Microplastics in the surface water of small-scale estuaries in Shanghai

The combination of detection and simulation for the distribution and sourcing of microplastics in Shing Mun River estuary, Hong Kong

For the first time, combined detection and simulation was performed on microplastic (MP) debris in surface water, sediment, and oyster samples at ten coastal sites of Shing Mun River estuary, Hong Kong at different tidal conditions. The MP debris were extracted and detected using Fourier transform infrared (FT-IR) spectroscopy, and the simulation was conducted using Weather Research & Forecasting Model (WRF) / Regional Ocean Modelling System (ROMS) coupled hydro-dynamic modelling and the subsequent Lagrangian particle tracking. The results demonstrated the majority of polyethylene (with partial chlorine substitution) debris among all the MPs found, and great spatial and tidal variabilities of MP concentrations were observed. The combination of MP observation and simulations referred to the interpretation that a considerable percentage of MPs found in this study originated from South China Sea. Those MPs were probably transported to Tolo Harbour through sea currents and drifted inshore and offshore with tides. This study provided baseline measures of MP concentrations in Shing Mun River estuary and comprehensive understanding for how MPs transport and distribute within a dynamic estuarine system.

Spatial distribution and risk assessment of microplastics in surface waters of the St. Lawrence Estuary

Development of effective prevention and mitigation strategies for marine plastic pollution requires a better understanding of the pathways and transport mechanisms of plastic waste. Yet the role of estuaries as a key interface between riverine inputs of plastic pollution and delivery to receiving marine environments remains poorly understood. This study quantified the concentration and distribution of microplastics (MPs) (50-3200 μm) in surface waters of the St. Lawrence Estuary (SLE) in eastern Canada. Microplastics were identified and enumerated based on particle morphology, colour, and size class. Fourier Transform Infrared (FTIR) spectroscopy was used on a subset of particles to identify polymers. Generalized linear models (Gamma distribution with log-link) examined the relationship between MP concentrations and oceanographic variables and anthropogenic sources. Finally, a risk assessment model, using MP concentrations and chemical hazards based on polymer types, estimated the MP pollution risk to ecosystem health. Mean surface MP concentration in the SLE was 120 ± 42 SD particles m-3; MP concentrations were highest in the fluvial section and lowest in the Northwest Gulf of St. Lawrence. However, MP concentrations exhibited high heterogeneity along the length and width of the SLE. Microplastics were elevated at stations located closer to wastewater treatment plant outflows and downstream sites with more agricultural land. Black, blue, and transparent fibers and fragments ≤250 μm were most commonly encountered. Predominant polymer types included polyethylene terephthalate, regenerated cellulose, polyethylene, and alkyds. While the overall risk to ecosystem health in the entire estuary was considered low, several stations, particularly near urban centres were at high or very high risk. This study provides new insights into the quantification and distribution of MPs and first estimates of the risk of MP pollution to ecosystem health in one of the world's largest estuaries.

A review of plastic debris in the South American Atlantic Ocean coast - Distribution, characteristics, policies and legal aspects

The presence of plastics in the oceans has already become a pervasive phenomenon. Marine pollution by plastics surpasses the status of an emerging threat to become a well-established environmental problem, boosting research on this topic. However, despite many studies on the main seas and oceans, it is necessary to compile information on the South American Atlantic Ocean Coast to identify the lack of research and expand knowledge on marine plastic pollution in this region. Accordingly, this paper conducted an in-depth review of monitoring methods, sampling, and identification of macroplastics and microplastics (MPs) in water, sediments, and biota, including information on legal requirements from different countries as well as non-governmental initiatives. Brazil was the country with the highest number of published papers, followed by Argentina. MPs accounted for 75 % of the papers selected, with blue microfibers being the most common morphology, whereas PE and PP were the most abundant polymers. Also, a lack of standardization in the methodologies used was identified; however, the sites with the highest concentrations of MPs were the Bahía Blanca Estuary (Argentina), Guanabara Bay (Brazil), and Todos os Santos Bay (Brazil), regardless of the method applied. Regarding legislation, Uruguay and Argentina have the most advanced policies in the region against marine plastic pollution due to their emphasis on the life cycle and the national ban on certain single-use plastics. Therefore, considering its content, this expert review can be useful to assist researchers dealing with plastic pollution along the South American Atlantic Ocean Coast.

The seasonal variation and ecological risk of microplastics in the Lower Ganges River, Bangladesh

Microplastic (MP) pollution has gained considerable attention in various ecosystems; however, it has received relatively less attention in freshwater-riverine environments than in other ecosystems. The Ganges River Delta, one of the world's most densely populated areas, is a potential source of MP pollution in the freshwater ecosystem. MPs were identified throughout the year in the lower Ganges River water. Seasonally, the highest abundance was observed during the monsoon (14.66 ± 2.06 MPs/L), followed by the pre-monsoon (13.46 ± 1.75 MPs/L) and post-monsoon (11.50 ± 0.40 MPs/L). Throughout the year, MP discharge was estimated at 4.12 × 1012 to 2.17 × 1013 MPs/year. Fourier transformed infrared spectroscopy identified plastic polymers in the water, like ethylene vinyl acetate, polystyrene, polypropylene, polyethylene, and nylon. Moderate contamination by MPs was assessed throughout the year. Significant correlations between MP abundance and both rainfall and discharge were observed. It is essential to implement preventative measures in the Ganges River Basin to mitigate MP pollution before the situation worsens. PRACTITIONER POINTS: Throughout the year, MP concentration ranged from 10.67 to 20.33 MPs/L The highest MP occurrence was observed in the monsoon season (14.66 ± 2.06 MPs/L) The lowest abundance was detected in the post-monsoon period (11.50 ± 0.40 MPs/L) There was a moderate level of MP contamination in the lower Ganges River water It was shown that discharge and rainfall were correlated with MP abundance.

