Microplastic pollution in the sediment of Jagir Estuary, Surabaya City, Indonesia

Microplastics as a Threat to Aquatic Ecosystems and Human Health

The threat posed by microplastics has become one of the world's most serious problems. Recent reports indicate that the presence of microplastics has been documented not only in coastal areas and beaches, but also in water reservoirs, from which they enter the bodies of aquatic animals and humans. Microplastics can also bioaccumulate contaminants that lead to serious damage to aquatic ecosystems. The lack of comprehensive data makes it challenging to ascertain the potential consequences of acute and chronic exposure, particularly for future generations. It is crucial to acknowledge that there is still a substantial need for rapid and effective techniques to identify microplastic particles for precise evaluation. Additionally, implementing legal regulations, limiting plastic production, and developing biodegradation methods are promising solutions, the implementation of which could limit the spread of toxic microplastics.

Comprehensive risk assessment of microplastics in tidal channel sediments in amazonian mangroves (northern Brazil)

Pollution by microplastics (MPs) in mangroves is a growing concern, given its potential ecological and human health impacts. The characteristics of microplastic pollution and a risk assessment of MPs in the Amazon region's coastal sediments are still insufficient, and information about MP pollution in the benthic component of the mangrove ecosystem is lacking. We analyzed MP concentrations in the surface sediment of 9 stations in three tidal channels along the Ajuruteua Peninsula connected to the Caeté River estuary, aiming to assess the hazard level on the environment based on the Pollution Load Index (PLI). Raman and Fourier transform infrared spectroscopy determined the MP's chemical composition. The results showed that the abundance of sediment MPs ranged from 100 to 1200 items kg-1, with an average of 433 ± 261.6 items kg-1. The MPs were mainly composed of transparent and blue fragments and fibers, ranging in size from 100 to 5000 μm. Six types of polymers were identified, including alkyd varnish (AV), resin dispersion (RD), chlorinated polyethylene (CPE), polyethylene-polypropylene (PE-PP), low-density polyethylene (LDPE), and hostaperm blue (HB). Hydrodynamic processes within estuaries and tidal channels play a crucial role in explaining the concentrations found, as circulation determines the pattern of sediment deposition and the particles adhered to it. PLI risk assessment showed that all sampling sites were at hazard level I: a low level of contamination in the mangrove sediments. However, a more comprehensive and systematic monitoring campaign is needed to expand our knowledge about pollution and contamination by MPs in Amazon mangrove areas.

Microplastic from beach sediment to tissue: a case study on burrowing crab Dotilla blanfordi

Background

Microplastics (MPs) are pervasive pollutants in the marine environment, exhibiting persistence in coastal sediment over extended periods. However, the mechanism of their uptake by marine organisms and distribution in habitat is less understood. The objective of the present study was to investigate the presence of MP contamination in burrow sediment, feeding pellets, and tissue of Dotilla blanfordi in the Gulf of Kachchh, Gujarat State.

Methods

A total of 500 g of burrow sediment, 100 g of feeding pellets, and body tissue of 10 resident D. blanfordi were pooled as one replica. Such seven replicas from each site were analyzed for MP extraction from three sites, including Asharmata, Mandvi, and Serena, located in the Gulf of Kachchh. The standard protocol was used during the analysis of the collected samples in order to isolate MPs.

Results

The abundance of MP was found higher in burrow sediment, feeding pellets and tissue of D. blanfordi at study site Mandvi, followed by Serena and Asharmata. The abundance of MP was found higher in D. blanfordi tissue, followed by burrow sediment and feeding pellet. A significant variation was observed in MP abundance among burrow sediment, feeding pellets, and tissue. MPs with various shapes (fiber, film, and fragment), sizes (1-2, 2-3, 3-4, and 4-5 mm), and colors (blue, green, black, pink, purple, red transparent) were recorded from all the study sites. Polyurethane and polyvinyl chloride were recognized as the chemical profile of the extracted MPs. The current investigation revealed greater accumulation of MPs in D. blanfordi's tissues compared to sediment and pellets, suggesting a risk of MP contamination in marine benthic fauna with a greater rate of bioaccumulation. D. blanfordi plays a significant role as a structuring agent for MP distribution in the intertidal flat through burrowing activity.

Tracing microplastic pollution in Mahi River estuary, Gulf of Khambhat, Gujarat, and their influence on functional traits of macrobenthos

Most maritime habitats contain microplastic (MPs) contamination. The quality of the benthic ecosystem's habitat is declining as MPs accumulate in marine system. The contamination of MPs must therefore be investigated. We studied MPs pollution in the Mahi River, estuary, and macrobenthos. In the present study, the abundance of MPs fragments gradually decreased from the high tide zone to the low tide zone and muddy sediment has high MPs concentrations due to sediment characteristics and particle size. The majority of sediment and biota MPs were fibrous and black. MPs in both silt and biota have identical chemical compositions (modified cellulose), shapes, and colors. A significant source of pollutants and MPs fluxing into the ocean is well within the river system. Perinereis aibuhitensis ingested the most MPs out of 11 species, whereas Amphipods did not show any presence of MPs. Our findings showed that functional characteristics are essential for macrobenthos MPs intake. MPs in macrobenthos are high due to biological functions such as feeding, ecological groups, feeding mechanisms, body size, and bioturbation. MPs in marine sediment and organisms are tracked down to the Mahi River exceeding 50 km. The present work has investigated the idea that the macrobenthos that live in the sediment are ingesting the MPs that are building up there and this ingestion relies on the macrobenthos' functional characteristics.

Presence of microplastics in estuarine environment: a case study from Kavvayi and Kumbla backwaters of Malabar Coast, Kerala, India

Microplastics (MPs) are gaining global attention in recent years due to its widespread distribution and potential health impacts. The present study focuses on the distribution and characterisation of microplastics in the sediments and its transfer into the organisms living in Kavvayi and Kumbla backwaters of Northern Malabar region, Kerala, India. MP isolation procedures including density separation, organic matter digestion, and membrane filtration followed by visual and spectral analyses using optical microscope and confocal Raman spectroscopy have been utilised for the microplastic evaluation. Microplastics of size range up to 1 μm was analysed, and the presence of MPs was detected in all samples with an average abundance of 99.5 ± 69.43 particles/kg and 96.57 ± 29.96 particles/kg in Kavvayi and Kumbla backwaters respectively. Raman spectral analysis confirmed that almost 50% of MPs to be synthetic elastomers with the remaining half encompassed by polyamide, polyethylene, polyester, polyurethane, and polypropylene. Higher abundance of MPs in the edible aquatic organisms like clams, prawns, and fishes confirmed the transfer of MP from the environment into living organisms envisages the need of further investigation on toxicological impacts and management strategies.

