Export of microplastics from land to sea. A modelling approach

Seasonal heterogeneity and a link to precipitation in the release of microplastic during COVID-19 outbreak from the Greater Jakarta area to Jakarta Bay, Indonesia

To reduce microplastic contamination in the environment, we need to better understand its sources and transit, especially from land to sea. This study examines microplastic contamination in Jakarta's nine river outlets. Microplastics were found in all sampling intervals and areas, ranging from 4.29 to 23.49 particles m^-3. The trend of microplastic contamination tends to increase as the anthropogenic activity towards Jakarta Bay from the eastern side of the bay. Our study found a link between rainfall and the abundance of microplastic particles in all river outlets studied. This investigation found polyethylene, polystyrene, and polypropylene in large proportion due to their widespread use in normal daily life and industrial applications. Our research observed an increase in microplastic fibers made of polypropylene over time. We suspect a relationship between COVID-19 PPE waste and microplastic shift in our study area. More research is needed to establish how and where microplastics enter rivers.

Occurrence of microplastics within a freshwater aquaculture system in the Pacific Islands, Viti Levu, Fiji

Microplastics (MPs) have become frequent topics of research within Pacific Islands (PIs) in recent years; however, within PI freshwater aquaculture systems, MPs have not yet been quantified. As such this study is aimed at quantifying and characterizing the MP load from across a freshwater aquaculture system within Fiji. Water, sediment, and fish samples were collected from various stages between water source and drainage channels of an aquaculture facility in Navua, Fiji. MPs were extracted using established protocols and analyzed for abundance, form type, size, and polymer composition. Results show no significant difference in MP abundance between sampling sites for, water (average: 3.2 ± 1.14 MP/L), sediment (average: 2.3 ± 0.7 MP/100 g DW), and fish (average: 2.7 ± 1.4 MP/fish). Fibers were the most frequent form type in all three elements (average: 2.9 ± 0.2 MP/L in water, 2.1 ± 0.75 MP/100 g DW, 2.8 ± 0.14 MP/fish); however, the difference across sites was significant within water samples only. In water and sediments, smaller MPs (< 1.4 mm) were the most frequent comprising > 35% in all three elements; however, the difference was not significant between sites. Polymer analysis found that polypropylene, polyurethane, and nylon were the most abundant polymers, which coupled with observed form type and size characteristics suggest a common sources of MPs across sites.

Deciphering the Mechanisms Shaping the Plastisphere Microbiota in Soil

The gradual accumulation of microplastics has aroused increasing concern for the unique niche, termed “plastisphere.” As research so far has focused on their characteristics in aquatic ecosystems, our understanding of the colonization and assembly of the attached bacterial communities on microplastics in soil ecosystems remains poor. Here, we aimed to characterize the plastisphere microbiomes of two types of microplastics (polylactic acid [PLA] and polyethylene [PE]) differing in their biodegradability in two different soils. After incubation for 60 days, considerably lower alpha diversity of bacterial community was observed on the microplastic surfaces, and prominent divergences occurred in the microbial community compositions between the plastisphere and the bulk soil. The temperature, rather than polymer type, significantly induced the differences between the plastisphere communities. The rRNA gene operon (rrn) copy numbers were significantly higher in the PLA plastisphere, suggesting potential degradation. The co-occurrence network analysis showed that the PE plastisphere exhibited greater network complexity and stronger stability than those in the PLA plastisphere. The stochasticity ratio indicated the remarkable importance of stochastic process on community assembly in PE and PLA plastispheres, while the null model analysis showed the nonnegligible roles of deterministic processes in shaping the plastisphere communities. Higher contributions of homogenous selection in the PLA plastisphere were observed in comparison with the PE plastisphere, which could probably be attributed to the selective pressure induced by microplastic degradation. Our findings enhance our mechanistic understanding of the diversity patterns and assembly processes of plastisphere in soil environments and have important implications for microbial ecology and microplastic risk assessment.

IMPORTANCE The increasing pervasive microplastic pollution is creating a new environmental compartment, termed plastisphere. Even though there was conclusive information characterizing the plastisphere, the underlying mechanisms shaping the bacterial communities in the plastisphere in the soil remain unclear. Therefore, we incubated two types of microplastics (PE and PLA) in two different soils and explored the differences between plastisphere and bulk soil communities. Additionally, the co-occurrence network and the assembly processes of plastisphere were subjected to further analysis. Our results highlight the importance of selective recruitment of microplastics and contribute to the understanding of the diversity patterns and assembly processes of plastisphere in soil environments.

Global transportation of plastics and microplastics: A critical review of pathways and influences

The rapid development of modern society has largely increased the usage of plastic. Concerns arise when vast amount of plastic waste has been generated and disposed. The accumulated evidences suggest that plastic waste in all the natural matrixes has become a global contaminant, principles such as geological and biogeochemical cycles for plastic pollution have been proposed. Before a full estimation of plastic mass flow, however, the pathways, directions and influences involved in plastic transportation are warranted to be addressed. We made this critical review based on the quantitative and narrative approaches in plastic and microplastic sources, sinks and transportation at global and historical scales. We also addressed the roles of anthropogenic influences in the global transportation of microplastic. The hydrological, meteorological, oceanic and even biological progresses naturally influence the plastic cycle and flow directions within the Earth's Four Spheres. Anthropogenic activities participated in all sections of plastic transportation, from sources to sinks. The contribution from anthropogenic activities remains unknown but several point sources including primary emissions and landfills have been confirmed. The primary outcomes point out that plastic pollution is highly complex issues in terms of natural and human-driven dynamics. We suggested that more efforts were needed in seeking the key sections in plastic transportation between environmental compartments at a global scale.

Differentiation in the expression of toxic effects of polyethylene-microplastics on two freshwater fish species: Size matters

The built up of microplastic (MPs) remains is shaping a new aquatic habitat and imposes the necessity for research of the effects that these relatively new pollutants exert on organisms, environment, and human health. The purpose of the present study was to verify if there is a particle-size dependence of fish response to MPs. Thus, we exposed two freshwater fish species, the zebrafish (Danio rerio) and perch (Perca fluviatilis) for 21 days to polyethylene microplastics (PE-MPs) sized 10-45 μm and 106-125 μm. Thereafter, in the liver and gills tissues, biochemical and molecular parameters and the metabolic profile were examined. Ex-vivo characterization by ATR-FTIR spectroscopy exhibited increased concentration of 10-45 μm PE-MPs in the liver of the two fish species while 106-125 μm PE-MPs mostly concentrated in fish gills. The penetration of PE-MPs to fish and the induced oxidative stress triggered changes in lipid peroxidation, DNA damage and ubiquitination and furthermore stimulated signal transduction pathways leading to autophagy and apoptosis. The smaller PE-MPs were more potent in inducing alterations to all the latter parameters measured than the larger ones. Tissue response in both fish seems to depend on the parameter measured and does not seem to follow a specific pattern. Our results showed that there is no clear sensitivity of one fish species versus the other, against both sizes of PE-MPs they were exposed. In perch the metabolic changes in gills were distinct to the ones observed in liver, following a size dependent pattern, indicating that stress conditions are generated through different mechanisms. All the parameters employed can be suggested further as biomarkers in biomonitoring studies against PE-MPs.

Identification, classification and quantification of microplastics in road dust and stormwater

Microplastics (MP) have become a major emerging class of pollutants representing significant eco-toxicological risks for ecosystems and marine environments. The aim of this study was to identify, classify and quantify MP present in both road dust and stormwater samples. A significantly higher level of MPs within road dust samples was detected from industrial area (1130 particles/kg of dust) than from residential area (520 particles/kg of dust), while stormwater samples from industrial and residential sites yielded 26 particles/L and 17 particles/L, respectively. Fiber-like shape accounted for 53% and 74% in road dust and stormwater samples, respectively. The main polymeric materials collected for both road dust and stormwater samples were, in order of occurrence (i) low-density polyethylene, (ii) high-density polyethylene, (iii) polypropylene, (iv) polyethylene terephthalate, (v) polystyrene, (vi) polyester and (vii) poly (amide). Most of the MP had an average maximum dimension smaller than 2 mm for both road dust and stormwater samples. The results from this study demonstrates that road dust is a significant contributor to MP pollution through direct polymeric materials wear off and transfer through stormwater, which eventually will end up in open water ways and broader ecological niches.

