Prevalence of microplastics in Singapore's coastal marine environment

Environmental impact of microplastics and potential health hazards

Microscopic plastic (microplastic) pollutants threaten the earth's biodiversity and ecosystems. As a result of the progressive fragmentation of oversized plastic containers and products or manufacturing in small sizes, microplastics (particles of a diameter of 5 mm with no lower limit) are used in medicines, personal care products, and industry. The incidence of microplastics is found everywhere in the air, marine waters, land, and even food that humans and animals consume. One of the greatest concerns is the permanent damage that is created by plastic waste to our fragile ecosystem. The impossibility of the complete removal of all microplastic contamination from the oceans is one of the principal tasks of our governing body, research scientists, and individuals. Implementing the necessary measures to reduce the levels of plastic consumption is the only way to protect our environment. Cutting off the plastic flow is the key remedy to reducing waste and pollution, and such an approach could show immense significance. This review offers a comprehensive exploration of the various aspects of microplastics, encompassing their composition, types, properties, origins, health risks, and environmental impacts. Furthermore, it delves into strategies for comprehending the dynamics of microplastics within oceanic ecosystems, with a focus on averting their integration into every tier of the food chain.

Biomonitoring of microplastics, anthropogenic microfibres and glass retroreflective beads by marine macroalgae

Microplastics and other microscopic debris are a concern in the coastal environment but measurements in the water column and sediment are often problematic and rely on non-standardised and highly variable methodologies. To this end, we explore the potential of different species of temperate-cold marine macroalgae as passive biomonitors of anthropogenic microparticles at three contrasting locations in southwest England. Specifically, fronds from samples of fucoids and Ulva lactuca (n = 9 in total, and three from each location) have been sectioned and analysed directly under a microscope and anthropogenic microparticles counted and subsequently characterised for chemical composition. Microparticles were heterogeneously distributed throughout sections from the same sample. However, on a dry weight basis, combined microparticle concentrations for each sample ranged from about 7.5 g-1 to 110 g-1, and from about 0.2 cm-2 to 0.9 cm-2, and for a given species were higher in samples from a semi-enclosed harbour and urban beach than in samples from a protected beach facing the open sea. These values compare with published concentrations of microplastics and microfibres reported for the regional water column on the order of 0.1 m-3. Most particles were cellulosic (e.g., rayon) and petroleum-based (mainly polyester and polyethylene terephthalate) fibres but plastic fragments were also present on most samples. Glass retroreflective beads derived from road markings were also present at up to 18 g-1 on fucoids from the urban beach because of its proximity to a stormwater effluent. Most microparticles were adhered to the smooth parts of the macroalgal surface but some displayed wrapping around edges and creases or entrapment by appendages. The practical and environmental implications of macroalgae passively capturing significant quantities of anthropogenic microparticles are discussed.

Representation of investigation results of microplastics on sandy beaches-accumulation rate and abundance in the entire study site

Long-term microplastics (MPs) environmental pollution trends cannot be understood only by investigating their presence on beaches. Without estimating MPs for the entire beach, comparisons between multiple beaches cannot be made. In this study, Nagasaki Prefecture was selected as the study site, we measured MPs accumulation rate to express the MPs pollution trend and weighted the measurement results to enable comparison of MPs content among multiple sandy beaches. The MPs accumulation rate in the study site was measured by periodic investigation at fixed spots. The average in the supratidal zone was 1.5 ± 0.9 mg-MPs/(m2-sand⋅ d) (n = 15). The weighting of the MPs content in hot spots and non-hot spots by their respective areas enabled us to obtain the representative value and the dispersion of the MPs content in the entire study site. The MPs contents in the three beaches were 298 ± 144, 1,115 ± 518, and 4,084 ± 2,243 mg-MPs/(m2-sand), respectively. Using these values, it is possible to compare the MPs contents of multiple beaches.

Marine litter and microplastic pollution in mangrove sediments in the Sea of Oman

Marine litter and microplastic pollution in mangroves pose significant threats. This study of litter in Omani mangroves revealed an average density of 0.83 to 21.92 items/m2. Quriyat lagoon emerged as the most contaminated area, hosting 133 items/m2, while Qurum Natural Reserve lagoon showed the least contamination at 10 items/m2. Plastics constituted 73-96 % of the litter, with microplastic levels in sediment ranging from 6 to 256 pieces/kg. Al-Sawadi's lagoon had the highest microplastic abundance (27.52 ± 5.32 pieces/kg), in contrast to Al Qurum's Marine Protected Area with the lowest (0.60 ± 1.12 pieces/kg). Microplastics, categorized as fragments, pellets, and fibers, were distributed across zones 40.05 % landward, 30.97 % seaward, and 28.98 % in the middle mangrove zones. Primary plastic polymers identified were Polyethylene (PE) at 40 % and High-Density Polyethylene (HDPE) at 28 %, along with others found in specific areas. Our findings provide essential baseline data for future monitoring efforts and management strategies in Oman and other countries.

Nano-scale and micron-scale plastics amplify the bioaccumulation of benzophenone-3 and ciprofloxacin, as well as their co-exposure effect on disturbing the antioxidant defense system in mussels, Perna viridis

Plastics ranging from nano-scale to micron-scale are frequently ingested by many marine animals. These particles exhibit biotoxicity and additionally perform as vectors that convey and amass adsorbed chemicals within organisms. Meanwhile, the frequency of detection of the benzophenone-3 and ciprofloxacin can be adsorbed on plastic particles, then accumulated in bivalves, causing biotoxicity. To understand their unknown accumulative kinetics in vivo affected by different plastic sizes and toxic effect from co-exposure, several scenarios were set up in which the mode organism were exposed to 0.6 mg/L of polystyrene carrying benzophenone-3 and ciprofloxacin in three sizes (300 nm, 38 μm, and 0.6 mm). The live Asian green mussels were chosen as mode organism for exposure experiments, in which they were exposed to environments with plastics of different sizes laden with benzophenone-3 and ciprofloxacin, then depurated for 7 days. The bioaccumulation and depuration kinetics of benzophenone-3 and ciprofloxacin were measured using HPLC-MS/MS after one week of exposure and depuration. Meanwhile, their toxic effect were investigated by measuring the changes in six biomarkers (condition index, reactive oxygen species, catalase, glutathione, lipid peroxidation, cytochrome P450 and DNA damage). The bioconcentration factors in mussels under different exposure conditions were 41.48-111.75 for benzophenone-3 and 6.45 to 12.35 for ciprofloxacin. The results suggested that microplastics and nanoplastics can act as carriers to increase bioaccumulation and toxicity of adsorbates in mussels in a size-dependent manner. Overproduction of reactive oxygen species caused by microplastics and nanoplastics led to increased DNA damage, lipid peroxidation, and changes in antioxidant enzymes and non-enzymatic antioxidants during exposure. Marked disruption of antioxidant defenses and genotoxic effects in mussels during depuration indicated impaired recovery. Compared to micron-scale plastic with sizes over a hundred micrometers that had little effect on bivalve bioaccumulation and toxicity, nano-scale plastic greatly enhanced the biotoxicity effect.