Microplastic pollution characteristics and ecological risk assessment in the Wuding River Basin, China

Microplastics (MPs), as a new type of environmental pollutant, have attracted extensive attention in recent years. However, there has been relatively little research specifically focusing on MPs in the Yellow River Basin, China, particularly regarding MP migration patterns. Based on surface water and sediment samples from 19 sampling sites in the Wuding River (WDR), the abundances and characteristic distributions of MPs were analyzed, and the environmental factors affecting their distribution and potential ecological risks were evaluated. The results showed that the MP abundances in surface water and sediments of the WDR were significantly different (P < 0.05), with mean values of 2.98 ± 0.69 items/L and 419.47 ± 75.61 items/kg, respectively. In terms of MP characteristics, the most common size class was 0.1-0.5 mm in surface water. Polyethylene (PE, 32.50%) and polypropylene (PP, 27.50%) were the main polymer types of MPs in surface water. Although similar MP characteristics were observed in sediments, there were significantly more particles in the <0.1 mm particle size (P < 0.05), which was 15.0% higher than in surface water. Also, more high-density MP fragments were observed in sediment samples. The retention of MPs in sediments was influenced by the MP characteristics (density, shape, particle size) and sediment particle size. In contrast, the MP abundance in surface water was more closely related to the presence of other environmental pollutants, such as total phosphorus (WTP) and ammonia nitrogen (WAN). Temperature (T), agricultural land (AGR), and residential land (RES) only had significant effects on the distribution of MPs in surface water (P < 0.05). Potential ecological risk assessments revealed that MP pollution in sediments was more serious than in surface water, especially in the middle and lower reaches. The results of this study are important for understanding MP transport in a sandy river and for eliminating potential sources of MPs.

Development of a polystyrene-based microplastic model for bioaccumulation and biodistribution study using radiotracing and nuclear analysis method

The investigation of micro or nano plastics behavior in the environment is essential to minimize the hazards of such pollutants on humans. While the conventional method requires sophisticated procedures and a lot of animal subjects, the nuclear technique confers a sensitive, accurate, and real-time method using radiolabeled micro or nano plastics as a tracer. In this study, polystyrene sulfonate-based microplastic (PSM) was developed with a size of around 3.6 μm, followed by radiolabeling with iodine-131 (131I) or zinc-65 (65Zn) for microplastic radiotracer model. After a stability study in seawater, phosphate buffer saline (PBS), and human serum albumin (HSA) for fifteen days, PSM-131I remained stable (>90 %), except in HSA (50-60 % after day-9), while PSM-65Zn was unstable (<50 %).

Exploring the microplastic pollution: Unveiling origins and varieties in coastal sediments and waters of the Bushehr Province, Persian Gulf, Iran

In this study, microplastic (MP) pollution in the coastal sediments and tidal waters of Bushehr province in the Persian Gulf was comprehensively investigated. The sampling stations were selected based on their proximity to various human activities in January and February 2022, such as tourism, fishing, urban development and industry. The results showed that the abundance of MP associated with different human activities varied. The highest concentrations were observed near the petrochemical industry in Asaluyeh, followed by the densely populated Bushehr and the fishing port of Dayyer. Other areas such as Ganaveh, Deylam and Mand also showed varying levels of MP contamination. The average MP concentration was 1.67 × 104 particles/km2 in surface water and 1346.67 ± 601.69 particles/kg in dry sediment. Fiber particles were in the majority in both sediment and water samples, mainly black. The sediment samples had a size range of 100-500 μm (41.34 %), while the water samples were between 500 and 1000 μm (33.44 %). The main polymers found were polyethylene (PE) and polypropylene (PP). This assessment highlights the widespread problem of microplastic pollution in the coastal and intertidal zones of Bushehr province in the Persian Gulf.

Microplastics Distribution in Sediments Collected from Myanmar

Microplastics (MPs) distributions have been increasingly reported in the terrestrial areas worldwide, but little information is available for ASEAN regions. In this study, 68 sediment samples of drainage channels, lakes, rivers and beaches from Myanmar were collected between 2014 and 2018, and analyzed to investigate the status of MPs concentration and prevalence. The high concentrations of MPs in sediments were found in urban cities called Yangon (13,855 pieces/kg dry weight), Mandalay (11,946 pieces/kg), and Pathein (12,583 pieces/kg), which were two orders of magnitude greater than the MPs concentrations in sediments collected in rural towns called Wundwin. These results suggested that the difference in high population densities and high municipal solid waste generation rates are related to the MPs contamination in sediments. Polyethylene, polypropylene and polyethylene terephthalate with fragments, lines/fibers and films/sheets were major polymers and shape in the sediment samples analyzed from Myanmar. To our knowledge, this is the first study to report the distribution of MPs in sediments from Myanmar.

The path of microplastics through the rare biodiversity estuary region of the northern Bay of Bengal

Due to its harmful effects on ecosystems and human health, microplastic (MP) pollution has become a significant environmental problem on a global scale. Although MPs' pollution path and toxic effects on marine habitats have been examined worldwide, the studies are limited to the rare biodiversity estuary region of Hatiya Island from the northern Bay of Bengal. This study aimed to investigate the MP pollution path and its influencing factors in estuarine sediments and water in rare biodiversity Hatiya Island in the northern Bay of Bengal. Sixty water and sediment samples were collected from 10 sampling sites on the Island and analyzed for MPs. The abundance of MPs in sediment ranged from 67 to 143 pieces/kg, while the abundance in water ranged from 24.34 to 59 pieces/m3. The average concentrations of MPs in sediment and water were 110.90 ± 20.62 pieces/kg and 38.77 ± 10.09 pieces/m3, respectively. Most identified MPs from sediment samples were transparent (51%), while about 54.1% of the identified MPs from water samples were colored. The fragment was the most common form of MP in both compartments, with a value of 64.6% in sediment samples and 60.6% in water samples. In sediment and water samples, almost 74% and 80% of MP were <0.5 mm, respectively. Polypropylene (PP) was the most abundant polymer type, accounting for 51% of all identified polymers. The contamination factor, pollution load index, polymer risk score, and pollution risk score values indicated that the study area was moderately polluted with MPs. The spatial distribution patterns and hotspots of MPs echoed profound human pathways. Based on the results, sustainable management strategies and intervention measures were proposed to reduce the pollution level in the ecologically diverse area. This study provides important insights into evaluating estuary ecosystem susceptibility and mitigation policies against persistent MP issues.

Microplastic pollution in rivers of the Adriatic Sea basin in Montenegro: Impact on pollution of the Montenegrin coastline

Concern regarding microplastic (MP) pollution in aquatic ecosystems has increased in recent years with growing awareness of the environmental harm that it causes. While most studies have focused on seas and oceans, knowledge of MP occurrence in freshwater sediments is limited. This study investigated MP concentrations at shore sediments of the Zeta, Morača, and Bojana rivers in Montenegro. The MP concentration in the studied samples varied depending on the river, location, and sampling season. MP abundance in river shore sediments varied between mean values of 145 ± 110 MPs/kg for the Zeta, 169 ± 113 MPs/kg for the Morača, and 180 ± 53.5 MPs/kg dry sediment for the Bojana. In comparison, the mean MP abundance in the three rivers combined was 163.6 ± 96.1 MPs/kg of dry sediment. The identified MPs were mainly fibres and fragments of blue, red and clear color, 0.5-1 mm in size, and mainly composed of polyethylene, polypropylene, polyamide and polyethylene terephthalate. The main contribution of this study is that it provides new insight into MP abundance in freshwater sediments of rivers, where the studied rivers were identified as a potential important sink and source of MP on the Montenegrin coast.

