Abundance, composition, and fate of microplastics in water, sediment, and shellfish in the Tapi-Phumduang River system and Bandon Bay, Thailand

Study on the toxic effect of seawater-aged microplastics on Philippine curtain clams

This study delved into the impact of aging on the properties of five common microplastic types, including polymethylmethacrylate (PMMA), polystyrene (PS), polyvinyl chloride (PVC), polyethylene (PE), and polypropylene (PP). The aging process significantly altered the particle size distribution: PS, PP, and PMMA underwent a contraction, with average sizes decreasing by 6.8%, 3.2%, and 1.7%, respectively, whereas PE and PVC experienced an expansion, with increases of 3.1% and 1.7%. Notably, aging generally increased the specific surface area of all microplastics by more than 20%, a change that could influence their environmental interactions. Scanning electron microscopy revealed marked surface cracks and depressions in aged PE and PVC, in contrast to minor surface alterations in PS and PMMA. Fourier transform infrared spectroscopy further indicated modifications in the characteristic peaks of aged PMMA, PP, and PE microplastics. Exposure experiments demonstrates that increasing microplastic concentrations from 100 mg/L to 5000 mg/L accelerated mortality rates in clams, with juveniles exhibiting slower mortality onset compared to adults. Prolonged exposure led to rising mortality rates across all groups, suggesting a cumulative toxic effect from long-term microplastic exposure. These findings underscore the environmental ecological risks associated with the altered physicochemical properties of aged microplastics, particularly for the Philippine clam. This study provides an essential insight for advancing our understanding of microplastic behavior and their ecological impacts, highlighting the need for further research to mitigate these environmental threats.

Microplastics in the European native oyster, Ostrea edulis, to monitoring pollution-related patterns in the Solent region (United Kingdom)

Microplastics (MPs) are the most abundant type of debris in the marine environment, creating a significant threat to aquatic ecosystems due to their persistence, ability to absorb organic pollutants and potential ingestion by marine fauna. Shellfish are particularly vulnerable to MPs accumulation as they filter large volumes of seawater, and they become an important route for human exposure to these particles. This study, the first to examine MPs in European flat oyster (Ostrea edulis) populations, aimed to quantify these particles in the gill and digestive tissues of oysters from the Solent region (southern England). Enzymatic digestion using Proteinase-K was used in this study and MPs were identified in every oyster sampled to determine whether differences in abundance, type and size of MPs exist between locations. Oysters near urban areas contained significantly more MPs than those near rural areas. Fibres were the most prevalent type of MPs, with sizes varying across locations. The study found no significant differences in MPs presence between gills and digestive tissues, and an inverse correlation between the size of MPs and oyster size. The presence of MPs in wild O. edulis could be an additional threat to the survival of an already threatened species and may pose health risks for predatory species and human consumers of seafood. The use of O. edulis as a biomonitoring species for marine MPs pollution could help determine the extent, distribution and sources of MPs, potentially informing management strategies to reduce pollution.

Fate, source, and ecological risk of microplastic in the surface sediment of the Beibu Gulf, the Northern South China sea

A large-scale investigation of the surface sediments in the Beibu Gulf was conducted in this study to reveal the contamination characteristics of microplastics in the surface sediments of the Beibu Gulf. The results showed that the abundance of microplastics ranged from 12.91 to 251.69 items/kg, dry weigh (DW), with an average abundance of 84.34 ± 51.85 items/kg (DW). The highest abundance of microplastics was found in the estuary of northwestern Hainan, influenced by the West Guangdong Coastal Current. The overall distribution of abundance showed a decreasing trend from nearshore to offshore. Microplastics in the surface sediments were predominantly in the form of fiber (87.51%), with a predominant white color. The polymer of microplastics in surface sediment was primarily polyester (43.43%). The main sources of microplastics include household items, textile products, food packaging, fishing activities, industrial activities, sewage discharges, and biochemical materials, of which household products and textile products are the most important sources. The results of the risk evaluation showed that the sediment of Beibu Gulf was contaminated with microplastics (pollution load index >1) and the polymer risk was at low to extremely high levels. The high abundance of microplastics and highly toxic polymers resulted in increased ecological risk. These findings highlight the urgent need to implement timely and effective measures to reduce the impact of intensive human activities on microplastic pollution. At the same time, the study data provide an important reference for future ecotoxicological investigations, pollution management strategies and microplastic policy development.

Analysing the influence of hydrodynamic and sedimentary factors on the microplastic distribution in the Ashtamudi estuary, India

This study evaluates the influence of water current and suspended sediment concentration (SSC) on microplastic distribution in various mixing regimes of the Ashtamudi estuary, India. Microplastic abundance ranged from 3.2 to 53 items/L, with highest concentrations observed near the confluence of the river and the sea. Partially mixed regions exhibited elevated near-bottom microplastic concentrations, identifying these zones as potential settling areas. Microplastic abundance showed a direct relationship with SSC and an inverse relationship with current. A non-linear model developed to predict microplastic abundance based on SSC and current demonstrated good performance, achieving an R2 value of 0.97. This model outperformed the SSC-only model, representing a significant advancement over previous studies. The findings highlight the critical roles of hydrodynamic and sedimentary factors in governing microplastic distribution within the water column. The developed model, after calibration, can be applied to other estuaries globally, supporting plastic monitoring programmes in implementing effective mitigation measures.

First evidence of microplastics in the Quilca-Vítor-Chili river basin, Arequipa region, Peru

The Chili, Vitor and Quilca rivers and their tributaries in Peru serve as a vital water resource for both irrigation and domestic use in the surrounding communities and agricultural areas. The purpose of this study was to establish, for the first time, the presence, abundance, distribution and chemical identity of polymer microparticles in aqueous samples from these river basins. The results showed that, on average, filaments were the most dominant (71.4 %), followed by fragments (17.2 %) and film (6.74 %). Identification of the polymer types revealed that the most abundant type of MPs is polyethylene (40.8 %), followed by polypropylene (23.8 %), synthetic fibres (15.8 %), and other synthetic polymers. All samples showed the occurrence of microplastics, with a mean concentration of 35.34 MPs/m3, a maximum value of 172.70 MPs/m3 and a minimum value of 3.59 MPs/m3. The results reported in this study establish a baseline for the study area for the first time; in addition, the areas were established with a Pollution Indicator, and the Pollutant Load Index (PLI) was calculated, which reinforced the proposed identification, alerting the need to control clandestine urban and rural landfills, as well as the indiscriminate use of PE big bags in the agricultural catchment.

How does the tidal cycle influence the estuarine dynamics of microplastics?

Estuaries are the main pathway for the microplastics (MPs) to enter into the oceans. However, factors that drive river-sea transport of MPs are not yet fully understood. Therefore, our research investigated the influence of the tidal cycle on the abundance and characteristics of MPs in an urban estuary, through high-frequency sampling (every 2-3 h) using a plankton net (120 μm mesh size) in two seasons (rainy and dry seasons). The results showed that the abundance of MPs decreased during the ebb tide and increased during the flood tide. A positive correlation was found between MP abundance and water height in both seasons. The shapes and colors of MPs varied significantly throughout the tidal cycle. The results show that tides are key agents in the transfer of MPs and cannot be neglected in models of the global contribution of plastic pollution from rivers to oceans.

Microplastic distribution and composition in mudflat sediments and varnish clams (Nuttallia obscurata) at two estuaries of British Columbia, Canada: An assessment of potential anthropogenic sources

Widespread microplastic contamination affects the marine-coastal ecosystems in British Columbia, Canada. To understand the characteristics and spatial distribution of of microplastics (MPs), we compared the MPs in sediments (n = 159) and Varnish clams (Nuttallia obscurata; n = 160) collected from two estuarine ecosystems (Cowichan and K'ómoks) experiencing different anthropogenic impacts; primarily resource extraction (i.e., logging) at Cowichan and urban development at K'omoks. Our objective wasto determine the MP abundance levels in sediments and clams and infer possible sources of MPs at the two estuaries. Microplastic polymer type was confirmed through FTIR spectrometry. The average abundance of MPs in sediments were 14.37 ± 11.57 particles/kg in the Cowichan Estuary and 30.96 ± 14.58 particles/kg in the K'ómoks Estuary. Varnish clam samples contained average abundance of 3.62 ± 2.58 particles/g and 2.24 ± 1.96 particles/g in Cowichan and K'ómoks estuaries, respectively. The Cowichan Estuary's marine terminal and K'ómoks Marina were found to be hotspots for MPs, likely due to a combination of industrial and local sources. Fibers were the most common type of MPs found in both sediment (53.34 %) and clam samples (53.5 %) from Cowichan, as well as in clam samples in% K'ómoks, indicating a potential link to textile sources contributing to the widespread presence of MPs in the marine environment. There was no clear signal based on the primary use of the estuary. Polyethylene was the predominant polymer type of MPs found in sediment and clam samples at Cowichan, whereas Polyester was most common at K'ómoks. Our study revealed the ubiquitous nature of these emerging pollutants in the sensitive estuarine environments of BC, with implications for plastic waste management and the reduction of plastic pollution at the regional level.