Abundance and distribution of microplastics on sandy beaches of the eastern Moroccan Mediterranean coast

Microplastics (MPs) were investigated at 19 sandy beaches along the eastern Mediterranean Moroccan coast. Sediment samples (5 mm-63 μm) were analyzed to identify MPs abundance, size, shape, color and nature. MPs concentration ranged from 40 ± 7.4 to 230 ± 48.6 MPs kg-1; fibrous MPs were the most abundant (74.72 %), followed by fragments (20.26 %), films (3.27 %), pellets (1.42 %) and foams (0.33 %). Large MPs (1-5 mm) accounted for 58 %, while small (< 1 mm) for 42 %. The 1-2 mm fraction of sediments presented the greatest amounts (30.67 %) of MPs. Transparent (50 %) and blue (17 %) were most common colors and most of particles were angular and irregularly shaped. Fourier Transform Infrared Spectroscopy (FTIR) analysis showed that PE (Polyethylene), PS (Polystyrene) and PP (Polypropylene) and PVC (Polyvinyl chloride) were the most common polymers. These findings revealed a moderate level of microplastic pollution along the beaches of the eastern Moroccan Mediterranean coast.

Environmental and ecological risk of microplastics in the surface waters and gastrointestinal tract of skipjack tuna (Katsuwonus pelamis) around the Lakshadweep Islands, India

The presence of microplastics (MPs) in marine ecosystems is widespread and extensive. They have even reached the deepest parts of the ocean and polar regions. The number of articles on plastic pollution has increased in recent years, but few have investigated the MPs from oceanic islands which are biodiversity hotspots. We investigated the possible microplastic contamination their source and characteristics in surface waters off Kavaratti Island and in the gastrointestinal tract (GT) of skipjack tuna, Katsuwonus pelamis collected from Kavaratti Island of the Lakshadweep archipelago. A total of 424 MP particles were isolated from the surface water samples collected from off Kavaratti Island with an average abundance of 5 ± 1nos./L. A total of 117 MPs were recovered from the GT of skipjack tuna from 30 individual fishes. This points to a potential threat of MP contamination in seafood around the world since this species has a high value in local and international markets. Fiber and blue color were the most common microplastic morphotypes and colors encountered, respectively, both from surface water and GT of fish. Smaller MPs (0.01-1 mm) made up a greater portion of the recovered materials, and most of them were secondary MPs. Polyethylene and polypropylene were the most abundant polymers found in this study. The Pollution Load Index (1.3 ± 0.21) of the surface water and skipjack tuna (1 ± 0.7) indicates a minor ecological risk for the coral islands, while the Polymer Hazard Index highlights the ecological risk of polymers, even at low MP concentrations. This pioneer study sheds preliminary light on the abundance, properties, and environmental risks of MPs to this highly biodiverse ecosystem.

Assessment of meso- and microplastics distribution in coastal sediments and waters at the middle estuary of the Rio De La Plata, Argentina (SW Atlantic Ocean)

Estuarine coastal water and sediments collected from multiple locations within the middle Río de la Plata (RDLP) estuary were analyzed in order to identify the presence of microplastics (MPs, <5 mm) and mesoplastics (MePs, 5-25 mm) in one of the most significant estuaries in the Southwestern Atlantic. The present study represents one of the first researches to survey MPs and MePs contamination in key stations at RDLP estuary. Average concentrations of 14.17 ± 5.50 MPs/L and 10.00 MePs/L were detected in water samples, while 547.83 ± 620.06 MPs/kg (dry weight) and 74.23 ± 47.29 MePs/kg d.w. were recorded in sediments. The greatest abundances were observed in the more anthropized areas, near urban settlements. Fibers were the most conspicuous plastic items in water and sediments, followed by fragments. On the other hand, surface sediments, and 50 cm and 100 cm-depth sediments also presented MPs and MePs indicating they could serve as a stratigraphic indicator for recently formed sediments. The main polymer type identified were acrylic fibers, followed by polypropylene (PP) and polyethylene terephthalate (PET). Besides, SEM-EDX detected the presence of Si, Fe, Ti, Al and Cl onto the plastics' surface. These elements may serve as additives to enhance the plastics' properties, such as in the case of Ti, or they could originate from the environment, like biogenic Si or Fe, and Al possibly as a component of the suspended particles or sediments adhered to the micro or meso plastics. Finally, the results of the present study showed that MPs and MePs are commonly found in waters and also tend to be trapped in sediments of the RDLP estuary supporting the assertion that these areas play a substantial role in influencing the transport, dispersion, and buildup of MPs in estuarine regions.

Microplastics and associated chemicals in drinking water: A review of their occurrence and human health implications

Microplastics (MPs) have entered drinking water (DW) via various pathways, raising concerns about their potential health impacts. This study provides a comprehensive review of MP-associated chemicals, such as oligomers, plasticizers, stabilizers, and ultraviolet (UV) filters that can be leached out during DW treatment and distribution. The leaching of these chemicals is influenced by various environmental and operating factors, with three major ones identified: MP concentration and polymer type, pH, and contact time. The leaching process is substantially enhanced during the disinfection step of DW treatment, due to ultraviolet light and/or disinfectant-triggered reactions. The study also reviewed human exposure to MPs and associated chemicals in DW, as well as their health impacts on the human nervous, digestive, reproductive, and hepatic systems, especially the neuroendocrine toxicity of endocrine-disrupting chemicals. An overview of MPs in DW, including tap water and bottled water, was also presented to enable a background understanding of MPs-associated chemicals. In short, certain chemicals leached from MPs in DW can have significant implications for human health and demand further research on their long-term health impacts, mitigation strategies, and interactions with other pollutants such as disinfection byproducts (DBPs) and per- and polyfluoroalkyl substances (PFASs). This study is anticipated to facilitate the research and management of MPs in DW and beverages.

A new approach to classifying polymer type of microplastics based on Faster-RCNN-FPN and spectroscopic imagery under ultraviolet light

Hazardous compounds from microplastics in coastal and marine environments are adsorbed by live organisms, affecting human and marine life. It takes time, money and effort to study the distribution and type of microplastics in the environment, using appropriate expensive equipment in a laboratory. However, deep learning can assist in identifying and quantifying microplastics from an image. This paper presents a novel microplastic classification method that combines the benefits of UV light with deep learning. The Faster-RCNN model with a ResNet-50-FPN backbone was implemented to detect and identify microplastics. Microplastic images from the field taken under UV light were used to train and validate the model. This classification model achieved a high precision of 85.5-87.8%, and the mAP scores were 33.9% on an internal test set and 35.7% on an external test set. This classification approach provides a high-accuracy, low-cost, and time-effective automated identification and counting of microplastics.

Study on the release of microplastic particles with different particle sizes in sediments caused by wave-induced liquefaction

Every year, almost 1.15-2.41 million tons of plastic from terrestrial rivers undergo fragmentation under certain conditions and settle in the estuarine delta and shallow marine shelf areas, making this region a "sink" for land-based microplastics. Owing to its fast deposition rate, relatively soft sediment bed, and shallow water depth, the estuarine delta region is prone to liquefaction under high wind and wave conditions. This could potentially release deeply buried microplastic particles during the liquefaction process, posing further threats to marine ecology and human health. To investigate this phenomenon, laboratory experiments were conducted using a water tank to simulate wave-induced liquefaction of sediment beds. The results showed that under the influence of wave-induced liquefaction, 56.2 % of microplastic particles were released back into the sediment surface, with larger particles being released to a greater extent. Based on these experimental results, this study also analyzed and discussed the release rate and mechanisms of microplastic particles from sediment during wave-induced liquefaction, estimating that the maximum release rate of microplastic particles under the experimental conditions could reach 0.34 mm/min.