Spatiotemporal distribution of microplastics in Miri coastal area, NW Borneo: inference from a periodical observation

The current study aims to investigate the spatiotemporal distribution of microplastics (MPs) in the Miri coast, targeting their occurrences, characterisation, and potential sources. For a periodical study, coastal sediments were collected from three different time intervals (monsoon, post-monsoon, and post-COVID) and subjected to stereomicroscope, ATR-FTIR, and SEM-EDX analyses. These results show a significant increase of MPs in post-COVID samples by approximately 218% and 148% comparatively with monsoon and post-monsoon samples, respectively. The highest concentration of MPs was detected near the river mouths and industrial areas where the waste discharge rate and anthropogenic activities dominate. Fibre-type MPs are the most abundant, with an average of nearly 64%, followed by fragments, films, microbeads, and foams. The most dominant polymer types were polytetrafluoroethylene (PTFE), polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyester (PET). Overall, the current study shows a better understanding of MPs occurrence and potential sources in the Miri coastal area.

Hydrostatic pressure drives microbe-mediated biodegradation of microplastics in surface sediments of deep reservoirs: Novel findings from hydrostatic pressure simulation experiments

Microplastics originate from the physical, chemical, or biological degradation of plastics in the environment. Once ingested by organisms at the bottom of the food chain, microplastics are passed on to organisms at higher trophic levels, posing a threat to human health. The distribution of microplastics and the metabolic pathways involved in their microbial degradation in surface sediments of drinking water reservoirs are still poorly understood. This study analyzed the occurrence patterns of microplastics and microbial community structure associated with microplastic biodegradation in surface sediments from a deep reservoir at various hydrostatic pressures. Based on the results of Fourier-transform and laser direct infrared spectroscopy, elevating the pressure resulted in altered sizes and shapes of microplastics in sediment samples with the presence of microorganisms. The influence of hydrostatic pressure on small-sized microplastics (20-500 μm) was pronounced. For instance, high pressure accelerated the breakdown of fibers, pellets, and fragments into smaller-sized microplastics. In particular, the mean size of polyethylene terephthalate microplastics decreased from 425.78 μm at atmospheric pressure to 366.62 μm at 0.7 Mpa. Metagenomic analysis revealed an increase in the relative abundances of plastic-degrading genera, such as Rhodococcus, Flavobacterium, and Aspergillus, in response to elevated pressures. Eight functional genes for biodegradation of polystyrene, polyethylene, and polyethylene terephthalate microplastics were annotated, including paaK, ladA, tphA3. Of these, tphA3 gene abundance was negatively influenced by hydrostatic pressure, providing direct evidence for the pathway by which microbial metabolism of polyethylene terephthalate led to decreased microplastic size under high pressure conditions. This study presents novel insights into hydrostatic pressure-driven microbial community structure, functional gene abundance, and key metabolic pathways associated with biodegradation of microplastics in reservoir sediments.

Distribution and characteristics of microplastics in sediment at representative dredged material ocean dumping sites, China

Dredged material ocean dumping activities are likely an important source of microplastics (MPs) in coastal areas but have received little attention globally. In this study, we investigated the spatiotemporal distribution and characteristics of MPs in sediments at eight dredged material dumping sites of China. MPs were separated from sediment through density flotation, and polymer types were identified using μ-FTIR. The results showed that the average MP abundance was 112.82 ± 109.68 items/kg d.w. The MPs were more abundant at nearshore dumping sites than at distant dumping sites. Dumping activities may be the main contributor of MPs to Site BD1, the farthest dumping site from shore, but only a minor source of MPs at the other dumping sites. The characteristics of MPs were dominated by transparent PET fibers <1 mm. Overall, sediments at the dumping sites exhibited relatively low to moderate concentrations of MPs in comparison to most other coastal sediments.

Effect of High-Density Polyethylene Microplastics on the Survival and Development of Eastern Oyster (Crassostrea virginica) Larvae

Microplastic (MP) pollution is a growing global concern-especially in estuarine areas that serve as natural habitats and nurseries for many marine organisms. One such marine organism is the Eastern oyster (Crassostrea virginica), which is a reef-forming keystone species in the Chesapeake Bay, the largest estuary in the United States. To understand the potential impacts of MP pollution on the estuary ecosystem, the effects of high-density polyethylene (HDPE) MPs on Eastern oyster larval survival and development were investigated. Three cohorts of larvae were exposed to HDPE MPs with a size of 10-90 µm at a 10 mg/L concentration, after 7 to 11 days of fertilization. After exposure, the number and size of oyster larvae were measured twice a week for approximately 2 weeks until larval settlement. The experiment found that there were no significant differences in the rate of survival between the control and MP-addition treatments. However, we noticed that larval development was significantly delayed with the MP treatment. The percentage of larvae that were ready to settle was 64% with the control treatment compared to 43.5% with the MP treatment. This delay in growth resulted in a delayed larval settlement, which could adversely affect the survival of the Eastern oyster due to the increased risk of predation. The current study demonstrates that MPs could be a risk to the ecology of estuaries, and plastic pollution management is needed for the preservation of these estuaries.

Distribution and flux assessment of microplastic debris in the middle and lower Chao Phraya River, Thailand

Microplastic (MP) debris is now a global concern. The Chao Phraya is the largest river in Thailand and transports MPs from terrestrial areas to the ocean. MP debris in its water and sediment were measured in March 2021, September 2021, and March 2022 in five provinces along the watercourse. Hydrological data were also collected to estimate the MP riverine flux between provinces. Size, shape, color, and types of MP polymers were observed, with sedimentation data collected for MP content. Results showed that MPs were found at all sample stations, with average abundance in all province water samples ranging from 0.54 ± 0.05 to 1.07 ± 0.28 pieces/L, while in sediment sample, numbers ranged from 183.84 ± 38.76 to 546.18 ± 86.84 pieces/kg dry weight throughout all seasons. Overall contamination and accumulation were similar between provinces but significantly different between seasons. Sizes of MPs in water varied between seasons with MPs in sediment mostly 330-5,000 μm (Kruskal-Wallis, P < 0.05). Sedimentation of MPs was different between seasons (Kruskal-Wallis, P < 0.05). The highest MP flux values discharged from Samut Prakan Province to the inner Gulf of Thailand were 1.83 × 10⁵ and 1.60 × 10⁵ million items/day in September 2021 and March 2022, respectively.

Occurrence and spatial distribution of microplastic contaminated with heavy metals in a tropical river: Effect of land use and population density

Microplastics are of concern due to their potential environmental risks. This research aims to find the effect of land use (agriculture, urban, and aquaculture) and population density on the abundance of microplastics contaminated with heavy metals in surface water and sediment of the Chao Phraya River in Thailand. Results indicated that population density is directly correlated with increased microplastic abundance. Most microplastics were found in the urban zone (water: 80 ± 38 items/m³ and sediment: 62 ± 11 items/kg) and were small fragments (0.05 to 0.3 mm). Polymer types of polypropylene and polyethylene were commonly found. Heavy metals of Cr, Cu, Cd, Pb, Zn, Ni, and Ti were detected in microplastics in water and sediment, with Cu, Pb, and Zn being the most dominant. Heavy metals in microplastics were highest in the agriculture zone. In general, the presence of metals on microplastics may potentially impact the ecosystem and human health.

