Microplastics and their associated organic pollutants from the coastal waters of the central Adriatic Sea (Italy): Investigation of adipogenic effects in vitro

Characterization of Microplastics and Adsorbed/Dissolved Polycyclic Aromatic Hydrocarbons in the Biggest River System in Saitama and Tokyo, Japan

This study presents a comprehensive characterization of microplastics (MPs) and adsorbed/dissolved polycyclic aromatic hydrocarbons (PAHs) in the Arakawa River, the largest river system in Saitama and Tokyo, Japan. The MPs were sampled at various points along the river, revealing an average number density of 2.21 ± 1.48 pieces/m3, with a predominant size range of 0.5-1 mm. Polymer analysis indicated that polyethylene (PE) comprised the highest proportion of MPs (55.9%), followed by polypropylene (PP) (22.4%) and polystyrene (PS) (21.7%). Seasonal fluctuations in MPs concentration were observed, with the highest values in winter and the lowest in summer. An analysis of adsorbed PAHs revealed a median partition coefficient (Kd) value of 3.58 × 104 L/kg for MPs, indicating their affinity for PAHs. Further PAHs analysis revealed that the PAHs with the highest mean values were bicyclic naphthalene, pyrene, and fluoranthene. A comparison with coastal MPs showed differences in PAH composition, with higher proportions of high-ring PAHs observed in coastal samples. The study also investigated the distribution of PAHs in the dissolved and suspended states in the river, finding that similar PAHs were distributed in both states, with the PAHs present in MPs being about 1/10,000 of those in the dissolved and suspended states. The study underscores the importance of the continued monitoring and management of MPs and associated pollutants in river ecosystems.

Microplastics in retail shellfish from a seafood market in eastern Thailand: Occurrence and risks to human food safety

This study aimed to investigate the presence of microplastics in three economically essential shellfish species: green mussels, cockles and spotted babylon. The average abundance of microplastics ranged from 2.41 to 2.84 particles/g wet weight. The predominant shape was fiber, with colors ranging from black-grey to transparent. The size of the microplastics discovered was <1.0 mm. Polystyrene and polyethylene were the most detected types in mussels and cockles, while linen was the predominant type in spotted babylon. The Thai population's estimated annual intake (EAI) of microplastics through shellfish consumption ranged from 20.23 to 1178.42 particles/person/year. The potential human health risks were evaluated using the polymer hazard index (PHI), which led to risk categories III-IV. These findings, along with others from the literature, indicate that shellfish consumption may pose risks to human health, depending on the species consumed and the origin of the specimens.

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

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

Mobilisation of textile waste to recover high added value products and energy for the transition to circular economy

The textile industry is a major contributor to global waste, with millions of tons of textiles being discarded annually. Material and energy recovery within circular economy offer sustainable solutions to this problem by extending the life cycle of textiles through repurposing, recycling, and upcycling. These initiatives not only reduce waste but also contribute to the reduction of the demand for virgin materials (i.e. cotton, wool), ultimately benefiting the environment and society. The circular economy approach, which aims to recreate environmental, economic, and societal value, is based on three key principles: waste reduction, material circulation, and ecological restoration. Given these difficulties, circularity incorporates the material recovery approach, which is focused on the conversion of waste into secondary raw resources. The goal of this notion is to extract more value from resources by prolonging final disposal as long as feasible. When a textile has outlived its functional life, material recovery is critical for returning the included materials or energy into the manufacturing cycle. The aim of this paper is to examine the material and energy recovery options of main raw materials used in the fashion industry while highlighting the need of close observation of the relation between circularity and material recovery, including the investigation of barriers to the transition towards a truly circular fashion industry. The final results refer to the main barriers of circular economy transition within the industry and a framework is proposed. These insights are useful for academia, engineers, policy makers and other key stakeholders for the clear understanding of the industry from within and highlight beyond circular economy targets, SDGs interactions with energy and material recovery of textile waste (SDG 7, SDG 11, SDG 12 etc.).