Microbial community structure and co-occurrence network stability in seawater and microplastic biofilms under prometryn pollution in marine ecosystems

Prometryn has been extensively detected in marine environment because of its widespread usage in agriculture and aquaculture and has been concerns since its serious effects on aquatic organisms. However, its impact on the microbial community in the marine ecosystem including seawater and biofilm is still unclear. Therefore, a short-term indoor microcosm experiment of prometryn exposure was conducted. This study found that prometryn had a more significant impact on the structure and stability of the microbial community in seawater compared to microplastic biofilms. Additionally, we observed that the assembly of the microbial community in biofilms was more affected by stochastic processes than in seawater under the exposure of prometryn. Our study provided evidence for the increasing impact of the microbial communities under the stress of prometryn and microplastics.

Length-dependent toxic effects of microplastic fibers on Chlorella pyrenoidosa

Microplastics (MPs), a pervasive pollutant in aquatic environments, are increasingly recognized for their detrimental effects on aquatic organisms. However, the present understanding of their impact on phytoplankton, particularly freshwater microalgae, remains limited. Furthermore, previous studies have predominantly focused on MP particles, largely overlooking the most prevalent form of MPs in aquatic settings-fibers. In this study, we scrutinized the toxicological implications of microplastic fibers (MFs) spanning four distinct lengths (50 μm, 100 μm, 150 μm, and 200 μm) on the protein-nucleated algae Chlorella pyrenoidosa over a six-day period. The study unequivocally demonstrated that MFs markedly impeded C. pyrenoidosa growth, diminished photosynthetic pigment content, and induced oxidative stress, with all observed effects exhibiting a length-dependent correlation. Electron microscopy further revealed notable damage to algal cell membranes. Cell membrane shrinkage, cytoplasm outflow, and abnormalities in cell division were observed in the 150 μm and 200 μm groups. Furthermore, C. pyrenoidosa clustered around the 200 μm MF were notably denser compared to other groups. The present study demonstrated that MFs had length-dependent toxic effects on C. pyrenoidosa. These findings offer novel insights into the deleterious impact of MFs on aquatic organisms, underscoring the pivotal role of length in influencing their toxicity.

Quantification, characterization and risk assessment of microplastics from five major estuaries along the northern Bay of Bengal coast

Microplastics (MPs) as hazardous contaminants has drawn the rapid attention of the general public due to their omnipresence and adverse impacts on ecosystems and human health. Despite this, understanding of MPs contamination levels in the estuarine ecosystems along the Bay of Bengal coast remains very limited. This research focused on the presence, spatial distribution, morpho-chemical characteristics and ecological implications of MPs in water and sediment from five key estuaries (Meghna, Karnaphuli, Matamuhuri, Bakkhali, and Naf rivers) within the Bengal delta. Out of the five estuaries, the Meghna exhibited the least amount of MPs in both surface water (150.00 ± 65.62 items/m3) and sediment (30.56 ± 9.34 items/kg). In contrast, the highest occurrence of MPs was recorded in Karnaphuli river water (350.00 ± 69.22 items/m3) and Matamuhuri river sediment (118.33 ± 26.81 items/kg). ANOVA indicated a statistically significant distinction (p < 0.01) among the examined estuaries. Most identified MPs were fibers and < 0.5 mm in size in both water and sediment samples. Transparent MPs were dominant in both water (42.28%) and sediment (45.22%). Besides violet, red, blue, pink and green colored MPs were also observed. Various polymer types, including PE, PP, PET, PS, Nylon, EVA, and ABS, were detected, with PE being the dominant one. Based on the polymer risk index (PHI), the estuaries were classified as hazard level V, signifying a severe level of MP contamination. However, the potential ecological hazardous index (PHI), potential ecological risk index (RI), and pollution load index (PLI) indicated moderate pollution levels. This study offers initial insights into the pollution caused by MPs in major estuaries of Bengal delta, which policymakers can utilize to implement suitable management strategies.

Freshwater algal biofilm assemblages are more effective than invertebrate assemblages at aggregating microplastics

Microplastics, plastic particles less than 5 mm in length, are a ubiquitous pollutant in the environment, but research on freshwater microplastic contamination is lacking. A possible fate of microplastics in freshwater environments is to become entangled or aggregated in biofilms, which are matrices of algae, bacteria, and micro invertebrates that grow on underwater surfaces, following a progression of settling algae, periphyton, and finally invertebrate colonization. This in-situ study at the Oasis Marina at National Harbor in Oxon Hill, Maryland, examined how the taxonomic assemblages of freshwater biofilms in the Potomac River are associated with the number of microplastics aggregated within them. Aluminum discs, acting as artificial substrate for biofilm growth, were deployed at the water's surface and at 2 m depth to survey biofilm assemblage and were sampled monthly from October 2021-October 2022. Microplastic abundances in the water column were measured every 2 weeks over the same period. Spatial and temporal trends in trapped and suspended microplastics, water quality parameters (temperature, dissolved oxygen, pH, salinity, conductivity, turbidity, ammonia, nitrate, and phosphate), and biofilm assemblages were measured and compared to explore factors affecting the abundance of microplastics and their partitioning between the water column and biofilms. Water quality had no measurable impact on microplastic abundance in the water column at either depth, but temperature was negatively correlated to microplastic abundance in biofilms. As the weather warmed and biofilms progressed to invertebrate settling, they tended to contain fewer microplastics. This may have occurred because less biologically rich biofilms, primarily composed of unicellular algal colonies, provide a favorable surface for microplastic deposition. Understanding seasonal changes in biofilm assemblage and microplastic abundance may help track the fate of microplastics in freshwater systems, particularly in their interactions with lower trophic organisms.

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.

Microplastic contamination in edible marine fishes from the upper Gulf of Thailand

Seafood consumption is a major source of microplastic exposure for humans. Here, we demonstrated microplastic contamination in marine food fishes from the upper Gulf of Thailand. Microplastics were found in gastrointestinal tracts of 46.9 % of fishes sampled, with a mean concentration of 1.6 ± 0.5 pieces per fish or 0.04 ± 0.01 pieces/g of fish tissue. Demersal fishes had higher contamination rates than pelagic fishes. Fibrous-type and blue-colored materials were the most abundant microplastics, while the most common polymers were polyester and polyethylene. No associations between microplastics and histopathological changes were detected. Estimated daily microplastic exposure for human marine fish consumers was 0.03 to 0.1 pieces per person. Although we expect a low risk of microplastic contamination in fish muscle because of very low calculated transfer rates, we recommend continuing surveillance, including evaluations of contamination in the food chain to ensure future seafood safety in this region.

Effects of near-bed turbulence on microplastics fate and transport in streams

Quantifying the impact of hyporheic exchange is crucial for understanding the transport and fate of microplastics in streams. In this study, we conducted several Computational Fluid Dynamics (CFD) simulations to investigate near-bed turbulence and analyze vertical hyporheic exchange. Different arranged spheres were used to represent rough and permeable sediment beds in natural rivers. The velocities associated with vertical hyporheic flux and the gravitational force were compared to quantify the susceptibility of microplastics to hyporheic exchange. Four scenario cases representing different channel characteristics were studied and their effects on microplastics movements through hyporheic exchange were quantitatively studied. Results show that hyporheic exchange flow can significantly influence the fate and transport of microplastics of small and light-weighted microplastics. Under certain conditions, hyporheic exchange flow can dominate the behavior of microplastics with sizes up to around 800 μm. This dominance is particularly evident near the sediment-water interface, especially at the top layer of sediments. Higher bed porosity enhances the exchange of microplastics between water and sediment, while increased flow conditions extend the vertical exchange zone into deeper layers of the bed. Changes in the bedform lead to the most pronounced vertical hyporheic exchange, emphasizing the control of morphological features on microplastics transport. Furthermore, it is found that sweep-ejection events are prevailing near the bed surface, serving as a mechanism for microplastics transport in rivers. As moving from the water column to deeper layers in the sediment bed, there's a shift from sweeps dominance to ejections dominance, indicating changes of direction in microplastics movement at different locations.

