Microplastic contamination of intertidal sediments of Scapa Flow, Orkney: A first assessment

Microplastic contamination in three environmental compartments of a coastal lagoon in the southern Gulf of Mexico

The Sontecomapan lagoon (Mexico) is a Ramsar site within the Los Tuxtlas Biosphere Reserve, facing the Gulf of Mexico. Although the site has a protected area status, it is vulnerable to microplastic contamination, whose long-term effects are uncertain. This study gives the first approach to the degree of contamination by microplastics in surface waters, zooplankton, and sediments in the lagoon. The samples in these three environmental compartments were collected in June 2018 and analyzed in the laboratory to extract and quantify the microplastics. The microplastics sampled were classified into fibers, fragments, and foams and identified as polyester, acrylic, and rayon, among others. In the surface waters, the mean concentration of microplastics was 7.5 ± 5.3 items/L, which is higher than the values registered in other protected coastal systems, perhaps because of differences in the methods used. Zooplankton, represented by copepods, luciferids, and chaetognaths, showed concentrations of 0.002 ± 0.005, 0.011 ± 0.011, and 0.019 ± 0.016 items/individual, respectively. These values were low compared to systems with high anthropic influence, and the differences between the three kinds of organisms were attributed to their feeding habits. In the sediments, the mean concentration was 8.5 ± 12.5 items/kg, lower than the values registered in sites of high human impact; the maximum value here found (43 items/kg) was recorded in the internal part of a lagoon arm of almost stagnant water. In general, the degree of contamination by microplastics in the lagoon was low; however, their presence indicates a potential risk to the biota.

Features of the highway road network that generate or retain tyre wear particles

The environmental accumulation of microplastics poses a formidable global challenge, with tyre wear particles (TWPs) emerging as major and potentially harmful contributors to this particulate pollution. A critical pathway for TWPs to aquatic environments is via road drainage. While drainage assets are employed worldwide, their effectiveness in retaining microplastics of highly variable densities (TWP ~ 1-2.5 g cm3) remains unknown. This study examines their ability to impede the transfer of TWPs from the UK Strategic Road Network (SRN) to aquatic ecosystems. Samples were collected from the influent, effluent and sediments of three retention ponds and three wetlands. The rate of TWP generation is known to vary in response to vehicle speed and direction. To ascertain the significance of this variability, we further compared the mass of TWPs in drainage from curved and straight sections of the SRN across eight drainage outfalls. Pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) was used to quantify tyre wear using benzothiazole as a molecular marker for TWPs (with an internal standard benzothiazole-D4). Tyre wear was present in drainage from the SRN at concentrations of 2.86 ± 6 mg/L and was found within every sample analysed. Drainage from curved sections of the SRN contained on average a 40% greater TWP mass than straight sections but this was not significant. The presence of wetlands and retention ponds generally led to a reduction in TWP mass (74.9% ± 8.2). This effect was significant for retention ponds but not for wetlands; most probably due to variability among sites and sampling occasions. Similar drainage assets are used on a global scale; hence our results are of broad relevance to the management of TWP pollution.

Meso- and microplastic composition, distribution patterns and drivers: A snapshot of plastic pollution on Brazilian beaches

Pollution by plastics is a worldwide problem on par with climatic change and biological invasions. In coastal sediments, plastic particles tend to accumulate and persist over the long term. We assessed the plastic pollution using a standardized surface sediment sampling protocol on 22 sandy beaches along >4600 km of the Brazilian coast. The abundance, size, color, type, and polymeric composition of all meso- and microplastic items found in the surveys were processed to disclose spatial patterns of distribution and pollution associated drivers. A General Linear Model (GLM) was run to investigate how the predictor variables influenced overall beach plastic amounts and by plastic type and size class. Overall, 3114 plastic items were found, with microplastics comprising just over half of all items (54 %). Most items were either white (60 %) or blue (13 %), while polystyrene foam (45 %) and fragments (39 %) comprised the most abundant plastic types. The principal polymers were Polyethylene (40 %) and Polypropylene (32 %). The analyses indicated that the distribution of plastic litter along beaches is determined by three predictive variables: the distance to the nearest estuary (-), tourism (+), and the number of inhabitants in the nearest urban center (+). Tourist (highly-visited) beaches and those near estuarine runoffs or urban centers presented the highest plastic pollution rates. The unveiling of plastic pollution patterns through a large-scale systematic survey is essential for future management guidance and science-based decisions for mitigating and solving the plastic pollution crisis.

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

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

Assessing the embodied carbon and energy required for manufacturing sustainable concrete blocks using plastic pollution as a fiber

This study explores the utilization of polyethylene bags and PET bottles as a fiber in the production of lightweight non-autoclaved plastic fiber-reinforced aerated concrete (NAPFRAC), which has the potential to replace conventional bricks. The study begins by examining global plastic pollutant production and their characterization and the need for a forecast of plastic pollution worldwide. Optimization using Design-Expert 9.0 is used to estimate the optimum mix of NAPFRAC. The mechanical properties of the optimum mix are determined, and a scaled-down model of wall panels is cast to study their behavior and vertical and horizontal ultimate load-carrying capacity. The results are compared to those of conventional first-class burnt clay bricks, and it is found that NAPFRAC wall panels show a 28% increase in vertical load-carrying capacity and 40% in horizontal load-carrying capacity. An analytical study of a high-rise building with NAPFRAC as infill panels is carried out to check the reduction of steel reinforcement in structural sections. Microstructural analysis using SEM (scanning electron microscopy) and XRD (X-ray diffraction) is conducted to identify the morphology and mineralogical composition of the NAPFRAC. Energy studies are also carried out on the mix ratio to identify the embodied carbon dioxide and energy required. Overall, this study highlights the potential of NAPFRAC as a lightweight alternative to conventional bricks. The use of plastic waste as a fiber in concrete production could have a positive impact on the environment by reducing plastic pollution. The results of this study could also have practical applications in the construction industry, especially in the design of high-rise buildings.

Occurrence and spatial distribution of microplastics in the intertidal sediments along the Oman Sea

Microplastics (MPs) have been found in marine systems more frequently. We aim to analyze the MPs abundances, distribution, and characteristics in the intertidal sediments along the Oman Sea. Samples were collected from 7 locations with three replicates. Density separation was used to extract MPs, which were then visually counted and categorized based on their size, shape, and color. MPs abundance ranged between 219.6 ± 38.3 particles.kg-1dw and 617.3 ± 99.9 particles.kg-1dw with a mean abundance of 315.4 ± 24.4 particles.kg-1 dw. Fragments and fibers were the dominant shapes. Red and blue colors were observed in 61.6 % of the collected MPs. In addition, 100-500 μm size range of MPs were more abundant. Micro-Raman spectroscopy analysis revealed polypropylene was the major polymer constituent. The present study revealed the widespread occurrence of MPs as anthropogenic pollutants throughout the Oman Sea and highlighted the urgent need for regulations and policies to reduce the entry of this material into marine environments.