Microplastics in commercial marine bivalves: Abundance, characterization and main effects of single and combined exposure

Microplastics (MPs) are persistent and ubiquitous pollutants in marine ecosystems, and they can be ingested and accumulated by marine organisms with economic value to humans, such as marine bivalves, which may pose a threat to the marine food chains and to human health. In this literature review, we summarized the recent findings on the abundance and main characteristics (shape, size, color, polymer) of MPs detected in valuable marine bivalve species. Furthermore, we surveyed the major impacts triggered by MP exposure, alone or in combination with other pollutants, in these organisms. Additionally, we discussed the methodologies, techniques and equipment commonly used by researchers for the determination of the abundance, characterization and effects of the MP particles in these organisms. We verified that MPs have been widely detected in multiple species of commercial marine bivalves, with a great variety of shapes, sizes, colors and polymer types. In general, the methodologies used by researchers to determine the MP abundance in marine bivalves need to be harmonized to facilitate the comparability between studies. So far, previous research showed that the main effects of MPs, either alone or combined with other pollutants, on commercial marine bivalves include the induction of immunological, physiological and behavioral responses, reproductive modifications, genotoxicity and neurotoxicity, which were surveyed by using a wide variety of techniques and analytical equipment. In the future, researchers should focus on less studied bivalve species and should use the most precise and innovative methodologies to assess the effects of MPs and other pollutants on marine bivalves.

The nexus of microplastics, food and antimicrobial resistance in the context of aquatic environment: Interdisciplinary linkages of pathways

The exponential rise in plastic production since the mid-20th century has led to the widespread existence of microplastics in various ecosystems, posing significant environmental and health concerns. Microplastics, defined as plastic particles smaller than 5 mm, have infiltrated diverse environments, including oceans, freshwater bodies, and even remote Arctic ice. Their ability to absorb toxic chemicals and serve as vectors for microbial colonization raises concerns about their impacts on aquatic organisms and human health. This review examines the pathways by which microplastics infiltrate the food chain, highlighting their presence in various food items consumed by humans. Furthermore, it explores the nexus between microplastics and antimicrobial resistance (AMR), elucidating how microorganisms inhabiting plastic surfaces facilitate the transmission of antibiotic resistance genes (ARGs). The review underscores the urgent need for interdisciplinary research integrating environmental science, microbiology, public health, and policy to address the multifaceted challenges posed by microplastics. Standardized protocols for sampling and analysis are essential to enable meaningful comparisons across research and regions. By collectively addressing these challenges, we can strive towards a more sustainable and resilient future for ecosystems and human societies.

Spatiotemporal dynamics and tidal transport of microplastics in the tropical waters of the Gulf of Thailand

Microplastics (MPs) contamination was investigated along a freshwater-seawater continuum from Chumphon River to the Gulf of Thailand. The vertical distribution in the water column and contamination in green mussels were also studied. MPs were detected in all water samples and sediment samples. Furthermore, MPs were detected in 75% of the green mussels. A higher abundance of MPs was observed in the river system than in the coastal region, indicating that river runoff associated with inland human activities is the major sources of MPs in the coastal regions and cultured green mussels. In the water column, a polymer gradient varying with depth existed where low-density particles decreased from surface to subsurface and sediment while high-density particles exhibited the opposite pattern. Polymers in surface and subsurface water were predominantly composed of low-density polyethylene, polypropylene, and polystyrene particles. However, sediment samples were equally dominated by those mentioned low-density polymers and high-density polyethylene terephthalate, polyamide, rayon, and cotton particles. Furthermore, fibers were the most common shape found in water, sediment, and mussel samples representing 95% of all particles in river water samples and were evenly distributed throughout the water column regardless of density. However, only shorter fiber (mostly <1 mm) was detected in green mussel samples similar to their living environment. Blue, black and white particles dominated all samples. During the tidal cycle, half of the MPs entering the Gulf of Thailand returned to the river during high tide. This backflow predominantly comprised small fibers and low-density polymer MPs. The average daily load of MPs from Chumphon River to the Gulf of Thailand was 3.33 × 102 million items/day.

In vitro and in vivo effects of commercial and environmental microplastics on Unio delicatus

Microplastics (MPs) are ubiquitous pollutants in freshwater environments. In this study, freshwater mussels, Unio delicatus, were exposed to both environmental MPs (e-MP) and commercial MPs (c-MP) that include green fluorescent MP (gf-MP), polyethylene (c-PE) and polystyrene (c-PS) at environmental concentrations (5 mg/L and 50 mg/L) over duration of 7 and 30 days. According to in vivo experiment results, both e-MPs and c-MPs induced significant changes in the total hemocyte counts of mussels (p < 0.05). Exposure to high concentrations of e-MPs and c-MPs for 7 days led to decreased cellular glutathione levels in the mussels, while exposure to low concentrations of e-MPs and c-PS for 7 days resulted in increased advanced oxidation protein products (AOPP). Mussels exposed to high concentrations of e-MPs for 30 days exhibited decreases in both glutathione levels and AOPP values. Although no damage was observed in tissues other than gills and digestive gland, histopathological alterations were observed in these tissues following exposure to 50 mg/L c-MPs. Additionally, MPs were observed in the intestine tissues. In vitro experiments using the MTT assay showed no significant difference in cell viability between the MP-exposed group and the control group at tested concentrations, with no observed dose-response relationship (p > 0.05). Nevertheless, certain cells exhibited signs of cell death, such as disrupted cellular structures, condensed nuclei, and loss of cellular integrity. These observations were consistent with mechanical compression, indicating that physical contact with MPs may result in cell damage or death. These findings demonstrate that environmentally relevant concentrations of MPs have toxic effects on freshwater mussels and multiple parameters provide valuable insight for the evaluation of health risks of organisms.

Spatial and seasonal abundance and characteristics of microplastics along the Red River to the Gulf of Tonkin, Vietnam

This study aimed to examine the occurrence of microplastics in surface water and sediment samples collected from Hanoi to the Ba Lat estuary along the Red River, the second-largest river in Vietnam (surface area: 156,451 km2). 21 stations were sampled during the dry (March 2023) and rainy (September 2023) seasons. The analytical procedure involved: digestion with hydrogen peroxide, flotation with potassium carbonate, and overflow filtration. The filters were analyzed by microscopy (Nikon SMZ645) to describe shapes and colors and by μ-FTIR (PerkinElmer Spotlight 400) to determine polymer types and abundances. Results showed that microplastic quantities throughout the river ranged from 10 to 203 items.m-3 in surface water and from 653 to 8069 and 990 to 21,610 items.kg-1 dried weight (d.w.) in sediment during the rainy and dry seasons, respectively. MPs were classified into two main shape groups: fiber and fragment, with fibers being predominant, representing 82.0 % and 75.5 % of microplastics in water and sediment, respectively. The primary colors identified were white/transparent, black, and blue. Particles between 13 and 200 μm were the predominant size class, accounting for 64.1 % and 72.4 % of the microplastics in water and sediment, respectively. Polyethylene, polypropylene, and polyethylene terephthalate were the main polymers, accounting for 71.5 % and 72.2 % of the microplastics in water and sediment, as revealed by μ-FTIR analyses. Overall, in the Red River, the MP pollution load is moderate, but the type of particles detected represents a high to dangerous polymer risk, resulting in a very high potential ecological risk on the river.