Microplastics in different tissues of historical and live samples of endangered mega-fish (Acipenser sinensis) and their potential relevance to exposure pathways

The Chinese sturgeon (Acipenser sinensis) is an endangered freshwater mega-fish (IUCN-red listed) that survives in the Yangtze River Basin, but the population of which has declined significantly in response to environmental pressures generated by human activities. In order to evaluate the interaction between Chinese sturgeon and microplastics (MPs) for the first time, we examined the gut and gills of historical samples (n = 27), in conjunction with the blood and mucus of live samples (n = 10), to explore the potential pathways involved in MP uptake. We detected MPs in 62.9 % of the field fish, with no significant difference between guts (mean=0.9 items/individual) and gills (mean=0.8 items/individual). The abundance of MPs in fish from 2017 was significantly higher than that from 2015 to 2016 with regards to both gills and gut samples. The size of MPs in gills was significantly smaller than those in guts, yet both contained mostly fibers (90.2 %). No MPs were confirmed in blood, however 62.5 % of mucus samples contained MPs. The MPs in mucus indicated the possibility of MPs entering Chinese sturgeons if their skins were damaged. The body size of Chinese sturgeons affected their MPs uptake by ingestion and inhalation, as less MPs were detected in the gut and gills of smaller individuals. Combining the evidence from historical and live samples, we revealed the presence of MPs in different tissues of Chinese sturgeon and their potential relevance to exposure pathways. Our work expands the understanding of multiple exposure pathways between MPs and long-lived mega-fish, while emphasizing the potential risks of long-term exposure in the field.

Risk assessment of cigarette butts and microplastic pollution in a drinking and irrigation water basin of West Anatolia, Türkiye

Cigarette butts (CBs) and Microplastics (MPs) have serious harmful effects on the environment and living organisms despite their small size. This research aims to investigate the abundance and pollution status of CBs and MPs in Tahtalı Dam Basin (West Anatolia, Türkiye) which is the most important drinking and irrigation water resources. Clean Environment Index (CEI) and Cigarette Butt Pollution Index (CBPI) were used to determine pollution degree of the basin. The total number of CBs were 1.478 items, the total number of MPs were 477 items/m2 in the basin. As a result of this study, MP particles weren't found in Balaban Stream. Highest number of MP particles observed in 100-250 μm (45%) size class. The most abundant MP type and colour were, fragment (54%) and white (42%), respectively. Polyethylene terephthalate (50%) was the most abundant type of polymer according to the ATR- FTIR analysis. As a result of the CEI and CBPI, the upstream stations of the stream were classified as "clean" status, while downstream sampling points of the stream and Balaban Lake coasts were classified as "extremely dirty" status. The calculated volumes of MP particulates from mining facility, agricultural and recreational activities indicate that anthropogenic factors are the most important MP source in the Tahtalı Dam Basin. This study is the first study about MP and CB pollution of the freshwater ecosystems in the region.

Dynamics of microplastic abundance under tidal fluctuation in Musi estuary, Indonesia

Tidal dynamics contribute to fluctuations in microplastic abundance (MPs). This is the first study to characterize MPs under the influence of tidal fluctuations in the Musi River Estuary. MPs samples were collected during flood and ebb tides at 10 research stations representing the inner, middle and outer parts of the Musi River Estuary. MPs were extracted to identify the shape, color and size. MP abundances were 467.67 ± 127.84 particles/m3 during flood tide and 723.67 ± 112.05 particles/m3 during ebb tide. The concentration of MPs in the outer zone of the estuary (ocean) was detected to be higher than in the inner zone of the estuary (river). The MPs found were dominated by black color, film shape and size 101-250 μm. A greater abundance of MPs at ebb tide than at flood tide implies that the Musi Estuary's largest source of emissions is discharge from the river.

Non-negligible impact of microplastics on wetland ecosystems

There has been much concern about microplastic (MP) pollution in marine and soil environments, but attention is gradually shifting towards wetland ecosystems, which are a transitional zone between aquatic and terrestrial ecosystems. This paper comprehensively reviews the sources of MPs in wetland ecosystems, as well as their occurrence characteristics, factors influencing their migration, and their effects on animals, plants, microorganisms, and greenhouse gas (GHG) emissions. It was found that MPs in wetland ecosystems originate mainly from anthropogenic sources (sewage discharge, and agricultural and industrial production) and natural sources (rainfall-runoff, atmospheric deposition, and tidal effects). The most common types and forms of MPs identified in the literature were polyethylene and polypropylene, fibers, and fragments. The migration of MPs in wetlands is influenced by both non-biological factors (the physicochemical properties of MPs, sediment characteristics, and hydrodynamic conditions) and biological factors (the adsorption and growth interception by plant roots, ingestion, and animal excretion). Furthermore, once MPs enter wetland ecosystems, they can impact the resident microorganisms, animals, and plants. They also have a role in global warming because MPs act as unique exogenous carbon sources, and can also influence GHG emissions in wetland ecosystems by affecting the microbial community structure in wetland sediments and abundance of genes associated with GHG emissions. However, further investigation is needed into the influence of MP type, size, and concentration on the GHG emissions in wetlands and the underlying mechanisms. Overall, the accumulation of MPs in wetland ecosystems can have far-reaching consequences for the local ecosystem, human health, and global climate regulation. Understanding the effects of MPs on wetland ecosystems is essential for developing effective management and mitigation strategies to safeguard these valuable and vulnerable environments.