Distribution, compositional characteristics, and historical pollution records of microplastics in tidal flats of South Korea

Studies on distribution of microplastics (MPs) in sediments of tidal flats are relatively scarce compared to other coastal areas. In this study, spatial and vertical distributions and compositions of MPs in tidal flat sediments along the west coast of Korea were investigated. The abundance of MPs in surface and core sediments ranged from 20 to 325 and 14 to 483 particles per 50 g dry weight, respectively. Polypropylene (51%) and polyethylene (36%) were the most dominant MPs; the size was <0.3 mm, and the shape was mostly fragments followed by fibers. The abundance of MPs in sediments has increased rapidly since the 1970s, and recently showed a slight decrease. Surface morphology of MPs analyzed using a scanning electron microscope revealed that the MPs in tidal flats were highly weathered mechanically and/or oxidatively. The results of this study provide valid baseline data on distributions of MPs in tidal flats.

Microplastic accumulation in Halophila ovalis beds in the Swan-Canning Estuary, Western Australia

Small ephemeral seagrass (Halophila ovalis) beds in the Swan-Canning Estuary, Western Australia, were sampled to determine if microplastics attach to seagrass blades and accumulate in higher concentrations in seagrass sediment compared to bare sediment. Three microplastics were observed attached to sampled seagrass blades (n = 108). Microplastics had a mean concentration in seagrass sediments of 1000 ± 100.37se particles kg^-1 and in bare sediment of 972 ± 92.19se particles kg^-1. ATR FTIR further verified 64.2 % of subsample particles as plastic (n = 28). This is the first known study to identify microplastics within the leaf canopy of H. ovalis however we could not support our hypothesis that this seagrass species acts as a sink for microplastic particles in sediments, as seen in studies on other seagrass species. The ability for seagrass habitats to trap and accumulate microplastics in sediments is likely influenced by species morphology, seagrass canopy density and life history.

Examining the release of synthetic microfibres to the environment via two major pathways: Atmospheric deposition and treated wastewater effluent

Research on the discharge of synthetic microfibres to aquatic environments has typically focused on laundering, where fibres can be discharged via wastewater effluent. However emerging research suggests that microfibres generated during the wear of textiles in normal use could present a major, additional, pathway for microfibre pollution to the environment. This study aimed to quantify and compare the quantities of microfibre entering the marine environment via both these pathways; wastewater discharge and atmospheric deposition. Areas of high and low population density were also evaluated. Samples were collected in and around two British cities (Bristol and Plymouth) both of which are located on tidal waters. Fibres originating from the atmosphere were deposited at an average rate of 81.6 fibres m² d^-1 across urban and rural areas. Treated wastewater effluent contained on an average 0.03 synthetic fibres L^-1. Based on our results we predict ~20,000-500,000 microfibres could be discharged per day from the Wastewater Treatment Plants studied. When the two pathways were compared. Atmospheric deposition of synthetic microfibres appeared the dominant pathway, releasing fibres at a rate several orders of magnitude greater than via treated wastewater effluent. Potential options to reduce the release of microfibres to the environment are discussed and we conclude that intervention at the textile design stage presents the most effective approach. In order to guide policy intervention to inform the Plastics Treaty UNEA 5.2, future work should focus on understanding which permutations of textile design have the greatest influence fibre shedding, during both everyday use and laundering.

Does microplastic exposure and sex influence shell selection and motivation in the common European hermit crab, Pagurus bernhardus?

Microplastics (<5 mm) are a threat to marine biodiversity however their effects on animal cognition and behaviour are unclear. We investigated whether microplastic exposure affects shell selection behaviour and motivation in the common European hermit crab, Pagurus bernhardus. Subjects were maintained for 5 days in tanks containing either: polyethylene microplastic spheres (n = 40), or no plastic (n = 40). They were then placed in low-quality shells and presented with an alternative high-quality shell. When they first touched the high-quality shell, the hermit crabs were startled using visual and aural stimuli. We recorded the post-startle latency to re-contact the high-quality shell, quantifying motivation to explore and acquire a better shell. Plastic-exposed females were more likely to select the high-quality shell than control females. As hypothesised, female hermit crabs had longer initial contact latencies, startle durations, and shell entry latencies than males. We also found an interaction effect on shell investigation duration: females from the control treatment spent longer investigating the high-quality shell compared to males. This was absent in the microplastic treatment with females behaving similar to males. This controlled study serves as a starting point to investigate the effects of microplastics and sex differences on behaviour when under predatory threat, and demonstrated sex dependent sensitivity to an environmental pollutant of global concern.

The spatiotemporal dynamics, distribution, and characteristics of beached plastics along the remote south coast of Western Australia

Understanding the accumulation mechanism for beached plastics is important for marine debris research. Similar to the global accumulation pattern for beached plastics, we find that along the remote south coast of Western Australia (SCWA) white, hard, microplastics dominate the microplastic pollution accumulating on beaches. We estimate that along the SCWA, plastics are present at a density of 2.01 items·m^-2, but also find that the density of plastic pollution is higher at the eastern end of bays. Significantly fewer plastics were found after easterly winds (austral summer-prevailing winds), and regional physical ocean process, including the Leeuwin Current, and the Ekman transport effect may be relevant to the rate of plastic accumulation on SCWA beaches.

Quantitative assessment of microplastic in sandy beaches of Gujarat state, India

The present study was carried out to quantify microplastic prevalence among 20 sandy beaches on the Gujarat coast. Beaches were categorised into three different classes, viz. low-impacted sites, moderately impacted sites, and highly impacted sites based on anthropogenic pressure. Microplastic (MP) (≤ 5 mm) contamination on the beaches varied with an average of 1.4 MPs/kg to 26 MPs/kg sediment. Sutrapada site-1 and Porbandar showed the highest and lowest mean abundance of microplastics, respectively, among 20 selected beaches. Out of the total assessed microplastics, threads were the maximum (89.98%), followed by the films (4.75%), fragments (3.36%) and foam (1.89%). In terms of colour and size, different microplastics were recorded in this study. The chemical composition of microplastics was identified by ATR-FTIR as polypropylene (47.5%), polyethylene (26%), and polystyrene (25%). Tourism and fishing activities are the possible sources of higher microplastic contamination at highly impacted sites.