Presence of microplastics during high rainfall events in the Cauvery River (South India): Ecological risk and cultural practices

Rivers directly support the development of a region/country; however, globally, these aquatic regions are impacted by recent human activity. During a rainfall event, we monitored the baseline information on the spatial variability of microplastics (MPs) in the Cauvery River in South India. Forty surface water samples from two selected sites were collected between 27 September and 16 October 2022 during the commencement of monsoon which indicates 69 and 43 pieces L-1 of MPs, respectively. SEM and FTIR analysis on the surface morphotypes (cracks, grooves, pits) and elemental (Si, Ti, Mg, Cu, Ta) presence/adsorption of these elements' (in particle) surface indicates surface deformation of fibers, which is mainly due to external input/forces. Fragments of polymers establish a high degree of deterioration indicating its longer trajectory in the aquatic environment. The origin of extended fiber ranges between 631.65 and 5639.9 µm, which is being associated with laundry activities for textiles, household items, and fishing gear. Toxicity and ecological risk assessment suggest significant degree of weathered MPs due to photo-oxidation process and aging owing to exposition of intense UV light. This research serves as a strong illustration of the multiple pressures from urban development and cultural practices that have a bigger influence on the river ecosystem like Cauvery River and regular monitoring.

Multiple effects of submerged plants on microplastics-heavy metals redistribution and combination in the hyporheic sediment

Submerged plants (SP) in the hyporheic sediment (HS) dynamically alter the spatial distributions of heavy metals (HMs) and microplastics (MPs). In this study, we examined the redistribution and combination of HMs and MPs in the HS surrounding the SP (SSP) and non-nearby the SP (NSP) in the Weihe River Basin. The strong bioconcentration capacity of SP directly caused a decrease of HMs in the SSP (Bioconcentration Factors: SSP>NSP, 1.07 >1.00). Algal proliferation at high nutrient concentrations strengthened the interception of MPs by SP (SSP-MPs >NSP-MPs, 495 >315 items/kg). The significant correlation between SSP-HMs and SSP-MPs indicates the formation of MPs-HMs. The concentration of SSP-HMs was greater than NSP-HMs (Mn (462.95 >437.66 mg/kg)>Zn (63.46 >60.51 mg/kg)>V (53.98 >50.67 mg/kg)>Pb (21.98 >18.47 mg/kg)>As (18.36 >15.65 mg/kg). This finding implies that the MPs trapped by the SP indirectly contribute to elevating SSP-HMs, which showed higher pollution risk (Nemerow Pollution Index: 1.37 >1.22; Contamination Factor: V, 0.87 >0.82, Zn, 0.95 >0.90, As, 1.61 >1.41, Pb, 0.98 >0.88). Furthermore, SP can reduce NSP contamination by proactively collecting pollutants into SSP, endangering the integrity of rivers through the ingesting of hydrobiont. Our study provides theoretical suggestions for the application of SP to improve ecological health in the complex environment.

Risk assessments of microplastic exposure in bivalves living in the coral reefs of Vietnam

This study aimed to assess the presence of microplastics in bottom sediment and bivalve species, including Pinna bicolor, Atrina vexillum, Saccostrea sp., and Pinctada margaritifera, living in coral reefs on Vietnam's Southern coastal. The average microplastic abundance were 0.45 ± 0.13 items/g of wet soft tissue weight or 5.60 ± 1.49 items/individual in bivalve samples and 294 ± 43 items/kg dry weight of sediment samples. The fragment shape, size smaller than 100 μm, and polyethylene, polyamide, cellophane and polyethylene terephthalate were identified as the predominant constituents of the microplastics. The pollution load and potential ecological risk index of microplastics were at a minor level, whereas the polymer hazard index was at a high level. Overall, this study provides a basis for assessing the risks posed by microplastics in the marine ecosystems of Vietnam.

Microplastics contamination and risk assessment in bivalves of economic importance from Beypore estuary, Southern India

Microplastics (MPs) are ubiquitous pollutant causing severe threat to the biotic and abiotic components of the coastal ecosystem. Accumulation of MPs in the commercially important bivalves Viz. Perna viridis (green mussel) and Meretrix casta (clam) collected from four different locations of Beypore estuary, Southern India was studied. The study focused on the accumulation, characteristics, diversity indices, and human health risk assessment of MPs in the bivalves of Beypore estuary. A total of 120 bivalve samples were examined for the MPs contamination. Whole tissue digestion method using 10% KOH was employed to retrieve the MP content. The results indicate that the average abundance of MPs in Perna viridis is 2.38 ± 1.56 MPs/individual and 0.15 ± 0.09 MP/g/wet weight whereas, for Meretrix casta it is 1.35 ± 1.02 MPs/individual and 0.3 ± 0.27 MP/g/wet weight. Spearman's correlation reveals that there is no significant correlation observed between the abundance of MPs in the bivalves with their morphomertric parameters. The characteristics of MPs in the bivalves are dominated by translucent colored particles (88.95%) in the form of films (45.13%) and fibers (33.6%) having a size ranged between 300 and 1000 μm (51.13%) and composed of polyethylene (54.5%) and polypropylene (20%) polymers. The microplastic index in Meretrix casta ranged between 0.02 and 0.07 whereas for Perna viridis it ranged between 0.08 and 0.10 indicating minimal to moderate MPs contamination. The microplastics diversity integrated index ranged between 0.67 and 0.69 for Meretrix casta whereas, for Perna viridis the value ranged between 0.34 and 0.60 suggests moderate diversity of MPs derived from multiple sources. Based on polymer hazard index, the potential health risk was assessed with a hazard level ranged between II and IV suggesting significant health risk. Systematic monitoring of MPs at river basin scale along with stringent plastic waste management is required to minimize plastic pollution load into the river system.

Characterization of microplastics in soil, leachate and groundwater at a municipal landfill in Rayong Province, Thailand

Recent years have witnessed a dramatic increase in global plastic production, leading to heightened concerns over microplastics (MPs) contamination as a significant environmental challenge. MP particles are ubiquitously distributed across both continental and marine ecosystems. Given the paucity of research on MPs in Thailand, particularly regarding MPs contamination in terrestrial environments, this study focused on investigating the distribution and characteristics of MPs in a landfill area. We collected 15 soil samples, 2 leachate samples, and 7 groundwater samples from both inside and outside a municipal landfill situated in the urbanized coastal region of Rayong Province. Our findings revealed variability in MPs concentration across different sample types. In soil, the MP count ranged from 240 to 26,100 pieces per kg of dry soil, 58.71 % of all sample sizes are lower than 0.5 mm. Similarly, the size found in the leachate sample, and the average MP in the leachate samples was 139 pieces per liter of MPs. The groundwater samples showed a fluctuation in MPs count from 18 to 94 pieces per liter, and the size of MPs ranged mostly from 0.5 to 1 mm. The predominant forms of MPs identified were sheets, followed by fragments, fibers, and granules. According to μ-FTIR analysis, the majority of the MPs were composed of polyethylene and polypropylene, commonly used in plastic packaging and ropes. The observed high concentrations and extensive distribution of MP contamination underscore the urgency for further studies and effective management strategies to mitigate the adverse impacts of this pollution on various organisms and ecosystems.

Occurrence and migration patterns of microplastics in different tidal zones of tourist beaches: A case study in the Bohai Bay, North China

Coastal areas are acknowledged to be significant reservoirs of microplastics, while limited research on their presence and migration in the intertidal zones. This study investigated in a tourist beach in northern China, to reveal the occurrence of microplastics at different intertidal heights, elucidates their migration patterns, and discusses the impact of tourist activities on microplastics. Results showed that the mean microplastic abundance was 2114.8 ± 933.2 items/kg in sediments and 30,670.8 ± 15,094.9 items/m3 in seawater. Fibers were the most common shape; transparent, blue, green and black prevailed in color; and cellulose and PET were the most common components. Microplastic abundances decreased from high tide zone to low tide zone, and the abundances of microplastics in seawater were positively correlated with those in the high tide zone and negatively correlated with those in the low tide zone. Compared to wave disturbance, human activities have a relatively limited impact on microplastic abundance. However, intensive tourist activities contribute to a higher diversity of microplastic types on tourist beaches. This study enhances the understanding of the occurrence and migration patterns of microplastics in tourist beaches, and provides a valuable dataset and theoretical basis for subsequent research on microplastic pollution in coastal areas.