Characteristics and distribution of microplastics in shoreline sediments of the Yangtze River, main tributaries and lakes in China-From upper reaches to the estuary

Microplastics (MPs) pervade the environment and increasingly threaten both natural ecosystems and human health. In this study, we investigated MP particle concentrations in sediment samples collected from 54 sites along the banks of the Yangtze River and its major tributaries and on lakeshores. The main polymer types found in the samples were polypropylene (PP), polystyrene (PS) and polyethylene (PE). MP particle abundance in the various types of locations was 35-51,968 particles/kg dry weight (d.w.) on the banks of the main river, 52-1463 particles/kg (d.w.) on the banks of tributaries and 2574-23,685 particles/kg (d.w.) on lakeshores. Correlation between MP abundance and mean annual runoff of each upstream tributary was significant, which suggests that increased runoff brings more microplastic waste to streambank sediments. The most common shape of MP particles in all upstream samples was flake, and in downstream samples it was foam. Small microplastic particles (< 0.50 mm) were predominant at all sites in this study, and the minimum particle size in samples from the Yangtze river banks was 0.065 mm. Average abundance of MP particles on the shores of the source lake was 9069 particles/kg around the inlet but only 866 particles/kg around the outlet; the difference was due to interception associated with sedimentation and precipitation in the lake. Our study represents the large-scale study of MPs contamination in sediment along the Yangtze River and provides important data regarding the accumulation and distribution of MPs in shoreline sediments of the upper, middle and lower reaches of the Yangtze River, main tributaries and lakes in China.

Mangrove forest: An important coastal ecosystem to intercept river microplastics

The research on transportation of river microplastics (MPs) mainly focuses on the estimations of the total contents of river MPs entering the ocean, while the related transportation processes and influence factors were still largely unknown. In our study, the role of mangrove forest, a special tropical ecosystem in the estuary, on the transportations of MPs from rivers to ocean was explored. Except for the ND river with the absence of mangrove forest, the MPs collected from the water sample of the river upstream were much higher than their corresponding downstream (p < 0.05), with the interception rate of riverine MPs by mangrove forests ranging from 12.86% to 56% in dry season and 10.57%-42% in rainy season. The MPs with the characteristics of high density, larger size and regular shape were more easily intercepted. Furthermore, the combined effects of ecological indicators, the properties of mangrove and the hydrodynamic factors jointly determined the interception rates of MPs. This study provides a new perspective and data support for quantifying mangrove forests intercepting MPs in rivers as a factor of MPs retention in global rivers.

Plastics, prawns, and patterns: Microplastic loadings in Nephrops norvegicus and surrounding habitat in the North East Atlantic

The presence of microplastics (MPs), a contaminant of emerging concern, has attracted increasing attention in commercially important seafood species such as Nephrops norvegicus. This species lend themselves well as bioindicators of environmental contamination owing to their availability, spatial and depth distribution, interactions with seafloor sediment and position in the ecosystem and food chain. This study assesses the abundance of MPs in N. norvegicus and in benthic sediments across six functional units in the North East Atlantic. Assessment of the relationship between MP abundance in N. norvegicus, their biological parameters and their surrounding environment was examined. Despite the lack of statistical significance, MP abundances, size, shape, and polymer type recorded in N. norvegicus mirrored those found in the surrounding environment samples. The three main polymers identified in both organisms and sediment were polystyrene, polyamide (nylons), and polypropylene. The level of MP contamination in N. norvegicus could be related to local sources, with relatively low abundances recorded in this study for the North East Atlantic in comparison to other regional studies. Furthermore, larger organisms contained a lower abundance of MPs, demonstrating no accumulation of MPs in N. norvegicus. Based on the results of this study, data on MP ingestion could be used to study trends in the amount and composition of litter ingested by marine animals towards fulfilling requirements of descriptor 10 of the Marine Strategy Framework Directive.

Environmental health impacts of microplastics exposure on structural organization levels in the human body

The ubiquitous prevalence of microplastics pollution has raised concerns about microplastics' potential risks and impacts on the global environment. However, the potential human health risks and impacts of microplastics remain largely unexplored. By providing an overview regarding the interaction of microplastics and human health, this review extends current knowledge on the potential impacts of microplastics pollution on humans from an environmental health perspective. The paper firstly presents the characteristics of microplastics as well as the status of global microplastics pollution. As for human health, the potential hazards of microplastics are reflected by toxic chemical components, vectors of contaminants, and physical damage. Extensive microplastic pollution on ecosystems due to human activities leads to inevitable human exposure, which may occur by dietary, inhalation and/or skin contact. Accordingly, microplastics exposure is closely associated with human health. This study explores the potential interactions of microplastics with the biological organization at various levels, including chemical, cellular, tissue, organ, and system levels. The review concludes by highlighting five urgent perspectives and implications for future research on microplastics: 1) Developing a standard terminology and research methods; 2) Reinforcing microplastics pollution governance; 3) Exploring innovative strategies and technologies; 4) Engaging the public and change behaviour; and 5) Adopting a transdisciplinary approach.

Internalization, reduced growth, and behavioral effects following exposure to micro and nano tire particles in two estuarine indicator species

Synthetic rubber emissions from automobile tires are common in aquatic ecosystems. To assess potential impacts on exposed organisms, early life stages of the estuarine indicator species Inland Silverside (Menidia beryllina) and mysid shrimp (Americamysis bahia) were exposed to three tire particle (TP) concentrations at micro and nano size fractions (0.0038, 0.0378 and 3.778 mg/L in mass concentrations for micro size particles), and separately to leachate, across a 5-25 PSU salinity gradient. Following exposure, M. beryllina and A. bahia had significantly altered swimming behaviors, such as increased freezing, changes in positioning, and total distance moved, which could lead to an increased risk of predation and foraging challenges in the wild. Growth for both A. bahia and M. beryllina was reduced in a concentration-dependent manner when exposed to micro-TP, whereas M. beryllina also demonstrated reduced growth when exposed to nano-TP (except lowest concentration). TP internalization was dependent on the exposure salinity in both taxa. The presence of adverse effects in M. beryllina and A. bahia indicate that even at current environmental levels of tire-related pollution, which are expected to continue to increase, aquatic ecosystems may be experiencing negative impacts.

A review of atmospheric microplastics pollution: In-depth sighting of sources, analytical methods, physiognomies, transport and risks

Micro-sized plastics were first examined for atmospheric environment in 2016. From then on, they have been detected in both indoor and outdoor atmospheric samples, with indoor environments demonstrated as containing a big proportion of these particles. The sparse distribution of these particles, is attributed to their swift and long distance transportation that is mainly eased by their tiny size (1 μm to 5 mm) and low density. Due to ongoing limitation on detectable size, analysis methods together with a lack of standardized sampling and analytical procedures, few studies were conducted on airborne microplastics (MPs). Thus, the facts regarding the occurrence, global spatial distribution, fate, and threats to ecosystem and human health of airborne MPs, are still far from being fully clarified. This literature review is a broad depiction of a state of knowledge on atmospheric MPs. Within it, robust and concise information on the sources, inspection, transport, and threats pertaining to airborne MPs are presented. Particularly, the paper entails some information concerning traffic-generated MPs pollution, which has not been frequently discussed within previously published reports. In addition, this paper has widely unveiled sectors and aspects in need of further attention, with the gaps to be filled pinpointed.