First long-term evidence of microplastic pollution in the deep subtropical Northeast Atlantic

No anthropogenic pollutant is more widespread in the aquatic and terrestrial environment than microplastic; however, there are large knowledge gaps regarding its origin, fate, or temporal variations in the oceans. In this study, we analyzed sediment trap material from the deep subtropical Northeast Atlantic (2000 m) in a long-term record (2003-2015) to assess the role of the deep ocean as a potential sink of microplastics. Microplastic particles were identified in all 110 analyzed samples with flux rates of 1.13-3146.81 items d^-1 m^-2. Calculated microplastic mass fluxes ranged between 0.10 and 1977.96 μg d^-1 m^-2, representing up to 8% of the particle flux. Between years, the composition of the different polymers changed significantly, dominated by polyethylene, whose amount was correlated with the lithogenic input. The correlation between polyethylene and the lithogenic fraction was attributed to an air transport pathway from northeast Africa and surrounding regions. The second most abundant polymer detected in our study was polyvinyl chloride, which is not correlated with lithogenic or biogenic particle flux fractions. Instead, we observed seasonality for polyvinyl chloride with recurring high fluxes in winter before the plankton bloom and significantly lower amounts in summer. Other polymers identified were polypropylene, polyethylene terephthalate, and lower numbers of polystyrene and polymethyl methacrylate. The average microplastic particle size for all samples and polymers was 88.44 ± 113.46 μm, with polyethylene and polyvinyl chloride having the highest proportion of small particles (<100 μm). Our findings provide first insights into temporal variations of sinking microplastics, which are crucial for understanding the fate of plastic in the oceans.

A screening-level human health risk assessment for microplastics and organic contaminants in near-shore marine environments in American Samoa

Solid waste disposal is a growing concern among Pacific Island nations. With severe limitations in land area, in combination with the lack of reuse or recycling options, many near-shore marine ecosystems across Oceania are highly impacted by locally derived marine debris, including plastics, microplastics and associated chemical contaminants. In order to catalyze improved solid waste management and plastic use policies, the potential ecological and public health risks must be clearly identified and communicated. Using an ecological risk assessment framework, potential risks to marine ecosystems and human health are explored by quantifying microplastics and organic contaminants in 4 study sites located in Tutuila, American Samoa. Results of sampled near-shore marine waters, marine sediments and molluscs indicate that microplastics are unevenly distributed in the marine environment, with the highest concentrations detected in marine molluscs (e.g. average of 15 and 17 particles per organism, the majority of which were microfibers identified as polyethylene terephthalate). These invertebrates also have the highest environmental concentrations of organic contaminants, including phthalates, pesticides and PCBs. However, based on estimated rates of invertebrate consumption, the risk of adverse impacts to human health are likely to be low. Regardless, future studies are recommended to better understand the environmental partitioning of microplastics in dynamic near-shore marine environments, as well as the specific pathways and consequences of the physical and chemical impacts of microplastics on marine species populations and overall marine ecosystem health.

Microplastic pollution in show cave sediments: First evidence and detection technique

Microplastic particles are a global problem, which has been widely found in marine and terrestrial environments. However, microplastic pollution in caves and karst aquifers is still poorly studied. To improve the current knowledge of microplastic pollution, we investigated the sediments of a show cave in Italy. We developed a methodology based on a cave-adapted version of the methods used in several studies to detect microplastics from sediments of different environments and with various laboratory tests. The microplastics were extracted from sediments via density separation and subjected to organic matter removal. Filters were observed with and without UV light under a microscope, before and after organic matter removal, and the microplastics were characterised according to shape, colour, and size, with visual identification. About 55% of the fibres observed under the microscope on filters were removed via organic matter removal. An average of 4390 items/kg dry weight was calculated for the touristic zone and 1600 items/kg dry weight for the speleological/research section. Fibre (84.9%) was the most abundant shape, and most microplastics were smaller than 1 mm, accounting for 85.4%, of which 58.4% were shorter than 0.5 mm. The highest microplastic abundance was fluorescent under UV light (87.7%); however, 12.3% of the microplastics observed on filters were not fluorescent. Most fluorescent fibres were transparent (84%), whereas blue (46.1%) and black (22.4%) fibres were more common for the non-fluorescent ones. Our results highlight the presence of microplastics in show caves, and we provide a valid non-invasive and non-expensive analytical technique for the preparation and isolation of microplastics from cave sediments, giving useful information for evaluating the environmental risks posed by microplastics in show caves.

Microplastic contamination and characteristics spatially vary in the southern Black Sea beach sediment and sea surface water

In this study, the abundance, and characteristics of the microplastics on the southern coast of the Black Sea were assessed. More than 70% of the detected microplastics were smaller than 2.5 mm and mostly consisted of fibers and fragments. The average microplastic abundance in the beach sediment and seawater were 64.06 ± 8.95 particles/kg and 18.68 ± 3.01 particles/m³, respectively. The western coast of the study area (Marmara region) was the most polluted area, and a spatially significant difference was determined in terms of abundance. The composition in the beach sediment (particles/kg) was dominated by styrene acrylonitrile copolymer (SAC) (40.53%), polyethylene terephthalate (PET) (38.75%), and polyethylene (PE) (6.91%), whereas the seawater (particles/m³) was dominated by PET (57.26%), PE (13.52%), and polypropylene PP (11.24%). The results of our study can be a baseline for environmental modeling studies and experimental studies on the marine organisms inhabiting the Black Sea.

Microplastic load and polymer type composition in European rocky intertidal snails: Consistency across locations, wave exposure and years

Microplastics (<5 mm) are emerging pollutants in oceans worldwide. As such small particles are easily ingested, microplastics are found in numerous pelagic and benthic organisms. However, information on microplastics in rocky intertidal organisms and habitats is relatively scant. Therefore, we examined snails and water samples from wave-sheltered and wave-exposed rocky intertidal habitats in Helgoland (North Sea), Cap Ferrat and Giglio (Mediterranean) and Madeira (Atlantic Ocean) in 2019-2020 for microplastics. Furthermore, we examined snails from the same habitats in Helgoland, Cap Ferrat and Giglio in 2007-2009. In total, we performed 362 individual micro-Fourier-transform infrared spectroscopy (μFTIR) measurements on the snails and water samples. While the snails contained 50 microplastics (composed of nine polymer types), the water samples contained 24 microplastics (comprising six polymer types). Microplastic load and polymer type composition in the snails were rather similar across locations, wave exposure and years. Also, microplastic load and polymer composition in the water samples were similar across locations and wave exposure. Moreover, snail and water microplastic loads were significantly correlated which indicates that snails are useful bioindicators for microplastic loads in rocky intertidal habitats. Interestingly, the majority of the microplastics consisted of paint chips that likely derived from ships. Overall, our study provides the first comprehensive microplastic record in rocky intertidal organisms across locations, wave exposure and years that can serve as a baseline to examine historic and future microplastic dynamics in rocky intertidal systems.

The abundance of microplastics in cnidaria and ctenophora in the North Sea

Microplastic (MP) ingestion has been widely recorded in aquatic organisms, but few studies focus on cnidarians and ctenophores, which form a significant contribution to marine trophic interactions. Scyphozoans (Cyanea capillata, C. lamarckii and Aurelia aurita), hydrozoan (Cosmetira pilosella) and ctenophores (Beroe cucumis and Pleurobrachia bachei) collected opportunistically from Orkney, Shetland and the North Sea were thermally disintegrated, with a subsample of ingested plastics analysed using FTIR. A total of 1,986 MPs were counted (94% fibres), the majority (84.4%) in the four cnidarian species. Highest MP concentrations were recorded in B. cucumis (0.956 ml^-1), whilst C. pilosella yielded the lowest (0.014 ml^-1). The main polymers in digestate were PET and PP, with 27% discounted as non-plastics. In feeding trials, A. aurita ingested a greater quantity of PET fibres (60-80%), compared to nylon (0%) and HDPE fibres (0%). This study demonstrates cnidarians and ctenophores, a largely overlooked group, are a potential route for MPs entry into food webs.