Monitoring of anthropogenic microplastic pollution in antarctic fish (emerald rockcod) from the Terranova Bay after a quarter of century

Monitoring the occurrence of microplastic contamination in the Antarctic area is the key to implement policy measures for waste regulations in the research stations. Antarctic fish Trematomus bernachii is a suitable species for establishing microplastic contamination and for investigating changes over time in the concentration and type of microplastics in the Antarctic region. In this paper a total of 78 fish, caught during the 37th Italian Antarctic expedition (2021-2022) in the Ross Sea (Antarctica) were analysed. Different microfibers and dyes were identified by Raman spectroscopy and the results were compared with those obtained for fish sampled in 1998. Differences in polymer type emerged with a predominance of synthetic fibers with respect to natural ones. These changes appear to be related to the increased human activities in the Antarctica over the last twenty years and highlights the need to improve the environmental sustainability of the numerous research stations operating throughout that area.

Coagulative removal of microplastics from aqueous matrices: Recent progresses and future perspectives

Coagulation-flocculation-sedimentation (CFS) system has been identified as one of the favored treatment technique in water/wastewater treatment systems and hence, it is crucial to comprehend the efficacy of different coagulants used in removing microplastics (MPs) from aqueous matrices. Henceforth, this study critically reviews the recent progress and efficacy of different coagulants used to date for MPs removal. This includes laboratory and field-scale studies on inorganic and organic coagulants, as well as laboratory-scale studies on natural coagulants. Inorganic and organic coagulants have varying MPs removal efficiencies such as: Fe/Al-salts (30 %-95 %), alum (99 %), and poly aluminum chloride (13 %-97 %), magnesium hydroxide (84 %), polyamine (99 %), organosilanes (>95 %), and polyacrylamide (85 %-98 %). Moreover, studies have highlighted the use of natural coagulants, such as chitosan, protein amyloid fibrils, and starch has shown promising results in MPs removal with sevral advantages over traditional coagulants. These natural coagulants have demonstrated high MPs removal efficiencies with chitosan-tannic acid (95 %), protein amyloid fibrils (98 %), and starch (>90 %). Moreover, the MPs removal efficiencies of natural coagulants are compared and their predominant removal mechanisms are determined. Plant-based natural coagulants can potentially remove MPs through mechanisms such as polymer bridging and charge neutralization. Further, a systematic analysis on the effect of operational parameters highlights that the pH affects particle surface charge and coagulation efficiency, while mixing speed affects particle aggregation and sedimentation. Also, the optimal mixing speed for effective MPs removal depends on coagulant type and concentration, water composition, and MPs characteristics. Moreover, this work highlights the advantages and limitations of using different coagulants for MPs removal and discusses the challenges and future prospects in scaling up these laboratory studies for real-time applications.

Microplastic contamination in bathing areas in the Central Amazon, Itacoatiara, Brazil

Due to the visible abundance of plastic improperly disposed of in the environment, the number of investigations has increased worldwide in different water bodies and biota. Despite this, studies of contamination by microplastics in freshwater environments in the Amazon are scarce. This study investigated microplastic contamination in sediment samples of bathing areas in the Central Amazon, in Itacoatiara, Amazonas, Brazil. A total of 202 microplastic particles were recorded in the five investigated areas that are used for recreation. These results indicate no significant difference in the number of microplastic particles among the establishments; however, the size of the microplastic particles differed significantly between the establishments. Both blue and red microplastic particles were recorded, with blue particles being the most abundant. The microplastic particles were in the form of fibers and fragments. The number of microplastic particles was significantly different between the areas within and adjacent to the bathing areas, though the size of the microplastic particles was not significantly different in the areas within and adjacent to the bathing areas. There was no significant correlation in the establishments in regard to their frequency of use and contamination (number of microplastic particles). This is the first study that indicates the anthropogenic impacts associated with microplastic contamination in recreation areas within the Amazon Forest, an area considered by the world to be of vital importance for conservation. The results of this study indicate that microplastics are present in these bathing areas of the Central Amazon and that contamination in areas used for recreation may be significantly higher than in areas not used for this purpose.

Spatiotemporal distribution of microplastic debris in the surface beach sediment of the southeastern coast of Bangladesh

This study undertakes a spatiotemporal analysis of microplastic pollution in surface beach sediments, covering 7 coastal beaches in Bangladesh and two seasons-monsoon and winter. The concentration of microplastics extracted from the surface beach sediment is 242.86 particles/kg dw. The results showed both significant seasonal (p value = 0.001) and spatial (p value = 0.004) variation. The abundance and polymer types were significantly higher (57 %) in winter than in the monsoon season (43 %). Touristic and commercial beaches showed higher levels of microplastic pollution than the non-touristic beaches. Polyethylene (28.8 %) and Polypropylene (27.6 %) were the most abundant polymer. The most dominant coloration of microplastics was white (42.6 %). The majority of the microplastics were fibers (33.5 %). Smallest particles measuring <1 mm constituted nearly half of the total microplastics load (48.5 %). This baseline data can be useful in terms of coastal zone management for the southeastern coastal beaches of Bangladesh.

Risk assessment of microplastic exposure: A case study near a refinery factory at the central coast of Vietnam

The goal of this study was to identify the presence of microplastics on the beach near a refinery in the central coast of Vietnam. In this study, 11 sampling sites were selected within a length of 300 m of the beach. The results showed that microplastics were presented in all collected samples with an average concentration of 1582 ± 660 MPs/kg. Fibers were the predominant shape of microplastics found in the samples, which accounted for 57.11 %, while the rest were classified as fragments. The average size of microplastics varied greatly around 83.1 ± 74.3 μm with the vast majority having a size smaller than 50 μm (41.84 %). A total of 11 polymers of microplastics were detected from collected samples, Polyethylene Terephthalate was the main polymer with 46.43 %. The pollution load index of microplastics was 3.15 showing that refinery activities could expose microplastic to the environment.

Unraveling the Marine Microplastic Cycle: The First Simultaneous Data Set for Air, Sea Surface Microlayer, and Underlying Water

Microplastics (MP) including tire wear particles (TWP) are ubiquitous. However, their mass loads, transport, and vertical behavior in water bodies and overlying air are never studied simultaneously before. Particularly, the sea surface microlayer (SML), a ubiquitous, predominantly organic, and gelatinous film (<1 mm), is interesting since it may favor MP enrichment. In this study, a remote-controlled research catamaran simultaneously sampled air, SML, and underlying water (ULW) in Swedish fjords of variable anthropogenic impacts (urban, industrial, and rural) to fill these knowledge gaps in the marine-atmospheric MP cycle. Polymer clusters and TWP were identified and quantified with pyrolysis-gas chromatography-mass spectrometry. Air samples contained clusters of polyethylene terephthalate, polycarbonate, and polystyrene (max 50 ng MP m-3). In water samples (max. 10.8 μg MP L-1), mainly TWP and clusters of poly(methyl methacrylate) and polyethylene terephthalate occurred. Here, TWP prevailed in the SML, while the poly(methyl methacrylate) cluster dominated the ULW. However, no general MP enrichment was observed in the SML. Elevated anthropogenic influences in urban and industrial compared to the rural fjord areas were reflected by enhanced MP levels in these areas. Vertical MP movement behavior and distribution were not only linked to polymer characteristics but also to polymer sources and environmental conditions.