Standardization of monitoring data reassesses spatial distribution of aquatic microplastics concentrations worldwide

Microplastics are found in continental and oceanic waters worldwide, but their spatial distribution shows an intricate pattern. Their driving factors remain difficult to identify and widely discussed due to insufficient and unstandardized monitoring data. Here, based on in situ experiments and hundreds of river samples from the Qinghai-Tibet Plateau, we formulate a model to standardize aquatic microplastic measurements. The model was applied to existing data on a global scale. These data are standardized to a 20 µm mesh size, resulting in a new spatial distribution of aquatic microplastic densities, with average concentrations of 554.93 ± 1352.42 items/m3 in Europe, 2558.90 ± 4799.62 in North America and 1741.94 ± 3225.09 in Asia. Excessive contaminations (microplastic concentration > 10⁴ items/m3) are in the Yangtze River, the Charleston Harbor Estuary, the Bodega Bay and the Winyah Bay. We show that, based on these standardized concentrations, new driving factors could be used to predict the global or regional microplastic distribution in continental waters, such as the Human Development Index with a correlation of 75.86% on a global scale, the nighttime lights with a correlation of 37.26 ± 0.30% in Europe and 39.02 ± 0.54% in Asia, and the Mismanagement Plastic Waste with a correlation of 61.21 ± 19.86% in North America. Mapping standardized concentrations of aquatic microplastics enables a better comparison of contamination levels between regions and reveals more accurate hotspots to better adapt remediation efforts and future plastic pollution scenarios.

Microplastics in packaged water, community stored water, groundwater, and surface water in rivers of Tamil Nadu after the COVID-19 pandemic outbreak

The increased load of plastic in waste streams after the COVID-19 pandemic outbreak has increased the possibility of microplastics (MPs) contamination channelling through the rivers and infiltrating the aquatic ecosystems. MPs in packaged water, community-stored water, groundwater, and surface water of Kaveri River (KR), Thamirabarani River (TR), Adyar River (AR), and Cooum River (CR) in Tamil Nadu were therefore investigated about 2 years after the COVID-19 pandemic outbreak. Using μFTIR and μRaman spectroscopy, polyamide, polypropylene, polyethylene, ethylene vinyl alcohol copolymer resin, and polyvinyl chloride were identified as the primary polymer types. The average number of MPs was 2.15 ± 1.9 MP/L, 1.1 ± 0.99 MP/L, 5.25 ± 1.15 MP/L, and 4 ± 2.65 MP/L in KR, TR, AR, and CR, respectively, and 1.75 ± 1.26 MP/L in groundwater, and 2.33 ± 1.52 MP/L in community stored water. Only LDPE was detected in recycled plastic-made drinking water bottles. More than 50% of MPs were found to be of size less than 1 mm, with fibrous MPs being the prevalent type, and a notable prevalence of blue-coloured microplastics in all the sample types. The Pollution Load Index (PLI) was >1 in all the rivers. Toxicity rating based on the polymer risk index (PORI) categorized AR and TR at medium risk (category II), compared to KR and CR at considerable risk (category III). Overall pollution risk index (PRI) followed a decreasing trend with CR > AR > KR > TR of considerable to low-risk category. Ecological risk assessment indicates a negligible risk to freshwater biota, except for four sites in the middle and lower stretches of Adyar River (AR - 2, AR - 4) and upper and lower stretches of Cooum River (CR - 1, CR - 3), located adjacent to direct sewer outlets, and one location in the lower stretch of Kaveri River (KR - 9), known for fishing and tourist activities.

Distribution and risk assessment of microplastic pollution in a rural river system near a wastewater treatment plant, hydro-dam, and river confluence

Rivers are the natural drainage system, transporting anthropogenic wastes and pollution, including microplastics (plastic < 5 mm). In a riverine system, microplastics can enter from different sources, and have spatial variance in concentration, physical and chemical properties, and imposed risk to the ecosystem. This pilot study presents an examination of microplastics in water and sediment samples using a single sample collection from the rural Raquette River, NY to evaluate a hypothesis that distinct locations of the river, such as downstream of a wastewater treatment plant, upstream of a hydro-dam, and river confluence, may be locations of higher microplastics concentration. In general, our results revealed the presence of high microplastic concentrations downstream of the wastewater treatment plant (in sediments), upstream of the hydro dam (both water and sediment), and in the river confluence (water sample), compared to other study sites. Moreover, the risk assessment indicates that even in a rural river with most of its drainage basin comprising forested and agricultural land, water, and sediment samples at all three locations are polluted with microplastics (pollution load index, PLI > 1; PLIzone = 1.87 and 1.68 for water and sediment samples respectively), with risk categories between Levels I and IV ("minor" to "danger"). Overall, the river stands in a "considerable" risk category (PRIzone = 134 and 113 for water and sediment samples respectively). The overall objective of this pilot study was to evaluate our hypothesis and advance our understanding of microplastic dynamics in rural river systems, elucidating their introduction from a point source (wastewater treatment plant), transit through an impediment (hydro-dam), and release into a vital transboundary river (confluence of Raquette-St. Lawrence Rivers).

An overview of microplastic pollution in the environment over the megacity of Shanghai during 2013-2022

Microplastics (MPs) are emerging pollutants that have been globally found in the environment, and have become a focus of intensive management for the Shanghai government in China. Although there are several studies reporting the abundance of microplastics (MPs) in different matrices in Shanghai city, the general data are still limited. This work comprehensively reviews microplastic (MP) pollution in the water, sediment, atmosphere, and soil of Shanghai during 2013-2022. A summary of characteristics such as the abundance, shape, and polymer composition of MPs is presented. Additionally, the pollution trends, traceability, and ecological risks of MPs are analyzed and evaluated. Based on the analytical results, we find that the inland water in Shanghai city is the most contaminated with the highest abundance of MPs at 14.76 × 103 particles/m3 on average, while the abundances of MPs in the external water, inland sediment, external sediment, indoor atmosphere, outdoor atmosphere, inland soil, and external soil are 2.78 × 103 particles/m3, 0.80 × 103 particles/kg, 1.37 × 103 particles/kg, 0.03 × 103 particles/m3, 0.08 × 103 particles/m3, 0.27 × 103 particles/kg, and 0.18 × 103 particles/kg, respectively. Polyethylene and polypropylene are the top two detected polymer compositions of MPs. Results of ecological risk assessment using risk index and pollution load index models indicate that the risks of MPs in the water and sediment of the Yangtze Estuary are high. It is noteworthy that the abundances of MPs at the junction site of Suzhou Creek and the Huangpu River as well as in the Yangtze Estuary exhibited an increasing trend between 2017 and 2019. This work contributes to a comprehensive overview of MPs in the environment of Shanghai city during 2013-2022 and provides important data for local governments to develop urgent strategies for the management of MP pollution. However, more investigations are increasingly needed for better understand the production, migration, ecological risk, and management of MPs in the environment of Shanghai city.