A proposed nomenclature for microplastic contaminants

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

Temporal patterns in the abundance, type and composition of microplastics on the coast of the Río de la Plata estuary

The objective was to establish possible temporal patterns in the microplastics (MPs) abundance in the water and in the intertidal sediment in an urbanized location of the Río de la Plata estuary (Argentina), in relation to environmental factors. The site was sampled monthly for a year (February 2019-January 2020). The presence of MPs was recorded, being more abundant in February in the water (110 MPs m^-3) and in April in the sediment (613 MPs m^-2). The types of MPs found were fibers, fragments, pellets, film and foam; while the polymers identified were polyethylene (PE) and polypropylene (PP). Regarding the environmental variables, the predominance of wind from the NE direction was related to a greater accumulation of MPs in the sediment, while wind from the NO direction was associated with a lower abundance of MPs in the water. Also, MPs abundance was negatively related to the larger sizes of sediment particles.

Seasonal microplastic variations in estuarine sediments from urban canal on the west coast of Thailand: A case study in Phuket province

To improve knowledge of the relationships of human activities with microplastic pollution in the urban estuary in Phuket province, which has a densely populated city on the western coast of Thailand, a total of 463 plastic-like items from 24 sediment samples in the dry and the rainy seasons were identified by micro-Fourier transform infrared spectroscopy. The microplastic abundance ranged in 300-900 and 33-400 items/kg dry weight in the dry and the rainy seasons, respectively, indicating that the estuary is moderately contaminated with microplastics. The most abundant polymer types were rayon and polyester with colored fibers, suggesting that the microplastics deposited in this area originate mainly from washing effluents. Additionally, our findings show that the microplastic distribution is significantly governed by hydrodynamic energy in the estuary. This provides basic information for a better understanding of the fate of microplastics within estuary, and for management actions to address microplastics in urban estuary.

The occurrence of microplastics in farmland and grassland soils in the Qinghai-Tibet plateau: Different land use and mulching time in facility agriculture

Microplastic (MP) pollution in the environment has aroused great concern. However, our knowledge of MP abundance and distribution in soil environment is scarce. This work investigated the MPs in the farmland and grassland at a remote area of China, namely, the eastern area of the Qinghai-Tibet Plateau (QTP). The average numbers of MPs were 53.2 ± 29.7 and 43.9 ± 22.3 items/kg in shallow and deep soil, respectively, from 35 soil samples. A remarkable difference in MP abundances was observed among soil samples from mulch farmland, greenhouses, farmland without covering, and grassland. The MPs were mostly in the form of a film and transparent in color in this study. The dominant polymers of MPs in the soil samples were polyester (PE) and polypropylene (PP). This study revealed the characteristics of MP distribution among different land use at the QTP, and MPs may stem from the fragmentation of plastic mulch in farmland soil. Notably, MP abundance increased with the increase in mulching time in facility agriculture. Additionally, human disturbances and increased mulching time in facility agriculture promote the fragmentation of soil MPs. This study provides important data for follow-up research on MPs in a plateau terrestrial ecosystem.

Anthropogenic particles in sediment from an Arctic fjord

The research on plastic pollution is increasing worldwide but little is known about the contamination levels in the Arctic by microplastics and other anthropogenic particles (APs) such as dyed fibres. In this study, two different sampling designs were developed to collect 68 sediment subsamples in five locations in a remote Arctic fjord, Kongsfjorden, northwest of Svalbard. Those five stations composed a transect from a sewage outlet recently installed close to the northernmost settlement, Ny-Ålesund, to an offshore site. Plastics and other APs were extracted by density separation and analysed by both Raman and Fourier Transform Infrared spectroscopy. Among the 37 APs found, 19 were microplastics. The others were classified as APs due to the presence of a dye or another additive. On average, 0.33 AP 100 g^-1 were found in the surface sediment and their sizes ranged between 0.10 and 6.31 mm. The site most polluted by APs was located at the mouth of the fjord while the less polluted ones were the offshore and the outlet sites. We believe that currents in the fjord have carried APs towards the mouth of the fjord where an eddy could retain APs which might sink the seafloor due to various reasons (ingestion & packaging, fouling-induced changes in buoyancy). In the cores, several different APs were found down to a depth of 12 cm. These APs may have been present in the sediments for decades or been transported deeper by biota. Here we provided data on plastic but also on other anthropogenic particles from a remote fjord in Svalbard.

Prevalence of microplastics in the sediments of Odisha beaches, southeastern coast of India

The prevalence of microplastics along the coastal habitats has become a global concern owing to the increased input of plastic debris from multiple sources. The present study is the first of its kind to examine the prevalence and distribution of microplastics in Odisha coast. The average microplastic abundance in the nine stations along Odisha coastal beach is 258.7 ± 90.0 particles/kg of beach sediment. Among the stations sampled, Swargadwara was reported with the highest microplastic abundance of 378.3 ± 39.7 particles/kg of beach sediment andAbhayachandpurwas found with the lowest number of 153.3 ± 27.3 particles/kg. Different types of microplastics varying in color, size, and shape were encountered in the study. From the Raman spectroscopic analysis, twelve types of polymers including High Density Polyethylene, Polystyrene, Polyvinyl chloride, and acrylonitrile copolymer were identified.

Exposure of coastal environments to river-sourced plastic pollution

Marine litter is a global problem which poses an increasing threat to ecosystem services, human health, safety and sustainable livelihoods. In order to better plan plastic pollution monitoring and clean-up activities, and to develop policies and programmes to deter and mitigate plastic pollution, information is urgently needed on the different types of coastal ecosystem that are impacted by land-sourced plastic inputs, especially those located in proximity to river mouths where plastic waste is discharged into the ocean. We overlayed the most current existing information on the input of plastic to the sea from land-based sources with maps of coastal environments and ecosystems. We found an inverse relationship exists between coastal geomorphic type, plastic trapping efficiency and the mass of plastic received. River-dominated coasts comprise only 0.87% of the global coast and yet they receive 52% of plastic pollution delivered by fluvial systems. Tide-dominated coasts receive 29.9% of river-borne plastic pollution and this is also where mangrove and salt marsh habitats are most common. Wave-dominated coasts receive 11.6% of river-borne plastic pollution and this is where seagrass habitat is most common. Finally, rocky shores comprise 72.5% of the global coast, containing fjords and coral reefs, while only receiving 6.4% of river-borne plastic pollution. Mangroves are the most proximal to river-borne plastic pollution point sources of the four habitat types studied here; 54.0% of mangrove habitat is within 20 km of a river that discharges more than 1 t/yr of plastic pollution into the ocean. For seagrass, salt marsh and coral reefs the figures are 24.1%, 22.7% and 16.5%, respectively. The findings allow us to better understand the environmental fate of plastic pollution, to advance numerical models and to guide managers and decision-makers on the most appropriate responses and actions needed to monitor and reduce plastic pollution.

