to be explored. In this study, a new method for the microplastics quantitatively and qualitatively analysis by two-phase (ethyl acetate-water) system combined with confocal Raman spectroscopy was developed. Microplastics can be separated from false-positive microplastics in beach sand and marine sediment, attributing to the hydrophobic-lipophilic interaction (HLI) of the two-phase system. Results show that the recovery rates of complex environment microplastics (polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyamide 66 (PA 66), polycarbonate (PC) and polyethylene (PE)) are higher than 92.98%. Moreover, the new technique can also be used to detect hydrophobic and lipophilic antibiotics, such as sulfamethoxazole (SMX), erythromycin (EM), madimycin (MD), and josamycin (JOS), which adsorbed on microplastics and are extracted based on the dissolving-precipitating mechanism. This innovative research strategy provides a new scope for further detection of marine environment microplastics and toxic compounds adsorbed on its surface.

The persistently breaking trade-offs of three-decade plastic film mulching: Microplastic pollution, soil degradation and reduced cotton yield

Plastic mulching has been extensively used for near 40 years in China because of the commonly recognized trade-offs between economic profit and adverse impacts. Whether the trade-offs is well kept after decades of mulching usage is poorly understood. In this study, microplastic (MP) pollution, soil physical properties, as well as the root traits and yields of cotton under plastic mulching for different years (up to 32 years) in northwest China were investigated. The results showed that average abundance of MPs in soil ranged from 28.00 to 1426.67 items kg^-1 and increased with time whereas size of MPs decreased with time. With respect to soil physical properties, bulk density and penetration resistance significantly increased with mulching time while saturated hydraulic conductivity and mean weight diameter of water-stable aggregates in cotton fields decreased over time, indicating that long-term plastic mulching has irreversible adverse impact on soil function. The significantly increased soil penetration resistance and decreased hydraulic conductivity substantially restricted root growth and this finally led to remarkable reduction of seed cotton yield. It is urgent for the agricultural departments to take appropriate measures to mitigate the constantly increased negative trade-offs of plastic mulching in the arid areas.

Distribution, sources, migration, influence and analytical methods of microplastics in soil ecosystems

Microplastics are ubiquitous in soil ecosystems all over the world through source and migration. It is even estimated that the content of microplastics in terrestrial ecosystems exceeds the number of microplastics entering sea ecosystems. However, compared with the research on microplastics in marine ecosystems, the research and discussion on microplastics in soil ecosystems are still less. Transportation, film mulching and sewage sludge are three main sources of soil microplastics. The abundance, polymer type, size and shape of the microplastics are related to the source and they help to clarify the source. The characteristics of microplastics, farming measures, soil animal activities and other factors promote the migration of microplastics, which bring new challenges to the soil ecosystems and humans. This article summarizes the latest research findings on the effects of soil microplasticity on soil properties, plants, animals and microorganisms. The analysis methods of microplastics in soil can refer to the analysis methods of microplastics of aquatic sediments, because soil and aquatic sediments are similar, both of which are complex solid substrates. At present, the development of analytical methods is limited due to the complex matrix of soil and the small volume of microplastics, which requires continuous development and innovation. Through the summary and analysis of related articles, this article reviews the distribution, sources, migration, influence and analysis methods of soil microplastics. This article also critically analyzes the deficiencies in the studies of microplastics in the soil ecosystems, and made some suggestions for future work. The microplastics in soil ecosystems need further research and summary, which will help people further understand the potential hazards of microplastics.