Microplastic inputs to the Mediterranean Sea during wet and dry seasons: The case of two Lebanese coastal outlets

Few studies have highlighted the impact of urbanization and meteorological events on the quantity of microplastics (MPs) discharged into the sea through rivers. To evaluate this issue in the Mediterranean Basin, surface water samples were collected from two more or less urbanized Lebanese Rivers: the Nahr Ibrahim (S1) and the Nahr Antelias (S2), during dry and wet periods. A significant higher abundance of 14.02 ± 9.8 particles/L was reported in the most industrialized river S2 compared to 1.73 ± 1.38 particles/L at S1. A correlation was found between particle contamination and the season at each site. Our results indicate that the MP concentrations were highest on the first sampling day of the wet season and tended to decrease progressively with increasing cumulative precipitation. Some polymers were identified only during one season. Meteorological events should be taken more specifically into account in order to define the influx of plastic pollution into coastal waters more accurately.

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.

Bioaccumulation of microplastics in the edible tissues of fish collected from urban lakes of Bangladesh: a potential exposure to public health

Microplastic (MP) pollution is an emerging environmental problem, due to its universal dispersion. In the present study, we determined the MP pollution in water, sediment, and fish samples of three different urban lakes of Bangladesh to assess the bioaccumulation of MPs from the lake environment to fish's edible (flesh) and inedible tissue (gut), ecological risk and consequent human exposure to MPs by fish consumption. A total of forty-three fishes were collected from Jahangirnagar Co-Operative Housing Society (JCHS), Dhanmondi Lake (DL), and Saturia Thana Lake (MST). The average MP concentration in sediment and water of the lakes is 7588 ± 4353 MPs/kg dry weights; 142 ± 22 MPs/L, respectively. MPs were identified in the edible (2.8-20.2 MPs/g) and inedible (2.27-20.93 MPs/g) tissue of all fish species. The highest number of MPs was observed in the flesh of Labeo bata of the JCHS Lake and in the gut of Catla catla of DL. The most dominant shape of MPs was fiber and fragment, 0.1-0.4 mm was the dominant size range, and blue, purple, and transparent were the dominant colors. The presence of six polymer types was revealed by FT-IR analysis, which were polystyrene, polypropylene, nitrile, ethylene vinyl acetate, high-density polyethylene, and nylon. The concentration of MPs in fish is found to increase with the increment in body weight. The bioconcentration factor (BCF) analysis reveals that among all the fish species, Labeo bata and Oreochromis mossambicus accumulate the highest number of MPs from the lake environment. The pollution load index of MPs indicates that the sampling sites were within hazard levels III-IV. Estimated annual intake reveals that humans will be exposed to the highest number of MPs if they consume the flesh of Labeo bata of DL and JCHS Lake.

Commercially important mangrove crabs are more susceptible to microplastic contamination than other brachyuran species

Brachyuran crabs are ecologically and economically important macrofauna in mangrove habitats. However, they are exposed to various contaminants, including plastics, which bioaccumulate in relation to their feeding modes. Setiu Wetlands is a unique place on the east coast of Peninsular Malaysia where different ecosystems such as mangroves, lagoon, beaches, etc., are duly connected and influencing each other. In recent years, the shifted river mouth has threatened these wetlands, causing severe hydrodynamic changes in the lagoon, especially in the core mangrove zone. The present study tested microplastics (MPs) contamination in the mangroves through brachyuran crabs as indicators. Three sampling sites, namely Pulau Layat, Kampung Pengkalan Gelap, and Pulau Sutung were chosen. The four abundant crab species Parasesarma eumolpe, Metaplax elegans, Austruca annulipes, and Scylla olivacea, which display different feeding behaviours were collected from all sites covering the dry (Feb-Mar 2021) and the wet (Dec 2021-Jan 2022) seasonal periods. There were significant differences in the seasonal abundance of MPs among crab species. The highest accumulation of MPs in the crab stomachs in the dry season could be linked to subdued water circulation and poor material dispersion. Besides the lower MPs in the wet period due to improved water exchange conditions, its significant presence in the stomachs of S. olivacea indicates the role of its feeding behaviour as a carnivore. In addition, the micro-Fourier transform infrared spectroscopy (micro-FTIR) revealed the widespread occurrence of polymers such as rayon and polyester in all species across the sites. Given the fact that crabs like S. olivacea are commercially important and the ones contaminated with MPs can cause detrimental effects on the local community's health, further managerial actions are needed to assure sustainable management of the Setiu Wetlands.