Floating plastics as integrative samplers of organic contaminants of legacy and emerging concern from Western Mediterranean coastal areas

This study investigates the role of floating plastics as integrative samplers of organic contaminants. To this end, plastics items were collected in two Western Mediterranean coastal areas: the Mar Menor lagoon, and the last transect of Ebro river. Floating plastics were identified and characterized by attenuated total reflection Fourier-transform infrared spectrometry. Then, organic contaminants were extracted from plastic items by ultrasonic extraction with methanol, and the concentrations of 168 regulated and emerging contaminants were analysed. These compounds were analysed by stir bar sorptive extraction coupled to gas chromatography-mass spectrometry (GC-MS), except for bisphenol analogues, which were analysed with a ultraperformance liquid chromatography pump coupled to a triple quadrupole mass spectrometer (UHPLC-MS/MS), and pharmaceutical compounds, determined by UPLC coupled to hybrid triple quadrupole-linear ion trap mass spectrometer (UPLC-MS/MS). All the contaminants groups considered were detected in the samples, being particularly relevant the contribution of plastic additives. The most frequently detected contaminants were UV-filters, PAHs, pharmaceuticals and synthetic musks. Apart from plasticizers, the individual contaminants octocrylene, homosalate, galaxolide, salycilic acid and ketoprofen were frequently detected in plastics items. The results pointed out to urban and touristic activities as the main sources of pollution in the coastal areas investigated. The utility of floating plastics as integrative samplers for the detection of organic contaminants in aquatic ecosystems has been demonstrated.

Microplastics: challenges of assessment in biological samples and their implication for in vitro and in vivo effects

Microplastics (MPs) have attracted global interest because they have been recognized as emerging pollutants that require urgent attention. MPs are plastic particles with a size between 1 micron and 5 mm (1 µm-5mm); those measuring less than 1 µm are known as nanoplastics (NPs). MP is distributed in the environment in various physical forms that depend on the degradation process, the erosion factors to which it was subjected, or the original form in which it was intentionally manufactured. Humans may be exposed to these pollutants mainly by ingestion or inhalation, which could adversely affect human health with effects that are still unknown due to limitations that are often dependent on their analytical determination and lack of studies over time, as it is a relatively new topic. Therefore, this review focuses on the challenges currently faced by laboratories for determining MPs in different matrices. We highlight the application of methods and techniques to assess the precise levels of exposure to MPs in biological samples. In addition, exposure pathways, sources, and evidence of adverse effects reported in vitro and in vivo studies are described to generate knowledge about their potential threat to human health.

Microplastics in the environment: An urgent need for coordinated waste management policies and strategies

Microplastics (MPs) have become a prevalent environmental concern, exerting detrimental effects on marine and terrestrial ecosystems, as well as human health. Addressing this urgent issue necessitates the implementation of coordinated waste management policies and strategies. In this study, we present a comprehensive review focusing on key results and the underlying mechanisms associated with microplastics. We examine their sources and pathways, elucidate their ecological and human health impacts, and evaluate the current state of waste management policies. By drawing upon recent research and pertinent case studies, we propose a range of practical solutions, encompassing enhanced recycling and waste reduction measures, product redesign, and innovative technological interventions. Moreover, we emphasize the imperative for collaboration and cooperation across sectors and jurisdictions to effectively tackle this pressing environmental challenge. The findings of this study contribute to the broader understanding of microplastics and provide valuable insights for policymakers, researchers, and stakeholders alike.

Fire and Oil Led to Complex Mixtures of PAHs on Burnt and Unburnt Plastic during the M/V X-Press Pearl Disaster

In May 2021, the M/V X-Press Pearl container ship burned for 2 weeks, leading to the largest maritime spill of resin pellets (nurdles). The disaster was exacerbated by the leakage of other cargo and the ship's underway fuel. This disaster affords the unique opportunity to study a time-stamped, geolocated release of plastic under real-world conditions. Field samples collected from beaches in Sri Lanka nearest to the ship comprised nurdles exposed to heat and combustion, burnt plastic pieces (pyroplastic), and oil-plastic agglomerates (petroplastic). An unresolved question is whether the 1600+ tons of spilled and recovered plastic should be considered hazardous waste. Due to the known formation and toxicity of combustion-derived polycyclic aromatic hydrocarbons (PAHs), we measured 20 parent and 21 alkylated PAHs associated with several types of spilled plastic. The maximum PAH content of the sampled pyroplastic had the greatest amount of PAHs recorded for marine plastic debris (199,000 ng/g). In contrast, the sampled unburnt white nurdles had two orders of magnitude less PAH content. The PAH composition varied between the types of spilled plastic and presented features typical of and conflicting with petrogenic and pyrogenic sources. Nevertheless, specific markers and compositional changes for burning plastics were identified, revealing that the fire was the main source of PAHs. Eight months after the spill, the PAH contents of sampled stray nurdles and pyroplastic were reduced by more than 50%. Due to their PAH content exceeding levels allowable for plastic consumer goods, classifying burnt plastic as hazardous waste may be warranted. Following a largely successful cleanup, we recommend that the Sri Lankans re-evaluate the identification, handling, and disposal of the plastic debris collected from beaches and the potential exposure of responders and the public to PAHs from handling it. The maritime disaster underscores pyroplastic as a type of plastic pollution that has yet to be fully explored, despite the pervasiveness of intentional and unintentional burning of plastic globally.