Influence of sediment texture on HDPE microplastics recovery by density separation

Microplastics (MPs) are an emerging environmental pollutant, threatening marine and terrestrial ecosystems. Because of their properties and their widely varying size (5mm-0.1 μm), it is still difficult to define a valid and efficient method for extracting MPs from solid matrices. Among the several methods proposed, density separation is the most practical and cost-effective one. Progress is still ongoing towards a deeper understanding of the advantages and limitations related to the application of density separation for MPs extraction, the recovery yields and the factors that may influence it. In this context, we introduce the following work, which provides an early-stage insight into how the sediment texture may influence the efficiency of this extraction method, and how parameters, such as sedimentation time and extraction cycles, can be modified to always achieve the best recovery. Our focus has been directed on evaluating the extraction efficiency of HDPE MPs by density separation using NaCl, from three types of sediment: sandy (SS), sandy loam (SLS) and sandy-clay loam (SCLS). We investigated the impact of sedimentation time (1, 6, 12, 24 h) and extraction cycles (3 cycles for each sedimentation time) on MPs recovery. Finally, we determined the minimum amount of MPs (MPs g/g sediment) below which it is not possible to quantify MPs with the method used. The results have shown that the recovery efficiency of MPs from sediment is structure dependent. The highest recoveries are reached after a settling time of 1 and 6 h. Furthermore, for samples with minimum clay content (SS), only one extraction cycle is needed, whereas two extraction cycles are required for SLS and SCLS. The outcomes about the detection limit (LOD) of the method, showed the existence of an interaction MPs-clay/sediment, which allowed us to understand how far this extraction method is suitable in field, thus defining the minimum grade of MPs pollution (MPs g/g sediment) below which this method is no longer capable to extract MPs from contaminated samples.

Reduction performance of microplastics and their behavior in a vermi-wetland during the recycling of excess sludge: A quantitative assessment for fluorescent polymethyl methacrylate

Large amounts of microplastics (MPs) that have accumulated in excess sludge may increase the environmental risk for its subsequent treatment. This study aimed to investigate the performance and mechanism of the reduction of MPs in excess sludge in a vermi-wetland. For this, 1 μm, 100 μm, and 500 μm of fluorescent MPs stained with Nile red were added to raw sludge, and their decreased numbers were quantified during the treatment of sludge. The results showed that the removal rates of chemical oxygen demand and total solids from the excess sludge were 63.44%-90.98% and 37.61%-51.56% in the vermi-wetland, respectively. The numbers of 1 μm, 100 μm, and 500 μm MPs could be reduced by 86.62%-95.69%, 95.44%-99.52%, and 100% in the vermi-wetland, respectively. These results indicate that the vermi-wetland is more effective at eliminating MPs. Further insight into the vermi-wetland stratification was obtained, and more than 74.87% of the MPs were intercepted in the vermicompost layer. Moreover, all the particle sizes of MPs were found in the excrement of earthworms. However, only 1 μm MPs were detected in their digestive organs. This study suggests that the interception effect is primarily responsible for elimination of MPs in excess sludge, and the bioturbation of earthworms plays an important role in the mobilization of MPs in vermi-wetlands.

Coverage of microplastic data underreporting and progress toward standardization

The analysis of microplastics in various environmental matrices is becoming more prevalent in almost every region of the world. Microplastics are underreported depending on how they are extracted and analyzed, and their magnitude and impacts are unknown or unstudied. This paper aims to synthesize a concrete assessment of the important factors that underpin microplastics data underreporting. Our analysis revealed that there is considerable evidence to highlight data underreporting on microplastic abundance and characteristics, which stems from a combination of partial evaluation, economic constraints, recovery efficiency of microplastic extraction, filter pore size used for microplastic separation, and the detection limit of the quantification and characterization method. The majority of unreported data fell into the category of significantly smaller-sized microplastic particles (1-300 μm), which are known to be more harmful to the environment and human health. Recommendations toward the improvement of methodologies for improving microplastic data, as well as the critical areas that will drive standardization ahead, are addressed.

Comment on the paper 'Soil microplastic pollution under different land uses in tropics, southwestern China'

Research on soil microplastics is currently at an early stage, and there is no widely approved sampling protocol. Even so, any basic research should minimize errors to ensure that they are not amplified in future research. This paper examines some weaknesses of the original research paper 'Soil microplastic pollution under different land uses in tropics, southwestern China' recently published in this journal. The authors neglected to report the equipment used for soil sampling and did not use field blank samples. There is also a soil layer that was incorrectly named. The type and pore size of filter paper used for filtration during pre-analytical soil sample preparation is very important. In this paper the nature of the filter paper used, and its larger pore sizes are questionable by today's scientists. In addition, the authors in the original paper also overlooked reporting the statistical package used for statical analysis and ensuring if all data sets obey normality, homogeneity, and equality before running the one-way ANOVA test. This statistical step is widely considered mandatory, especially in the soil science community. So, this makes it difficult to trust the results documented. Furthermore, in the original paper, the needle and stereo microscope instruments used to sort microplastic-like materials prior to proper analysis are not reliable.