Microplastics and heavy metals in a tropical river: Understanding spatial and seasonal trends and developing response strategies using DPSIR framework

Microplastics (MPs) have become an increasingly popular topic in recent years due to the growing concern about their impact on human health and the environment. Rivers in Southeast Asia are the dominant source of plastics and MPs into the environment; however, research on MPs in rivers from the region is insufficient. This study aims to investigate the impacts of spatial and seasonal variations on the distribution of MPs with heavy metals in one of the top 15 rivers releasing plastics into oceans (Chao Phraya, Thailand). Findings from this study are analyzed using the Driver-Pressure-State-Impact-Response (DPSIR) framework for proposing strategies to minimize plastic and MPs in this tropical river. Spatially, most MPs were detected in the urban zone, while the lowest was in the agricultural zone. Also, MP levels in the dry season are higher than at the end but lower than at the beginning of the rainy season. MPs with fragment morphology were mainly found in the river (70-78 %). Polypropylene was found with the highest percentage (54-59 %). MPs in the river were mostly detected in the size range of 0.05-0.3 mm (36-60 %). Heavy metals were also found in all MPs collected from the river. Higher metal concentrations were detected in the agricultural and estuary zones in the rainy season. Potential responses, including regulatory and policy instruments, environmental education, and environmental cleanups, were drawn from the DPSIR framework.

Using optimized particle imaging of micro-Raman to characterize microplastics in water samples

Characterizing the chemical properties, morphologies, size, and quantities of microplastics (MPs) in water samples with high precision is critically important for understanding the environmental behaviors of MPs. Traditional detection methods, such as Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy point-by-point detection, provide worthy reference techniques but are time- and labor-consuming. We established a super time-saving and high-precision technique to characterize MPs using micro-Raman automatic particle identification (MR-API). Based on the identification of PS spheres, screen magnification, exposure time, and the number of scans are selected as crucial detection parameters for MR-API analysis, which highly affect the precision of the results. Detecting particles down to 1 μm requires magnification of the mosaic until the scale showed 200 μm. The recommended setting parameters were 83.33 or 100 ms exposure time, 20 scans, 7 mW laser power, and 1 μm image pixel size, suitable for polystyrene (PS), polypropylene (PP), polyethylene terephthalate (PET), polyethylene (PE), polyvinyl chloride (PVC), and polyamide (PA) particles detection. With the complete procedure of MR-API measurements, the recovery of MPs was 61.67-90.00 %. To validate the feasibility of the MR-API, the method was used to detect samples of known plastic types (mask leachates) and unknown plastic types (urban lake). A total of 4540 particles in the sample of mask leachates consuming 35 h 50 min 43 s, and 0.92 ± 0.49 % of particles were identified as MPs. The urban river sample efficiently identified PP, PET, PE, PVC, PS, EVA, and VC/VAC MPs using this method. The detected MPs size ranged from 8.3 to 5000 μm, saving 75.03 % and 58.38 % of the time compared to the conventional micro-FTIR and micro-Raman point-by-point methods, respectively. Therefore, this method is effective for detecting MPs in the environmental samples and has excellent prospects.

Using Data-Driven Methods and Aging Information to Quantitatively Identify Microplastic Environmental Sources and Establish a Comprehensive Discrimination Index

The global distribution of microplastics (MPs) across various environmental compartments has garnered significant attention. However, the differences in the characteristics of MPs in different environments remain unclear, and there is still a lack of quantitative analysis of their environmental sources. In addition, the inclusion of aging in source apportionment is a novel approach that has not been widely explored. In this study, we conducted a meta-analysis of the literature from the past 10 years and extracted conventional and aging characteristic data of MPs from 321 sampling points across 7 environmental compartments worldwide. We established a data-driven analysis framework using these data sets to identify different MP communities across environmental compartments, screen key MP features, and develop an environmental source analysis model for MPs. Our results indicate significant differences in the characteristics of MP communities across environments. The key features of differentiation were identified using the LEfSe method and include the carbonyl index, hydroxyl index, fouling index, proportions of polypropylene, white, black/gray, and film/sheet. These features were screened for each environmental compartment. An environmental source identification model was established based on these features with an accuracy of 75.1%. In order to accurately represent the single/multisource case in a more probabilistic manner, we proposed the MP environmental source index (MESI) to provide a probability estimation of the sample having multiple sources. Our findings contribute to a better understanding of MP migration trends and fluxes in the plastic cycle and inform effective prevention and control strategies for MP pollution.

Effects of tidal action on the stability of microbiota, antibiotic resistance genes, and microplastics in the Pearl River Estuary, Guangzhou, China

In this study, the 16S rRNA gene amplicon sequencing technique was used to explore the microbial diversity and differences in the water environment of the Pearl River Estuary in Nansha District with various land use types such as the aquaculture area, industrial area, tourist area, agricultural plantation, and residential area. At the same time, the quantity, type, abundance, and distribution of two types of emerging environmental pollutants, antibiotic resistance genes (ARGs) and microplastics (MPs), are explored in the water samples from different functional areas. The results show that the dominant phyla in the five functional regions are Proteobacteria, Actinobacteria and Bacteroidetes, and the dominant genera are Hydrogenophaga, Synechococcus, Limnohabitans and Polynucleobacter. A total of 248 ARG subtypes were detected in the five regions, belonging to nine classes of ARGs (Aminoglycoside, Beta_Lactamase, Chlor, MGEs, MLSB, Multidrug, Sul, Tet, Van). Blue and white were the dominant MP colors in the five regions; 0.5-2 mm was the dominant MP size, and cellulose, rayon, and polyester comprised the highest proportion of the plastic polymers. This study provides the basis for understanding the environmental microbial distribution in estuaries and the prevention of environmental health risks from ARGs and microplastics.

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.