Evidence of microplastics in leachate of Randegan landfill, Mojokerto City, Indonesia, and its potential to pollute surface water

About 80-90 tons municipal solid waste (MSW) in Mojokerto City, Indonesia, is disposed of into Randegan landfill daily. The landfill was facilitated with a conventional leachate treatment plant (LTP). The plastic waste component in the MSW, which is 13.22 % weight, possibly contaminates leachate with microplastics (MPs). This research aims to determine the presence of MPs in leachate of the landfill, its characteristics, and the removal efficiency of the LTP. The potential of leachate as MP pollutant source to surface water was also discussed. Raw leachate samples were collected from the LTP inlet channel. Leachate samples were also taken from each LTP's sub-units. Leachate collection was performed two times using a 2.5 L glass bottle during March 2022. The MPs were treated using Wet Peroxide Oxidation method, and filtered using PTFE membrane. MP size and shape were determined using a dissecting microscope with 40-60 x magnifications. The polymer types in the samples were identified using Thermo Scientific™ Nicolet™ iS™ 10 FTIR Spectrometer. The average MP abundance in raw leachate was 9.00 ± 0.85 particles/L. MP shape in the raw leachate was dominated by fiber (64.44 %), followed by fragment (28.89 %), and film (6.67 %). The majority of the MPs were of black color (53.33 %). Abundance of 350 - <1000 μm sized MPs was the highest (64.44 %) in the raw leachate, followed by those of 100-350 μm (31.11 %), and 1000-5000 μm (4.45 %). MP removal efficiency of the LTP was 75.6 %, leaving <100 μm fiber shaped MP residuals of 2.20 ± 0.28 p/L in the effluent. Based on these results, effluent of the LTP is considered potential as MP contamination source to surface water.

Spatio-temporal evaluation and risk assessment of microplastics in nearshore surface waters post-2018 Kerala deluge along the southwest coast of India

Spatial and temporal distribution of microplastics along the nearshore surface waters of Kerala after the floods of 2018 was studied. Results indicated a seven-fold increase in its mean concentration (7.14 ± 3.03 items/m³) post deluge. The average abundance was highest during pre-monsoon (8.27 ± 3.09 items/m³). Fibres were the dominant group, with blue and black being the most prevalent colours. Polyethylene and polypropylene were the most commonly found polymers, possibly gaining entry through sewage waste or land-based plastic litter. Highest abundance of microplastic was recorded off Kochi categorising it at Hazard Level I under Pollution Load Index assessment. Similarly high levels of Pollution Hazard Index and Potential Ecological Risk Index were also reported due to the presence of hazardous polymers PVC and PU that can cause concern to marine life. The differential weathering pattern and surface morphology analysis suggested microplastics to be relatively old that had undergone substantial mechanical and oxidative weathering.

Investigation of microplastic ingestion in commercial fish from Surabaya river, Indonesia

Microplastics (MPs) were recognized as emerging environmental contaminants and ubiquitously distributed in aquatic environments, including in commercial biota. Fish are estimated as one of the most susceptible aquatic biota to ingesting microplastic (MP). Commercial fish cultivation is commonly developed in urban rivers. This situation may lead to food web safety and human health risks because most fish products are commercially available for consumption. Surabaya River, one of the main rivers in Indonesia, has been polluted by MPs. This river takes essential parts for providing clean water for Surabaya City and fishery. This study aimed to investigate: (1) MP ingestion, abundance, characteristics in commercial fish species in Surabaya River, and (2) potential influencing factors to MP ingestion in the fish. The MP ingestion was found in gills and gastrointestinal tracts (GITs) of seven commercial fish species from the Surabaya River. The highest MP abundance was found in the gill of Trichopodus trichopterus (280.73 ± 162.25 particles/g WW), in the GIT of Rasbora argyrotaenia (358.75 ± 121.98 particles/g WW), and in Notopterus notopterus (186 ± 130.81 particles/individual). The MP abundance was positively correlated to fish body size. The predominant MP polymer in both fish organs was cellophane. These MPs were mostly fiber-shaped, large-sized, and black-colored. The MP ingestion in the fish might be influenced by active/passive uptake routes, specific feeding habits, preference habitats, fish size, and MP characteristics. This investigation reveals the occurrence of MP ingestion in commercial fish, which is closely associated with human health risks via trophic transfer by accidental consumption.

Microplastics in aquatic species of Anzali wetland: An important freshwater biodiversity hotspot in Iran

Coastal wetlands are sensitive ecosystems that give habitat to large number of species. The extent of the impact of microplastic pollution in the aquatic system and humans is not known. In this study, the occurrence of microplastics (MPs) was assessed in 7 aquatic species from the Anzali Wetland (40 fish and 15 shrimp specimens), a listed wetland on the Montreux record. Specifically, the tissues analyzed were gastrointestinal (GI) tract, gills, skin, and muscles. The total frequency of MPs (all detected MPs in the GI tract, gill and skin samples) varied from 5.2 ± 4.2 MPs/specimen for Cobitis saniae to 20.8 ± 6.7 MPs/specimen for Abramis brama. Among all tissues studied, the GI tract of the Chelon saliens, a herbivorous demersal species, had the greatest level of MPs (13.6 ± 10 MPs/specimen). Significant differences (p < 0.05) were found between the abundance of MPs in different species, tissues, living domains and feeding habit types. The findings support that fish may uptake MPs through adherence in gills (respiration) in addition to ingestion. White/transparent and black/grey polyamide (PA) fibers were the most common type of MP which may be originated from municipal wastewater and intensive fishing activities. About 34% of the MPs were in the range of 250 μm-500 μm, and those >100 μm were not detected in muscles from the study fish. All species had unhealthy weight according to the Fulton's condition index (K). Positive relationships existed between biometric properties (total length and weight) of species and the total frequency of uptaken MPs, pointing to detrimental impact of MPs in the wetland.

Microplastics in coastal urban sediments: Discrepancies in concentration and character revealed by different approaches to sample processing

Intertidal, silty sediment samples have been collected from three coastal locations with different uses and anthropogenic signatures in the vicinity of Plymouth, southwest England, and analysed for microplastics (MPs) by two independent means. Firstly, MPs were counted and characterised directly on unprocessed dried sediment under a stereo microscope, and secondly MPs were isolated from sediment by flotation in ZnCl₂ solution and filtration before analysis. Direct counting resulted in average (± one standard deviation) numbers of MPs per g of dry sediment of 0.77 ± 0.16 at a marina-harbour, 0.58 ± 0.30 under a busy road bridge and 0.79 ± 0.43 adjacent to country parkland. After flotation and filtration, concentrations were reduced to 0.24 ± 0.11, 0.18 ± 0.06 and 0.48 ± 0.38 MP g^-1, respectively. Observations were attributed to hetero-aggregation of small fibres with settling sediment during flotation, and the presence of MPs (including paints) that were too dense to float or that had aggregated or agglomerated with denser sediment and construction material in situ. The findings have implications for the efficacy of flotation procedures, accurate estimations of MP concentrations in sediment and the representativeness of MPs by type, and inter-site comparisons of MPs that are widely reported in the literature.

Overview of microplastics in the environment: type, source, potential effects and removal strategies

The introduction of plastic sectors has resulted in the presence of microplastics (MPs) in water systems, which has become a global issue that has attracted scientific and community awareness. MPs can be detected in a variety of sources such as beauty products, manufacturing effluent, or fishing activities. This study examined the repercussions posed by MPs' prevalence on land and marine environments and human health issues. Henceforth, remediation technologies must be introduced to shift out MPs from the water supplies in order to sustain the environmental quality for future generations, the benefits and drawbacks of the technology applied. This study also portrays difficulties encountered in MP research as the hurdles must be mastered in order to properly comprehend the MPs. The cooperation between nations is the most critical aspect in fully tackling MP issues as it can be easily carried by wind or water and its damage can be larger than predicted.