Effect of polycyclic aromatic hydrocarbons on homeobox gene expression during embryonic development of cuttlefish, Sepia officinalis

Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants (POPs) commonly found in marine environments. Their bioaccumulation can cause harm to aquatic organisms, including invertebrates, particularly during the early stages of embryonic development. In this study, we evaluated, for the first time, the patterns of PAH accumulation in both capsule and embryo of common cuttlefish (Sepia officinalis). In addition, we explored the effects of PAHs by analysing the expression profiles of seven homeobox genes [i.e., gastrulation brain homeobox (GBX), paralogy group labial/Hox1 (HOX1), paralogy group Hox3 (HOX3), dorsal root ganglia homeobox (DRGX), visual system homeobox (VSX), aristaless-like homeobox (ARX) and LIM-homeodomain transcription factor (LHX3/4)]. We found that PAH levels in egg capsules were higher than those observed in chorion membranes (35.1 ± 13.3 ng/g vs 16.4 ± 5.9 ng/g). Furthermore, PAHs were also found in perivitellin fluid (11.5 ± 5.0 ng/ml). Naphthalene and acenaphthene were the congeners present at highest concentrations in each analysed egg component suggesting higher bioaccumulation rates. Embryos with high concentrations of PAHs also showed a significant increase in mRNA expression for each of the analysed homeobox genes. In particular, we observed a 15-fold increase in the ARX expression levels. Additionally, the statistically significant variation in homeobox gene expression patterns was accompanied by a concomitant increase in mRNA levels of both aryl hydrocarbon receptor (AhR) and estrogen receptor (ER). These findings suggest that bioaccumulation of PAHs may modulate developmental processes of cuttlefish embryos by targeting homeobox gene-mediated transcriptional outcomes. Mechanisms underlying the upregulation of homeobox genes could be related to the ability of PAHs to directly activate AhR- or ER-related signaling pathways.

Microplastics in sediments from the southern Gulf of Mexico: Abundance, distribution, composition, and adhered pollutants

Approximately 23 Mt of plastics reaches the ocean each year, fragmented into microplastics (MP). MPs are widely dispersed in the sea, becoming deposited in sediments. MPs are considered carriers of pollutants such as heavy metals and polycyclic aromatic hydrocarbons and, when ingested by biota, pose a high health risk. This study determined metals and PAHs in sedimentary microplastics from the southern Gulf of Mexico (GOM). One hundred twenty-four sediment samples were collected, covering an area of 26,220 km². The mean (±SD) of MPs in sediments was 16.46 ± 17.76 MPs/kg. The most abundant polymers were cellophane (CE), polyvinylidene fluoride (PVDF), polyethylene (PE), polyamides (PA), and nylon (NYL). A strong correlation (r: 0.83) was found between MP density and sediment depth. PA and PE were found near shorelines and PVDF near oil platforms. Aluminum, arsenic, and tin had the highest concentration (89.6 ± 94.6, 23.1 ± 70.3, and 19 ± 29.2 μg g^-1, respectively), and acenaphthylene was the PAH with the highest concentration (3.4 ± 12.6 μg g^-1). This study shows that MP with a higher density is found at greater depths, and this research is one of the first to cover a large area of the Gulf of Mexico.