Effects of land use on the distribution of soil microplastics in the Lihe River watershed, China

Soil contamination by microplastics (MPs) has gained widespread attention, whose fate may be influenced by land use types. The effects of land use types and the intensity of human activities on the distribution and sources of soil MPs at the watershed scale are unclear. In this study, 62 surface soil sites in representing five land use types (urban, tea garden, dryland, paddy field and woodland) and 8 freshwater sediment sites were investigated in the Lihe River watershed. MPs were detected in all samples, and the average abundance of soil and sediments was 401.85 ± 214.02 and 222.13 ± 54.66 items/kg, respectively. The soil MPs abundance followed the sequence: urban > paddy field > dryland > tea garden > woodland. Soil MP distribution and MP communities were significant different (p < 0.05) among land use types. The similarity of MP community highly correlated with geographic distance, and woodlands and freshwater sediments may be a potential fate for MPs in the Lihe River watershed. Soil clay, pH, and bulk density significantly correlated with MP abundance and fragment shape (p < 0.05). The positive correlation between population density, Total- Point of Interest (POI) and MP diversity indicates the importance of intensity of human activities in exacerbating soil MP pollution (p < 0.001). Plastic waste sources accounted for 65.12%, 58.60%, 48.15% and 25.35% of MPs in urban, tea garden, dryland and paddy field soils, respectively. Differences in the intensity of agricultural activities and cropping patterns were associated with different percentages of mulching film sources in the three types of agricultural soils. This study provides new ideas for the quantitative analysis of soil MP sources in different land use types.

Microplastics in water systems: A review of their impacts on the environment and their potential hazards

Microplastics, the microscopic plastics, are fragments of any type of plastic that are being produced today as plastic waste originating from anthropogenic activities. Such microplastics are discharged into the environment, and they enter back into the human body through different means. The microplastics spread in the environment due to environmental factors and the inherent properties of microplastics, such as density, hydrophobicity, and recalcitrance, and then eventually enter the water environment. In this study, to better understand the behavior of microplastics in the water environment, an extensive literature review was conducted on the occurrence of microplastics in aquatic environments categorized by seawater, wastewater, and freshwater. We summarized the abundance and distribution of microplastics in the water environment and studied the environmental factors affecting them in detail. In addition, focusing on the sampling and pretreatment processes that can limit the analysis results of microplastics, we discussed in depth the sampling methods, density separation, and organic matter digestion methods for each water environment. Finally, the potential hazards posed by the behavior of aging microplastics, such as adsorption of pollutants or ingestion by aquatic organisms, due to exposure to the environment were also investigated.

Seasonal influence on pollution index and risk of multiple compositions of microplastics in an urban river

Emerging contaminant microplastics (MPs) are getting worldwide attention for their ubiquitous occurrence and potential risk to the environment. However, the seasonal influence on freshwater MP pollution remains poorly understood. To better understand and evaluate the riverine MPs in different seasons, this study conducted the risk assessment of MPs in an urban river, Houjin River, during the different seasons. The present study found that the MPs (0.1-5 mm, mostly 0.1-2 mm) were more abundant in the dry season (183.33 ± 128.95 items/m³) compared with the wet season (102.08 ± 45.80 items/m³). Similarly, the mixture of different MPs polymers was more diverse in the dry season. The related pollution indices such as the contamination factor (CF) and pollution load index (PLI) showed that average CF and PLI were 5.15 and 2.10 in the dry season, which significantly decreased to 1.58 and 1.25, respectively, in the wet season (p < 0.05). Additionally, significant difference of the average risk quotient (RQ) was observed, which was 0.037 in the dry season and 0.021 in the wet season (p < 0.05). To sum up, the results of this study indicate the seasonal effects on the pollution and risk of multiple compositions of MPs in the urban river, suggesting higher impacts of riverine MPs pollution in the dry season, as well as the potential increase of MPs, may lead to environmental risk in the future.

Pollution characteristics and ecological risk of microplastic in sediments of Liaodong Bay from the northern Bohai Sea in China

Microplastics (MPs) are widely distributed in marine environments. The pollution characteristics and risk assessment of MPs in estuarine sediments are still insufficient. In this study, the MPs pollution characteristics in surface sediments of the Liao Estuary and Daliao Estuary were investigated. The characteristics of MPs in sediments were determined by stereo microscopy and micro-Fourier transform infrared spectroscopy. The results showed that the average MPs abundance ranged from 32.33 to 49.91 items·kg^-1 d.w. The MPs were mainly composed of 500-2000 μm black and blue fibers. Five polymer types were identified, including rayon (RA) (87.46 %), polyethylene terephthalate (PET) (6.81 %), polyamide (PA) (2.94 %), polypropylene (PP) (2.17 %) and polyethylene (PE) (0.62 %). The pollution load index (PLI) risk assessment showed that all sampling sites were at Hazard Level I. Our results can provide useful information for assessing the environmental risks of MPs in coastal areas of China.

Different functional areas and human activities significantly affect the occurrence and characteristics of microplastics in soils of the Xi'an metropolitan area

Microplastics (MPs) pollution in the environment has become a global hotspot, but there is insufficient research on MPs in soils of large cities. This study investigated the pollution status of MPs in soils in different functional areas (commercial, tourist, industrial, and residential areas) of the Xi'an metropolitan area. The average abundances of MPs were 2218 items/kg in Xi'an city, 1329 items/kg in Xianyang city and 1400 items/kg in Yangling city. All MPs presented different shapes and were dominated by fragment and fiber. The 0-0.5 mm MPs accounted for the largest proportion. Polyethylene terephthalate (PET) was the predominant polymer type for MPs. The results showed that the soil in the Xi'an metropolitan area was polluted by MPs, with the pollution of MPs in Xi'an city being more severe than other two cities. This could be related to the advanced urbanization and industrialization process. Moreover, industrial and tourist areas had frequent industrial and human activities, so their MPs pollution was the worst. In addition, residential areas and some commercial areas far away from pollution sources had lower pollution levels and a more uniform distribution of MPs. This study may provide data and valuable reference for the investigation of soil MPs pollution in the Xi'an metropolitan area.