Microplastic pollution in the surface water and sediments from Kallar Kahar wetland, Pakistan: occurrence, distribution, and characterization by ATR-FTIR

This study reports the distribution of microplastics in surface water and sediments collected from Kallar Kahar wetland, Punjab, Pakistan, which is a game reserve and hosts migratory birds during winter season. Microplastics were extracted using density separation and wet oxidation method. The microplastics identification was done under a stereo-microscope, and their polymer compositions were characterized using an attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The average abundance of microplastics in water and sediment samples was 88 ± 14.5 items/L and 5720 ± 2580 items/kg, respectively. The dominant shape groups of microplastics in water were fiber (58.7%), irregular fragments (32.4%), and beads (8.7%) with dominant colors as transparent > black > yellow ≈ white > red > green > pink > blue. Similar distribution in sediments was found, i.e., fiber (61.2%), irregular fragments (28.4%), and beads (10.3%) with dominant colors as transparent > pink > white > red ≈ black > blue > brown > green ≈ yellow. The ATR-FTIR spectra of visible microplastics were identified to be polypropylene (PP), high density polyethylene (HDPE), ethylene vinyl acetate (EVA), low density polyethylene (LDPE), nitrile, polymethyl methacrylate (PMMA), latex, and polyethylene terephthalate (PETE). In the study area, recreational activities, improper waste disposal, and runoff from catchment areas are the main reasons for the contamination of microplastics in the Lake. The pollution load can be minimized by taking measures such as creating awareness, promotion of ecotourism, and reducing plastic use.

Microplastics in plant-microbes-soil system: A review on recent studies

Microplastics (MPs) and nanoplastics (NPs) have been widely studied, mostly focusing on the methods of separation, detection, and adsorption or the ecological effects in aquatic ecosystems. When different sources and types of MPs/NPs enter the soil, they can affect the biogeochemical cycle in terms of the direct impacts on soil physicochemical properties and soil organisms, and the indirect impact on soil biota through changes in soil material cycling. To date, a few studies have focused on the effects of MPs/NPs on soil ecosystems, including soil properties, microbial communities, soil fauna, and plants, as well as the potential or affirmed correlations among them. In this review, we summarized the recent literature on soil MPs/NPs focusing on their types, sources, separation, and ecological impacts on soil properties, microbes, and plants. We attempted to establish an overall relationship between MPs/NPs and soil plant system. Based on existing studies, we also highlight the research gaps and propose several directions for future studies.

A straightforward method for microplastic extraction from organic-rich freshwater samples

The extraction of microplastics from organic-rich freshwater samples is challenging and limited information is available in the literature. This study aims at developing efficient methods for water volume reduction and organic matter removal in freshwater samples, while focusing on the reduction of the economic and environmental costs, maintaining microplastics integrity and avoiding contamination. For the water volume reduction approach, centrifuging freshwater samples (water, sediment, algae, leaves, driftwood, fish tissue) at different speeds (3500, 6000 rpm) and times (5, 10 min) showed that 3500 rpm for 5 min was efficient to settle the mineral and organic material, while preserving the polymers and showing high microplastic recovering rates (93 ± 6%). These recovery rates were significantly higher than the traditional sieving approach (77 ± 22%). The posterior minimal consumption of reagents resulting from the reduction of water volume helped to reduce the economic and environmental costs of the devised methodology, becoming more aligned with green chemistry principles. For biogenic organic matter removal, four digestion solutions were tested on freshwater samples, namely 10% potassium hydroxide, Fenton reagent (30% H₂O₂ + Fe(II)), 7% and 10% sodium hypochlorite (NaClO), under 3 periods of time (1, 6 and 15 h), at 50 °C. Both 7% and 10% NaClO showed the highest rates of organic matter removal (86 ± 1% and 90 ± 1%, respectively), after 6 h at 50 °C. Exposure of virgin and aged polymers (polyethylene, polypropylene, polystyrene, polyvinyl chloride, nylon, polyethylene terephthalate) to NaClO showed no weight, visual, surface structure, Fourier transform infrared spectra and carbonyl index changes, except for nylon, although not to an extent that affected its identification. This method resulted in high recovery rates of polymers (92 ± 6%). Thus, 7% NaClO at 50 °C for 6 h (or overnight) may be efficiently used for microplastic analysis in organic-rich freshwater samples.