Simulation of encounter rates between zooplankton organisms and microplastics in a tropical estuary

Coastal estuarine systems may hold a large number of microplastic particles, which predators often mistake for prey. This study estimated the encounter rates between microplastics (alleged prey) and zooplankton having different feeding modes, trophic positions, swimming velocities, and perception distances, under calm and turbulent conditions, and during two seasons. Surface water samples were taken at 10/12 sites of the Sontecomapan lagoon, southern Gulf of Mexico, to quantify microplastic concentration. Zooplankton organisms considered were copepods, chaetognaths, and luciferids, common organisms in the lagoon. In June, at surface waters and during calm conditions, mean encounter rates were 1.5, 2450, and 980 particles per individual per hour, that is, for copepods, chaetognaths, and luciferids, respectively. When the wind blows (0.8 m s-1) encounter rates were 1.2, 1.4, and 2.6 times higher than in calm conditions. In October, mean encounter rates under calm conditions were 0.2, 355, and 142 particles per individual per hour, for copepods, chaetognaths, and luciferids; these values increase 1.3, 1.6, and 3.3 times when the wind blows (1.12 m s-1). The major number of encounters in June was due to a higher concentration of microplastics, despite the lower turbulent velocity. Regarding their trophic position, we propose that secondary consumers (chaetognaths and luciferids) are more affected because they could eat microplastics via contaminated prey or accidentally ingest them owing to confusion in the motion signals, especially under turbulent conditions. Another consequence of encounters could be the entanglement of microplastics in the body of the animals, especially in those with complex morphology, such as crustaceans. Encounters between zooplankton and microplastics do not always result in ingestion or entanglement, but the encounters are the first step in the case of occurrence.

Microplastics in the Taiwan Strait and adjacent sea: Spatial variations and lateral transport

This study investigates the distribution, structural properties, and potential impacts of oceanic processes on microplastics (MPs) in the Taiwan Strait (TWS) and surrounding seas. With an average of 174 particles/m3, the MP abundance in surface seawater ranged from 84 to 389 particles/m3. MP abundance ranged from 16 to 382 particles/kg in sediments, with a median of 121 particles/kg. Fragment and fiber were the two most frequently detected shapes. These MPs were found to be composed primarily of carbon and oxygen elements at 70-90% levels using energy-dispersive X-ray spectroscopy. Additionally, several examples had trace levels of metallic components. Black was the color that MPs saw the most often out of all the hues. The two main types of polymers are polyester and rayon, and their production is influenced by home sewage discharge and synthetic fiber production. The main routes of MP transport were land source input, riverine input, and oceanic currents. This study showed that salinity affects the distribution of MPs, with high-salinity seawater serving to saturate their presence. On the other hand, upwelling raises MP concentrations by bringing nutrients from the deep to the surface. Furthermore, it has been discovered that the dilution of the Pearl River plume increases the MP prevalence in the region. The South China Sea Warm Current had the highest lateral MPs transport flux (2.1 × 1014 particles/y), which was followed by the Taiwan Strait Current area (1.0 × 1014 particles/y) and the Guangdong coastal areas (8.6 × 1013 particles/y). In sediments, the MP prevalence was inversely correlated with particle size. Flocculation processes probably made it easier for MPs to travel down the water column and deposit themselves on the aquatic substrate. Although the relationship between MPs, total organic carbon, and total organic nitrogen was not correlated, a favorable trend showed that MPs may discreetly contribute to carbon storage in coastal sediment.

Occurrence of Microplastics in Most Consumed Fruits and Vegetables from Turkey and Public Risk Assessment for Consumers

Microplastics are transferred to humans through the food chain by consuming food contaminated with microplastics. However, the knowledge about the risks of dietary exposure for humans to these particles is very limited. Moreover, only a few studies on microplastic pollution in fruit and vegetables have been carried on. Thus, this study aims to investigate the presence of microplastics in some of the most consumed fruits and vegetables (pear (Pyrus communis), apple (Malus domestica), tomato (Solanum lycopersicum), onion (Allium cepa), potatoes (Solanum tuberosum), and cucumber (Cucumis sativus)) from Turkey and to evaluate the potential risk for consumers. Fruits and vegetable samples were purchased from different markets and fruiterer (two of each) in Muğla province, Southwest of Turkey. Microplastic extraction processes were carried out on the edible parts of the samples. According to the results obtained, a total of 210 particles (2.9 ± 1.6 particle g-1) were detected in all samples. Any significant difference occurred among the different markets. The maximum average amount of microplastic was determined in tomato samples (3.63 ± 1.39 particle g-1). The highest microplastic intake was with tomato (398,520 particles individual-1 year-1 for Estimated Annual Intake (EAI) and Estimated Daily Intake (EDI) for children 68.24 particles kg-1 day-1). The occurrence of microplastics of big size, that are not allowed to pass by plant xylem transport, suggests that fresh vegetables and fruits can be contaminated with plastic, especially during the production phase, during agricultural activities and during the marketing process (transport to the market and purchasing process).

Understanding microplastic pollution of marine ecosystem: a review

Microplastics are emerging as prominent pollutants across the globe. Oceans are becoming major sinks for these pollutants, and their presence is widespread in coastal regions, oceanic surface waters, water column, and sediments. Studies have revealed that microplastics cause serious threats to the marine ecosystem as well as human beings. In the past few years, many research efforts have focused on studying different aspects relating to microplastic pollution of the oceans. This review summarizes sources, migration routes, and ill effects of marine microplastic pollution along with various conventional as well as advanced methods for microplastics analysis and control. However, various knowledge gaps in detection and analysis require attention in order to understand the sources and transport of microplastics, which is critical to deploying mitigation strategies at appropriate locations. Advanced removal methods and an integrated approach are necessary, including government policies and stringent regulations to control the release of plastics.

Extensive estuarine sedimentary storage of plastics from city to sea: Narragansett Bay, Rhode Island, USA

Plastics are an important new component of the global sedimentary system, and much concern exists about their transport, fate and impact. This study presents the first system-scale assessment of sedimentary storage of microplastic for an estuary, Narragansett Bay, RI (USA), and the measurements of shoreline and seabed sediments add to the growing body of literature demonstrating high coastal concentrations. Microplastic concentrations in sediments ranged from 396 to over 13,000 MP particles kg^-1 dry sediment (DW), comparable to other shoreline and seafloor sites located near urban centers. As previously reported for fine sediment and other pollutants, estuarine plastic storage is extensive in Narragansett Bay, especially within the upper urbanized reaches. Over 16 trillion pieces of plastic weighing near 1000 tonnes is calculated to be stored in surface sediments of the Bay based on a power-law fit. This work highlights that estuaries may serve as a significant filter for plastic pollution, and this trapping may have negative consequences for these valuable, productive ecosystems but offer potential for efficient removal.