First assessment of microplastic and artificial microfiber contamination in surface waters of the Amazon Continental Shelf

The composition and distribution of microplastics (MPs) in the Brazilian Amazon Continental Shelf surface waters are described for the first time. The study was conducted during the 2018 rainy and dry seasons, using 57 water samples collected with aluminum buckets and filtered through a 64-μm mesh. The samples were vacuum-filtered in a still-air box, and the content of each filter was measured, counted, and classified. A total of 12,288 floating MPs were retrieved; particles were present at all 57 sampling points. The mean MP abundance was 3593 ± 2264 items·m^-3, with significantly higher values during the rainy season (1500 to 12,967; 4772 ± 2761 items·m^-3) than in the dry season (323 to 5733; 2672 ± 1167 items·m^-3). Polyamides (PA), polyurethane (PU), and acrylonitrile butadiene styrene (ABS) were the most common polymers identified through Fourier Transform Infrared Spectroscopy (FTIR) analysis. Cellulose-based textile fibers were also abundant (~40%). Our results indicate that the Amazon Continental Shelf is contaminated with moderate to high levels of MPs; the highest abundances were recorded at stations near land-based sources such as river mouths and large coastal cities.

Occurrence, identification, and discharge of microplastics from effluent and sludge of the largest WWTP in Iran-South of Tehran

Microplastic pollution is a serious threat to the biota and humans, and wastewater treatment plants act as a pathway for entering microplastics into the environment. This study discusses the identification and quantification of microplastics in the south of Tehran municipal WWTP. The sampling was repeated three times in a month, overall, nine times for water samples and once a month in total, three times for digested sludge samples by steel bucket with the WPO method. The microplastics from water and digested sludge samples were identified using the micro-Raman microscope. According to this study, 98.9% of microplastic particles in effluent and 99.2% of microplastics particles in the sludge were fibers. The influent contained an average of 180 ± 4.3 MP/L and was reduced to 5.3 ± 0.31 MP/L in the final effluent. Despite this significant reduction, we calculate that this WWTP releases 2.3 × 10⁹ microplastics per day through final effluent and 1.61 × 10¹⁰ particles per day through dried sludge into the environment. We performed micro-Raman analyses and ICP mass to measure the amount of heavy metal absorption of MPs. In addition, SEM analyses were used to study the surface morphology of microplastic particles. PRACTITIONER POINTS: Fourteen different polymers were identified in the influent, effluent, and digested sludge. The main collected shapes obtained were fiber, film, and fragment, which fiber was the predominant polymer in this WWTP. The plant releases 2.3 * 10⁹ MPs per day to its downstream environment. This WWTP has average removal with an efficiency of 99.06%.

Retention and dispersion of buoyant plastic debris in a well-mixed estuary from drifter observations

Buoyant plastics enter estuaries largely from urban streams and an unknown fraction is retained before further transport to the open ocean. Plastic drifters were launched in a well-mixed estuary to simulate the movement of surface buoyant plastics. Two experiments were conducted, one during spring tides and one during neap tides, both with similar river flows and winds. Stronger tidal currents during spring tides resulted in larger dispersion and further downstream transport of the drifters. Half of the drifters were grounded within two tidal cycles. During the neap experiment, even more of the drifters (87%) were retained in the estuary. The grounding of such a high proportion of drifters suggests that much of the plastic pollution in estuaries of this type remains close to the riverine source. These findings imply that local clean-up programs removing grounded litter can reduce over half of the plastic pollution input to these estuaries.

Influence of seasonal variations on the distribution characteristics of microplastics in the surface water of the Inner Gulf of Thailand

This study collected 100-1000 L of surface water from 70 to 74 sites in the Inner Gulf of Thailand in both dry and wet seasons to investigate the relationship between the spatiotemporal distribution of microplastics and environmental variables. The quantity of microplastics in the wet season (34.59 ± 46.02 pieces/L) was significantly higher than the dry season (8.70 ± 15.34 pieces/L). Spatial distribution revealed an abundance of microplastics in river estuaries and seasonal current circulations. Polymeric characterization results showed that the plastic samples primarily consisted of polypropylene and polyethylene. New functional groups, including carbonyl, hydroxyl, and vinyl groups, were found in the chemical structures of the microplastic samples. The amount of freshwater runoff and the negative relationship with salinity confirmed that the river is the key factor in the transportation of microplastics to the coastal sea.

Microplastics in the surface seawater of Bandon Bay, Gulf of Thailand

This study aimed to evaluate the microplastics abundance, composition and distribution in Bandon Bay's surface seawater, in southern Thailand. Samples of microplastics were collected from 48 transects using a surface manta trawl at four different estuaries that support human activities. The results showed that the highest microplastic abundance occurred in the fishery and aquaculture areas with a mean abundance of 0.33 particles/m³. Fragments were the dominant form at all stations. Microplastics with <1 mm were the dominant size, and white was the colour most found in all stations. Polypropylene was the major type of microplastic, accounting for 57% overall. This study is an important reference for understanding the microplastics status in the surface seawater of Bandon Bay, as it will allow relevant agencies to accurately assess the pollution level of microplastics in the bay. It is of practical significance to understand the sources and sinks of microplastics.

Composition and spatial distribution of floating plastic debris along the estuarine ecocline of a subtropical coastal lagoon in the Western Atlantic

With the objective of characterizing the composition and spatial distribution of plastic fragments in a subtropical lagoon system, five sample areas affected by various anthropogenic impacts were chosen in the southern part of the Estuarine Lagoon System in Laguna, Santa Catarina, Brazil. The total density of the floating meso- and microplastics encountered was 7.32/m³, with the greatest density in the access channel and external area of the lagoon. Plastic filament was the most abundant and mainly comprised polyester (PET), polypropylene (PP) and polyethylene (PE) from 0.05 to 0.71 mm². Fishing and urbanization were the main sources of the meso- and microplastics in the environment. This is the first study to evaluate contamination by meso- and microplastics in the southern part of the Estuarine Lagoon System and provides information about the nature and extent of contamination by plastics in this estuarine ecosystem.