An overview of microplastics in oysters: Analysis, hazards, and depuration

Microplastic pollution has become an emergent global environmental issue because of its ubiquitous nature and everlasting ecological impacts. In marine ecosystems, microplastics can serve as carriers to absorb various contaminants and the ingestion of microplastics in oysters is of concern because they can induce several adverse effects. The analytical process of microplastics in oysters commonly consists of separation, quantification, and identification. Quantification of microplastics is difficult since information regarding the analytical methods is incoherent, therefore, standard microplastic analytical methods for shellfish should be established in the future. The depuration process can be used to reduce the level of microplastics in oysters to ensure safe consumption of oysters and longer depuration time facilitates improved depuration efficacy. In summary, this review aims to help better understand microplastic pollution in oysters and provide useful suggestions and guidance for future research.

Joint effects of micro-sized polystyrene and chlorpyrifos on zebrafish based on multiple endpoints and gut microbial effects

Microplastics often co-occur with a variety of organic contaminants in aquatic environment and pose combined risks to aquatic wildlife. Here, we investigated joint effects of micro-sized polystyrene (mPS, 5 µm) and an organophosphate pesticide chlorpyrifos on zebrafish, using multiple endpoints at both fish individual and gut microbiota levels. It was revealed that mPS ingested by zebrafish accumulated in gut and liver, and caused oxidative stress, hyperactive swimming performance and histological damages in fish, and induced disorders and diversity alterations of the gut microbial community. More importantly, mPS exhibited considerable adsorption capacity against chlorpyrifos, and those adsorbing chlorpyrifos presented greater effects on fish individuals but no different effects on gut microbiota compared to single mPS exposure. Together with body residues of chlorpyrifos in zebrafish, it was proposed that the joint effects between mPS and chlorpyrifos were attributed to the chlorpyrifos released from mPS within zebrafish. The present results provided a comprehensive understanding of joint effects of mPS and contaminants co-occurring in the environment and emphasized the importance of considering the adsorbed chemicals in toxicological studies of microplastics.

A global snapshot of microplastic contamination in sediments and biota of marine protected areas

Microplastics (MPs) become ubiquitous contaminants in Marine Protected Areas (MPA) that have been planned as a conservation strategy. The present study provides a comprehensive overview of the occurrence, abundance, and distribution of MPs potentially affecting MPA worldwide. Data on MP occurrence and levels in sediment and biota samples were collected from recent peer-reviewed literature and screened using a GIS-based approach overlapping MP records with MPA boundaries. MPs were found in 186 MPAs, with levels ranging from 0 to 9187.5 items/kg in sediment and up to 17,461.9 items/kg in organisms. Peaked MPs concentrations occurred within multiple-use areas, and no-take MPAs were also affected. About half of MP levels found within MPA fell into the higher concentration quartiles, suggesting potential impacts on these areas. In general, benthic species were likely more affected than pelagic ones due to the higher concentrations of MP reported in the tissues of benthic species. Alarmingly, MPs were found in tissues of two threatened species on the IUCN Red List. The findings denote urgent concerns about the effectiveness of the global system of protected areas and their proposed conservation goals.

Organic Pollutants Associated with Plastic Debris in Marine Environment: A Systematic Review of Analytical Methods, Occurrence, and Characteristics

Plastic pollution has become one of the most serious environmental problems, and microplastics (MPs, particles < 5 mm size) may behave as a vehicle of organic pollutants, causing detrimental effects to the environment. Studies on MP-sorbed organic pollutants lack methodological standardization, resulting in a low comparability and replicability. In this work, we reviewed 40 field studies of MP-sorbed organic contaminants using PRISMA guidelines for acquiring information on sampling and analytical protocols. The papers were also scored for their reliability on the basis of 7 criteria, from 0 (minimum) to 21 (maximum). Our results showed a great heterogeneity of the methods used for the sample collection, MPs extraction, and instruments for chemicals' identification. Measures for cross-contamination control during MPs analysis were strictly applied only in 13% of the studies, indicating a need for quality control in MPs-related research. The most frequently detected MP-sorbed chemicals were polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and organochlorine pesticides (OCPs). Most of the studies showed a good reliability (>75% of the total score), with 32 papers scoring 16 or higher. On the basis of the collected information, a standardizable protocol for the detection of MPs and MP-sorbed chemicals has been suggested for improving the reliability of MPs monitoring studies.