Micro- and nanoplastic toxicity: A review on size, type, source, and test-organism implications

Polymeric wastes are among the current major environmental problems due to potential pollution and contamination. Within the spectrum of polymeric waste, microplastics (MPs) and nanoplastics (NPs) have gained ground in recent research since these particles can affect the local biota, inducing toxic effects on several organisms. Different outcomes have been reported depending on particle sizes, shape, types, and exposed organisms and conditions, among other variables. This review aimed to compile and discuss the current knowledge and possible literature gaps regarding the MPs and NPs generation and their toxicological effects as stressors, considering polymer type (as polyethylene, polypropylene, polyethylene terephthalate, polystyrene, polyvinyl chloride, or others), size (micro- or nano-scale), source (commercial, lab-synthesized, or environmental) and test organism group. In that sense, 615 publications were analyzed, among which 72 % discussed micro-sized plastics, while <28 % assayed the toxicity of NPs (<1 μm). For most polymers, MPs and NPs were commercially purchased and used without additional size reduction processes; except for polyethylene terephthalate studies that mostly used grinding and cutting methods to obtain MPs. Polystyrene (PS) was the main polymer studied, as both MPs and NPs. PS accounts for >90 % of NPs reports evaluated, reflecting a major literature gap if compared to its 35.3 % share on MPs studies. Among the main organisms, arthropods and fish combined accounted for nearly 40 % of toxicity testing. Overall, the different types of plastics showed a tendency to report toxic effects, except for the 'Survival/lethality' category, which might indicate that polymeric particles induce mostly sublethal toxic effects. Furthermore, despite differences in publication numbers, we observed greater toxicity reported for NPs than MPs with oxidative stress among the majorly investigated endpoints. This study allowed a hazard profile overview of micro/nanoplastics (MNPs) and the visualization of literature gaps, under a broad diversity of toxicological evidence.

The microscopic threat with a macroscopic impact: Microplastics along the southeast Florida reef tract

Microplastics decrease oceanic water quality and negatively impact marine life. This research quantified and classified marine plastic pollution along the Southeast Florida Reef Tract (SEFRT) to estimate the risk of microplastic damage to corals in this region. Surface and bottom water samples were collected at seven sites along the SEFRT over the course of six months and were analyzed for microplastic content. FTIR spectrophotometry was used to evaluate microplastic composition. Overall, seven plastic polymers were found across a total of 1204 microplastic items. Five contaminants were also identified, indicating that microplastics may be congregators of these hazardous contaminants. Significantly more total plastics were found in surface samples than in bottom samples, but plastic quantities were not significantly different when month, depth, and location were combined. Plastics were determined to have entered the ocean from multiple sources; in order to protect vulnerable reef ecosystems in this area, a two-factor approach is necessary to halt the release of microplastics into the ocean, including widespread plastic clean-up efforts and improvements to plastic waste management.

New insights into the migration, distribution and accumulation of micro-plastic in marine environment: A critical mechanism review

Microplastics (MPs) are widely distributed in the marine environment, posing a significant threat to marine biota. The contribution of anthropogenic and terrestrial sources to the aquatic ecosystem has led to an increase in MPs findings, and their abundance in aquatic biota has been reported to be of concern. MPs are formed mainly via photo degradation of macroplastics (large plastic debris), and their release into the environment is a result of the degradation of additives. Eco-toxicological risks are increasing for marine organisms, due to the ingestion of MPs, which cause damage to gastrointestinal (GI) tracts and stomach. Plastics with a size <5 mm are considered MPs, and they are commonly identified by Raman spectroscopy, Fourier transfer infrared (FTIR) spectroscopy, and Laser direct infrared (LDIR). The size, density and additives are the main factors influencing the abundance and bioavailability of MPs. The most abundant type of MPs found in fishes are fiber, polystyrenes, and fragments. These microscale pellets cause physiological stress and growth deformities by targeting the GI tracts of fishes and other biota. Approximately 80% MPs come from terrestrial sources, either primary, generated during different products such as skin care products, tires production and the use of MPs as carrier for pharmaceutical products, or secondary plastics, disposed of near coastal areas and water bodies. The issue of MPs and their potential effects on the marine ecosystem require proper attention. Therefore, this study conducted an extensive literature review on assessing MPs levels in fishes, sediments, seawater, their sources, and effects on marine biota (especially on fishes), chemo-physical behavior and the techniques used for their identification.

Insights into the release of triclosan from microplastics in aquatic environment assessed with diffusive gradient in thin-films

Organic chemicals associated with microplastics (MPs) can be released and thus pose potential risks during weathering processes. However, the thermodynamics and kinetics of their release processes still need to be better understood. Herein, the adsorption and desorption kinetics of triclosan on polystyrene (PS) and polyvinyl chloride (PVC) were investigated by using both batch experiments and diffusive gradients in thin-films (DGT) technique. The pseudo-second-order model fitted the data best, implying that both intraparticle diffusion and external liquid film diffusion influence the adsorption and desorption processes. DGT continuously accumulated triclosan from MP suspensions but slower than theoretical values, indicating some restrictions to desorption. The DGT-induced fluxes in Soils/Sediment (DIFS) model, employed to interpret DGT data, gave distribution coefficients for labile species (K_dl) of 5000 mL g^-1 (PS) and 1000 mL g^-1 (PVC) and the corresponding response times (T_c) were 10 s and 1000 s, respectively. Higher K_dl but smaller T_c for PS than PVC showed that more triclosan adsorbed on PS could be rapidly released, while there were some kinetic limitations for triclosan on PVC. A novel finding was that pH and ionic strength individually and interactively affected the supply of triclosan to DGT. This is the first study to quantify interactions of organics with MPs by using DGT, aiding our understanding of MPs' adsorption/desorption behavior in the aquatic environment.

Microplastic pollution in the offshore sea, rivers and wastewater treatment plants in Jiangsu coastal area in China

Offshore areas are particularly important in recognizing microplastics pollution because they are sinks of land imports and sources of ocean microplastics. This study investigated the pollution and distribution of microplastics in the offshore Sea, rivers and wastewater treatment plants (WWTPs) in Jiangsu coastal area in China. Results showed that microplastics were widely present in the offshore area, with an average abundance of 3.1-3.5 items/m³. Significantly higher abundance was present in rivers (3.7-5.9 item/m³), municipal WWTPs (13.7 ± 0.5 item/m³), and industrial WWTPs (19.7 ± 1.2 item/m³). The proportion of small-sized microplastics (1-3 mm) increased from WWTPs (53%) to rivers (64%) and the offshore area (53%). Polyamide (PA), polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), polystyrene (PS), and rayon (RA) were dominant types of microplastics. Both living and industrial sources contributed to the prevalent microplastics in the offshore Sea. Redundancy analysis showed that small-sized microplastics (1-3 mm) were positively correlated to total phosphorus (TP), while large-sized microplastics (3-5 mm) were positively correlated to TP and NH₃-N. The abundance of PE, PP and PVC microplastics were positively correlated to TP and total nitrogen (TN), thus nutrients could be indicators of microplastics pollution in the offshore area.

The risks of marine micro/nano-plastics on seafood safety and human health

A considerable mass of plastics has been released into the marine environment annually through different human activities, including industrial, agriculture, medical, pharmaceutical and daily care products. These materials are decomposed into smaller particles such as microplastic (MP) and nanoplastic (NP). Hence, these particles can be transported and distributed in coastal and aquatic areas and are ingested by the majority of marine biotas, including seafood products, thus causing the contamination of the different parts of aquatic ecosystems. In fact, seafood involves a wide diversity of edible marine organisms, such as fish, crustaceans, molluscs, and echinoderms, which can ingest the micro/nanoplastics particles, and then transmit them to humans through dietary consumption. Consequently, these pollutants can cause several toxic and adverse impacts on human health and the marine ecosystem. Therefore, this chapter provides information on the potential risks of marine micro/nanoplastics on seafood safety and human health.