Microplastic Extraction from the Sediment Using Potassium Formate Water Solution (H2O/KCOOH)

Microplastics (MPs) are considered an important stratigraphic indicator, or ‘technofossils’, of the Anthropocene. Research on MP abundance in the environment has gained much attention but the lack of a standardized procedure has hindered the comparability of the results. The development of an effective and efficient method of MP extraction from the matrix is crucial for the proper identification and quantifying analysis of MPs in environmental samples. The procedures of density separation used currently have various limitations: high cost of reagents, limited solution density range, hazardous reagents, or a combination of the above. In this research, a procedure based on density separation with the use of potassium formate water solution (H2O/KCOOH) in controlled conditions was performed. Experimental sediment mixtures, spiked with polyethylene (PE), polystyrene (PS), polyurethane (PUR) and polyethylene terephthalate (PET) particles were prepared and an extraction procedure was tested in the context of a weight-based quantitative analysis of MPs. This article discusses the effectiveness and safety of the method. It additionally provides new information on the interactions between MP particles and the mineral matter of the sediment. Results were acquired with the use of instrumental methods, namely thermogravimetry (TG), Fourier Transform Infrared (FTIR) spectroscopy, Field Emission Scanning Electron microscopy and Energy Dispersive spectrometry (SEM/EDS), as well as X-ray fluorescence (XRF) analysis.

Critical steps for microplastics characterization from the atmosphere

The microplastics found in many environments, whether in atmospheric, terrestrial, aquatic marine, or freshwater systems, result from exaggerated consumption of plastics. These, when discarded incorrectly, persist in the environment, and degrade into many forms. Researchers have studied microplastics using many collection and characterization methodologies, yet often obtaining divergent results for the same environments. This study presents a bibliographic review of sampling and characterization methodologies for nano and microplastics in the atmospheric environment. Part I of this review presents sampling types and pre-treatment microplastics found in the air to elucidate the principal means of separating plastic species with consequent polymer identification. In Part II, Infrared and Raman Spectroscopy techniques are evaluated for their precision in microplastic identification. The study demonstrates by a systematic revision that depending on the MPs origin, certain characterization techniques are more appropriate. Considering the direct influence of sample impurities, sample pre-treatment is a critical step for correct chemical identification.

Analyzing microplastics with Nile Red: Emerging trends, challenges, and prospects

The development and applications of effective analytical techniques for identification and quantification of microplastics in diverse spheres are increasing in the scientific arena. Nile Red (NR) staining has progressed as a low-cost, simple-to-use approach for analyzing the environmental impact of a wide spectrum of microplastics (e.g., ≥ 3 µm - ≤ 5 mm; polyethylene, polypropylene, and polyvinyl chloride etc.). Given the recent surge of research into this methodology, it is critical to examine the findings and present future directions. Herein, we review accomplishments to date of the current protocols describing the sample preparation, staining and fluorescence conditions, contamination measures, and data analysis based on 56 field observations focusing on microplastic pollution and NR staining technique. Additionally, we discuss the challenges in current analyses towards standardization and recommendations related to it. Finally, we conclude that, despite methodological discrepancies, the NR method has emerged as a viable standalone substitute for visual identification; yet not all that fluoresce with NR are microplastics, which necessitates extensive sample preparation or additional spectroscopy techniques for chemical analysis to validate the results. This article informs the reader about how the NR technique is advancing microplastic research and identifies current needs for future advancements.