Microplastic pollution and its implicated risks in the estuarine environment of Tamil Nadu, India

Estuaries are transition zones between freshwater and seawater. There are only few studies on microplastic (MPs) pollution in estuaries. In this study, investigating the spatiotemporal variations of MPs in water, sediment and biota samples of 19 estuaries in Tamil Nadu, India, we assessed the chemical and human exposure risks of MPs. MPs extracted by digestion and density separation and characterized them using microscope, Fourier transform infrared spectroscopy and scanning electron microscopy with energy dispersive analysis of X-rays. MP abundancesin summer and monsoon range from 31.7 ± 3.8 to 154.7 ± 4.2 items/L in water and 51.7 ± 3.6 to 171.4 ± 9.1 items/kg in sediment. Highest MPs abundance is found in water and sediment of the urbanized Adayar estuary. MP levels are higher in monsoon than in summer (P < 0.05) due to the discharge of wastewater via storm water outlets. More small-size MPs are found in summer (<0.5-1 mm) while monsoon has a greater diversity of MP polymers (MPDII: 0.81). MP abundance in fish varies from 0.01 ± 0.003 to 0.15 ± 0.03 items/g, and in shellfish from 0.75 ± 0.12 to 9.7 ± 0.28 items/g. In fish, more MPs are found in intestine than in gill or muscle. Shell fishes contain more MPs than fishes. In all the matrices, fibers of different sizes, and polymers of polyethylene and polypropylene are commonly found. An average local person is likely to ingest 781 items of MPs via fish and 2809 items via shellfish annually. Polymer hazard index shows hazard levels of IV to V indicating the serious MP pollution trend, which poses a risk to the biota. In conclusion, MPs observed in this study show that estuaries are a major pathway for land-derived plastics to reach the ocean. The results will help implement remedial/clean-up measures for the estuary for better ecosystem conservation.

Microplastics in surface sediments of a highly urbanized wetland

This study investigates the incidence of MPs in surface sediment samples, collected from the Anzali Wetland, Gillan province, North of Iran. This natural habitat receives municipal wastewater effluents and hosts industries and recreational activities that could release plastic to the wetland. There is need for studies to understand MPs pollution in wetlands. A total of 40 superficial sediment samples were taken covering potential pollution hotspots in the wetland. The average level of MPs was 362 ± 327.6 MP/kg: the highest MPs levels were near the outlet of a highly urbanized river (Pirbazar River) (1380 MP/kg), which runs through Rasht city. This was followed by 1255 MP/kg where there was intense fishing, boating and tourism activities in the vicinity of Bandar-e Anzali city. Fibers were the most common type of MPs (80% of the total MPs detected). The MPs polluting the wetland were predominantly white/transparent (42%), and about 40% of them were >1000 μm. Polypropylene (PP) and polyethylene (PE) prevailed in MPs found. MPs were characterized with polarized light microscopy, Raman spectroscopy, Scanning Electron Microscopy coupled with Energy-Dispersive X-ray spectroscopy. Microplastics levels were found to correlate significantly (p > 0.7) with electrical conductivity (EC) and sand-size fraction of the sediments. Coarse-grained sediments presented large capacity to lodge the MPs. This study can be used to establish protection policies in wetlands and newly highlights the opportunity of intercepting MPs in the Anzali Wetland, which are generally >250 μm, before they fragment further.

Microplastics in Sediments of East Surabaya, Indonesia: Regional Characteristics and Potential Risks

The presence of microplastics (MPs) in marine environments has become increasingly apparent. Owing to the lack of effective solid waste management, Indonesia is the second largest producer of ocean plastic waste after China. Currently, information about pollution of MPs in the sediments of East Surabaya, Indonesia, is not available, and this issue is addressed in this study for the first time. Sediment samples were collected from 16 sampling sites along urban and mangrove coastal areas. MPs were observed in most of the sampling sites, with abundances ranging from ND (not detected) to 598 items/kg. MP shapes constituted fragments (30%), foam (28%), granules (22%), and fibers (20%). The 500-1000 µm fraction was the dominant size of MPs. Polypropylene was the major polymer constituent, followed by high-density polyethylene and polyethylene. Findings from Spearman's correlation coefficients, principal component analysis, and hierarchical cluster analysis reveal that the spatial pattern of MPs is closely related to coastal characteristics and population density. MPs in different coastal regions were assessed by the polymer risk index. Results reveal that coastal areas in the Bulak district exhibit the highest risk. Our results confirm the prevalence of MPs as anthropogenic pollutants in East Surabaya and highlight the importance of management action and education on environmental protection for the mitigation of MP pollution.

Microplastic contamination in the sediments of Qarasu estuary in Gorgan Bay, south-east of Caspian Sea, Iran

Given the important ecological role of estuaries and implications of microplastics (MPs) in ecosystems, we assessed the occurrence, abundance, size, and polymer types of MPs present in the sediments of the Qarasu estuary in 2019. MPs were extracted from sediments by density separation, after which they were detected under a stereomicroscope and considered according to shape, size and color. Identification was implemented using Fourier-Transform Infrared Spectroscopy (FT-IR). The abundance and size of MPs in the samples ranged between 40 and 460 particles/kg and 200-5000 μm, respectively. The dominant shape of MPs was fiber (72%), followed by fragment (26%) and film (2%). Black and white were the most abundant colors with 48% and 29%, respectively. In total, 4 MPs polymers including polypropylene (33%), polyethylene (24%), polyamide (21%), and polystyrene (14%) were identified. Results from PCA showed that stations with a high abundance of microplastics had a significant correlation with the amount of clay.

Spatial distribution and risk assessments due to the microplastics pollution in sediments of Karnaphuli River Estuary, Bangladesh

Microplastics (MPs) have become an emerging global pollutant due to their widespread dispersion and potential threats to marine ecosystems. However, studies on MPs in estuarine and coastal ecosystems of Bangladesh are very limited. Here, we conducted the first study on abundance, distribution, characteristics, and risk assessment of microplastics in the sediment of Karnaphuli River estuary, Bangladesh. Microplastic particles were extracted from sediments of 30 stations along the estuary by density separation and then enumerated and characterized using a stereomicroscope and Fourier Transform Infrared (FT-IR) spectroscopy. In the collected sediment of the Karnaphuli River estuary, the number of MPs varied from 22.29 to 59.5 items kg^-1 of dry weight. The mean abundance was higher in the downstream and left banks of the estuary, whereas the predominant shape, colour, and size of MPs were films (35%), and white (19%), and 1-5 mm (30.38%), respectively. Major polymer types were polyethylene terephthalate, polystyrene, polyethylene, cellulose, and nylon. MPs were found to pose risks (low to high) in the sediment of the estuary, with the highest risk occurring at one station near a sewage outlet, according to the results of risk analyses using the pollution risk index, polymer risk index (H), contamination factors, and pollution load index (PLI). The single value index, PLI, clearly demonstrated that all sampling sites were considerably polluted with microplastics (PLI > 1). H values showed toxic polymers, even in lower proportions, possess higher polymeric hazard scores and vice versa. This investigation uncovered new insights on the status of MPs in the sediments of the Karnaphuli River estuary, laying the groundwork for future research and control of microplastic pollution and management.