Microplastics in commercial bivalves from coastal areas of Thailand and health risk associated with microplastics in ingested bivalves

Microplastics (MPs) contamination in marine organisms is a significant threat to seafood consumers worldwide. This study is the first to investigate the abundance of MPs in the commercial bivalves from six sites along Thailand's coastline, the daily exposure of bivalve consumers to MPs, and potential associated health risks. The microplastic occurrence varied from 69 % to 93 % in four bivalve species while the average abundance of MPs was 1.87 ± 0.86 items/individual or 0.46 ± 0.43 items/g ww. Benthic bivalves (cockles and clams) contained more MPs than their pelagic counterparts (mussels and oysters). Small blue microfibers (<500 μm) were the most abundant. The most common polymers were natural based polymers (cotton and rayon) and polyethylene terephthalate (PET). The daily microplastic exposure for consumers was 0.52 items/person. Although the risk of microplastic contamination is low, we recommend investigation into the transfer of MPs within the food web, notably as it may pose significant human health concerns.

Microplastic pollution in coastal surface seawater of Southern Vietnam

Microplastics have recently emerged as a significant environmental concern due to their direct impacts on marine ecosystems. Vietnam, with its 3260-km coastline, faces an elevated risk of microplastic pollution due to various coastal anthropogenic activities. This study explored microplastic distribution in coastal surface seawater in the Southern Vietnam regions of Tien Giang, Can Gio, and Vung Tau. A total of 45 samples were collected in April, 2019, and the results showed that microplastics present at all sampling sites, with the abundance varying from 0.074 ± 0.109 pieces/m3 in Can Gio to 0.56 ± 0.35 pieces/m3 in Tien Giang. Estuarial sites showed higher abundances for all regions. Most microplastics were under 2.8 mm, fragmented, and primarily white or transparent. Polypropylene, polyethylene, and ethylene-vinyl acetate were the dominant polymers. This research indicates the urgency of further investigations to comprehensively understand the influence of wind patterns and other environmental factors on microplastic distribution.

Microplastic's Contamination in the Hemolymph and Organs (Gills and Hepatopancreas) of Perna viridis

The issue of microplastics (MPs) has emerged as a significant concern globally, with discussions surrounding the potential environmental impact of these tiny plastic particles becoming increasingly prevalent. This study aimed to identify the concentration and characteristics of MPs in hemolymph and organs (gills and hepatopancreas) of green mussels (Perna viridis) that are frequently consumed by people in Pangkajene Kepulauan, South Sulawesi Province, Indonesia. Green mussels were collected from two different sampling sites for comparison. Screening was carried out on dispensed hemolymph and dissected organs to identify the characteristics of MPs. Surface seawater sampling was added as information on MP's characteristics from the mussel habitat. Visual observation of MP's characteristics using a stereomicroscope in laminar flow is to prevent contamination. The identification of MP's polymer type is using FTIR-ATR. The results showed that hemolymph, hepatopancreas, gills, and surface water were concentrated with MPs. Small (2-3.9 cm) green mussels accumulated more MPs than medium (4-5.9 cm) and large (> 6 cm). MPs characteristics of fiber shape, transparent color, and size 0.1-0.5 mm were dominant in all samples. A total of seven polymers of MPs were identified with polyethylene and polystyrene types most frequently found from all samples. Based on this study, green mussels are good for biomonitoring of MPs.

Potential risks of accumulated microplastics in shells and soft tissues of cultured hard clams (Meretrix taiwanica) and associated metals

Microplastics (MPs) pose risks to both aquatic ecosystems and human health. This study investigated MPs in the shells and soft tissues of hard clams (Meretrix taiwanica) cultured in the inland waters of Taiwan. This study further developed two novel risk indices for assessing the potential ecological and health consequences of MPs. Moreover, the metal concentrations in the clam's soft tissues and the associated consumption health risks were investigated. Clamshells contained significant amounts of MPs with an average abundance of 16.6 ± 6.9 MPs/ind., which was higher than in the soft tissues (2.7 ± 1.7 MPs/ind.). The distribution and sizes of MPs in shells and soft tissues were similar, primarily small-sized (<2 mm, >99 %), blue (>65 %), and fibrous (>99 %). Dominant MP polymer types included rayon (83.5 %), polyethylene terephthalate (11.8 %), and polyacrylonitrile (3.6 %). The proposed MP potential ecological risk index indicates a higher potential ecological MP risk in soft tissues (302-423) than in shells (270-278) of the clams. The MP potential hazard risk index showed that the risk of exposure to MP through shellfish consumption decreased with age. The total hazard index (THI) value suggested negligible health hazards from metal exposure through shellfish consumption. Moreover, there was no significant correlation between MPs and metal concentrations in soft tissues, suggesting that metals bound to MPs contribute minimally to the total accumulated metals in clam's soft tissues. This study confirms the presence of MPs in clam shells and provides a novel tool to assess the potential ecological and health risks associated with MPs in shellfish.

First-of-Its-Kind: Nationwide meta-analysis of microplastic pollution and risk assessment in Thailand

Thailand ranks as the sixth largest contributor to global microplastic pollution, which is exacerbated by extensive plastic use. Despite rising concerns, no comprehensive review is available on microplastic contamination and its potential risk in Thailand. This review synthesised data on microplastic abundance and characteristics within the country from 118 peer-reviewed publications (2017-2024). We found predominant microplastic presence in crustaceans (1.69-160.15 items/g), followed by Mollusca (0.03-9.5 items/g) and fishes (0.01-28.17 items/g), with higher abundances in wastewater (4 × 102 to 6.09 × 105 items/m3) compared to that in freshwater (1.44-2.92 × 106 items/m3) and seawater (2.70 × 10-1 to 6.25 × 104 items/m3). Marine sediments (48.3-2.13 × 104 items/kg) also showed significantly higher microplastic concentrations than terrestrial sediments (3-2.92 × 103 items/kg). Predominant microplastics were identified as fibers (59.36% and 35.05% for biological and environmental samples, respectively) and fragments (24.14%, 30.68%) in blue (25.95%, 18.64%), and colourless/transparent (20.01%, 14.47%), primarily composed of polyethylene terephthalate (19.46%, 9.19%), nylon (3.23%, 9.99%), polypropylene (19.78%, 24.23%), and polyethylene (14.81%, 11.66%). The potential ecological risk was low in all ecosystems except for wastewater. Shrimp and fish were more susceptible to microplastics compared to other studies in the region. Additionally, the sources, transport, and pathways of microplastic pollution in Thailand's aquatic territories and the current measures and policies implemented by the government to address plastic pollution are discussed. This review has compiled up-to-date insights into the prevalence, distribution, and risks associated with microplastics, which is instrumental in formulating effective strategies for contaminant control and ultimately reducing plastic pollution.

Occurrence of microplastics in store-bought fresh and processed clams in Italy

Compared to the large amount of data on wild samples, only a few studies reported microplastic occurrence in store-bought bivalves in which the production chain can be the main contamination route. Microplastic occurrence was herein investigated in 100 samples of store-bought clams sold as fresh or processed (vacuum-frozen or in brine) in Italy. A 10 % KOH was used for soft tissue digestion and FT-IR spectroscopy for polymer identification. A total of 135 potential microplastics ranging in size between 20 μm and 5000 μm were enumerated estimating an annual dietary intake via clam consumption of 59.472 microplastics/person. No significant difference in the average abundance between the two commercial conditions was observed, while a prevalence of smaller particles was detected in processed samples suggesting a detrimental effect of cooking during production. Polyethylene (PE), polyethylene terephthalate (PET), and polystyrene (PS) were identified posing an overall low risk (class II). Microplastic occurrence in store-bought seafood requires additional and specific attention and future studies should investigate microplastic contribution linked to the production chain.

Occurrence and abundance of microplastics in surface water of Songkhla Lagoon

Background

Microplastic (MP) pollution is now a global critical issue and has been the subject of considerable worry for multiple various types of habitats, notably in lagoons which are coastal areas connected to the ocean. MPs are of concern, particularly because floating MP in surface water can be ingested by a number of marine organisms. There are several lagoons along Southeast Asia's coastline, but Songkhla Lagoon is Thailand's only exit with a rich biodiversity. To date, there has been little research undertaken on MP in this lagoon, so there is a pressing need to learn more about the presence of MP in the lagoon's water.