Oil extraction following digestion to separate microplastics from mussels

Mussels are often used as biological indicators for monitoring marine microplastic pollution. The crucial procedure during monitoring is the separation of microplastics from mussel samples. We investigated the separation efficiencies of six combinations of two digestion solutions (10% KOH and 30% H₂O₂) and three extraction solutions (NaCl, oil in H₂O, and oil in NaCl) for mussels with low- and high-density microplastics. After KOH digestion, no polyethylene terephthalate (PET) could be extracted using the three extraction solutions, which might be due to the degradation of PET. After H₂O₂ digestion, the total extraction recovery rates of polypropylene, polyvinyl chloride, and PET for oil in H₂O and oil in NaCl solution ranged from 95.6% ± 5.09%-100%, which were higher than those of the saturated NaCl solution (51.1% ± 17.1%-67.8% ± 13.9%). The first extraction recovery rates of oil in NaCl solution for PP, PET, and PVC were higher than those of oil in H₂O. In this study, extraction by oil in NaCl solution after 30% H₂O₂ digestion was suggested to separate microplastics from mussels. This method is conducive to promoting the standardization of microplastic monitoring in mussels and might be suitable for large-scale monitoring of marine microplastic pollution.

Selection of a density separation solution to study microplastics in tropical riverine sediment

Microplastics (MPs) are small (< 5 mm) plastic particles that are widely found in marine, freshwater, terrestrial and atmospheric environments. Due to their prevalence and persistence, MPs are considered an emerging contaminant of environmental concern. The separation and quantitation of MPs from freshwater sediments is a challenging and critical issue. It is necessary to identify the fate and sources of MPs in the environment, minimise their release and adverse effects. Compared to marine sediments, standardised methods for extracting and estimating the amount of MPs in freshwater sediments are relatively limited. The present study focuses on MP recovery efficiency of four commonly used salt solutions (NaCl, NaI, CaCl₂ and ZnCl₂) for isolating MPs during the density separation step from freshwater sediment. Known combinations of artificial MP particles (PS, PE, PVC, PET, PP and HDPE) were spiked into standard river sediment. Extraction using NaI, ZnCl₂ and NaCl solutions resulted in higher recovery rates from 37 to 97% compared to the CaCl₂ solution (28-83%) and varied between polymer types. Low-density MPs (PE, HDPE, PP and PS) were more effectively recovered (> 87%) than the denser polymers (PET and PVC: 37 to 88.8%) using NaCl, NaI and ZnCl₂ solutions. However, the effective flotation of ZnCl₂ and NaI solutions is relatively expensive and unsafe to the environment, especially in the context of developing countries. Therefore, considering the efficiency, cost and environmental criteria, NaCl solution was selected. The protocol was then tested by extracting MPs from nine riverine sediment samples from the Red River Delta. Sediments collected from urban rivers were highly polluted by MPs (26,000 MPs items·kg^-1 DW) compared to sediments located downstream. Using a NaCl solution was found to be effective in this case study and might also be used in long-term and large-scale MP monitoring programmes in Vietnam.

Removal of microplastics from water by magnetic nano-Fe3O4

Microplastics (MPs) have been widely detected in aquatic environments, and become emerging contaminants of growing concern. It is urgently needed to explore how to effectively remove MPs from water. This study first established an alternative method of removing MPs by magnetic nano-Fe₃O₄. Results showed that 1.3 g·L^-1 nano-Fe₃O₄ and 150 min treatments caused optimal magnetization of MPs via surface absorption. Then, magnetized MPs in water can be conveniently removed by suction of the magnet. The average removal rate of four common types of MPs including polyethylene, polypropylene, polystyrene and polyethylene terephthalate in size of approximately 200-900 μm was 86.87 ± 6.92%, 85.05 ± 4.70%, 86.11 ± 6.21%, and 62.83 ± 8.34%, respectively. The removal rate varied among polymer- and size-different MPs, and was positively related to the density of nano-Fe₃O₄ absorbed on MP surfaces. In addition, the removal rate of MPs in artificial seawater was relatively high in comparison to pure water. Furthermore, the established approach was effectively applied to remove MPs in environmental water bodies including river water, domestic sewage, and natural seawater, with the removal rate of higher than 80%. Altogether, this study provided a novel and simple removal approach to remove MPs in water, which has a certain application prospect.