Microplastics accumulation in gastrointestinal tracts of Mullus barbatus and Merluccius merluccius is associated with increased cytokine production and signaling

There is clear evidence that different marine species can be impacted by microplastic (MP) ingestion accumulating such MPs mainly in the gastrointestinal tract. However, there is still limited knowledge on the consequences of MPs' accumulation in the gut. The present study aims to assess MPs and their potential immunotoxic effects in the digestive tract of two species showing different ecological traits: the red mullet (Mullus barbatus) and the European hake (Merluccius merluccius). Infrared spectroscopy (FTIR-ATR), micro-Raman and electron scanning microscope (SEM) were used to accurately identify the main plastic polymers detected in gut contents. In addition, we investigated the association between MP uptake and intestinal inflammation by evaluating expression and secretion of proinflammatory cytokines. MP abundance ranged from 1 to 20 items/individual in red mullet and from 2 to 15 items/individual in European hake. The majority of ingested MPs were fibers, while the dominant colors were black and blue in both species. Chemical characterization indicated polyethylene and polypropylene as the most common polymer types. Moreover, it was observed that MP abundance was highly positive correlated to cytokines (i.e. interleukin-1β, 10, and interferon) and antioxidant enzyme (i.e. catalase and superoxide dismutase) transcript levels suggesting ROS generation and an infiltration of immune cells in the gut. Our findings provide evidence that the induction of cytokine-dependent signaling pathways is one aspect of the complex mechanism by which MPs affect the gut system in fish.

A battery of baseline toxicity bioassays directed evaluation of plastic leachates-Towards the establishment of bioanalytical monitoring tools for plastics

There are increasing concerns regarding the ecological risks of plastics to the natural environment, especially the potential effects of plastic leachates on organisms, which contain various toxic components. However, appropriate methods to assess the overall environmental risks of plastics are limited. In this study, five different plastic products (three conventional and two biodegradable plastics) were immersed in simulated freshwater, and their toxicity was assessed using a battery of bioassays. We evaluated the effects of plastic leachates effects on organisms from four trophic levels of species (nematodes, Caenorhabditis elegans; algae, Scenedesmus obliquus; daphnids, Daphnia magna; and fish, Danio rerio) by measuring their acute and chronic toxicity. Our results indicated that all plastic leachates exhibited poor acute and chronic toxicity to the organisms. The acute toxicity of conventional plastic leachates with EC₂₀ values <1.6 g plastic/L was higher than that of the biodegradable polydioxanone (PPDO) leachate (EC₂₀: 16.2-796.1 g plastic/L); however, the toxicity of PPDO-octane (EC₂₀: 0.04-1.9 g plastic/L) was similar to that of polyethylene or polystyrene (excluding toxicity in D. magna). Similarly, the leachates of the three conventional plastics and PPDO-octane had obvious inhibitory effects on the growth of C. elegans at exposure concentrations higher than 0.01 g plastic/L; however, the toxicity of the PPDO leachates was at least an order of magnitude lower. Therefore, the environmental related concentration of the plastic leachates did not have significant toxic effects. Considering that a single bioassay does not provide comprehensive information on biological implications, this study provided a new integrated and efficient method for the environmental risk assessment (ERA) of plastic leachates. Moreover, the toxicity sensitivity of different organisms varied following exposure to different plastics, thus demonstrating that multiple organisms from different trophic levels should be included in the ERA for plastics.

Microplastics in the Gulf of Mexico: A Bird’s Eye View

Microplastic debris is a persistent, ubiquitous global pollutant in oceans, estuaries, and freshwater systems. Some of the highest reported concentrations of microplastics, globally, are in the Gulf of Mexico (GoM), which is home to the majority of plastic manufacturers in the United States. A comprehensive understanding of the risk microplastics pose to wildlife is critical to the development of scientifically sound mitigation and policy initiatives. In this review, we synthesize existing knowledge of microplastic debris in the Gulf of Mexico and its effects on birds and make recommendations for further research. The current state of knowledge suggests that microplastics are widespread in the marine environment, come from known sources, and have the potential to be a major ecotoxicological concern for wild birds, especially in areas of high concentration such as the GoM. However, data for GoM birds are currently lacking regarding typical microplastic ingestion rates uptake of chemicals associated with plastics by avian tissues; and physiological, behavioral, and fitness consequences of microplastic ingestion. Filling these knowledge gaps is essential to understand the hazard microplastics pose to wild birds, and to the creation of effective policy actions and widespread mitigation measures to curb this emerging threat to wildlife.