Efficient Atmospheric Transport of Microplastics over Asia and Adjacent Oceans

We developed a regional atmospheric transport model for microplastics (MPs, 10 μm to 5 mm in size) over Asia and the adjacent Pacific and Indian oceans, accounting for MPs' size- and shape-dependent aerodynamics. The model was driven by tuned atmospheric emissions of MPs from the land and the ocean, and the simulations were evaluated against coastal (n = 19) and marine (n = 56) observations. Our tuned atmospheric emissions of MPs from Asia and the adjacent oceans were 310 Gg y^-1 (1 Gg = 1 kton) and 60 Gg y^-1, respectively. MP lines and fragments may be transported in the atmosphere >1000 km; MP pellets in our model mostly deposited near-source. We estimated that 1.4% of the MP mass emitted into the Asian atmosphere deposited into the oceans via atmospheric transport; the rest deposited over land. The resulting net atmospheric transported MP flux from Asia into the oceans was 3.9 Gg y^-1, twice as large as a previous estimate for the riverine-transported MP flux from Asia into the oceans. The uncertainty of our simulated atmospheric MP budget was between factors of 3 and 7. Our work highlighted the impacts of the size and morphology on the aerodynamics of MPs and the importance of atmospheric transport in the source-to-sink relationship of global MP pollution.

Environmental contamination by microplastics originating from textiles: Emission, transport, fate and toxicity

Microplastic (MP) pollution has become a global concern in terms of its environmental abundance and potential detrimental effects. Fibrous microplastics (FMPs) released from synthetic textiles are believed to contribute significantly to environmental MP pollution. This review provides an overview of current knowledge relating to the environmental impact of FMPs through a summary and discussion of (1) the concentrations in different environmental compartments including water, soil and air, (2) emission from wastewater treatment plants: via effluent discharges to waters and via sludge to land, (3) environmental transport and fate, and (4) toxicity and associated effects. How the properties of FMPs influence these aspects is discussed and their behaviour is compared to MPs of other shapes. We have summarised the Environmental Concentrations and derived Predicted No-Effect Concentrations for a preliminary risk assessment of FMPs by extrapolating the risk quotient for each respective environmental compartment. The uncertainties surrounding current assessment methods are discussed. In particular we address the need to improve determination of exposure levels and to better characterise the effects of FMPs. We conclude by presenting topics for future studies to address, which will improve our still limited understanding of the interactions between FMPs and the environment.

Chemical Leaching from Tire Wear Particles with Various Treadwear Ratings

Physical friction between a tire and the road surface generates tire wear particles (TWPs), which are a source of microplastics and particulate matter. This study investigated the trends of chemical leaching from TWPs depending on the treadwear rating of the tire. A road simulator was used to produce TWPs from tires with various treadwear ratings. Liquid chromatography–tandem mass spectrometry was used to analyze the chemical leaching from TWPs, with a particular focus on benzothiazole and its derivative 2-hydroxy benzothiazole. However, chemical mapping via high-resolution tandem mass spectrometry detected another derivative: 2-mercaptobenzothiazole. The benzothiazole groups were observed to have different leaching tendencies, implying that using benzothiazole as a marker compound may lead to incorrect TWP quantitation. The results of this research also suggest that the ecotoxicological influence of TWPs can vary with the treadwear rating of a tire.

Deposition and in-situ translocation of microplastics in floodplain soils

The microplastic (MP) contamination of oceans, freshwaters, and soils has become one of the major challenges within the Anthropocene. MP is transported in large quantities through river systems from land to sea and is deposited in river sediments and floodplains. As part of the river system, floodplains and their soils are known for their sink function with respect to sediments, nutrients, and pollutants. However, the questions remain: To what extend does this deposition occur in floodplain soils? Which spatial distribution of MP accumulations, resulting from possible environmental drivers, can be found? The present study analyzes the spatial distribution of large (L-MP, 2000-1000 μm) and medium (M-MP, 1000-500 μm) MP particles in floodplain soils of the Lahn River (Germany). Based on a geospatial sampling concept, the MP contents in floodplain soils are investigated down to a depth of 2 m through a combined method approach, including MP analyses, soil surveys, properties, and sediment dating. The analysis of the plastic particles was carried out by density separation, visual fluorescence identification, and ATR-FTIR analysis. In addition, grain-size analyses and ²¹⁰Pb and ¹³⁷Cs dating were performed to reconstruct the MP deposition conditions. The results prove a more frequent accumulation of MP in upper floodplain soils (0-50 cm) deposited by flood dynamics since the 1960s than in subsoils. The first MP detection to a depth of 2 m and below recent (>1960) sediment accumulation indicates in-situ vertical transfer of mobile MP particles through natural processes (e.g., preferential flow, bioturbation). Furthermore, the role of MP as a potential marker of the Anthropocene is assessed. This study advances our understanding of the deposition and relocation of MP at the aquatic-terrestrial interface.

A Deep Dive into the Complex Chemical Mixture and Toxicity of Tire Wear Particle Leachate in Fathead Minnow

The ecological impact of tire wear particles in aquatic ecosystems is a growing environmental concern. We combined toxicity testing, using fathead minnow (Pimephales promelas) embryos, with nontarget high-resolution liquid chromatography Orbitrap mass spectrometry to characterize the toxicity and chemical mixture of organic chemicals associated with tire particle leachates. We assessed: 1) exposure to tire particle leachates after leaching for 1-, 3-, and 10-d; and 2) the effect of the presence and absence of small tire particulates in the leachates. We observed a decrease in embryonic heart rates, hatching success, and lengths, as well as an increase in the number of embryos with severe deformities and diminished eye and body pigmentation, after exposure to the leachates. Overall, there was a pattern whereby we observed more toxicity in the 10-d leachates, and greater toxicity in unfiltered leachates. Redundancy analysis showed that several benzothiazoles and aryl-amines were correlated with the toxic effects observed in the embryos. These included benzothiazole, 2-aminobenzothiazole, 2-mercaptobenzothiazole, N,N'-diphenylguanidine, and N,N'-diphenylurea. However, many other chemicals characterized as unknowns are likely to also play a key role in the adverse effects observed. Our study provides insight into the types of chemicals likely to be important toxicological drivers in tire leachates, and improves our understanding of the ecotoxicological impacts of tire wear particles. Environ Toxicol Chem 2022;41:1144-1153. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Future microplastics in the Black Sea: River exports and reduction options for zero pollution

The Black Sea receives increasing amounts of microplastics from rivers. In this study, we explore options to reduce future river export of microplastics to the Black Sea. We develop five scenarios with different reduction options and implement them to a Model to Assess River Inputs of pollutaNts to seA (MARINA-Global) for 107 sub-basins. Today, European rivers draining into the Black Sea export over half of the total microplastics. In 2050, Asian rivers draining into the sea will be responsible for 34-46% of microplastic pollution. Implemented advanced treatment will reduce point-source pollution. Reduced consumption or more collection of plastics will reduce 40% of microplastics in the sea by 2050. In the optimistic future, sea pollution is 84% lower than today when the abovementioned reduction options are combined. Reduction options affect the share of pollution sources. Our insights could support environmental policies for a zero pollution future of the Black Sea.

Microplastics in two German wastewater treatment plants: Year-long effluent analysis with FTIR and Py-GC/MS

Microplastics (MP) have been recorded in various environments around the globe. For a better understanding of distribution patterns and for providing a basis for risk assessments, detailed data on MP concentrations and polymer compositions are required. This study investigated the effluents of two German wastewater treatment plants (WWTP) monthly over one year, in order to better understand their temporal input of MP into the receiving river systems. MP item data down to 11 μm were obtained by means of Fourier Transform Infrared (FTIR) spectroscopy under the application of an improved polymer database. Complementary mass data were obtained by pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) (for one WWTP). Both FTIR and Py-GC/MS analysis revealed a homogeneous polymer composition over the year, with a general dominance of polyolefins. Elevated MP item and mass concentrations (maximum: 3 × 10⁴ items m^-3 and 3.8 × 10³ μg m^-3) were observed during winter months and were accompanied by either heavy rainfall (increased discharge and total organic carbon) or elevated turbidity values. These observations emphasize the need for the assessment of background parameters in future MP monitoring studies. By providing monthly data over one year on MP items and masses in WWTP effluents, this study helps enhancing the understanding of temporal MP dynamics and can act as a valuable reference point for future assessments.