Microplastic footprints in the Qinghai-Tibet Plateau and their implications to the Yangtze River Basin

Microplastics (MPs) are pervasive in the environment and have posed growing threat to ecosystems and human health. This study investigated MP abundances in surface water (fresh and salt lakes, urban and rural rivers, etc.) from 28 stations in the Qinghai-Tibet Plateau. MPs were detected in 25 out of 28 water samples with relatively low abundance (average 584.82 particles m^-3). Fibers were the most frequently observed shape, particle sizes mostly ranged from 100 to 500 µm, and the greatest number of MPs was polypropylene. Source analysis identified the major sources of domestic wastewater and tourism in some areas. The concentration and proportion of small MPs (20-100 µm) in salty water were apparently greater than that in fresh water, indicating Salt intrusion accelerated MPs fragmentation. As the study area is the origin of the Yangtze River, we further compared the MP distribution throughout the watershed. Nearly two orders of magnitude in MP concentrations were increased associated with urban agglomeration in the middle and downstream areas, but the highest level was marked around the Yichang City (location of the Three Gorges Reservoir) due to interception associated with sedimentation and precipitation. This study provides data and theoretical bases for analyzing MPs migration and degradation processes in high altitudes.

Characteristics of microplastics in shoreline sediments from a tropical and urbanized beach (Da Nang, Vietnam)

Microplastics in shoreline sediments were investigated from Da Nang beach for the first time. Sediment samples at the two depth strata (0-5 cm and 5-10 cm) at eight sites along the entire coast were collected for identifying the characteristics of microplastics, including their concentration, size, shape, color, and nature. The synthetic fiber was the predominant type of microplastics, accounting for 99.2% of the total items. Blue (59.9%) and white (22.9%) were the most common colors of the fibers. Synthetic fibers showed a homogenous distribution at all sampling sites with a mean concentration of 9238 ± 2097 items kg^-1 d.w. Meanwhile, the fibers tended to concentrate much more at the surface stratum than the deeper stratum. A large number of synthetic fibers (81.9%) were in the size range of 300-2600 μm, which might pose a threat to marine biota and human health.

High Abundances of Microplastic Pollution in Deep-Sea Sediments: Evidence from Antarctica and the Southern Ocean

Plastic pollution in Antarctica and the Southern Ocean has been recorded in scientific literature since the 1980s; however, the presence of microplastic particles (<5 mm) is less understood. Here, we aimed to determine whether microplastic accumulation would vary among Antarctic and Southern Ocean regions through studying 30 deep-sea sediment cores. Additionally, we aimed to highlight whether microplastic accumulation was related to sample depth or the sediment characteristics within each core. Sediment cores were digested and separated using a high-density sodium polytungstate solution (SPT) and microplastic particles were identified using micro-Fourier-transform infrared spectroscopy (μFTIR). Microplastic pollution was found in 93% of the sediment cores (28/30). The mean (±SE) microplastics per gram of sediment was 1.30 ± 0.51, 1.09 ± 0.22, and 1.04 ± 0.39 MP/g, for the Antarctic Peninsula, South Sandwich Islands, and South Georgia, respectively. Microplastic fragment accumulation correlated significantly with the percentage of clay within cores, suggesting that microplastics have similar dispersion behavior to low density sediments. Although no difference in microplastic abundance was found among regions, the values were much higher in comparison to less remote ecosystems, suggesting that the Antarctic and Southern Ocean deep-sea accumulates higher numbers of microplastic pollution than previously expected.

The fate of microplastic in marine sedimentary environments: A review and synthesis

A review of 80 papers on microplastic (MP) particles in marine sediments was conducted for different sedimentary environments. The papers were assessed for data on average MP concentration, MP morphotype (fibres, fragments, films, etc.), MP particle size distribution, sediment accumulation rates and correlations with total organic carbon (TOC) and sediment grain size. The median concentration of MP particles is highest in fjords at 7000 particles kg^-1 dry sediment (DS) followed by 300 in estuarine environments, 200 in beaches, 200 in shallow coastal environments, 50 on continental shelves and 80 particles kg^-1 DS for deep sea environments. Fibres are the dominant MP type and account for 90% of MP on beaches (median value) and 49% of particles in tide-dominated estuaries. In order to advance our understanding of the fate of MP in the ocean, quantitative assessments are needed of MP flux rates (g m^-2 year^-1) in a range of sedimentary environments.

Characterization of microplastic pollution in tadpoles living in small water-bodies from Rize, the northeast of Turkey

Microplastic pollution is a growing problem for Turkey and other countries, but most studies focus on the pollution in oceans and seas. To understand the relationship between microplastics, fresh water, and terrestrial environment, we examined Pelophylax ridibundus and Rana macrocnemis tadpoles that can inhabit a wide range of both terrestrial and aquatic habitats, ecoregions and elevations, and that are members of Ranidae family. We characterized microplastics (MPs) in sediments, surface water, and tadpoles from the Rize province in northeastern of Turkey. The content of MPs in sediments, surface water, and tadpoles, ranged 64.17-472.1 items/kg, 1-13 items/L and 302.62-306.69 items/g, respectively. In sediment samples, polypropylene (PP) and polyethylene (PE) were the dominant pollutants; whereas, nylon and polyethylene terephthalate (PET) were found in surface water. In tadpoles, PET, nylon, and polyacrylic were the dominant MPs.

The role of wet wipes and sanitary towels as a source of white microplastic fibres in the marine environment

Understanding source elements of the ocean plastic crisis is key to effective pollution reduction management and policy. The ubiquity of microplastic (MP) fibres in the oceans is considered to derive primarily from clothing fibres released in grey water. Microplastic fibres degraded from widely flushed personal care textile products (wet wipes and sanitary towels) have not been clearly identified in aquatic systems to date. Unregulated personal hygiene and sanitary product labelling fails to identify textile materials. This study demonstrated that white MP fibres in sediments adjacent to a wastewater treatment plant (WWTP) are comparable with white fibres from sewage-related waste and commercially available consumer sanitary products. Commercially available non-flushable wipes are manufactured from either polyethylene terephthalate (PET), polypropylene (PP), or a combination of PET and cellulose. Fifty percent of brands labelled flushable that were tested were comprised of a mixture of PET and cellulose and the remainder of cellulose alone. Sanitary towels are made from PP, PE, or a combination of high-density polyethylene (HDPE) and PP. The accumulation of large quantities of washed-up sewage-related macro-debris (including wet wipes and sanitary towels) intermingled with seaweed biomass adjacent to the WWTP was associated with a combined sewer overflow. Microplastic fibres extracted from this waste were similar to those extracted from intertidal sediments in close proximity to the WWTP over a ten-month period. In comparison, fibres extracted from locations spatially removed from the WWTP were primarily comprised of ABS, PP and polystyrene. The results confirm that wet wipes and sanitary towels flushed down toilets are an underestimated source of white MP fibres in the environment. Given the global distribution and projected growth of the non-woven textile industry, there is a need for increased public awareness of MP pollution in the marine environment from the inappropriate disposal of sanitary products down the toilet, instead of diversion to alternative land-based waste management.