First evidence of in vitro cytotoxic effects of marine microlitter on Merluccius merluccius and Mullus barbatus, two Mediterranean commercial fish species

Marine litter is composed mainly of plastics and is recognized as a serious threat to marine ecosystems. Ecotoxicological approaches have started elucidating the potential severity of microplastics (MPs) in controlled laboratory studies with pristine materials but no information exists on marine environmental microlitter as a whole. Here, we characterized the litter in the coastal Northern Tyrrhenian sea and in the stomach of two fish species of socio-economic importance, and exposed primary cell cultures of mucosal and lymphoid organs to marine microlitter for evaluating possible cytotoxic effects. An average of 0.30 ± 0.02 microlitter items m^-3 was found in water samples. μFT-IR analysis revealed that plastic particles, namely HDPE, polyamide and polypropylene were present in 100% and 83.3% of Merluccius merluccius and Mullus barbatus analyzed, which overall ingested 14.67 ± 4.10 and 5.50 ± 1.97 items/individual, respectively. Moreover, microlitter was confirmed as a vector of microorganisms. Lastly, the apical end-point of viability was found to be significantly reduced in splenic cells exposed in vitro to two microlitter conditions. Considering the role of the spleen in the mounting of adaptive immune responses, our results warrant more in-depth investigations for clarifying the actual susceptibility of these two species to anthropogenic microlitter.

Organochlorine pesticides, polycyclic aromatic hydrocarbons, metals and metalloids in microplastics found in regurgitated pellets of black vulture from Campeche, Mexico

Plastics are produced by the millions of tons worldwide each year, with their final deposition in landfills (LFs). Plastics deposited in LFs can fragment over time, giving rise to mesoplastics and later to microplastics (MPs), in which toxic chemicals such as heavy metals, organochlorine pesticides, and polycyclic aromatic hydrocarbons can adhere. MPs can be vectors for the exposure to pollutants of black vultures (Coragyps atratus) due to feeding in LFs, resulting in accidental ingestion of MPs. It is also possible that MPs can adsorb pollutants from vultures during the digestion process. The aim of this study was to estimate the risk of black vulture exposure to MPs, heavy metals (HMs), organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs). Fifty-eight black vulture pellets were collected at the Campeche LF during 2019 (n = 24) and 2020 (n = 34). The pellets, on average, had an MP load per pellet of 6.7 ± 5.8 MPs/total pellets. The greatest abundance of MPs was detected in 2019, with 225 particles in total. The concentrations of Cd, Pb, Cu, Cr, Hg, As, and Al were detected in the MPs, with the greatest average concentration of 35.59 ± 32.39 μg·g^-1 (2019) and 15.82 ± 17.47 μg·g^-1 (2020) for Al. In 2020, ∑endosulfans were present in all MPs at 0.97 ± 1.47 ng·g^-1. Among the PAHs, 15 of the 16 compounds indicated as priorities by the US EPA were quantified. The compound with the greatest total concentration for both years was acenaphthylene (3 rings), with 10.51 ± 7.88 ng·g^-1 (2019) and 10.61 ± 18 ng·g^-1 (2020). More research is needed regarding the origin of the contaminants detected in the MPs extracted from the pellets, since the contaminants may come from the environment or possibly from the digestion processes in the stomach of avian raptors and scavengers.

Transport characteristics of fragmental polyethylene glycol terephthalate (PET) microplastics in porous media under various chemical conditions

Transport characteristics of fragmental polyethylene glycol terephthalate (PET) microplastics in porous media were elucidated via column experiments under a series combination of electrolytes, pH, and humic acid (HA) conditions. Fragmental PET microplastics showed low mobility in porous media with a small mass recovery rate (<50.1%) even under unfavorable retention conditions. The electrolyte, pH, and HA showed combined impact on PET microplastic transport. PET microplastics mobility was enhanced with decreasing electrolyte concentration, increasing pH, and increasing HA concentration. Basic properties (e.g. destiny and shape) of PET microplastics showed stronger effect on their transport behaviors in porous media rather than the experimental chemical conditions. In general, both environmental factors and basic properties played important roles in controlling the retention and transport of PET microplastics in porous media. A numerical model considering the second order kinetic deposition sites was applied to depict the retention and transport of PET microplastics in porous media. Model simulations well matched the experimental breakthrough curves. Given the fragmental PET microplastics have more realistic and irregular shapes, results from this study can improve present knowledge of the environmental fate and risk of microplastics in underground soil and water systems.