Preparation and Characterization of Model Tire–Road Wear Particles

Tire tread wear particles (TWPs) are one of major sources of microplastics in the environment. Tire–road wear particles (TRWPs) are mainly composed of TWPs and mineral particles (MPs), and many have long shapes. In the present work, a preparation method of model TRWPs similar to those found in the environment was developed. The model TRWPs were made of TWPs of 212–500 μm and MPs of 20–38 μm. Model TWPs were prepared using a model tire tread compound and indoor abrasion tester while model MPs were prepared by crushing granite rock. The TWPs and MPs were mixed and compressed using a stainless steel roller. The TWPs were treated with chloroform to make them stickier. Many MPs in the model TRWP were deeply stuck into the TWPs. The proper weight ratio of MP and TWP was MP:TWP = 10:1, and the double step pressing procedure was good for the preparation of model TRWPs. The model TRWPs were characterized using scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The model TRWPs had long shapes and the MP content was about 10%. The model TRWPs made of TWPs and asphalt pavement wear particles showed plate-type particles deeply stuck into the TWP. Characteristics of model TRWPs can be controlled by employing various kinds and sizes of TWPs and MPs. The well-defined model TRWPs can be used as the reference TRWPs for tracing the pollutants.

Hazardous effects of road-side soils on the redox and cholinesterasic homeostasis of mound-building termite (Cornitermes cumulans)

For our knowledge, the roadside soils end up being the deposit of various residues discarded by drivers or passengers, plus, that coming from the runoff of rainwater. Basically, we do not know the impacts that this pollution causes on animals which inhabit these environments. Thus, in this study, our objective was to evaluate how the presence of plastic microfibers (MPFs), organic compounds and heavy metals affect the redox and cholinesterase homeostasis of mound-building termite [Cornitermes cumulans (workers) adults]. As a result, we noticed that MPFs were present in all sampled areas, being higher in road area (RA). Regardless of the presence of these pollutants, animals sampled in the RA were those in which we observed greater production of reactive oxygen species (ROS), hydrogen peroxide (H₂O₂) and nitric oxide (NO) (via nitrite), whose higher activities of antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT), was not able to counterbalance the oxidative stress suggested by the evaluated biomarkers. Moreover, we observed increase in acetylcholinesterase (AChE) activity in these same animals, which suggests a cholinesterasic effect. Such alterations were positively correlated with the contamination of soil samples by Cd, Pb, Zn, Fe and Cu, as well as with the presence of the 11,10-guaiane-type sesquiterpenoid compound, identified only in the RA. Thus, our unique study reveals that the contamination of roadside soils constitutes an additional environmental stressor to populations of C. cumulans, which reinforces the need for greater attention and further investigation to be given to the pollution of these environments.

Microplastics in the sediments of small-scale Japanese rivers: Abundance and distribution, characterization, sources-to-sink, and ecological risks

Microplastic pollution in small-scale river sediments remains mostly unknown. This study explored microplastics in the sediments of four small-scale Japanese rivers in Yamaguchi Prefecture: the Awano, Ayaragi, Asa, and Majime. Sediment samples (n = 23) were collected from the selected stations. Density separation and wet peroxidation methods were applied to extract microplastics. Polymers were detected through attenuated total reflectance-Fourier transform infrared spectroscopy. Microplastic abundance indicated relatively moderate values in the small-scale Japanese rivers compared to other rivers around the world. Large microplastics (1-5 mm) in size, fragments in shape, and high-density particles of diverse polymers dominated. Polyvinyl chloride, polyethylene, and polypropylene were the major polymers. The polymers-polyvinyl chloride, polymethylmethacrylate, polyurethane, fluorinated ethylene propylene, and polybutylene in sediments were distinct from those detected in surface water, as were the predominance of large-size (1-5 mm) and fragment-shape microplastics. In contrast to surface water, sediments preserved both common and distinctive microplastics. Thus, the riverine sediment compartment acted as microplastic sink. Scanning electron microscopic (SEM) analysis suggested the presence of weathered microplastics in sediments. Energy dispersive X-ray spectroscopic analysis (EDX) revealed metal contaminants on the microplastic surfaces, indicating synergistic hazard potentials in the riverine ecosystems. Ecological risk assessment results suggested low to very high risks of microplastic pollution for the rivers. The higher abundances of microplastics and highly toxic polymers contributed to the elevated ecological risks. Polyvinyl chloride, acrylonitrile butadiene styrene, polyurethane, and polymethylmethacrylate were the detected highly toxic polymers. The urban and residential areas affected stations ranked high to very high ecological risks. The sites posing very high ecological risks were regarded as pollution hotspots. Overall, this study developed new insights into microplastic pollution in the small-scale rivers and ecological risks for riverine environments, as well as providing a baseline for more comprehensive risk assessments and developing pollution control and management strategies.

An affordable method for monitoring plastic fibre ingestion in Nephrops norvegicus (Linnaeus, 1758) and implementation on wide temporal and geographical scale comparisons

Although the ingestion of plastics has been reported in a wide variety of organisms, there remains a lack of knowledge regarding the extent of spatial and temporal gradients and no consensus concerning the definition of monitor species for benthic marine environments. The present study aims at demonstrating the correlation between the presence of tangled balls of fibres and high levels of total plastic fibre ingestion in Nephrops norvegicus to assess the potential use of the prevalence of tangled balls as indicators of fibre pollution. To do so, the presence of plastics in stomach contents from several European populations of N. norvegicus is characterized in detail, including size distribution and polymer composition, and then its correlation with the prevalence of balls tested. Our results demonstrate that the prevalence of balls (>20%) is significantly correlated to higher levels of plastic ingestion, regardless of polymer composition and size distribution of ingested fibres. Plastic fibre ingestion levels across wide temporal and geographical scales are assessed using only the prevalence of balls, highlighting areas of increased fibre ingestion (e.g., the Gulf of Cadiz, N Barcelona) and areas of potentially lower fibre pollution (e.g., the Ebro Delta, the NW Iberian margin). Moreover, the relationship between the prevalence of balls and diet composition is analysed to discard a potential relationship with geographical differences in diet habits. Finally, we discuss the benefits and drawbacks of the use of the prevalence of tangled balls of fibres as an affordable, cost-effective and easy to implement indicator of fibre pollution for monitoring purposes in this species.

The occurrence and abundance of microplastics in surface water of the midstream and downstream of the Cisadane River, Indonesia

This study investigates microplastic contamination in the midstream to downstream of the Cisadane River and its confluence with the Java Sea. The abundance ranged between 13.33 and 113.33 particles m^-3 in surface water samples. Microplastic abundance in the downstream area was higher than midstream. We discovered 11 microplastic polymer types, with polyethylene, polystyrene, and polypropylene dominating (>70%) the chemical composition study result, which we hypothesized was owing to their ubiquitous use in daily household and industrial activities. Microplastic fragments with a diameter of 500-1000 m predominated in surface water samples. This study identifies possible microplastics pollution hotspots throughout the Cisadane rivers and selects sites that require additional sampling. Runoff from cities and landfills has the potential to have a significant impact on the accumulation and movement of microplastics from the inland to the Cisadane estuarine area. Additional research is necessary to determine how and where these microplastics particles enter rivers.

Missing relationship between meso- and microplastics in adjacent soils and sediments

Meso- and microplastics (MMPs) have attracted attention as globally dispersed environmental pollutants. However, little is known about the transfers of MMPs between aquatic and terrestrial systems. A large watershed-estuarine area of Bohai Sea was used as a case study, and soils and sediments were sampled adjacent to each other at a wide range of sites. MMPs were detected in all sediments (6.7-320 MMPs/kg) and soils (40-980 MMPs/kg), with the average abundance in soils double that in sediments on a dry mass basis. MMPs < 1 mm were most abundant and the dominant shape was film in both sediments and soils. Over twenty polymer types were detected and their compositions in sediments and soils were different. MMP abundance in sediments was lower in the upper catchment than the lower catchment, while the abundance of soil MMPs was the opposite. Despite the proximity of the sampling locations, no clear relationship was identified between the soil and sediment MMPs, suggesting low transfer between the two compartments and high heterogeneity of the sources. The missing associations between aquatic and terrestrial MMPs should be systematically examined in future studies, which is crucial for understanding the environmental fate and impacts of MMPs.