Methods

We investigate MPs in the surface water of Songkhla Lagoon, Thailand. Sampling took place at ten stations in the lagoon during the wet season in December 2022 and the dry season in February 2023. Samples were digested with hydrogen peroxide to remove organic matter followed by density separation using saturated sodium chloride. MPs were visually examined under a stereo microscope to describe and determine the shape, size, and color. Polymer type was identified using a micro Fourier transform infrared (FTIR) spectrometer. Moreover, the in-situ of water quality of the surface water was measured using a multi-parameter probe. A Mann-Whitney U test was performed to investigate the variations in MP levels and water quality parameters between the wet and dry seasons. Correlation analysis (Spearman rho) was used to determine the significance of correlations between MP and water quality (p < 0.05).

Results

MPs were detected at all ten of the sites sampled. The most abundant MPs were small size class (<500 µm, primarily consisting of fibers). Five types of polymers were seen in surface water, including polyethylene terephthalate, rayon, polypropylene, polyester, and poly (ethylene:propylene). Rayon and polyester were the dominant polymers. Additionally, the most dominant color of MPs in the wet and dry season was black and blue, respectively. The mean contents of MPs in the wet and dry season were 0.43 ± 0.18 and 0.34 ± 0.08 items/L, respectively. The Mann-Whitney U test suggested a significant difference between water quality in the wet and dry seasons (p < 0.05). Correlation analysis (Spearman rho) indicated a negative significant difference relationship between the MPs and the values of total dissolved solid (TDS) in the wet season (r = -0.821, p = <0.05), revealing that the large amounts of MPs may possibly be dispersed within surface water bodies with low TDS concentrations. Based on the overall findings, MP pollution in the surface water of the lagoon is not found to be influenced by the seasonal context. Rivers flowing into the lagoon, especially the U-Taphao River, may be a principal pathway contributing to increased MP pollution loading in the lagoon. The results can be used as baseline data to undertake further research work relevant to sources, fates, distribution, and impacts of MPs in other coastal lagoons.

Beneath the surface: Exploring microplastic intricacies in Anadara granosa

Anadara granosa or blood cockles have been reported to be a candidate for biomonitoring agents due to their sedimentary nature and their nutrient uptake mechanisms. Yet, this bivalve is still regarded as a delicacy in Asian cuisine. Malaysia is the largest exporter of this sea product that contaminated cockles may also be experienced by the importing countries. However, the bioaccumulation of microplastics in A. granosa cultivated in Malaysia has not been extensively studied. It is crucial to comprehend the risk posed to humans by consuming A. granosa in their diet. Therefore, the purpose of this research is to investigate the levels of microplastic accumulation in A. granosa from major exporters in Peninsular Malaysia, to evaluate the associated risk of microplastics on the species, and to estimate daily human consumption of microplastics through the consumption of A. granosa. The abundance of microplastics was quantified through the use of a stereo microscope, and the polymer type was determined using FTIR and micro-FTIR. Findings from this investigation revealed that all samples of A. granosa were contaminated with microplastics, with the highest levels of accumulation found in bivalves collected from the west coast (0.26 ± 0.15 particles/g) of Peninsular Malaysia. Fragment and fiber microplastics, measuring between 0.05 and 0.1 mm in size, were found to be the most prevalent in A. granosa, with blue being the dominant identified colour and rayon being the most common polymer type. Microplastic risk assessment due to the presence of polyacrylate, polycarbonate (PC), and polymethyl methacrylate (PMMA) resulted in a high risk of contamination for A. granosa. It was further determined that the current estimated dietary intake (EDI) suggests that consumers of A. granosa uptake approximately 21.8-93.5 particles/person/year of microplastics. This study highlights that A. granosa accumulates microplastics, which could potentially result in bioaccumulation and biomagnification in humans through consumption.

Microplastics pollution in the Surma River, Bangladesh: A rising hazard to upstream water quality and aquatic life

The ecological health of freshwater rivers is deteriorating globally due to careless human activities, for instance, the emission of plastic garbage into the river. The current research was the first assessment of microplastics (MPs) pollution in water, sediment, and representative organisms (fish, crustacean, and bivalve) from the Surma River. Water, sediment, and organisms were sampled from six river sites (Site 1: Charkhai; Site 2: Golapganj; Site 3: Alampur; Site 4: Kazir Bazar; Site 5: Kanishail and Site 6: Lamakazi), and major water quality parameters were recorded during sampling. Thereafter, MPs in water, sediment, and organism samples were extracted, and then microscopically examined to categorize selected MPs types. The abundance of MPs, as well as size, and color distribution, were estimated. Polymer types were analyzed by ATR-FTIR, the color loss of MPs was recorded, the Pollution Load Index (PLI) was calculated, and the relationship between MPs and water quality parameters was analyzed. Sites 4 and 5 had comparatively poorer water quality than other sites. Microplastic fibers, fragments, and microbeads were consistently observed in water, sediment, and organisms. A substantial range of MPs in water, sediment, and organisms (37.33-686.67 items/L, 0.89-15.12 items/g, and 0.66-48.93 items/g, respectively) was recorded. There was a diverse color range, and MPs of <200 μm were prevalent in sampling areas. Six polymer types were identified by ATR-FTIR, namely Polyethylene (PE), Polyamide (PA), Polypropylene (PP), Cellulose acetate (CA), Polyethylene terephthalate (PET), and Polystyrene (PS), where PE (41%) was recognized as highly abundant. The highest PLI was documented in Site 4 followed by Site 5 both in water and sediment. Likewise, Sites 4 and 5 were substantially different from other study areas according to PCA. Overall, the pervasiveness of MPs was evident in the Surma River, which requires further attention and prompt actions.

Terrestrial wildlife as indicators of microplastic pollution in western Thailand

Plastic pollution in terrestrial wildlife represents a new conservation challenge, with research in this area, especially within protected areas (PAs), being scant. This study documents the accumulation of microplastics (MPs) in terrestrial wildlife both inside and outside PAs in western Thailand. Carcasses of road-killed vertebrates in good condition, as well as live tadpoles, were collected to examine their exposure to plastic pollution. The digestive tracts of the vertebrate carcasses and the entire bodies of tadpoles were analyzed for MPs, which were identified if they measured over 50 µm. A total of 136 individuals from 48 vertebrate species were examined. The sample comprised snakes (44.12%), birds (11.03%), lizards (5.15%), tadpoles (32.25%), amphibians (5.88%), and mammals (1.47%). In total, 387 MPs were found in 44 species (91.67%), with an average occurrence of 3.25 ± 3.63 MPs per individual or 0.05 ± 0.08 MPs per gram of body weight. The quantities of MPs significantly varied among the animal groups, both in terms of number per individual (p < 0.05) and number per gram of body weight (p < 0.01). Furthermore, a significant difference in MP quantities was observed between specimens collected inside and outside PAs on an individual basis (p < 0.05), but not on a body weight basis (p = 0.07). Most MPs were fibers (77%), followed by fragments (22.22%), with only a minimal presence of film (0.52%) and foam (0.26%). Of all the MPs identified, 36.84% were confirmed as plastics or fibers made from natural materials, and 31.58% were plastics, including Polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), Polyvinylidene chloride (PVDC), and polyester (PES). Additionally, fibers made of cotton, and those containing polyurethane (PU), rayon, PES, and combinations of rayon and PU, were identified. The quantities of MPs were significantly influenced by animal body weight, factors associated with human settlement/activity, and land use types. Our findings highlight the prevalence of plastic pollution in terrestrial vertebrates within Thai PAs. Further toxicological studies are required to establish plastic pollution standards. It is proposed that snakes, obtained from road kills, could serve as a non-invasive method for monitoring plastic pollution, thus acting as an indicator of the pollution threat to species within terrestrial ecosystems. There is an urgent need for the standardization of solid waste management at garbage dump sites in remote areas, especially within PAs. Conservation education focusing on MP occurrence, potential sources, and impacts could enhance awareness, thereby influencing changes in behaviors and attitudes toward plastic waste management at the household level.