A proposed nomenclature for microplastic contaminants

Microplastics are emerging contaminants with a wide environmental distribution and potential to elicit adverse impacts on organisms. Despite this lack of consistency among reports, data obtained from different investigations are often compared, resulting in the potential for misrepresentation of global microplastic contamination. Major interlaboratory variability in quantification of microplastic levels stem from size-related differences in sampling and analysis with different density solutions to separate microplastics. Herein, we propose a nomenclature that provides key information relating to the microplastics abundance in samples. That is, the proposed nomenclature, MPs_c^{a, b}, informs on mesh or filter size used in sampling, the density of flotation solution used to separate the microplastics, and the detection limit during the analysis progress of microplastics. This proposed nomenclature would facilitate comparisons among studies to avoid over- or under-estimation of global microplastic levels. Moreover, it would also facilitate the interpretation of meta-data in future assessments.

Extraction of microplastics from sediment matrices: Experimental comparative analysis

Microplastics are small (<5 mm) fragments of plastic debris that are ubiquitous in oceans and terrestrial ecosystems. Studies on microplastics in sediment and soil matrices are particularly challenging because of the need to separate the plastics from the sediments. We investigated the efficiencies of 18 combinations of six extracting solutions (ESs) (oil, water, oil-in-water, NaCl, oil-in-NaCl, and NaI) and three isolation methods (IMs) (hand stirring, centrifugation, and aeration) for fine and coarse sediments, with low and high density polymers. IMs did not affect the extraction efficiency. Except in case of oil, all ESs enabled good extraction (84 ± 17%) of light polymers (PE and PE-ABS). NaI presented the best extraction efficiency (71 ± 17%) for the densest polymers (PET, PES, and PA). For these ESs, fibers were extracted at a lower efficiency than pellets and fragments, and sediment gran size did not affect the extraction. For other ESs, mean extraction rates ranged from 5% to 48%. Overall, the extraction efficiencies were lower than those found in the literature, despite repeating the separation process three times. The collection of floating materials remained a problem, as plastics tended to adhere to the glass wall. Our work will help the comparability between previous and future monitoring results and the selection of the most suitable protocols for future studies. This work clearly demonstrates also that there is no robust protocol for extracting all types and forms of microplastics from fine sediments and that research efforts to arrive at a reliable method remain by taking account the interaction of MPs with other particles as well as the electrostatic properties of MP.

Disparities in Methods Used to Determine Microplastics in the Aquatic Environment: A Review of Legislation, Sampling Process and Instrumental Analysis

Plastic particles smaller than 5 mm, i.e., microplastics, have been detected in a number of environments. The number of studies on microplastics in marine environments, fresh water, wastewater, the atmosphere, and the human body are increasing along with a rise in the amounts of plastic materials introduced into the environment every year, all contributing to a range of health and environmental issues. Although the use of primary microplastics has been gradually reduced by recent legislation in many countries, new knowledge and data on these problems are needed to understand the overall lifecycle of secondary microplastics in particular. The aim of this review is to provide unified information on the pathways of microplastics into the environment, their degradation, and related legislation, with a special focus on the methods of their sampling, determination, and instrumental analysis. To deal with the health and environmental issues associated with the abundance of microplastics in the environment, researchers should focus on agreeing on a uniform methodology to determine the gravity of the problem through obtaining comparable data, thus leading to new and stricter legislation enforcing more sustainable plastic production and recycling, and hopefully contributing to reversing the trend of high amounts of microplastics worldwide.