Mathematical modeling of microplastic abundance, distribution, and transport in water environments: A review

Microplastic pollution in marine and riverine environments is a threat not only for the aquatic ecosystem itself but also for human activity and life. Although there are reviews regarding microplastic debris in environments, most of them focus on the studies on their type, occurrence, and distribution. Only a limited number of these studies focus on the modeling methods, usually concentrating on particular aspects, such as settling or bioaccumulation. In this paper, physically-based existing microplastics modeling studies are classified and reviewed according to the environment, modeling methodology, and input-output relationships. Considering the strengths and weaknesses of all modeling methodologies, it is deduced that more reliable results are obtained using hybrid methods, especially the coupling of hydrodynamic and process-based models, and hydrodynamics and statistical models. The significance of having much more consideration and knowledge on the microplastics' physical properties and the environmental processes affecting their fate and transport in the aquatic environments is revealed for future research. It has also been recommended that a standardized method for data calibration, validation, and verification is necessary to be able to compare the modeling results with field investigations more efficiently than it is currently.

Microplastics pollution in the terrestrial environments: Poorly known diffuse sources and implications for plants

Research on microplastics (MPs) in the terrestrial environment is currently at a still embryonal stage. The current knowledge concerning poorly known diffuse sources of MPs pollution in terrestrial ecosystems have been considered in this work. In addition, a particular focus on the presence, mechanism of absorption and effects of MPs in plants has also been provided. Research concerning microplastics in urban areas and their intake by Tyre and Road Wear Particulates (TWRP) demonstrated a high contribution of this plastic debris to microplastic pollution, although quantification of these inputs is challenging to assess because studies are still very few. Around 50% of particles are expected to remain in the roadside soil, while the rest is transported away by the runoff with high concentrations of TRWP with a size ranging between 0.02 and 0.1 mm. Natural and anthropic environments like temporary ponds, stormwater retention ponds and small waterbodies were considered sensitive connecting ecosystems rich in biodiversity between terrestrial and aquatic environments. Even if studies are not yet exhaustive and just eight studies were currently published concerning these ecosystems, considerable values of MPs were already observed both in the sediment and water phase of ponds. Although still poorly explored, agricultural environments were already demonstrated to hide a significant number of microplastics linked mainly to agricultural activities and practices (e.g. mulch, sewage and compost fertilisation). However, the microplastics transportation processes into the soil are still understudied, and a few works are available. Microplastics and primarily nanoplastics presence was also observed in common edible plants (fruit and vegetables) with alarming Estimated Daily Intakes ranging from 2.96 × 10⁰⁴ to 4.62 × 10⁰⁵ (p kg^-1 day^-1) for adults depending on species. In addition, adverse effects on plants growth, photosynthetic activity, antioxidant system and nutritional values of several common fruits and vegetables were also demonstrated by several studies.

Spatial Connections between Microplastics and Heavy Metal Pollution within Floodplain Soils

Soils contain an increasing number of different pollutants, which are often released into the environment by human activity. Among the “new” potential pollutants are plastics and microplastics. “Recognized” pollutants such as heavy metals, of geogenic and anthropogenic origin, now meet purely anthropogenic contaminants such as plastic particles. Those can meet especially in floodplain landscapes and floodplain soils, because of their function as a temporary sink for sediments, nutrients, and pollutants. Based on a geospatial sampling approach, we analyzed the soil properties and heavy metal contents (ICP-MS) in soil material and macroplastic particles, and calculated total plastic concentrations (Ptot) from preliminary studies. Those data were used to investigate spatial connections between both groups of pollutants. Our results from the example of the Lahn river catchment show a low-to-moderate contamination of the floodplain soils with heavy metals and a wide distribution of plastic contents up to a depth of two meters. Furthermore, we were able to document heavy metal contents in macroplastic particles. Spatial and statistical correlations between both pollutants were found. Those correlations are mainly expressed by a comparable variability in concentrations across the catchment and in a common accumulation in topsoil and upper soil or sediment layers (0–50 cm). The results indicate comparable deposition conditions of both pollutants in the floodplain system.

Controlling Factors of Microplastic Riverine Flux and Implications for Reliable Monitoring Strategy

A significant proportion of marine plastic debris and microplastics is assumed to be derived from river systems. In order to effectively manage plastic contamination of the marine environment, an accurate quantification of riverine flux of land-based plastics and microplastics is imperative. Rivers not only represent pathways to the ocean, but are also complex ecosystems that support many life processes and ecosystem services. Yet riverine microplastics research is still in its infancy, and many uncertainties still remain. Major barriers exist in two aspects. First, nonharmonized sampling methodologies make it problematic for compiling data across studies to better estimate riverine fluxes of microplastics globally; Second, the significant spatiotemporal variation of microplastics in rivers which was affected by the river characteristics, MPs properties, etc. also have important influence on the estimation of riverine MPs fluxes. In this study, we made a comprehensive review from the above two aspects based on published peer-reviewed studies and provide recommendations and suggestions for a reliable monitoring strategy of riverine MPs, which is beneficial to the further establish sampling methods for rivers in different geographical locations. Besides, methods for achieving a high level of comparability across studies in different geographical contexts are highlighted. Riverine microplastic flux monitoring is another important part of this manuscript. The influential factors and calculation methods of microplastic flux in rivers are also discussed in this paper.

An Overview of Chemical Additives on (Micro)Plastic Fibers: Occurrence, Release, and Health Risks

Plastic fibers are ubiquitous in daily life with additives incorporated to improve their performance. Only a few restrictions exist for a paucity of common additives, while most of the additives used in textile industry have not been clearly regulated with threshold limits. The production of synthetic fibers, which can shed fibrous microplastics easily (< 5 mm) through mechanical abrasion and weathering, is increasing annually. These fibrous microplastics have become the main composition of microplastics in the environment. This review focuses on additives on synthetic fibers; we summarized the detection methods of additives, compared concentrations of different additive types (plasticizers, flame retardants, antioxidants, and surfactants) on (micro)plastic fibers, and analyzed their release and exposure pathways to environment and human beings. Our prediction shows that the amounts of predominant additives (phthalates, organophosphate esters, bisphenols, per- and polyfluoroalkyl substances, and nonylphenol ethoxylates) released from clothing microplastic fibers (MFs) are estimated to reach 35, 10, 553, 0.4, and 568 ton/year to water worldwide, respectively; and 119, 35, 1911, 1.4, and 1965 ton/year to air, respectively. Human exposure to MF additives via inhalation is estimated to be up to 4.5–6440 µg/person annually for the above five additives, and via ingestion 0.1–204 µg/person. Notably, the release of additives from face masks is nonnegligible that annual human exposure to phthalates, organophosphate esters, per- and polyfluoroalkyl substances from masks via inhalation is approximately 491–1820 µg/person. This review helps understand the environmental fate and potential risks of released additives from (micro)plastic fibers, with a view to providing a basis for future research and policy designation of textile additives.

Hallmarking microplastics of sediments and Chamelea gallina inhabiting Southwestern Black Sea: A hypothetical look at consumption risks

The consumer preference of bivalves originating from fishery or aquaculture has gained momentum in response to higher nutrition, quality, and market availability. However, potential toxicity caused by plastics, the pollution icons of the current era, could raise concerns for the sources of essential nutrients provided by bivalves. Thus, we investigated the abundance, spatial distribution, polymer composition, size, and the shapes of the microplastics (MPs) in the sediment and Chamelea gallina from 15 sites at gradual depths (10 and 30 m) along the Southwestern Black Sea coast. The abundance of the MPs ranged from 28 to 684 MP kg^-1 in the sediments and the amount of 0.22-2.17 MP individual^-1 (or 0.20-2.16 MP g^-1 fresh weight soft tissue) in C. gallina. Seven types of polymers were detected by FTIR, and the most abundant type was polyethylene terephthalate (34.2-35.1%), polyethylene (28-31.1%), and polypropylene (18.9-21%). MP sizes were ranged from 73 to 4987 μm. 47% and 65% of the MPs in the sediments and C. gallina, respectively, were <1000 μm in size. The most dominant shape of the MPs was found as fibers (56.5% for sediments and 68.9% for C. gallina). The risk data predicted that people are exposed to 304 MPs when consuming a single portion of C. gallina weekly. Hypothetical calculations performed with a chemical additive simulation (bisphenol A) showed that the risk associated with the MP-contaminated C. gallina model is negligible, and the consumption is rather beneficial due to already known positive aspects.