Microplastics in aquatic ecosystems of Africa: A comprehensive review and meta-analysis

Microplastic pollution is a global issue of great public concern. Africa is flagged to host some of the most polluted water bodies globally, but there is no enough information on the extent of microplastic contamination and the potential risks of microplastic pollution in African aquatic ecosystems. This meta-analysis has integrated data from published articles about microplastic pollution in African aquatic ecosystems. The data on the microplastic distribution and morphological characteristics in water, sediments and biota from African rivers, lakes, oceans and seas were extracted from 75 selected studies. Multivariate statistics were used to critically analyze the effects of sampling and detection methods, ecological risks, spatial distribution and similarity of microplastics in relation to the geographical distance between sampling sites. This study found that sampling methods have significant effect on abundance and morphological characteristics of microplastics and that African aquatic ecosystems are highly contaminated with microplastics compared to global data. The most prevalent colors were white, transparent and black, the most prevalent shapes were fibres and fragments, and the most available polymers were polypropylene (PP), polystyrene (PS) and polyethene terephthalate (PET). Microplastic polymers similarity decreased with an increase in geographical distance between sites. Risk levels of microplastics in African aquatic ecosystems were comparatively high, and more than 40 % of water and sediments showed highest level of ecological risk. This review provides recent information on the prevalence, distribution and risks of microplastics in African aquatic ecosystems.

Microplastic contamination in different shell length in Tivela mactroides (Born, 1778)

Microplastic identification and distribution throughout oceans has become a great concern due to its substantial uprising and its consequent interactions with marine biota. Microplastics can be absorbed and adsorbed by several marine species owing to their very small size. Among these organisms are bivalves, including ones used as food for humans. In this context, this research aims to understand the absorption scale of microplastics by Tivela mactroides according to their size and consequently life stage. Thus, T. mactroides mussels were collected at Camburi Beach (Brazil) and grouped into 30 different size classes from 06 to 35 mm. Later, 20 specimens from each size class (N = 600) had the soft tissues removed and a pool was performed through digestion with 10 % KOH solution. Results showed the presence of microplastics in all size classes of T. mactroides, evidencing that organisms from 06 mm can already be contaminated by microplastics and a tendency of the number of microplastics particles to increase as shell size increases. Furthermore, the amount of blue filament-type MPs was significantly higher than the other types and colors. Additionally, analyzes performed by Raman spectroscopy showed that the blue filaments have a PET composition. Finally, larger individuals presented larger quantities of MPs, as well as larger filaments. This might suggest that there are differences between the assimilation of the size of MPs in the different size classes, i.e. that size makes a difference.

The comparative plastisphere microbial community profile at Kung Wiman beach unveils potential plastic-specific degrading microorganisms

Background

Plastic waste is a global environmental issue that impacts the well-being of humans, animals, plants, and microorganisms. Microplastic contamination has been previously reported at Kung Wiman Beach, located in Chanthaburi province along with the Eastern Gulf of Thailand. Our research aimed to study the microbial population of the sand and plastisphere and isolate microorganisms with potential plastic degradation activity.

Methods

Plastic and sand samples were collected from Kung Wiman Beach for microbial isolation on agar plates. The plastic samples were identified by Fourier-transform infrared spectroscopy. Plastic degradation properties were evaluated by observing the halo zone on mineral salts medium (MSM) supplemented with emulsified plastics, including polystyrene (PS), polylactic acid (PLA), polyvinyl chloride (PVC), and bis (2-hydroxyethyl) terephthalate (BHET). Bacteria and fungi were identified by analyzing nucleotide sequence analysis of the 16S rRNA and internal transcribed spacer (ITS) regions, respectively. 16S and ITS microbiomes analysis was conducted on the total DNA extracted from each sample to assess the microbial communities.

Results

Of 16 plastic samples, five were identified as polypropylene (PP), four as polystyrene (PS), four as polyethylene terephthalate (PET), two as high-density polyethylene (HDPE), and one sample remained unidentified. Only 27 bacterial and 38 fungal isolates were found to have the ability to degrade PLA or BHET on MSM agar. However, none showed degradation capabilities for PS or PVC on MSM agar. Notably, Planococcus sp. PP5 showed the highest hydrolysis capacity of 1.64 ± 0.12. The 16S rRNA analysis revealed 13 bacterial genera, with seven showing plastic degradation abilities: Salipiger, Planococcus, Psychrobacter, Shewanella, Jonesia, Bacillus, and Kocuria. This study reports, for the first time of the BHET-degrading properties of the genera Planococcus and Jonesia. Additionally, The ITS analysis identified nine fungal genera, five of which demonstrated plastic degradation abilities: Aspergillus, Penicillium, Peacilomyces, Absidia, and Cochliobolus. Microbial community composition analysis and linear discriminant analysis effect size revealed certain dominant microbial groups in the plastic and sand samples that were absent under culture-dependent conditions. Furthermore, 16S and ITS amplicon microbiome analysis revealed microbial groups were significantly different in the plastic and sand samples collected.

Conclusions

We reported on the microbial communities found on the plastisphere at Kung Wiman Beach and isolated and identified microbes with the capacity to degrade PLA and BHET.

Microplastics, their abundance, and distribution in water and sediments in North Chennai, India: An assessment of pollution risk and human health impacts

Plastic particles, measuring <5 mm in size, mainly originate from larger plastic debris undergoing degradation, fragmenting into even smaller fragments. The goal was to analyze the spatial diversity and polymer composition of microplastics (MPs) in North Chennai, South India, aiming to evaluate their prevalence and features like composition, dimensions, color, and shape. In 60 sediment samples, a combined count of 1589 particles were detected, averaging 26 particles per 5 g-1 of dry sediment. The water samples from the North Chennai vicinity encompassed a sum of 1588 particles across 71 samples, with an average of 22 items/L. The majority of MPs ranged in size from 1 mm to 500 μm. The ATR-FTIR results identified the predominant types of MPs as polystyrene, polyvinyl chloride, polyethylene, polyethylene terephthalate, and polypropylene in sediment and water. The spatial variation analysis revealed high MPs concentration in landfill sites, areas with dense populations, and popular tourist destinations. The pollution load index in water demonstrated that MPs had contaminated all stations. Upon evaluating the polymeric and pollution risks, it was evident that they ranged from 5.13 to 430.15 and 2.83 to 15,963.2, which is relatively low to exceedingly high levels. As the quantity of MPs and hazardous polymers increased, the level of pollution and corresponding risks also escalated significantly. The existence of MPs in lake water, as opposed to open well water, could potentially pose a cancer risk for both children and adults who consume it. Detecting MPs in water samples highlights the significance of implementing precautionary actions to alleviate the potential health hazards they create.

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

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

Evaluation of the microplastics in bivalves and water column at Pantai Teluk Likas, North Borneo, Malaysia

Microplastics (MPs) are a pervasive pollutant in the marine environment. Pantai Teluk Likas in Sabah, Malaysia is one of the most visited beaches where tourism, recreational, and fisheries activities are high in this area. Hence, the area suffers from severe pollution, particularly from plastics. This study aims to quantify the microplastic composition in terms of color, shapes, and polymer types in marine bivalves (Anadara granosa, Glauconome virens, and Meretrix lyrata) and water column samples from Pantai Teluk Likas. All samples were digested using sodium hydroxide (NaOH) and incubated in the oven for at least 48 h. Serial filtration was done for each sample before they were observed under the dissecting microscope. The microplastics were identified and counted based on their physical attributes which were colors and shapes. The functional group of the polymers was determined using FTIR spectroscopy. Microplastics were found present in all samples collected. G. virens had the highest abundance of microplastics at 113.6 ± 6.5 particles/g followed by M. lyrata at 78.4 ± 3.7 particles/g. On the contrary, A. granosa had the least microplastics with an abundance of 24.4 ± 0.6 particles/g. Meanwhile, 110.0 ± 36.2 particles/L of microplastics were found in water column samples from Pantai Teluk Likas. Based on the analysis, fibers were the most common shape in bivalves, while fibers and films were common in the water column. In terms of colors, black, blue, and red were a few of the most abundant colors observed in both samples. The most common polymer detected in all bivalve species and water column samples is polycarbonate (PC), followed by polymethyl methacrylate (PMMA). Future study that focuses on the correlation between microplastic abundance in the marine biota and the water column is recommended to better understand microplastic availability and exposure.

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

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

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.