Expanding the Sediment Transport Tracking Possibilities in a River Basin through the Development of a Digital Platform—DNS/SWAT

Simulation of stochastic and variable sediment transport processes within models still poses a big challenge, especially in mountainous areas. Since sediment transport, including erosion and deposition, remains an unceasing problem in many areas, sediment modeling is perceived as a possible solution. This article combines a review of the selected sediment models with a presentation of the effects of several years of research using the DNS digital platform in the Western Carpathians. The review focuses on the main advantages and gaps in selected modeling tools with particular emphasis on one of the most popular: SWAT. The description of the digital platform—DNS is an example of how to answer these gaps by combining subsequent models, methods, and databases using their best features. To accentuate the benefits of such an approach, the effects of combining subsequent models (AdH/PTM) and methods (fingerprinting) on a common digital DNS space are presented, on the example of the Raba River (basin). In this way, both unique possibilities of estimating the amount of contamination carried with sediment particles and their sources, as well as sequencing of sedimentation in the reservoir, taking into account its subsequent zones, were obtained.

Transport mechanisms and fate of microplastics in estuarine compartments: A review

Despite the importance of estuaries as transition zones between freshwater and marine compartments, their role in the transport of microplastics is still unclear. This review analyzes the findings pertaining to the transport mechanisms and other factors that influence the fate of microplastics in estuaries. It was found that the concentration of microplastics temporally varies under daily tides, monthly tides, and seasonal flows. Moreover, it spatially varies due to density effects, biofouling, aggregation, and salinity. Wind direction and intensity impact the spatiotemporal distribution of microplastics in the water column. Some of these processes transport microplastics to the estuarine sediments. Thereafter, microplastics are prone to resuspension by turbulence and bioturbation. Hence, estuaries act as temporary sinks that retain microplastics before being flushed to the ocean. Finally, a review of highly plastic-emitting rivers shows differences in the factors affecting the transport mechanisms of microplastics, which calls for regionalization when modelling their fate henceforward.

Distribution Characteristics and Source Analysis of Microplastics in Urban Freshwater Lakes: A Case Study in Songshan Lake of Dongguan, China

Current studies on microplastic pollution mainly focus on marine systems. However, few studies have investigated microplastics in an urban lake. This research intends to use an urban lake (Songshan Lake) as an example to explore the pollution characteristics of microplastics and use the principal component as well as the heat map analysis to discuss the relationships between different shapes of microplastics. According to this study, the average abundance of microplastics in the surface water and surface sediments of Songshan Lake were, respectively, 2.29 ± 0.98 items/m3 and 244 ± 121 items/kg; thin films were the major microplastics in both media; transparent this type of color has the most microplastic content. The particle size of microplastics was mainly 0.18–0.6 mm (43.3%) in surface water and 1–2 mm (48.3%) in surface sediments. The composition included five polymers: polyethylene (PE), polypropylene (PP), polypropylene–polyethylene copolymer (PP–PE copolymer), polystyrene (PS), and polyvinyl chloride (PVC), among which PE (47%) and PP (36%) were the main components. Principal component analysis (PCA) showed that there was a positive correlation among the four shapes of microplastics: films, fragments, foams, and fibers. The heat map analysis showed that the same category of shape distribution features may be similar for each sampling site.

Urban drainage channels as microplastics pollution hotspots in developing areas: A case study in Da Nang, Vietnam

This study provides information on the current situation of microplastics contamination in inland freshwater bodies in Vietnam. An urban drainage channel in Da Nang City was selected as a case study. Receiving mainly domestic wastewater and landfill leachate, the channel itself is becoming a microplastic pollution hotspot with a microplastic concentration of 1482.0 ± 1060.4 items m^-3 in waters and 6120.0 ± 2145.7 items kg^-1 in sediments. The dominant shapes of microplastics were fibers and fragments, in which the polymer types were mainly polyethylene, polypropylene, and polyethylene terephthalate. Microplastics with sizes ranging from 1000 to 5000 μm tended to be distributed primarily in surface waters, whereas particles from 300 to 1000 μm accumulated in sediments. The channel places Da Nang Bay at a high risk for microplastic pollution, with an estimated pollution load of approximately 623 × 10⁶ items d^-1 in dry weather.

Microplastic pollution in surface seawater and beach sand from the shore of Rayong province, Thailand: Distribution, characterization, and ecological risk assessment

The distribution, characteristics, and ecological risk of microplastics in beach sand and seawater samples collected along the shore of Rayong province, Thailand, were investigated in this study. The average microplastics abundance in beach sand and seawater was 338.89 ± 264.94 particles/kg d.w. and 1781.48 ± 1598.36 particles/m³, respectively. Beach sand and seawater had the most yellow-brown particles and transparent microfibers, respectively. The most common microplastics (100-500 μm) and polyethylene were found. In beach sand, the potential ecological risk (RI) is classified as minor, while in seawater, it is classified as medium. The PLI_zone in beach sand and seawater was Hazard Level II and Hazard Level IV, respectively. Despite their apparent proximity, the non-correlation between risk levels in beach sand and seawater may be due to polymer type variations influenced by the different land-based and sea-based sources.

Marine microplastics in the ASEAN region: A review of the current state of knowledge

Microplastic pollution is a prevalent and serious problem in marine environments. These particles have a detrimental impact on marine ecosystems. They are harmful to marine organisms and are known to be a habitat for toxic microorganisms. Marine microplastics have been identified in beach sand, the seafloor and also in marine biota. Although research investigating the presence of microplastics in various marine environments have increased across the years, studies in Southeast Asia are still relatively limited. In this paper, 36 studies on marine microplastic pollution in Southeast Asia were reviewed and discussed, focusing on microplastics in beach and benthic sediments, seawater and marine organisms. These studies have shown that the presence of fishing harbours, aquaculture farms, and tourism result in an increased abundance of microplastics. The illegal and improper disposal of waste from village settlements and factories also contribute to the high abundance of microplastics observed. Hence, it is crucial to identify the hotspots of microplastic pollution, for assessment and mitigation purposes. Future studies should aim to standardize protocols and quantification, to allow for better quantification and assessment of the levels of microplastic contamination for monitoring purposes.

Microplastics retention by reeds in freshwater environment

Microplastic pollution has recently gained increasing attention. The accumulation of microplastics in plants has been confirmed in the marine environment. However, the extent of the microplastic retention in freshwater plants is still unknown. In this study, sediment and plant samples from six reed farms in the wetland of East Dongting Lake were collected and analyzed. The abundance of microplastics in the sediment of reed farms varied from 125.7 to 1219.5 items/kg dry weight (dw), with an average of 511.2 ± 295.0 items/kg. Moreover, different levels of microplastic abundance were found in reeds from 0 to 14 items/individual. The abundance of microplastics in sediment samples was moderate compared to that worldwide and higher than that in other regions of Dongting Lake. The microplastic pollution level was significantly higher in the reed vegetation belt than that in other sampling positions. On the basis of the distribution and characteristics of the collected microplastics, lake water and fishery are suggested as important sources of microplastics. Furthermore, the factors influencing microplastic retention in the reeds are discussed. This study, as the first direct evidence demonstrating that freshwater reeds tend to accumulate microplastics, constitutes valuable reference for future research.

Anthropogenic impact on Indonesian coastal water and ecosystems: Current status and future opportunities

Indonesia, the world's largest archipelagic country and the fourth most populated nation, has struggled with coastal water pollution in the last decades. With the increasing population in coastal urban cities, more land-based pollutants are transported to the coastal water and adversely affected the tropical ecosystems. This paper provides an overview of anthropogenic pollutant studies in Indonesian coastal water and ecosystems from 1986 to 2021. Nutrients, heavy metals, organic pollutants, and plastic debris are the most-studied contaminants. We found that 82%, 54% and 50% of the studies exceeding nutrients, heavy metals, and organic pollutants standard limit, respectively; thus, indicating poor water quality status in part of Indonesian coastal water. The coral reef ecosystems is found to be the most sensitive to anthropogenic disturbance. The potential effect of climate change, new coastal pollution hotspots in eastern Indonesia, marine anthropogenic sources, legacy/emerging pollutants, and the need for research related to the biological contamination, are discussed for future opportunities.