How to detect small microplastics (20-100 μm) in freshwater, municipal wastewaters and landfill leachates? A trial from sampling to identification

The quantification of microplastics (MPs), especially small MPs (20-100 μm), in freshwater environment and wastewaters is a great challenge due to the complexity of environmental compartment. In the present study, a novel method based on the optimization of sampling, pretreatment, and detection was developed for small MPs (20-100 μm) in freshwater and wastewaters. A customized plankton sampler was installed to efficiently collect MPs and avoid sampler clogging; a novel dual filter system simplified the pretreatment, achieving full examination for small MPs in the samples. The recoveries of small MPs at environmental abundance, which were specified for the first time, verified the feasibility of the developed method. The method was successfully applied for small MPs detection in river, municipal wastewaters and landfill leachates, demonstrating a large bias in the determination of MPs if small MPs were not involved in quantification. To the authors' knowledge, it is the first study that realized the determination of such small MPs in the high-strength wastewater, i.e. landfill leachates.

Microplastics in sediments from an interconnected river-estuary region

Microplastics are an emerging pollutant of international concern due to its wide distribution through various pathways. Estuary is an important pathway for land microplastics to enter into the oceans by rivers. In this study, we hypothesized that microplastics would sink into estuary sediment during diffusion and transmission from river before entering into the sea, which results in higher accumulation of microplastics in proximity to river-estuary than in the oceans. In order to demonstrate this hypothesis, sediment samples were collected from an estuary and its two main inputting rivers and the microplastics in these samples were analyzed. In the collected sediment samples, 19 types of polymers, including the three most common polymers (polyethylene, polyethylene terephthalate, and poly(propylene:ethylene)), were identified and confirmed by FT-IR. Eight types of polymers were consistently detected in all samples, while 11 types of polymers were occasionally found in some samples. These microplastics exhibited four shapes and their percentages followed the high-to-low order of film, fragment, fiber and pellet. A relatively lower abundance of microplastics was found in river sediments from Shuangtaizi River with an average of 170 ± 96 particles/kg d.w., compared to that from Daliao River with an average of 237 ± 129 particles/kg d.w., but it was higher than that from Liaohe Estuary with an average of 120 ± 46 particles/kg d.w. Furthermore, the highest concentration of microplastics was found at the mouth of rivers, showing high accumulation where the freshwater and saltwater meet. Results from this study, including the abundance, characteristics and spatial distribution of microplastic pollution in sediments from an interconnected river-estuary system, revealed the fate and distribution of microplastics in the river and estuary environment.

Microplastic pollution in intertidal sediments along the coastline of China

Research on microplastic (MP) pollution in the marine environment has received widespread attention in recent years. To assess the degree of MP contamination in the intertidal zone of China, the abundance, shape, particle size and composition of MPs in sediment were investigated in this study. Sediment samples were collected from 13 stations along the coast of China. The density separation method was employed to isolate MPs from sediment and the polymer types of the MPs were determined by Fourier transform infrared microspectroscopy. Our study demonstrated that MP pollution was widespread in the 13 intertidal stations. The average abundance of MPs was 309 ± 81 items/kg dry weight. Fiber accounted for 71.5% of the isolated MPs, and the particles of less than 500 μm accounted for the highest proportion (35.0%). A total of 12 polymers were identified; the main types were rayon (RY), polypropylene (PP), polyethylene terephthalate (PET) and polyethylene (PE). The shape and chemical composition of the MPs from the intertidal sediments of South and North China were different. In South China, MP fragments were more extensive, and PP was a more important component. In contrast, the intertidal sediments of North China contained more MP fibers with the majority being RY, indicating that the major source of MPs in the intertidal zone of North China may be domestic sewage. Additionally, the abundance of MPs in the intertidal sediments of the Pearl River and Jiulong River estuaries was higher than at other sites. A Spearman's correlation analysis showed that there was no correlation between MP abundance and sediment grain size or organic matter content. Our study highlights the ubiquitous distribution of MPs in the sediment along the coast of China and provides valuable information for risk assessment and source control of MP pollution in China's intertidal zone.

Occurrence, distribution and composition of microplastics in the sediments of South Andaman beaches

Herein, we report the prevalence of microplastics in the South Andaman beaches, India. The average microplastic abundance of the eight stations covered along the South Andaman beach was found to be 414.35 ± 87.4 particles per kilogram of beach sediment. Among the stations sampled, Kodiyaghat was found with highest microplastic abundance of 973.3 ± 76.59 particles per kilogram of beach sediment and Burmanullah recorded the lowest number of 161.7 ± 32.51. Microplastic particles of different types, size, color and shape were present in all the eight stations sampled. From the Raman spectral analysis, thirteen different types of polymers were identified. The microplastic pollution may be attributed to improper solid waste management, tourism activities and maritime activities. The present study will help in understanding the prevalence, source and pathway of microplastic particles and their affiliated risk to the fragile marine ecosystem.

Occurrence and characterization of surface sediment microplastics and litter from North African coasts of Mediterranean Sea: Preliminary research and first evidence

The aim of this research work is to investigate the abundance of macroplastics and microplastics from North African coasts of Mediterranean Sea in the Gulf of Annaba (Algeria). The study areas are well known for the high population and high industrial activities that can contribute to the plastic pollution. In this case, microplastics were sampled from the surface sediments at four different stations representing different local activities. The microplastics were extracted by the density separation method from collected samples. Each particle was identified using Fourier transform infrared spectroscopy (ATR-FTIR). Furthermore, beach litters were obtained according to the adopted methodology - guidance on monitoring of marine litter in European seas. The obtained mean concentrations are 182.66 ± 27.32 and 649.33 ± 184.02 kg^-1 sediment (DW), respectively. A detailed spatial and quantitative analysis revealed that their distribution was a function of proximity to populated areas and associated with wastewater effluents, industrial installations, degree of shore exposure and complex tidal flow patterns. Five types of microplastics were identified; the most common were fibers (70%), fragments (21%), pellets (5%), films (2%) and foams (2%). Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) analysis showed that the main polymers detected in the studied microplastics were polyethylene (48%), polypropylene (16%), polyethylene terephthalate (14%), polystyrene (9%), butyl branham (7%), ethylene propylene (3%) and cellulose tri acetate (3%). The obtained results provided a holistic view of the abundance, distribution, and characteristics of microplastics in the Gulf of Annaba. This study confirmed the presence of microplastics in the Gulf of Annaba, albeit further studies remain necessary for better understanding of sources and fate.