Microplastic particles in river sediments and water of southwestern Nigeria: insights on the occurrence, seasonal distribution, composition, and source apportionment

Microplastics (MPs) are globally recognized as an emerging environmental threat, particularly in the aquatic environment. This study presents baseline data on the occurrence and distribution of MPs in sediments and surface water of major rivers in southwestern Nigeria. Microplastics were extracted by density separation and polymer identification using Fourier transformed infrared spectroscopy in attenuated total reflectance mode (FTIR-ATR). The abundance of MPs in surface sediment and water samples across all locations ranged from 12.82 to 22.90 particle/kg dw and 6.71 to 17.12 particle/L during the dry season and 5.69 to 14.38 particle/kg dw and 12.41 to 22.73 particle/L during the wet season, respectively. On average, fiber constituted the highest percentage of MP in sediments (71%) and water (67%) while foam accounted for the lowest values of 0.6% and 1.7%, respectively. Polypropylene (PP) and polyethylene (PE) were the main MPs across all locations based on Fourier transform infrared spectroscopy (FTIR). MPs of size < 1 mm were the most abundant (≥ 55%) on average in both water and sediments. The study identified run-off from human activities and industrial wastewater as potential sources of MP exposure based on positive matrix factorization. The study suggests assessing the impact of different land-use activities on MPs occurrence and distribution in addition to quantifying MPs in seafood as a way forward in food safety management systems for further studies. This study confirmed the occurrence and widespread distribution of MPs in surface water and sediments and provides a database on MP pollution in Nigeria.

Research progress on occurrence characteristics and source analysis of microfibers in the marine environment

Synthetic microfiber pollution is a growing concern in the marine environment. However, critical issues associated with microfiber origins in marine environments have not been resolved. Herein, the potential sources of marine microfibers are systematically reviewed. The obtained results indicate that surface runoffs are primary contributors that transport land-based microfibers to oceans, and the breakdown of larger fiber plastic waste due to weathering processes is also a notable secondary source of marine microfibers. Additionally, there are three main approaches for marine microplastic source apportionment, namely, anthropogenic source classification, statistical analysis, and numerical simulations based on the Lagrangian particle tracking method. These methods establish the connections between characteristics, transport pathways and sources of microplastics, which provides new insights to further conduct microfiber source apportionment. This study helps to better understand sources analysis and transport pathways of microfibers into oceans and presents a scientific basis to further control microfiber pollution in marine environments.

Catch assemblages in the small-scale trap fishery with relation to hydrographic features of a tropical bay in the Gulf of Thailand

Catches from the small-scale trap fishery in Bandon Bay, Suratthani, Thailand, were monitored from 14 sites around the Bay, then disturbance to aquatic communities and catch assemblage were examined. At the same time, the hydrographical features of the bay were surveyed. The study was conducted throughout 2019 except in December, when a tropical cyclone made sampling impossible. In total, 17,373 animals from 118 species or species groups of aquatic animals were collected. The main target of the fishery, blue swimming crab Portunus pelagicus, contributed about 10% of the total catch in terms of number; meanwhile, another crab, Charybdis affinis, was the most dominant species (41% of total). W-statistics of Abundance-Biomass Comparison curves ranged between -0.025 and 0.031, indicating light disturbance to the communities in this fishing ground. The catch assemblage, based on number in catch composition, were divided into three main clusters and six sub-clusters by using the self-organizing map (SOM) technique. The SOM results showed that the catch assemblages differed based largely on temporal variation. The hydrographic features of Bandon Bay at times exhibited a layered structure and had strong spatial variation. The bay's current system was governed by motion of tidal currents; meanwhile, the circulation was governed by monsoonal wind and freshwater discharges. Tidal current was strong and ranged between approximately 0.6 m to 2.2 m. Water within the bay was always warmer than the outer sea. High water temperature was observed two times during the year: during monsoon transition 1 (April to May) and transition 2 (October). Salinity showed great spatial and temporal variation, differing by more than 5-10 ppt horizontally. It was possible to use these dynamic hydrological features of Bandon Bay to explain assemblage patterns of the trap-net catches.

Seasonal variation in the abundance of microplastics in three commercial bivalves from Bandon Bay, Gulf of Thailand

This study investigated the abundance of microplastics in three commercial bivalves found at Bandon Bay. Spatial-temporal differences in the concentration of microplastics were evaluated during the dry and wet seasons. The results showed that the highest abundance of microplastics in oysters, blood cockles, and green mussels was observed in fishery and aquaculture areas during the dry season, with 1.42 particles/g (w/w), 1.01 particles/g (w/w) and 0.87 particles/g (w/w), respectively. Microplastics were more abundant during the dry season compared to the wet season (p < 0.05), with fibre being the predominant shape and black being the major colour of particles. Cellophane was the most common type of polymer in all bivalves. This result is an important reference for understanding the status of microplastics in three commercial bivalves during different seasons and in different human activities, which should aid in understanding the sources of microplastics in Bandon Bay.

Microplastic pollution and regulating factors in the surface sediment of the Xuande Atolls in the South China Sea

Microplastics are widely present in the marine environment, but their pollution and potential risk assessment in the seabed sediments have not been well addressed in remote sea areas. In this study, microplastics in 50 surface sediment samples from the Xuande Atolls at the Xisha of the South China Sea were studied. There were 20 samples with detectable microplastics of 5-20 items kg-1. They were all fibers in shapes and blue/transparent in colors with the dominant chemical component of polyester and the typical size of 0.02-3 mm. We found a large spatial variability of microplastic abundance in the surface sediment with generally low or undetectable levels in the lagoon deposits and the offshore deep-sea sediments but elevated abundances in the slope sediments of the Xuande Atolls. Correlation analyses suggested that microplastic variability in the Xisha sediment was less affected by local environmental parameters such as water depth, sediment particle size, organic carbon content, and sediment types. We also found that elevated microplastics in the seabed sediments on various sides of the Xuande Atolls could be related to the seasonal change in monsoon-driven currents. Finally, a low risk of microplastic pollution in the surface sediment of the Xisha is concluded based on the assessments of the polymer hazard index and the pollution load index. These findings provide not only a baseline understanding of microplastics but also their dynamics in the surface sediment of the remote Xisha area of the South China Sea.

Distribution, characterization and contamination risk assessment of microplastics in the sediment from the world's top sediment-laden estuary

Microplastics (MPs) have gained a serious attention as an emerging contaminant throughout the world because of their persistence and possible risks to aquatic ecosystems and human well-being. However, knowledge on MPs contamination from sub-tropical coastal systems is limited, and no study has been conducted on the MPs contamination in sediment from one of the highest sediment-laden estuaries, Meghna River, in the world. This is the first study to examine the quantity, morpho-chemical characteristics and contamination risk level of MPs from this large scale river. MPs were extracted from the sediment samples of 10 stations along the banks of the estuary by density separation, and then characterized using a stereomicroscope and Fourier Transform Infrared (FTIR) spectroscopy. The incidence of MPs varied from 12.5 to 55 item/kg dry sediment with an average of 28.67 ± 10.80 item/kg. The majority (78.5%) of the MPs were under 0.5 mm in size, with fibers being the most (74.1%) prevalent MPs type. Polypropylene (PP) was found to be the predominant polymer (53.4%), followed by polyethylene (PE, 20%), polystyrene (PS, 13.3%), and polyvinyl chloride (PVC, 13.3%). The highest occurrence of PP indicted the MPs in the estuary might be originated from clothing and dying industries, fishing nets, food packages, and pulp industries. The sampling stations were contaminated with MPs as shown by the contamination factor (CF) values and pollutant load index (PLI), both of which were >1. This study exposed new insights on the status of MPs in the sediments of the Meghna River, laying the groundwork for future research. The findings will contribute to estimate the global share of MPs to the marine environment.

Microplastics in marine-derived traditional Chinese medicine, potential threat to patients

Microplastics (MPs) contamination is widely found in marine organisms. Marine traditional Chinese medicines (MTCM) are derived from marine organisms, but there are no relevant reports on detecting MPs in MTCM. This study selected samples of MTCM from two representative pharmaceutical companies, Brand F and Brand Z, including mother-of-pearl, stone cassia, seaweed, pumice, oyster, kombu, calcined Concha Arcae, cuttlebone, and clam shell to detect and analyze the presence of MPs. The abundance, type, color, size, and composition of MPs were investigated. Varying degrees of MPs contamination was present in all MTCM. The abundance of MPs in different MTCM ranged from 0.07 to 9.53 items/g. Their type, color, and size are similar, mainly fiber, transparent and size <2 mm. The composition of MPs is primarily made of cotton, cellulose and rayon. This study contributes to the first record of MPs in MTCM. Our results show that microplastic pollution is common in MTCM, which may cause potential risk to patients consuming MTCM.