Commercial Gilthead Seabream (Sparus aurata L.) from the Mar Menor Coastal Lagoon as Hotspots of Microplastic Accumulation in the Digestive System

This paper presents the results on the presence and characterization of microplastics (MP) in the gastrointestinal tract of gilthead seabream (Sparus aurata L.), a species of commercial interest from the Mar Menor coastal lagoon in Southeast Spain. This is the first time that microplastic ingestion is recorded in any species from this semi-enclosed bay. Stomach and intestine from a total of 17 specimens captured by local fishermen were processed, and microplastic particles and fibers found in all of them were displayed. Overall, 40.32% (279/692) of total isolated microparticles proved to be microplastics; i.e., <5 mm, as identified by FTIR spectroscopy. The average value by fish was 20.11 ± 2.94 MP kg^-1, corresponding to average concentrations of 3912.06 ± 791.24 and 1562.17 ± 402.04 MP by kg stomach and intestine, respectively. Four MP forms were isolated: fiber (71.68%), fragment (21.15%), film (6.81%), and microbead (0.36%), with sizes ranging from 91 µm to 5 mm, an average of 0.83 ± 0.04 mm, and no statistically significant differences between mean sizes in stomach and intestine samples (F-test = 0.004; p = 0.936). Nine polymer types were detected, although most of fibers remained unidentified because of their small size, the presence of polymer additives, or closely adhered pollutants despite the oxidizing digestion carried out to eliminate organic matter. No significant correlation was found between main biological parameters and ingested microplastics, and high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyethylene polypropylene (PEP), and polyvinyl (PV) were identified as the most abundant polymers. The average microplastic ingestion in this study area was higher than those reported in most studies within the Mediterranean Sea, and closely related to microplastic pollution in the surrounding area, although with a predominance of fiber form mainly due to fishery activities.

Assessment of Microplastics in a Municipal Wastewater Treatment Plant with Tertiary Treatment: Removal Efficiencies and Loading per Day into the Environment

This study investigates the removal of microplastics from wastewater in an urban wastewater treatment plant located in Southeast Spain, including an oxidation ditch, rapid sand filtration, and ultraviolet disinfection. A total of 146.73 L of wastewater samples from influent and effluent were processed, following a density separation methodology, visual classification under a stereomicroscope, and FTIR analysis for polymer identification. Microplastics proved to be 72.41% of total microparticles collected, with a global removal rate of 64.26% after the tertiary treatment and within the average retention for European WWTPs. Three different shapes were identified: i.e., microfiber (79.65%), film (11.26%), and fragment (9.09%), without the identification of microbeads despite the proximity to a plastic compounding factory. Fibers were less efficiently removed (56.16%) than particulate microplastics (90.03%), suggesting that tertiary treatments clearly discriminate between forms, and reporting a daily emission of 1.6 × 107 microplastics to the environment. Year variability in microplastic burden was cushioned at the effluent, reporting a stable performance of the sewage plant. Eight different polymer families were identified, LDPE film being the most abundant form, with 10 different colors and sizes mainly between 1–2 mm. Future efforts should be dedicated to source control, plastic waste management, improvement of legislation, and specific microplastic-targeted treatment units, especially for microfiber removal.

Detection of Microplastic in Salts Using Terahertz Time-Domain Spectroscopy

We report on a prototypical study of the detection of microplastic embedded in table salts by using terahertz time-domain spectroscopy. In the experiment, high-density polyethylene (HDPE) of sizes from 150 to 400 μm are used as a representative microplastic and mixed with table salts. Analyzing terahertz transmittance with an effective medium model, we extract various optical properties such as refractive index, absorption coefficient, and real/imaginary parts of the dielectric constant of the mixture. Consequently, the optical properties exhibit volume-ratio-dependence in 0.1-0.5 THz regimes. Especially, the refractive index and the real part of the dielectric constant possess monotonic frequency dependence, meaning that the quantities can be relevant indicators for the detection of the microplastic in terms of practical applications. Our work proves that terahertz time-domain spectroscopy can pave a way to recognize microplastic mixed with salts and be expanded for detecting various micro-sized particles.