Updated review on microplastics in water, their occurrence, detection, measurement, environmental pollution, and the need for regulatory standards

The gravity of the impending threats posed by microplastics (MPs) pollution in the environment cannot be over-emphasized. Several research studies continue to stress how important it is to curb the proliferation of these small plastic particles with different physical and chemical properties, especially in aquatic environments. While several works on how to monitor, detect and remove MPs from the aquatic environment have been published, there is still a lack of explicit regulatory framework for mitigation of MPs globally. A critical review that summarizes recent advances in MPs research and emphasizes the need for regulatory frameworks devoted to MPs is presented in this paper. These frameworks suggested in this paper may be useful for reducing the proliferation of MPs in the environment. Based on all reviewed studies related to MPs research, we discussed the occurrence of MPs by identifying the major types and sources of MPs in water bodies; examined the recent ways of detecting, monitoring, and measuring MPs routinely to minimize projected risks; and proposed recommendations for consensus regulatory actions that will be effective for MPs mitigation.

Assessment of Microplastic Size Range and Ingestion Intensity by Gmelinoides fasciatus Stebbing, an Invasive Species of Lake Onego

To indicate the potential role of Gmelinoides fasciatus, an invasive species of Lake Onego, in the inclusion of microplastics into food webs, several indicators were evaluated: its ability to ingest microplastics, the preferred size ranges, and the ingestion intensity. For this purpose, irregularly shaped polystyrene copolymer particles (acrylonitrile butadiene styrene plastics, artificially crushed) of four size classes (<50, 50-100, 100-250, >250 µm) were used. Gmelinoides fasciatus actively ingested microplastic particles, and in treatment with particles of 100-250 µm in size, the consumption rate was the highest. The crustaceans that survived the experiment ingested smaller particles than the deceased ones. Based on the size-frequency distributions of the ingested particles and the same in the suspension, crustaceans preferred smaller particles than those in suspension. The mean size of the ingested particles was 100 ± 5 µm. However, considering the actual concentration of microplastic fragments in the sediments of Lake Onego, in natural conditions, a negative effect of microplastic fragments on the G. fasciatus population is unlikely. At the same time, the ability of the invasive species G. fasciatus to consume microplastics and their active integration into the food webs of Lake Onego through consumption by fish can be considered reliable factors of the entry of microplastics in the fish of Lake Onego. Environ Toxicol Chem 2022;41:184-192. © 2021 SETAC.

Continental microplastics: Presence, features, and environmental transport pathways

Microplastics (MPs) are ubiquitous contaminants of great concern for the environment. MPs' presence and concentration in the air, soil, marine, and freshwater environments have been reported as a matter of priority in recent years. This review addresses the current knowledge of the main pathways of MPs in air, soil, and freshwater reservoirs in order to provide an integrated understanding of their behaviors in the continental environment. Therefore, MPs' occurrence (as particle counts), sources, and how their features as shape, size, polymer composition, and density could influence their transport and final sink were discussed. Wind resuspension and atmospheric fallout, groundwater migration, runoff from catchments, and water flow from rivers and effluents were pointed as the principal pathways. MPs' size, shape, polymer composition, and density interact with environmental variables as soil structure and composition, precipitation, wind, relative humidity, water temperature, and salinity. Sampling designs for MPs research should further consider soil characteristics, climate variability and extreme events, time lag and grasshopper effects, morphological and hydrological features of aquatic systems, and water currents, among others. Furthermore, long-term monitoring and lab experiments are still needed to understand MPs' behavior in the environment. This information will provide a unified understanding of the continental MPs pathways, including the key main findings, knowledge gaps, and future challenges to understand this emerging contaminant.

Static modelling of the material flows of micro- and nanoplastic particles caused by the use of vehicle tyres

The emissions of tyre wear particles (TWPs) into the environment are increasing and have negative impacts on the environment and human health. The aim of this study was therefore to establish a mass balance for vehicle tyres und TWP emissions in Austria using static material flow analysis, which enabled a quantification of mass flows of rubber including carbon black as the most mass-relevant tyre filler. Vehicle-specific and mileage-dependent emission factors were used to calculate the TWP emissions. The results for the year 2018 indicate that 80% of the tyre rubber remained in use, while 14% was re-treaded, recycled, incinerated or exported as end-of-life tyres and 6% was emitted as TWPs to air, soil or surface water. Of these 21,200 t/y released and dissipative lost TWPs, 6% were microscale, with a possible size between 0.1 and 10 μm, and 0.3% were nanoscale below 0.1 μm. The mass balance on the substance level shows that the TWPs contained 5,500 t/y of carbon black emitted in the form of airborne TWPs (6%) or entering in the soil or surface waters (47% each). Regarding air pollution from road vehicles, about 3,600 t/y were non-exhaust emissions, including tyre, brake and road-surface wear, which contributed to 9% of total dust emissions across Austria. Scenario analysis for 2050 with regard to e-mobility and the European Green Deal reveals that non-exhaust emissions can only be significantly reduced by a general reduction of the mileage or an environmentally friendly tyre design. This modelling approach provides a solid basis for decision makers in traffic planning as well as for chemical risk assessment. However, dynamic models with higher temporal and spatial resolution are needed to predict future mass flows of TWPs and their environmental fate, including their degradation products and possible accumulation effects.

Emission, Transport, and Deposition of visible Plastics in an Estuary and the Baltic Sea-a Monitoring and Modeling Approach

was to assess whether a comprehensive approach linking existing knowledge with monitoring and modeling can provide an improved insight into coastal and marine plastics pollution. We focused on large micro- and mesoplastic (1-25 mm) and selected macroplastic items. Emission calculations, samplings in the Warnow river and estuary (water body and bottom sediments) and a flood accumulation zone monitoring served as basis for model simulations on transport and behavior in the entire Baltic Sea. Considered were the most important pathways, sewage overflow and stormwater. The coastline monitoring together with calculations allowed estimating plastics emissions for Rostock city and the Warnow catchment. Average concentrations at the Warnow river mouth were 0.016 particles/m³ and in the estuary 0.14 particles/m³ (300 µm net). The estuary and nearby Baltic Sea beaches were hot-spots for plastic accumulation with 6-31 particles/m². With increasing distance from the estuary, the concentrations dropped to 0.3 particles/m². This spatial pattern, the plastic pollution gradients and the observed annual accumulation values were consistent with the model results. Indicator items for sewer overflow and stormwater emissions exist, but were only found at low numbers in the environment. The considered visible plastics alone can hardly serve as indicator for microplastic pollution (<1 mm). The use of up-scaled emission data as input for Baltic Sea model simulations provided information on large scale emission, transport and deposition patterns of visible plastics. The results underline the importance of plastic retention in rivers and estuaries.

Evidence for Microplastics Contamination of the Remote Tributary of the Yenisei River, Siberia—The Pilot Study Results

This study is a pioneering attempt to count microplastics (MPs) in the Yenisei River system to clarify the role of Siberian Rivers in the transport of MPs to the Arctic Ocean. The average MPs content in the surface water of the Yenisei large tributary, the Nizhnyaya Tunguska River, varied from 1.20 ± 0.70 to 4.53 ± 2.04 items/m3, tending to increase along the watercourse (p < 0.05). Concentrations of MPs in bottom sediments of the two rivers were 235 ± 83.0 to 543 ± 94.1 with no tendency of downstream increasing. Linear association (r = 0.952) between average organic matter content and average counts of MPs in bottom sediments occurred. Presumably MPs originated from the daily activities of the in-situ population. Further spatial-temporal studies are needed to estimate the riverine MPs fluxes into the Eurasian Arctic seas.