Microplastics in water from the confluence of tropical rivers: Overall review and a case study in Paraiba do Sul River basin

Rivers are known for carrying out a fundamental role in the transportation of human debris from continental areas to the marine environment and have been identified as hotspots for plastic pollution. We characterized microplastics (MPs) along confluence areas in the Paraíba do Sul River basin, the biggest river in southeastern Brazil. This water body crosses highly industrialized areas, with the highest population density, and the major water demand in South America. Considering the important ecological function of this extensive watershed and the implications of MP pollution, we evaluate the spatial variation of MP concentration in the confluence areas and upstream from the confluence. Samples were taken from the superficial layer of the water column in February and June 2022, using manta net with 300 μm mesh size. A total of 19 categories and 2870 plastic particles were determined. The confluences areas of rivers showed the highest concentration of MPs, highlighting the confluences of the Paraiba do Sul and Muriaé rivers (0.71 ± 0.25 MP/m3), followed by Paraíba do Sul and Dois Rios rivers (0.42 ± 0.23 MP/m3) and Paraíba do Sul and Pomba rivers (0.38 ± 0.14 MP/m3). Black fibers were the main category, followed by blue fibers and blue fragments. The MPs in the surface waters of Paraíba do Sul River is significantly influenced by the sampling points spatiality. This result corroborates other studies around the world and reinforces the argument that affluents are important sources for the introduction of MPs in larger rivers. Nevertheless, our results provide a better understanding of the different contributing factors and occurrence of MPs in river basins.

Microplastic pollution in typical seasonal rivers in northern China: temporal variation and risk assessment

Rivers are important channels for the transport of microplastics (MPs) from land to sea. In this work, the temporal variation and risk assessment of MP pollution in the surface water of the Wei River, a typical seasonal river in northern China, were quantified. The number abundance of MPs in the dry season was significantly higher than that in the wet season (p < 0.05). Fiber was the most abundant type of MP in both dry and wet seasons. Infrared spectrometer and Raman spectroscopy identification showed that polypropylene (PP) and polyethylene (PE) were the major polymers found in both dry and wet seasons, and the mixture of different MP polymers was more diverse in the dry season. The risk assessment showed that the average pollution load index (PLI) and risk quotient (RQ) were 2.10 and 1.19 in the dry season, which significantly decreased to 1.25 and 0.74, respectively, in the wet season (p < 0.05). In total, the results from this study highlight the characteristics of seasonal rivers that influence the temporal distribution and risk assessment of microplastics, providing scientific reference for policymakers and river managers to effectively deal with MP pollution.

Assessment of filter subsampling and extrapolation for quantifying microplastics in environmental samples using Raman spectroscopy

A common method for characterizing microplastics (MPs) involves capturing the plastic particles on a filter after extraction and isolation from the sediment particles. Microplastics captured on the filter are then scanned with Raman spectroscopy for polymer identification and quantification. However, scanning the whole filter manually using Raman analysis is a labor-intensive and time-consuming process. This study investigates a subsampling method for Raman spectroscopic analysis of microplastics (operationally defined here as 45-1000 μm in size) present in sediments and isolated onto laboratory filters. The method was evaluated using spiked MPs in deionized water and two environmentally contaminated sediments. Based on statistical analyses, we found quantification of a sub-fraction of 12.5 % of the filter in a wedge form was optimal, efficient, and accurate for estimating the entire filter count. The extrapolation method was then used to assess microplastic contamination in sediments from different marine regions of the United States.

Riverine and submarine groundwater nutrients fuel high primary production in a tropical bay

River discharge has long been recognized as a major source of nutrients supporting high primary production (PP) in Bandon Bay, while submarine groundwater discharge (SGD) and atmospheric deposition have largely been overlooked. In this study, we evaluated contributions of nutrients via river, SGD and atmospheric deposition, and their roles on PP in the bay. Contribution of nutrients from the three sources during different time of the year was estimated. Nutrients supply from Tapi-Phumduang River accounted for two-fold the amount from SGD while very little supply was from atmospheric deposition. Significant seasonal difference in silicate and dissolved inorganic nitrogen were observed in river water. Dissolved phosphorous in river water was mainly (80 % to 90 %) of DOP in both seasons. For the bay water, DIP in wet season was two-fold higher than in dry season while dissolved organic phosphorus (DOP) was only one half of those measured in dry season. In SGD, dissolved nitrogen was mostly inorganic (with 99 % as NH₄⁺), while dissolved phosphorous was predominantly (DOP). In general, Tapi River is the most important source of nitrogen (NO₃^-, NO₂^-, and DON), contributing >70 % of all considered sources, especially in wet season, while SGD is a major source for DSi, NH₄⁺ and phosphorus, contributing 50 % to 90 % of all considered sources. To this end, Tapi River and SGD deliver a large quantity of nutrients and support high PP in the bay (337 to 553 mg-C m^-2 day^-1).

Occurrence and Characteristics of Microplastics in Wild and Farmed Shrimps Collected from Cau Hai Lagoon, Central Vietnam

This study investigated the occurrence of microplastics (MPs) in the gastrointestinal tracts (GT) and tissues of four common shrimps (including two wild-caught shrimps and two farmed shrimps) collected from a high-diversity lagoon in central Vietnam. The numbers of MP items in greasy-back shrimp (Metapenaeus ensis), green tiger shrimp (Penaeus semisulcatus), white-leg shrimp (Litopenaeus vannamei), and giant tiger shrimp (Penaeus monodon), determined per weight and individual, were 0.7 ± 0.3, 0.6 ± 0.2, 1.1 ± 0.4, and 0.5 ± 0.3 (items/g-ww), and 2.5 ± 0.5, 2.3 ± 0.7, 8.6 ± 3.5, 7.7 ± 3.5 (items/individual), respectively. The concentration of microplastics in the GT samples was significantly higher than that in the tissue samples (p < 0.05). The number of microplastics in the farmed shrimp (white-leg shrimp and black tiger shrimp) was statistically significantly higher than the number of microplastics in the wild-caught shrimp (greasy-back and green tiger shrimps) (p <0.05). Fibers and fragments were the dominant shapes of the MPs, followed by pellets, and these accounted for 42-69%, 22-57%, and 0-27% of the total microplastics, respectively. The chemical compositions determined using FTIR confirmed six polymers, in which rayon was the most abundant polymer, accounting for 61.9% of the MPs found, followed by polyamide (10.5%), PET (6.7%), polyethylene (5.7%), polyacrylic (5.8%), and polystyrene (3.8%). As the first investigation on the MPs in shrimps from Cau Hai Lagoon, central Vietnam, this study provides useful information on the occurrences and characteristics of the microplastics in the gastrointestinal tracts and tissues of four shrimp species that live in different living conditions.

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.

Tracking the behavior and characteristics of microplastics using a multi-analytical approach: a case study in two contrasting coastal areas of Japan

The global survey for the presence of microplastics (MPs) in aquatic environments has attracted widespread scientific attention over the past decade. However, evaluating the composition and characteristics of these anthropogenic debris using highly sensitive techniques is still under consideration. This study demonstrates a multidimensional analytical approach, including isotopic and thermogravimetric analyses to evaluate characteristics and behavior of MPs in the environment. The MP samples were collected in two contrasting coastal areas of Japan. The stable carbon isotope (δ¹³C) ratios of field-collected polyethylene (PE), polypropylene (PP), and polystyrene (PS) MPs ranged from -25.6‰ to -31.4‰, -23.4‰ to -30.9‰, and -27.3‰ to -28.6‰, respectively. The detected isotope signatures were similar to those of commercial products. In addition, the differences in δ¹³C signature were determined between MPs with different colors. Through thermal analysis, the single-step endothermic process was observed for environmental PE and PS-MPs. Patterns in the thermograms revealed dissimilarities in degradability among the PE-MPs with different colors. The results reveal that degradation (aging) may play a significant role in the behavior and characteristics of MP debris in the aquatic environment. The present study provides fundamental data of environmental MPs from the isotopic and thermogravimetric aspects and highlights the usefulness of the approach for advances in MP research.