Microplastic accumulation in a Zostera marina L. bed at Deerness Sound, Orkney, Scotland

Seagrasses have global distribution and are highly productive and economically valuable habitats. They are sensitive and vulnerable to a range of human-induced pressures, including ongoing exposure to marine litter, such as microplastic particles (<5 mm). In this study, a Zostera marina bed in Deerness Sound, Orkney was selected to determine whether microplastics accumulate in seagrass beds and adhere to seagrass blades. Sediment, seagrass blade, biota and seawater samples were collected. 280 microplastic particles (0.04 to 3.95 mm (mean = 0.95 mm ± 0.05 SE)) were observed in 94% of samples collected (n = 111). These were visually categorised into type (fibre, flake, fragment) and colour, and 50 were successfully identified as plastic using ATR-FTIR. Fibres contributed >50% of the total microplastics observed across all samples. This is the first known study on Z. marina to describe microplastic loading within a seagrass bed and to identify microplastic adherence to seagrass blades.

Microplastic contamination in Auckland (New Zealand) beach sediments

We report the first large-scale investigation of microplastic contamination in beach sediments across Auckland, New Zealand's most populous region. Sediment samples were taken from the high tide and intertidal zones at 39 sites across estuary, harbour and ocean environments of the East and West Coasts. Microplastic contamination was present at the majority of beaches studied with a mean abundance of 459 particles.m^-2 ranging from 0 to 2615 particles.m^-2. High variability was observed between the sites, indicating the importance of small-scale factors on microplastic contamination. Samples from high and intertidal zones showed no significant difference in microplastic contamination (p = 0.225). The West Coast beaches exhibited higher microplastic contamination compared with East Coast beaches (p = 0.004). Microplastics were predominately fibres (88%), with lower proportions of fragments (8%) and films (4%). The majority of the microplastics analysed were regenerated cellulose (34%), polyethylene terephthalate (22%) and polyethylene (15%).

Characterisation of microplastic contamination in sediment of England's inshore waters

Plastic litter is an increasingly significant problem in the marine environment. Our study looks at a cost-effective method to quantify larger fractions of microplastics in marine sediments as an opportunistic addition to standard benthic infauna sampling. A subsample of microplastics (>1 mm) were enumerated and categorised from sediment samples collected as part of standard benthic habitat monitoring in twenty-two Marine Protected Areas across English inshore waters. Microplastic particles were found in 61.2% of the samples collected, with mean density per study site ranging from 0.2 in Dover to Deal MCZ to 42.7 in The Mersey Estuary Special Protection Area microplastic particles per 0.1 m². High densities of plastic were found at remote sites, as well as those closer to urban or industrialised areas. Spatial protection measures such as MPAs are not themselves a suitable tool to tackle marine plastic pollution which should be addressed upstream at source.

Variation in microplastics composition at small spatial and temporal scales in a tidal flat of the Yangtze Estuary, China

Microplastics are small, degrade slowly, and easily persist in the water column because they are close to neutrally buoyant. Understanding the distribution of microplastics is fundamental to evaluating the ecological risks that they cause and to identifying ways to control microplastics pollution. Most of the existing research on the distribution of microplastics in the coastal zone has focused on large spatial and temporal scales. To build on past work, we investigated variation in microplastics in a tidal flat of the Yangtze Estuary on small spatial (sediment depth, mudflat vs. vegetation zone) and temporal (fortnightly and semidiurnal) scales. Microplastics were more abundant in surface (0-2 cm) sediments during neap versus spring tide cycles, likely indicating increased deposition during periods with calm waters and increased suspension when water was more turbulent, but did not vary at greater depths in the sediment. Individual microplastics particles were also larger during neap versus spring tide periods. In contrast to the variation between spring and neap tide periods, we found no variation in the abundance of microplastics on the semidiurnal scale. Microplastics were also more abundant in the transect in the vegetation than at slightly lower elevations in the adjacent mudflat. Across all samples, the abundance of microplastics was negatively correlated with the strength of hydrological processes such as submergence time and flow velocity. Our results showed that sampling of microplastics in the intertidal environment needs to consider variation among spring and neap tide cycles, and also among different intertidal habitats that may differ only slightly in elevation. We encourage coupling sampling with direct measures of hydrological processes so that variation in microplastics abundance and size can be rigorously linked to hydrological processes.

Interrelationship of microplastic pollution in sediments and oysters in a seaport environment of the eastern coast of Australia

Since the middle of the twentieth century, microplastics have emerged as a pollutant of concern. Sea ports are recipients of large amount of discharges through ballast water, ship traffic and other commercial activities, which may additionally add to the overall marine microplastic pollution. The aim of this study was to determine the interrelationship of microplastic pollution in the sediments and oysters at six major seaports (Port Jackson, Botany, Kembla, Newcastle, Yamba and Eden) of New South Wales (NSW). The results revealed the significant abundance of microplastic particles both in sediments and oysters in all the studied seaports which were estimated to be around 83-350 particles/kg dry weight in the sediments and 0.15-0.83 particles/g wet weight in the oysters. Although, the abundance of microplastics showed similar pattern in the sediments and oysters of the studied seaports, oysters had higher number of microplastics than sediments in all sea ports. Moreover, the results showed that the shapes, size and colours in the oysters did not necessarily match the main components in the sediments, although the polymer types matched well between each other. Black fibres between 0.1mm-0.5mm in size were the most abundant microplastics in oysters, whereas white spherules between 0.5mm-1mm in size were dominant in the sediments of NSW seaports. Moreover, the analysis of variance between microplastic abundance in sediment and oysters showed a non-significant positive linear relationship. Fourier Transform Infrared analysis further indicated that both sediments and oysters contained microplastics with two main polymers, polyethylene terephthalate and nylon, which suggests that the abundance of microplastics in the study ports was highly influenced by the port activities, mainly the intensive commercial fishing and fish processing activities along with intensive anthropogenic and industrial activities inside and surroundings the port environments.

Microplastic prevalence in the beaches of Puducherry, India and its correlation with fishing and tourism/recreational activities

The prevalence of microplastics in the sediments of six beaches of the Puducherry coast in India was studied and its correlation to fishing activities and recreational activities was analysed. On an average, 72.03 ± 19.16 microplastic particles/100 g dry weight of sediments is found to be the microplastic abundance in the study. A Strong positive correlation (Pearson's R = 0.92, p = 0.0103) between fishing activity and microplastic abundance and a weak correlation (Pearson's R = 0.04, p = 0.932) between microplastic abundance and recreational activities is found. Majority (65.12%) of the microplastics belongs to the size bracket of 300 μm-1 mm and only 34.88% were large microplastics (>1 mm). The Polymers of the microplastics were identified as Polypropylene, HDPE, LDPE, Polystyrene, Polyurethane etc. using Raman spectroscopy. Microplastic fragments comprise 56.32% of the total particles. In terms of colour of the microplastics, white (26.92%) is the most abundant.