Research progresses of microplastic pollution in freshwater systems

Microplastics (MPs) have received widespread attention as an emerging environmental pollutant. They are ubiquitous in the freshwater system, causing a global environmental issue. The current features and perspectives of MPs in the freshwater systems can provide the concerns of their ecological effects, which has not been addressed widely. Therefore, in this study, we reviewed the characteristics of MPs in freshwater environments and discussed their sources and potential impacts. The abundance of MPs in freshwater system ranged from approximately 3-6 orders of magnitude in different regions. There colors were mainly white and transparent, with polypropylene (PP) and polyethylene (PE) as the major polymers. The main shape of these MPs was fibers with dominant size of less than 1 mm. Analysis indicated MPs in freshwater system mostly originated from human activities such as sewage discharge in highly contaminated areas, while atmospheric long-distance transport and precipitation deposition played an important role in remote areas. Freshwater MPs pollutants also affected drinking water and aquatic organisms. Because the abundance of MPs in organisms was relatively balanced, the pollution level of biological MP pollution cannot accurately characterize the pollution status in the watershed currently. Future research should focus and strengthen on periodic monitoring to characterize the temporal and spatial changes of MPs, and enhance toxicological research to explore MPs pollution impact on biota and humans.

Environmental occurrence, fate, impact, and potential solution of tire microplastics: Similarities and differences with tire wear particles

Tire microplastics (TMPs) are identified as one of the most abundant types of microplastics, which originate from rubber with intended or unintended release. While increasing knowledge about TMPs concentrates on tire wear particles (TWPs), TMPs from other potential sources like recycled tire crumb (RTC) and tire repair-polished debris (TRD) are much less understood. Excessive levels of TMPs and their additives have been fragmentarily reported in the environment. The accumulating environmental TMPs from different sources may directly or indirectly cause adverse impacts on the environment and human health. The objectives of this review are to (1) summarize the properties, abundance, and sources of TMPs in the environment; (2) analyze the environmental fates and behaviors of TMPs, including their roles in carrying abiotic and biotic co-contaminants; (3) evaluate the potential impacts of TMPs on terrestrial and aquatic organisms, as well as human; and (4) discuss the potential solutions to mitigate the TMP pollution. By collecting and analyzing the up-to-date literature, this review enhances our better understanding of the environmental occurrence, fates, impacts, and potential solutions of TMPs, and further highlights critical knowledge gaps and future research directions that require cooperative efforts of scientists, policymakers, and public educators.

Toxicity and Functional Tissue Responses of Two Freshwater Fish after Exposure to Polystyrene Microplastics

Microplastics (MPs)' ingestion has been demonstrated in several aquatic organisms. This process may facilitate the hydrophobic waterborne pollutants or chemical additives transfer to biota. In the present study the suitability of a battery of biomarkers on oxidative stress, physiology, tissue function and metabolic profile was investigated for the early detection of adverse effects of 21-day exposure to polystyrene microplastics (PS-MPs, sized 5-12 μm) in the liver and gills of zebrafish Danio rerio and perch, Perca fluviatilis, both of which are freshwater fish species. An optical volume map representation of the zebrafish gill by Raman spectroscopy depicted 5 μm diameter PS-MP dispersed in the gill tissue. Concentrations of PS-MPs close to the EC50 of each fish affected fish physiology in all tissues studied. Increased levels of biomarkers of oxidative damage in exposed fish in relation to controls were observed, as well as activation of apoptosis and autophagy processes. Malondialdehyde (MDA), protein carbonyls and DNA damage responses differed with regard to the sensitivity of each tissue of each fish. In the toxicity cascade gills seemed to be more liable to respond to PS-MPs than liver for the majority of the parameters measured. DNA damage was the most susceptible biomarker exhibiting greater response in the liver of both species. The interaction between MPs and cellular components provoked metabolic alterations in the tissues studied, affecting mainly amino acids, nitrogen and energy metabolism. Toxicity was species and tissue specific, with specific biomarkers responding differently in gills and in liver. The fish species that seemed to be more susceptible to MPs at the conditions studied, was P. fluviatilis compared to D. rerio. The current findings add to a holistic approach for the identification of small sized PS-MPs' biological effects in fish, thus aiming to provide evidence regarding PS-MPs' environmental impact on wild fish populations and food safety and adequacy.

Estimation of soil microplastic input derived from plastic gauze using a simplified model

Plastic gauzes have been widely used in the BTH region against haze events and for agricultural practices. The breakage of plastic gauzes would lead to the release of microplastics into soils, but it is difficult to estimate the inputs due to their wide implementation. In this study, we have conducted an estimation model based on the remote sensing technology for plastic gauze identification and the data from field experiments and literature. This model first managed to interpret the distribution of plastic gauzes from the Landsat8 images with the average overall accuracy at 0.92 and the average kappa at 0.77. By deeming the implementation duration of plastic gauzes from their distribution and using the breakage rates of plastic materials in soils reported in the literature, the model estimated that on average 1629.68 tons of microplastics have been released to soils from plastic gauze annually in the BTH region. Comparing with the microplastics released from other sources (e.g., personal care products, household dusts, laundry, and tire wear), plastic gauze could be a considerable contributor to soil microplastics.

Occurrence of microplastic in the water of different types of aquaculture ponds in an important lakeside freshwater aquaculture area of China

Aquaculture ponds are exposed to numerous potential microplastic sources, but studies on their microplastic pollution are still limited. Various culture species may influence the occurrence of microplastic in ponds. In the present study, the occurrence of microplastics was studied in aquaculture ponds for fish, crayfish, and crab, as well as in the natural lake near the aquaculture area around the Honghu Lake, which is the principal freshwater aquaculture area of China. The microplastic abundances ranged from 87 items/m³ to 750 items/m³ in the aquaculture ponds, and 117 items/m³ to 533 items/m³ in the lake. The crab ponds contained higher abundances of microplastics than fish ponds and the nearby natural lakes. Microplastics that were between 100 and 500 μm and larger than 1000 μm in size were predominant in the ponds and nearby lakes, whereas the proportion of microplastics that were smaller than 100 μm was higher in crab ponds than those in other ponds. Fragments and fibers were the predominant shapes of microplastics in the ponds. The proportion of smaller microplastics in the ponds had a positive correlation with the proportion of fragment microplastics. The results of this study implied that differences in the use of plastics in various types of aquaculture ponds might affect their microplastic pollution characteristics. Microplastics discharged from ponds to nearby lakes through drainage processes require attention in further studies.

Microplastic pollution in the Weser estuary and the German North Sea

Microplastics (MP) are defined as synthetic organic pollutants sized <5 mm and have been recorded in various environments worldwide. Due to their small size, they pose a potential risk for many organisms throughout the food web. However, little is known about MP distribution patterns and associated transport mechanisms. Rivers may act as pathways for MP into marine environments. In this study, we investigate the occurrence of MP in the estuary and lower stretch of the second-largest German River, the Weser, representative of a significant interface between fresh water and marine environments. The aim of the study was to enhance the general understanding by providing novel, comprehensive data and suggestions for future studies on estuarine systems. Surface water samples of two different size classes were collected by ship using an on-board filtration system (11-500 μm fraction) and net sampling (500-5000 μm fraction). After a thorough sample preparation, all samples were analysed with Focal Plane Array (FPA) Fourier Transform Infrared (FTIR) spectroscopy and Attenuated Total Reflection (ATR) FTIR spectroscopy in order to obtain information on MP concentrations, polymer composition and size distribution. Our findings show highest concentrations in the 11-500 μm fraction (2.3 × 10¹ - 9.7 × 10³ MP m^-3), with the polymer cluster acrylates/polyurethanes(PUR)/varnish being dominant. The >500 μm fraction was dominated by polyethylene. Estimated MP concentrations generally increased in the Turbidity Maximum Zone (TMZ) and decreased towards the open sea. This study contributes to the current research by providing novel insights into the MP pollution of the estuary and lower stretch of an important European river and provides implications for future MP monitoring measures.