Microalgae colonization and trace element accumulation on the plastisphere of marine plastic debris in Monastir Bay (Eastern Tunisia)

In this study, we examined the toxicity potential of the epiplastic microalgal community that developed on low-density polyethylene (LD-PE) plastic debris found in two distinct regions of the Monastir Bay (Tunisia): the coast exposed to anthropogenic discharges and the open sea in front of the Kuriat Islands. Concentrations of potentially toxic elements (PTEs) accumulated in sediments and plastisphere were compared in order to determine their toxicity potential to biological life. The collected plastispheres were predominantly composed of cyanobacteria, chlorophytes, and diatoms. Diatoms display a relatively high diversity (25 species). At all stations, potentially harmful microalgae (PHM) were more abundant in the plastisphere than in seawater and the coastal zone seems to harbour increased number of potentially harmful cyanobacteria within the plastisphere. At the offshore station S1, the PHM community was dominated by the potentially harmful diatoms belonging to the genus Pseudo-nitzschia. Phormidium sp. was the main potentially harmful cyanobacterium identified in the plastisphere of S1. PTEs concentration in the plastisphere was higher than in sediment and ranking with very high contamination factors at all sites according to the sequence Pb > Cu > Cd > Ni > Zn. The highest accumulation of PTEs in the plastisphere was recorded near harbors and industrial zones with important human interference. This work shows that plastisphere can be a threat to vulnerable species not only because it can contain PHM but also because it can accumulate PTEs.

Microplastics pollution in the river Karnaphuli: a preliminary study on a tidal confluence river in the southeast coast of Bangladesh

Bangladesh is a deltaic country in Asia, and its riverine systems ultimately drain into the Bay of Bengal. Plastic is a severe environmental issue for coastal-marine ecosystems due to the indiscriminate usage and discarding of plastic items in the upstream river that eventually find their route into the Bay of Bengal. Microplastics (MPs) are widespread pollutants in almost all environmental compartments, including aquatic environments. This study aimed to quantify and understand the distribution of microplastics in surface water and sediments of the river Karnaphuli, a tidal confluence river adjacent to the Chattogram seaport city of Bangladesh, a highly inhabited and industrial area on the southeast coast of the Bay of Bengal. A manta trawl net (300-µm mesh size) was used to collect surface water samples, while an Ekman dredge was used to collect sediment samples. The concentrations of microplastics in the surface water of the river Karnaphuli during late monsoon, winter, and early summer were recorded to be 120,111.11, 152,222.22, and 164,444.44 items/km², respectively, while in sediments, those were recorded to be 103.83, 137.50, and 103.67 items/kg, respectively. A higher abundance of microplastics was observed in downstream surface water (228,888.88 items/km²) and sediments (164.17 items/kg). Smaller sizes (0.3 to 0.5 mm) of microplastics were predominant, fibers or threads were the frequent types, and black was the most common color in the river Karnaphuli. The Fourier transform infrared analysis revealed that polyethylene terephthalate (surface water: 22%, sediments: 19%), polyamide (surface water: 15%, sediments: 13%), polyethylene (surface water: 12%, sediments: 18%), polystyrene (surface water: 13%, sediments: 11%), and alkyd resin (surface water: 13%, sediments: 10%) were the most prevalent polymers in the river Karnaphuli. Moreover, there was a moderate positive correlation between MPs abundance in surface water and sediments. Therefore, improved long-term research (in different seasons with horizontal and vertical monitoring) is necessary in order to accurately determine the flux of microplastics from the river Karnaphuli to the Bay of Bengal.

Microplastics in terrestrial ecosystem: Sources and migration in soil environment

Plastics, especially microplastics in soils, are considered a severe environmental issue worldwide. However, globally, the main research focus is on microplastic pollution in the marine environment, the microplastic pollution on soils and sediments remains on the sideline so far. But the fact is that microplastics are omnipresent in terrestrial systems in the form of microbeads in industrial systems and in sewage sludge. Their presence in agricultural soils and sediments is enormously increased due to plastic mulching, plastic greenhouses and compost and extensive use of controlled release fertilizers. Therefore, this review outlines the global scenario regarding plastics and microplastics production, consumption, and possible pathways of penetration into the soil environment. Various mechanisms to restrict and manage the pathways of plastics and microplastics into the soil environment are also discussed. This review also focuses on the challenges and limitations on the use of plastic alternates such as bioplastics and oxo plastics. Also, the knowledge gaps on the source of microplastics in the environment and their deleterious effects on properties of soil, soil health and focused light on their soil trophic transfer in food chains via plants. This review provides a detailed insight on the management and possible control measures to alleviate the potential risk caused by microplastics pollution in the soil environment and the overall ecosystem's health. In spite of the occurrence and fate of microplastics on terrestrial environment, knowledge gaps and challenges for tackling this contamination are also explored which facilitates the policy makers to develop regulatory measures towards the containment of microplastics in living ecosystem.

Microplastic abundance, distribution, and characterization in freshwater sediments in Iran: a case study in Kermanshah city

This paper focuses on abundance, distribution, and characteristics of microplastics (MPs) in freshwater sediments of Sarab Niloofar Lake, Kermanshah, Iran. After selecting an appropriate method for extraction of MPs, the characterization such as polymer types, surface morphology, and trace elements has been determined using Fourier transform infrared spectroscopy, scanning electron microscopic, and energy-dispersive X-ray spectroscopic analysis, respectively. The results highlighted that all sampling locations were contaminated by MP abundance ranged from 1733.33 to 4400 items kg^-1 d.w with an average of 2483.59 ± 805.30 items kg^-1 d.w. MPs with a size range of 0.025 to 1 mm (25-1000 μm) were the most frequently detected MPs in size (62%). Furthermore, the MPs found in this area mainly contain fiber (61%), fragment (19%), film (9%), foam (6%), and pallet (5%). The main color for detected MPs in sampling stations was black (51%) and followed by white/transparent (27%), red (11%), blue (7%), and yellow (4%). The results of polymer identification revealed that the polyethylene, polystyrene, polyurethane, and polypropylene were the principal polymers. This research work emphasized that various types of MPs have been distributed in freshwater sediments of Sarab Niloofar Lake, which is a first useful data for MPs in one the most important Kermanshah's tourist area.

The toxic differentiation of micro- and nanoplastics verified by gene-edited fluorescent Caenorhabditis elegans

The increased emission and accumulation of micro- or nanoplastics (M-NPs) have posed a severely threaten to organisms in the environment. Though the toxicity of M-NPs has been observed in many species, the fundamental factors determining the biotoxicity are rarely expounded on. In this work, typical polystyrene (PS) M-NPs were set up with a multiparameter variation in size gradient, surface charge contrast and concentration variant, and evaluated by the Caenorhabditis elegans (C. elegans) model. From the endpoints of body length, brood size, survival rate and lifespan, an adverse effect was found on the growth and development of C. elegans caused by PSs. In general, the toxicity of PS was found to be concentrated- and size-dependent, with 100 nm positively charged nano-PS having the highest physio-toxicity. Monitoring by fluorescent imaging, it showed that positively charged nano-PS was mainly ingested and accumulated in the intestinal tract of C. elegans. In addition, the penetrated PS induced severe biological stress reactions with the increase of reactive oxygen species (ROS) and lipofuscin. Furthermore, the following expression of antioxidation-related enzymes was activated in vivo as indicated by the GFP-labelled C. elegans. All the results supplied visually toxic parameters of M-NPs to organisms, which sheds light on the biosecurity and ecological risks of M-NPs in the future.