Associations between microplastic pollution and land use in urban wetland sediments

Microplastic pollution is concerning because it is widespread in aquatic environments and there is growing evidence of negative biological effects. Here, we present one of the first studies to examine microplastic pollution (plastic particles < 1 mm) in urban wetlands and investigate relationships between contamination and urban land use. Sediment samples were collected from 20 independent urban wetlands, each with different types of urban land use within their catchments. Microplastics were observed at all wetlands, with an average abundance of around 46 items/kg of dry sediment. Plastic fragments were the most common type of microplastic, accounting for 68.5% of all microplastics found. Consistent with other studies, microplastic abundance was positively correlated with increased catchment urbanisation. On closer examination, plastic fragments and beads correlated with catchment urbanisation. Fragment abundance also increased in wetlands with catchments that had a higher proportion of industrial land use and decreased in catchments with higher residential densities. This study demonstrates the susceptibility of urban wetlands to microplastic pollution, further highlighting the ubiquitous nature of microplastic pollution. The prevalence of microplastic fragments indicates that plastic litter degradation is a significant source of microplastics in urban environments, especially in industrial areas.

Microplastics at the strandlines of Slovenian beaches

Sediment samples were randomly taken in March and August 2017 at the strandlines of nine locations along the coast of Slovenia (Adriatic Sea, Mediterranean). Microparticles were isolated by density separation in saturated aqueous NaCl-solutions and analysed by infrared spectroscopy (ATR-FTIR). 11.3% of these particles were unambiguously confirmed as microplastics. Another 8.2% showed plastic characteristics but failed ATR-FTIR validation. 4.3% were naturally organic. The rest was unidentified material (76.2%). The average microplastic densities were 0.5 ± 0.5 MP kg^-1 in March and 1.0 ± 0.8 MP kg^-1 in August. The microplastics comprised fragments, fibres, films, and foams. The characteristics of the microplastics suggest origin from single-used plastic products and from aquaculture. Compared to other studies and sites, the microplastic pollution of the Slovenian coast appeared low. The validity of the results is discussed with respect to microplastic distribution and patchiness, sampling strategies, methodology, and scientific claims.

Occurrence and distribution of microplastics in the surface water and sediment of two typical estuaries in Bohai Bay, China

Estuaries are considered to be seriously polluted by microplastics. As the most important water body in North China, the pollution level of microplastics in two typical estuaries (Haihe Estuary (HHE) and Yondingxinhe Estuary (YDXE)) of Bohai Bay is not well understood. The occurrence and distribution of microplastics in the surface water and sediment of HHE and YDXE were investigated. The mean concentration of microplastics in surface-water samples was 1485.7 ± 819.9 items per m3 for HHE and 788.0 ± 464.2 items per m3 for YDXE, respectively, whereas the concentration of microplastics in sediment was 216.1 ± 92.1 items per kg dw for HHE and 85.0 ± 40.1 items per kg dw for YDXE, respectively. The concentration of microplastics in surface-water and sediment-samples of HHE was higher than that of YDXE, though YDXE is a typical sewage-received river. Anthropogenic activities and the river input were the main sources of microplastic pollution in estuarine areas. Sewage rivers could be point sources of microplastic pollution on a small scale. The small size (particle diameter < 1 mm) of microplastics was a dominant feature, the most abundant shape was fiber and colored microplastics were found widely in YDXE and HHE. We provided detailed information on microplastic pollution to support their control and management in HHE and YDXE.

Microplastic pollution in the rivers of the Tibet Plateau

The Tibet Plateau, the so-called Third Pole of the world, is home to the headstreams of many great rivers. The levels of microplastic pollution in those rivers, however, are unknown. In this study, surface water and sediment samples were collected from six sampling sites along five different rivers. The surface water and sediment samples were collected with a large flow sampler and a stainless steel shovel, respectively. The abundance of microplastics ranged from 483 to 967 items/m³ in the surface water and from 50 to 195 items/kg in the sediment. A large amount of small, fibrous, transparent microplastics were found in this study. Five types of microplastics with different chemical compositions were identified using micro-Raman spectroscopy: polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyamide (PA). These results demonstrate that rivers in the Tibet Plateau have been contaminated by microplastics, not only in developed areas with intense human activity but also in remote areas, where microplastic pollution requires further attention.

Distribution of plastic polymer types in the marine environment; A meta-analysis

Despite growing plastic discharge into the environment, researchers have struggled to detect expected increases of marine plastic debris in sea surfaces, sparking discussions about "missing plastics" and final sinks, which are hypothesized to be coastal and deep-sea sediments. While it holds true that the highest concentrations of plastic particles are found in these locations (10³-10⁴ particles m^-3 in sediments vs. 0.1-1 particles m^-3 in the water column), our meta-analysis also highlights that in open oceans, microplastic polymer types segregated in the water column according to their density. Lower density polymers, such as polypropylene and polyethylene, dominated sea surface samples (25% and 42%, respectively) but decreased in abundance through the water column (3% and 2% in the deep-sea, respectively), whereas only denser polymers (i.e. polyesters and acrylics) were enriched with depth (5% in surface seawater vs. 77% in deep-sea locations). Our meta-analysis demonstrates that some of the most abundant and recalcitrant manufactured plastics are more persistent in the sea surface than previously anticipated and that further research is required to determine the ultimate fate of these polymers as current knowledge does not support the deep sea as the final sink for all polymer types.

Biochemodynamic Features of Metal Ions Bound by Micro- and Nano-Plastics in Aquatic Media

A simple model, based on spherical geometry, is applied to the description of release kinetics of metal species from nano- and micro-plastic particles. Compiled literature data show that the effective diffusion coefficients, D _eff, for metal species within plastic polymer bodies are many orders of magnitude lower than those applicable for metal ions in bulk aqueous media. Consequently, diffusion of metal ions in the aqueous medium is much faster than that within the body of the plastic particle. So long as the rate of dissociation of any inner-sphere metal complexes is greater than the rate of diffusion within the particle body, the latter process is the limiting step in the overall release kinetics of metal species that are sorbed within the body of the plastic particle. Metal ions that are sorbed at the very particle/medium interface and/or associated with surface-sorbed ligands do not need to traverse the particle body and thus in the diffusion-limiting case, their rate of release will correspond to the rate of diffusion in the aqueous medium. Irrespective of the intraparticulate metal speciation, for a given diffusion coefficient, the proportion of metal species released from plastic particles within a given time frame increases dramatically as the size of the particle decreases. The ensuing consequences for the chemodynamics and bioavailability of metal species associated with plastic micro- and nano-particles in aquatic systems are discussed and illustrated with practical examples.