Microplastic pollution in inshore and offshore surface waters of the southern Caspian Sea

In this study, as the first comprehensive monitoring, the occurrence of microplastics (MPs) in inshore and offshore surface waters of the southern Caspian Sea was investigated. Our data indicated that MPs, which were detected in all the samples, were widely distributed in the thirteen studied stations. Non-normally distribution of the MPs was observed among the studied stations (p<0.05). The average concentration of microplastics in the selected stations was 0.246 ± 0.020 MP/m³. In most of the transects, negative gradients of MPs from coastal waters to deeper waters were observed. The dominant size and color of MPs in the inshore and offshore water samples was 1000-5000 μm and white-transparent, respectively. Films and fibers constituted about 50% and 40% of the total number of MPs of the water samples, respectively. Also, polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET) were the three main polymer types of microplastics in the inshore and offshore surface waters. Our data provide valuable evidence for the comparative assessing of future data regarding decreases or increases of MPs in the southern Caspian Sea.

Typhoon-induced turbulence redistributed microplastics in coastal areas and reformed plastisphere community

The increasing microplastic pollution together with the plastisphere-associated ecological threats in coastal areas have aroused global concern. Tropical cyclones have been increased in both frequency and intensity under global warming, causing intense impact on the microplastics distribution and the structure of coastal ecosystems. However, until most currently, the extent to which typhoon impacts the microplastics and plastisphere community remains poorly known. This study analyzed the effects of Typhoon Wipha (Code: 1907) on microplastics abundance and composition in surface water and sediment crossed coastal areas of Shenzhen. Here we found a significant typhoon-induced increase in microplastics abundance in surface water, whereas an opposite trend was observed in sediment. Despite the evident transportation of microplastics from sediment to surface water by agitation, a possible microplastics influx was introduced by typhoon as evidenced by the large attribution of unknown force in source tracking analysis. Furthermore, typhoon had adeptly uniformed the plastisphere community in the sediment along the 190 km costal line overnight. A significant increase of nitrogen fixer, Bradyrhizobiaceae, was observed ubiquitously after typhoon, which might alter the nitrogen cycling and increase eutrophic condition of the coastal ecological system. Together, this study expanded the knowledge about the impact of typhoon-induced influx of the microplastics on coastal biogeochemical cycling. Moreover, the microplastics and the plastisphere compositional pattern revealed here will underpin future studies on adsorption behavior, interfacial processes and ecotoxicity of the coastal microplastic pollution.

Spatiotemporal microplastic occurrence study of Setiu Wetland, South China Sea

This study reports the distribution of microplastics (MPs) in surface water and estuarine sediments in South and North Setiu Wetland in the South China Sea. Sampling was conducted bimonthly for one year from November 2016 to November 2017, including the northeast and southwest monsoons. Water surface and sediment samples were collected from six different sampling stations (STs). Samples were sorted based on physical analysis (optical observation) and selected particles were further analyzed by chemical characterizations. The findings of this study indicate that a total of 0.36 items/L and 5.97 items/g particles of MPs were found from characterizations surface water and dry sediment, respectively. Among the selected stations included in this research, ST3 (1.375 ± 0.347 items/L) and ST2 (14.250 ± 4.343 items/g) were individually identified as high potential MP sinking areas, exacerbated during the northeast and southwest monsoons. Transparent, film, and filament MP types were consistently found across all stations. Microplastic filaments revealed a functional group of polypropylenes based on the main peak spectrum at 2893-2955 cm^-1 (CH alkyl stretching), 1458 cm^-1 (CH₂ bending), and 1381 cm^-1 (CH₃ bending). Microplastic materials were thermally decomposed by pyrolysis-gas chromatography-mass spectrometry (Pyr-GC/MS) and identified as cyclohexane and cyclohexene derivatives, as well as precursors of polymer blends. The distribution of MPs in both matrices varied according to different seasons. These findings provide useful baseline information on the distribution of MPs from the estuarine area in Malaysia and South China Sea waters.

Microplastics pollution on Colombian Central Caribbean beaches

The growing literature on microplastics (MPs) in coastal and marine environs reflects the seriousness of this pollutant category. Diverse litter studies on Colombia's Central Caribbean Coast have not presented detailed study of MPs' typology, magnitude or distribution. This baseline study presents for first time the MPs problem on 23 beaches in 75 km coastal reach between Punta Roca and Galerazamba, on the central Colombian Caribbean Coast. The Microplastics Pollution Index (MPPI) and Coefficient of Microplastic Impact (CMPI) were developed and applied along with the Environmental Status Index (ESI) and their integration through sector analysis, and mapping using Agglomerative Hierarchical Clustering and Multidimensional Scaling, and Principal Components Analysis. Microplastics abundances (densities) ranged from 2457 to 557 MPs/kg, similar to other global beaches and bays. The MPs Index for the 23 beaches classified 8 beaches as "Moderate," 10 beaches as "High" and 5 as "Very High." Microplastic fibers were the dominant typology at 83% of the combined beaches total (ranging from Moderate to Very High for individual beaches).

Occurrence, abundance, and distribution of microplastics pollution: an evidence in surface tropical water of Klang River estuary, Malaysia

Microplastics have been considered as contaminants of emerging concern due to ubiquity in the environment; however, the occurrence of microplastics in river estuaries is scarcely investigated. The Klang River estuary is an important ecosystem that receives various contaminants from urbanised, highly populated areas and the busiest maritime centre in Selangor, Malaysia. This study investigates the abundance and characteristics of microplastics in surface water of the Klang River estuary. The abundance of microplastics ranged from 0.5 to 4.5 particles L^-1 with a mean abundance of 2.47 particles L^-1. There is no correlation between the abundance of microplastics and physicochemical properties, while there is a strong correlation between salinity and conductivity. The microplastics were characterised with a stereomicroscope and attenuated total reflection-Fourier transform infrared spectroscopy to analyse size, shape, colour, and polymer composition. The microplastics in the surface water were predominantly in the 300-1000 μm size class, followed by > 1000 μm and < 300 μm, and were mostly transparent fibres, fragments, and pellets. Polyamide and polyethylene were the main polymer types in the composition of the microplastics, suggesting that the microplastics originated from heavily urbanised and industrial locations such as the port, jetty, and residential areas. The widespread occurrence of microplastics in the environment and subsequent penetration of aquatic food webs may pose a serious threat to organisms. This study provides baseline data and a framework for further investigation of microplastic contamination in estuaries.

Environmental Microplastic Particles vs. Engineered Plastic Microparticles-A Comparative Review

Microplastic particles (MPs) pose a novel threat to nature. Despite being first noticed in the 1970s, research on this topic has only surged in recent years. Researchers have mainly focused on environmental plastic particles; however, studies with defined microplastic particles as the sample input are scarce. Furthermore, comparison of those studies indicates a discrepancy between the particles found (e.g., in the environment) and those used for further research (e.g., exposure studies). Obviously, it is important to use particles that resemble those found in the environment to conduct appropriate research. In this review, different categories of microplastic particles are addressed, before covering an overview of the most common separation and analysis methods for environmental MPs is covered. After showing that the particles found in the environment are mostly irregular and polydisperse, while those used in studies with plastic microparticles as samples are often not, different particle production techniques are investigated and suggestions for preparing realistic plastic particles are given.