Settling velocity of irregularly shaped microplastics under steady and dynamic flow conditions

The behavior of microplastics (MPs) in aquatic environments can vary significantly according to their composition, shape, and physical and chemical properties. To predict the settling trajectory of MPs in aquatic environments, this study investigates the settlement law of MPs under static and dynamic conditions. Four types of materials were analyzed, namely polystyrene, polyamide, polyethylene terephthalate, and polyvinyl chloride. Approximately 1270 MP particles with irregular shapes (near-sphere, polygonal ellipsoid, and fragment) were selected for the settling experiments. The experimental results show that the main factors affecting the settling velocity of MPs were shape irregularity, density, and particle size. The settling velocity of irregular MPs was significantly lower than that of perfectly spherical MPs. We proposed a model that predicts the correlation between the settling velocity of MPs and their shape, density, particle size, and water density.

Microplastic pollution in sophisticated urban river systems: Combined influence of land-use types and physicochemical characteristics

In the past decades, research on water pollution microplastics (MPs) has intensified tremendously. However, the relationship between MPs and environmental factors in urban river networks is under researched. Our study selected 65 sampling sites from a sophisticated urban river network system in Shanghai Municipality, China. Here, the combined influence of land-use types, river width, and water quality parameters to explore MPs distribution patterns. We found that MPs abundance ranged from 0.7 to 24.3 items/L, and the spatial difference in abundance was significant at a limited number of sampling sites. Fibrous MPs were the most abundant MPs in the river system. 72.7% of MPs <3 mm. Of the ten polymers detected, polypropylene and polyethylene terephthalate were predominant. In addition, cotton fiber was the main non-plastic component found in the samples. Moreover, land-use types showed no significant impact on MPs in the buffer zone of the sampling sites. However, point source pollution may cause an abnormal increase in MPs abundance. Through redundant analysis, we found that the phytoplankton abundance (e.g., chlorophyll-a) was influenced by MPs shape, while the river width influence MPs size. Construction activities were identified as the leading point source of pollution for the abnormal increase in local MPs pollution. Our results will inform on MPs distribution patterns in the super-metropolis river system.

Seasonal distributions of microplastics and estimation of the microplastic load ingested by wild caught fish in the East China Sea

Microplastic (MP) pollution in marine environments and organisms has received substantial international attention. However, long-term field studies of MPs are scarce. Here, we assessed the seasonal variation in MP abundance in the Zhoushan fishing ground (ZFG), one of the most abundant and productive fishing grounds worldwide, and analyzed the long-term MP accumulation in fish gastrointestinal tracts from September 2017 to June 2018. The most common MP particles in the ZFG were polyethylene terephthalate and polypropylene. After four seasons of continuous monitoring, we did not find accumulation of MPs in the fish after 10% KOH digestion. In total, 254 MP particles were removed from the gastrointestinal tracts of all fish. The average number of particles per fish was lower than that reported in previous global marine studies. There were significant differences among species. Moreover, this study provides the calculation of the weight of MPs ingested by fish and an estimate of the load of accumulated MPs in fish. According to the estimation, the load of MPs ingested by fish annually was approximately 3 kg in ZFG. These findings provide the long-term evidence of MP contamination in biota from the ZFG. The amounts of MPs ingested by fish require more detailed and improved investigation and estimation in further studies.

Inclusion of shape parameters increases the accuracy of 3D models for microplastics mass quantification

As microplastics may bring about adverse effects on living organisms, it is important to establish more precise quantification approaches to better understand their dynamics. One method to determine the concentration of microplastics is to estimate their mass using three-dimensional (3D) models, but its accuracy is not well known. In this study, we evaluated the shape of the particles and verified the accuracy of a 3D model-based mass estimation using samples from a tidal flat facing Tokyo Bay. The particle shape evaluation suggested that the microplastics were flat and irregular in shape; based on these data, we created two types of models to estimate their mass. As a result, an accuracy of mass estimation by our model was higher than other models that consider the slenderness and flatness of particles. The optimization of mass estimation methods based on 3D models may improve the reliability of microplastic evaluation in monitoring studies.

Behavior of Microplastics in Inland Waters: Aggregation, Settlement, and Transport

Inland waters are the main medium transporting microplastics to the ocean. Aggregation, vertical settlement, and horizontal transport will occur when microplastics enter the inland waterbodies. This paper reviews these behaviors of microplastics in inland waters and their influencing factors. The aggregation of microplastics were divided into homogeneous aggregation and heterogeneous aggregation, which are critical for the settlement of microplastics. The settlement of microplastics in inland water bodies is influenced by microplastic properties (size, density, and shapes) and environmental conditions (microorganisms, sedimental properties, hydraulic conditions, and so on). Horizontal transport of microplastics in water is influenced by hydrologic conditions, rainfall, river morphologies, dams, vegetation, etc. Future perspectives including laboratory simulations and numerical models involving multiple factors, the behaviors of degradable plastics, and the influence of hydrologic conditions have been proposed.

Measurement, quantification, and potential risk of microplastics in the mainstream of the Pearl River (Xijiang River) and its estuary, Southern China

The goals of this study were to investigate the distribution profiles, sources, and inventory of microplastics in the surface water of the mainstream of the Pearl River (Xijiang River) and its estuary, China, and to assess the potential ecological risks of the microplastics in this subtropical riverine habitat. The results showed that the microplastic abundances of the Humen (HUM, 16.33 ± 0.88 items/L), Zhaoqing (ZQ, 15.33 ± 0.67 items/L), and Hutiaomen (HTM, 14.67 ± 1.33 items/L) sites were significantly higher than those of the other sampling sites, indicating that the microplastics in Xijiang River and its estuary exhibited an unbalanced spatial distribution. The most common microplastic color was transparent and the major shape of the microplastics was fragments. Microplastics with a size of 0.01-0.1 mm were dominant throughout the 16 sampling sites. Polyolefin elastomer (POE, 33.33%), polyethylene terephthalate (PET, 23.81%), and polyurethane acrylate (PUA, 14.29%) were the dominant microplastic polymers. The microplastic abundance co-varied with most of the selected socio-economic indicators, including the population density, urban land area, gross domestic product (GDP), freshwater aquatic products, and freshwater cultivated area, but without significant differences, indicating that there are additional factors affecting the microplastic abundance. The potential risk (i.e., the potential ecological risk, RI; polymer risk index, H; and pollution load index, PLI) posed by the microplastics was higher in HUM, followed by ZQ and HTM, and it was lower for the other sites, suggesting that the main outlets and the biggest city on the Xijiang River contributed more to the high risks of microplastic pollution. Consistent with microplastic abundance distribution profiles, the average potential risk index values of the western river outlets were higher than those of the eastern river outlets and the Xijiang River, implying that the western river outlets had non-negligible potential ecological risks. Our findings deepen the understanding of the risks posed by microplastics and further contribute to microplastic risk management of riverine ecosystems.

Exploring the impacts of microplastics and associated chemicals in the terrestrial environment - Exposure of soil invertebrates to tire particles

Abrasion of tire wear is one of the largest sources of microplastics to the environment. Although most tire particles settle into soils, studies on their ecotoxicological impacts on the terrestrial environment are scarce. Here, the effects of tire particles (<180 μm) on three ecologically relevant soil invertebrate species, the enchytraeid worm Enchytraeus crypticus, the springtail Folsomia candida and the woodlouse Porcellio scaber, were studied. These species were exposed to tire particles spiked in soil or in food at concentrations of 0.02%, 0.06%, 0.17%, 0.5% and 1.5% (w/w). Tire particles contained a variety of potentially harmful substances. Zinc (21 900 mg kg^-1) was the dominant trace element, whilst the highest concentrations of the measured organic compounds were detected for benzothiazole (89.2 mg kg^-1), pyrene (4.85 mg kg^-1), chlorpyrifos (0.351 mg kg^-1), HCB (0.134 mg kg^-1), methoxychlor (0.116 mg kg^-1) and BDE 28 (0.100 mg kg^-1). At the highest test concentration in soil (1.5%), the tire particles decreased F. candida reproduction by 38% and survival by 24%, and acetylcholinesterase (AChE) activity of P. scaber by 65%, whilst the slight decrease in the reproduction of E. crypticus was not dose-dependent. In food, the highest test concentration of tire particles reduced F. candida survival by 38%. These results suggest that micro-sized tire particles can affect soil invertebrates at concentrations found at roadsides, whilst short-term impacts at concentrations found further from the roadsides are unlikely.