Quantification of ternary microplastic mixtures through an ultra-compact near-infrared spectrometer coupled with chemometric tools

The ubiquitous distribution of plastics and microplastics (MPs) and their resistance to biological and chemical decay is adversely affecting the environment. MPs are considered as emerging contaminants of concern in all the compartments, including terrestrial, aquatic, and atmospheric environments. Efficient monitoring, detection, and removal technologies require reliable methods for a qualitative and quantitative analysis of MPs, considering point-of-need testing a new evolution and a great trend at the market level. In the last years, portable spectrometers have gained popularity thanks to the excellent capability for fast and on-site measurements. Ultra-compact spectrometers coupled with chemometric tools have shown great potential in the polymer analysis, showing promising applications in the environmental field. Nevertheless, systematic studies are still required, in particular for the identification and quantification of fragments at the microscale. This study demonstrates the proof-of-concept of a Miniaturized Near-Infrared (MicroNIR) spectrometer coupled with chemometrics for the quantitative analysis of ternary mixtures of MPs. Polymers were chosen representing the three most common polymers found in the environment (polypropylene, polyethene, and polystyrene). Daily used plastic items were mechanically fragmented at laboratory scale mimicking the environmental breakdown process and creating "true-to-life" MPs for the assessment of analytical methods for MPs identification and quantification. The chemical nature of samples before and after fragmentation was checked by Raman spectroscopy. Sixty three different mixtures were prepared: 42 for the training set and 21 for the test set. Blends were investigated by the MicroNIR spectrometer, and the dataset was analysed using Principal Component Analysis (PCA) and Partial Least Square (PLS) Regression. PCA score plot showed a samples distribution consistent with their composition. Quantitative analysis by PLS showed the great capability prediction of the polymer's percentage in the mixtures, with R² greater than 0.9 for the three analytes and a low and comparable Root-Mean Square Error. In addition, the developed model was challenged with environmental weathered materials to validate the system with real plastic pollution. The findings show the feasibility of employing a portable tool in conjunction with chemometrics to quantify the most abundant forms of MPs found in the environment.

Microplastics in marine beach and seabed sediments along the coasts of Dar es Salaam and Zanzibar in Tanzania

Microplastics (MPs) pollution in the marine environment has been one of the biggest challenge in developing countries due to a lack of proper solid waste management strategies. This study reports the distribution and types of MPs in beach and seabed zones of the Dar es Salaam and Zanzibar coasts. A total of 641 MPs were identified across all sites, of which 84 % and 16 % originated from beach and seabed sediments, respectively. Fragment and fibers were the most common types in both seabed and beach zone confirming the secondary sources of the MPs. Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR), revealed four types of polymers with polyethylene (PE) (56%) and polyester (PS) (24 %) being the most common. Microplastics were more abundant on beaches than in seabed zone. A larger abundance of PE and PS reveals a wide range of MPs entering the Ocean.

Effects of land use and landscape on the occurrence and distribution of microplastics in soil, China

Microplastic pollution in the soil environment has gathered widespread attention. However, little is known about the effects of land use and landscape patterns on the occurrence and distribution of microplastics in the soil. Herein, the microplastic pollution in different land uses (facility farmland, traditional farmland, orchard, grassland, and woodland) in Yuanmou County, Yunnan Province was investigated. The results showed that the abundance of microplastic ranged from 50.000 to 3450.0 items·kg^-1, with an average abundance of 595.00 ± 740.00 items·kg^-1 and a median of 375.00 items·kg^-1. Microplastics were found to primarily be green-coloured (28.4 %), fragment (72.7 %) in shape, <1 mm (75.7 %) in size, and composed of polypropylene (51.4 %). There were significant differences in the abundance and characteristics of the microplastics between different land use types. Microplastic abundance in facility farmlands, traditional farmlands, and orchard lands was significantly higher than that of grasslands and woodlands (p < 0.05). The main shape of the microplastics in facility farmlands, traditional farmlands, and orchards was fragments and it was fibers in grasslands and woodlands. The median particle size of microplastics in facility farmlands (539.50 μm) and traditional farmlands (574.00 μm), was smaller than those in the orchard (737.60 μm), grasslands (697.60 μm), and woodlands (1239.4 μm). Discrepancies among different land uses may be due to various reasons, such as different pollution sources and the weathering degree of microplastics. The results of the redundancy analysis showed that the microplastic abundance was negatively correlated with the largest patch index. It also showed that microplastic pollution was closely related to human activities. This study provides an important basis for further research on microplastic ecosystem risks that are associated with land use and provides a data basis for formulating effective prevention and control strategies and measures to mitigate soil microplastic pollution.

Microplastics in ASEAN region countries: A review on current status and perspectives

A literature assessment was conducted to determine the current state of microplastics research in ASEAN countries focusing on 1) microplastics in water, sediment, and water organisms; 2) microplastics' sources and dispersion; and 3) microplastics' environmental consequences, including human toxicity. ASEAN countries contributed only about 5 % of the global scholarly papers on microplastics, with Indonesia contributing the most followed by Malaysia and Thailand. The lack of standard harmonized sampling and processing methodologies made comparisons between research difficult. ASEAN contributes the most to plastic trash ending up in the ocean, indicating a need for more work in this region to prevent plastic pollution. Microplastics are found in every environmental compartment; however, their distribution and environmental consequences have not been sufficiently investigated. There are very few studies on microplastics in the human blood system as well as respiratory organs like the lungs, indicating that more research is needed.

Microplastics separation using stainless steel mini-hydrocyclones fabricated with additive manufacturing

Microplastics have been widely detected in natural and engineered water systems and removing microplastics from various water matrices has become a major challenge. Mini-hydrocyclones (MHCs) have been previously applied to separate mediums of different phases. Given MHCs' capability of separating fine particles from liquid phase, three MHCs were designed and fabricated in stainless steel with 3D printing. Microplastics of densities that were both lower (<1 g·cm^-3) and higher (>1 g·cm^-3) than water's density were used to test the separation efficiency in ultra-purified water. The separation test was performed on single-stage MHC as well as MHCs in series in a closed hydraulic circuit. A range of important operational parameters, including split ratio, feed pressure, feed flow rate, and solid concentration, were evaluated to optimize the separation efficiency. The single-stage MHC experiment revealed that >80 % microplastics >20 μm can be effectively removed at the concentration tested, and the separation efficiency peaked at the split ratio of 35 %. MHCs in series demonstrated their ability to further enhance the separation efficiency of the ones with the same density, as well as separate microplastics of different densities. Mini-hydrocyclones' were also used to separate microplastics in synthetic stormwater, and separation efficiency reached 84 % and 98.1 % for low-density polyethylene (LDPE) and polyamide (PA). The results indicated the MHCs' potential for large-scale application in microplastic separation for industrial and municipal wastewater.

Polystyrene microplastic exposure induces insulin resistance in mice via dysbacteriosis and pro-inflammation

Microplastics (MPs) as emerging contaminants have become a global environmental problem. However, studies on the effects of MPs on metabolic diseases remain limited. Here, we evaluated the effects of polystyrene (PS), one of the most prominent types of MPs, on insulin sensitivity in mice fed with normal chow diet (NCD) or high-fat diet (HFD), and explained the underlying mechanisms. Mice fed with NCD or HFD both showed insulin resistance (IR) after PS exposure accompanied by increased plasma lipopolysaccharide and pro-inflammatory cytokines such as tumor necrosis factor-α and interleukin-1β. Exposure to PS also resulted in a significant decrease in the richness and diversity of gut microbiota, particularly an increase in the relative abundance of Gram-negative bacteria such as Prevotellaceae and Enterobacteriaceae. Additionally, PS with a small particle size (5 μm) accumulated in the liver, kidneys and blood vessels of mice. Further analyses showed inhibition of the insulin signaling pathway in the liver of PS exposed mice, such as inhibition of IRS1 and decreased expression of PI3K. Hence, the mechanism of PS exposure to induce IR in mice might be mediated through regulating gut microbiota and PS accumulation in tissues, stimulating inflammation and inhibiting the insulin signaling pathway. In conclusion, PS might be a potential environmental contaminant that causes metabolic diseases associated with IR.