Characterization and distribution of microplastics in estuarine surface sediments, Kayamkulam estuary, southwest coast of India

The present study aims to formulate the characterization and distribution of microplastic in the estuarine surface sediments of Kayamkulam estuary, southwest coast of India. The sediments were dominated by fibre and film shaped microplastic substances. The surface sediments were dominated by <1000 μm microplastics. The composition of microplastics in descending order was as follows: polyester > polypropylene > polyethylene. The distribution of microplastics was significantly higher than that observed in the other study regions, except for Pearl river estuary and Guanabara Bay. The distribution of microplastics was chiefly controlled by estuarine inundating water and the distance of the sampling site from the open sea.

Microplastic fibers in the gut of highly consumed fish species from the southern Caspian Sea

This study assesses the frequency, distribution, characteristics, and chemical composition of microplastics (MPs) in the gut of highly consumed fish species, namely leaping mullet (Chelon saliens), common carp (Cyprinus carpioi), and Caspian kutum (Rutilus caspicus), in the southern Caspian Sea biome. Fibers are found to be the only shape of MPs. Black MPs and polystyrene, polypropylene, and polyethylene terephthalate polymers are dominant. MP frequency is highest in leaping mullet's gut, while kutum specimens exhibited the lowest MP frequency, reflecting that leaping mullet is a neritic species and thus highly exposed to MP influx in shallow coastal water, while the other species are benthopelagic. The estimated condition index reflected a significant difference between the species, implying that MPs may pose adverse health impacts on leaping mullet and common carp, with no undesirable effect on Caspian kutum. No significant relationship exists between biological parameters and the MP frequency in the fish gut.

Distribution and Seasonal Variation of Microplastics in Tallo River, Makassar, Eastern Indonesia

Attention towards microplastic (MP) pollution in various environments is increasing, but relatively little attention has been given to the freshwater-riverine environment. As the biggest city in the eastern Indonesia region, Makassar can be a potential source of MP pollution to its riverine area. This study aimed to determine the spatial trends, seasonal variation, and characteristics of MPs in the water and sediment of Tallo River, as the main river in Makassar. Water samples were collected using a neuston net and sediment samples were collected using a sediment corer. The samples collected contained MPs with an abundance ranging from 0.74 ± 0.46 to 3.41 ± 0.13 item/m³ and 16.67 ± 20.82 to 150 ± 36.06 item/kg for water and sediment samples, respectively. The microplastic abundance in the Tallo River was higher in the dry season and tended to increase towards the lower river segment. Fragments (47.80–86.03%) and lines (12.50–47.80%) were the predominant shapes, while blue (19.49–46.15%) and transparent (14.29–38.14%) were the most dominant color. Polyethylene and polypropylene were the common MP polymers found in the Tallo river. Actions to prevent MP pollution in the Makassar riverine area are needed before MP pollution becomes more severe in the future.

Microplastic sampling techniques in freshwaters and sediments: a review

Pollution by microplastics is of increasing concern due to their ubiquitous presence in most biological and environmental media, their potential toxicity and their ability to carry other contaminants. Knowledge on microplastics in freshwaters is still in its infancy. Here we reviewed 150 investigations to identify the common methods and tools for sampling microplastics, waters and sediments in freshwater ecosystems. Manta trawls are the main sampling tool for microplastic separation from surface water, whereas shovel, trowel, spade, scoop and spatula are the most frequently used devices in microplastic studies of sediments. Van Veen grab is common for deep sediment sampling. There is a need to develop optimal methods for reducing identification time and effort and to detect smaller-sized plastic particles.

Microplastic particles in sediments and waters, south of Caspian Sea: Frequency, distribution, characteristics, and chemical composition

This study assesses the occurrence of microplastics (MPs) in coastal and sea surface sediments, as well as water samples, collected from the coastal region of the southern Caspian Sea, Mazandaran province, Iran. A total of 32 sediment and 10 water samples were studied. The mean concentration of MPs was 15 units kg^-1 in the sediments and 710 units m^-3 in the coastal water. Fibers constituted by far the dominant MPs in both media, accounting for 97% of the MPs in both sediment and water samples. The MPs were mainly black in color. The dominant size of MP particles in sediment samples was between 250 and 500 μm, while the fraction >1000 μm dominated in the water samples. Polyethylene terephthalate (PET), polystyrene (PS), and nylon (NYL) were the main polymers and/or copolymers composing MPs in both sediment and water samples. The MP particles had a relatively smooth surface morphology, although signs of weathering were observed. The number of MP particles in sediment and water samples showed a general decrease from west to east in the study area. This may be reflecting the spreading of MP loading from the outlets of Sefidrud, Tonekabon, Chalus, the major rivers entering the Caspian Sea just west of the study area, and the overall decrease in the spatial distribution of touristic and fishery activity. The main sources of MP particles could be local emissions from a large number of domestic wastewater effluents and urban surface runoff due to high population density, and industrial and fishing activities in this region. This study indicated that MP particles, based on their characteristics and chemical composition, are circulated between coastal waters, and shore and sea surface sediments of the Caspian Sea, leading to their uneven distribution in the different depths. To the best of our knowledge, this is the first work studying the distribution of MP particles in sea surface sediments and also the most comprehensive on MPs in shoreline sediments and coastal waters in the southern Caspian Sea.

Microplastics pollution with heavy metals in the aquaculture zone of the Chao Phraya River Estuary, Thailand

Microplastics have received special attention due to their potential risks to environments. However, data on microplastics in estuaries of the Southeast Asian region is still insufficient. This study investigated the abundance and characteristics of microplastics in the sediment and surface water of the Chao Phraya River Estuary, Thailand. Concentrations of heavy metals extracted from microplastics were also reported. The abundance of microplastics in surface water and sediment was 48 ± 8 items/m³ and 39 ± 14 items/kg, respectively. Microplastics with small sizes of 0.05-0.3 mm were predominant in all collected samples. Polypropylene and polyethylene particles were the most abundant in the surface water and sediment, respectively. Toxic metals (Cr, Cu, Ni, Pb, Cd, and Zn) were found in microplastics from surface water samples. Since Chao Phraya River Estuary is an important aquaculture zone in Thailand, the presence of microplastics in this area may severely impact on aquaculture and human health.

Microplastics in the environment: Interactions with microbes and chemical contaminants

Microplastics (MPs) are contaminants of emerging concern that have gained considerable attention during the last few decades due to their adverse impact on living organisms and the environment. Recent studies have shown their ubiquitous presence in the environment including the atmosphere, soil, and water. Though several reviews have focused on the occurrence of microplastics in different habitats, little attention has been paid to their interaction with biological and chemical pollutants in the environment. This review therefore presents the state of knowledge on the interaction of MPs with chemicals and microbes in different environments. The distribution of MPs, the association of toxic chemicals with MPs, microbial association with MPs and the microbial-induced fate of MPs in the environment are discussed. The biodegradation and bioaccumulation of MPs by and in microbes and its potential impact on the food chain are also reviewed. The mechanisms driving these interactions and how these, in turn, affect living organisms however are not yet fully understood and require further attention.

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.