Characteristics and source-pathway of microplastics in freshwater system of China: A review

China plays a key role in global plastic production, consumption and disposal, which arouses growing concern about microplastics (MPs) contamination in Chinese freshwater systems. However, few reviews have discussed the characteristics of MP pollution in whole freshwater systems at a national scale. In this review, we summarized the characteristics, sources and transport pathways of MPs in Chinese freshwater systems including surface water and sediment. Results showed that current research mainly focused on the middle and lower reaches of the Yangtze River and its tributaries, as well as lakes and reservoirs along the Yangtze River. Large-scale reservoirs, rivers and lakes located in densely populated areas usually showed higher abundances of MPs. The majority of MPs in Chinese surface water and sediment mainly consisted of polyethylene and polypropylene, and the most common morphologies were fibers and fragments. To identify the sources and pathways, we introduced the source-sink-pathway model, and found that sewage system, farmland and aquaculture area were the three most prevalent sinks in freshwater systems in China. The source-sink-pathway model will help to further identify the migration of MPs from sources to freshwater systems.

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.

Microplastic Variations in Land-Based Sources of Coastal Water Affected by Tropical Typhoon Events in Zhanjiang Bay, China

Increasingly serious microplastic pollution in coastal areas and the ecological threats associated with plastics have attracted global attention. The frequency and intensity of typhoons have increased owing to global warming, strongly influencing the distribution and composition of microplastics in coastal ecosystems. In this study, the abundance, composition, diversity, and flux of microplastics in three estuaries and one sewage outlet in Zhanjiang Bay (ZJB) were analyzed. The average abundance of microplastics from land-based sources increased 3.6-fold from 14.19 ± 3.60 items/L before Typhoon Kompasu to 51.19 ± 28.53 items/L after the typhoon (p < 0.05). In addition, the proportion of fiber and large microplastics increased after the typhoon. In all samples, microplastics 100–330 μm in size were predominant, and blue was the most abundant color. The diversity in the color and size of microplastics increased after Typhoon Kompasu. The total daily flux of microplastics at the four stations entering ZJB was 3.95 × 1011 items before the typhoon and 9.93 × 1011 items after the typhoon, showing a 2.5-fold increase. This study demonstrated the influence of Typhoon Kompasu on microplastics from land-based sources of ZJB coastal waters and provided vital data for further study on MP pollution in coastal water ecosystems and the impact of typhoons on microplastics.

Floating microplastic debris in a rural river in Germany: Distribution, types and potential sources and sinks

Microplastic debris affects marine as well as freshwater ecosystems and an increasing number of studies have documented the contamination in aquatic environments worldwide. However, while the research focuses on oceans and larger rivers, little is known about the situation in smaller rivers within rural catchments. Since microplastics pose various risks to ecosystems, wildlife and human health, it is important to identify potential sources, sinks and transport patterns, which are probably different for small rivers. In this study, we investigate the contamination with microplastic debris of the river Ems, representing a smaller river in Northwest Germany with an agricultural catchment. We hypothesised that with increasing river length the plastic concentration increases, especially downstream of towns, waste water treatment plant (WWTP) effluents and major tributaries as they may be important point sources of microplastics. We collected 36 surface water samples at 18 sampling sites within the first 70 km using manual driftnets. We sampled every 7 km and upstream and downstream of three larger towns, four major tributaries and four WWTP effluents. Overall, we found 1.54 ± 1.54 items m^-3, which corresponds to the plastic concentrations in larger streams. However, the shape of the detected items differed as we did not find potential primary microplastic. Furthermore, the pattern contradicts our assumption, that the contamination increased with distance to the river's source. Downstream of towns, we found significantly less floating microplastic indicating possible sinks due to sedimentation at sites with slowing flow velocity caused by weirs in towns. Hence, the non-linear distribution pattern of microplastics indicates potential sinks of microplastics due to flow alterations on the river course. This should be considered in future studies modelling microplastic distribution and transport. Furthermore, studies especially in smaller rivers are urgently needed to identify and quantify sources and sinks and to find applicable solutions to reduce microplastic loads.

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.

Pollution characteristics and source analysis of microplastics in the Qiantang River in southeastern China

Microplastic pollution resulting from industrialization and urbanization is increasingly serious. Hangzhou is a city with high industrial/urban growth in Southeast China. Focusing on the microplastic pollution in the Hangzhou section Qiantang River, six samples were collected and analyzed during different hydrological periods (normal, wet, and dry periods) and the relationship between microplastic pollution and economic development was investigated. Results showed that more microplastics were found during the dry period than that of the wet period (49.8 vs. 13.2%). Microplastic abundance was 1.5-9.4 items L^-1, showing significant spatial differences in sampling sites. Among the collecting microplastics, debris and fibers accounted for 36.4 and 30.9%. Polyethylene terephthalate and polyvinyl chloride were the main polymers, accounting for 48.3 and 31.8%, respectively. Microplastics with size <1 mm accounted for 60% of the microplastics in surface water samples. Spatially, microplastic abundance was the highest in the middle of the river. Redundant analysis revealed that the per capita GDP (p = 0.002), high-end equipment industry (p = 0.028) and fashion manufacturing (p = 0.006) influenced microplastic abundance. Urbanization coupled with rapid economic development led to increase in local microplastic pollution. Our results provide insight into microplastic distribution patterns in urban river systems in China.

Aggregate exposure pathways for microplastics (mpAEP): An evidence-based framework to identify research and regulatory needs

Microplastics as emerging contaminants have been detected from peaks to poles. High concerns on the risks of microplastic pollution to humans and ecosystems have therefore been raised in the past decade. While a large number of studies have been conducted to investigate the environmental levels and toxicity of microplastics, the information generated to support risk assessment is fragmented and the coherence between different types of study is largely lacking. Here we introduced the Aggregate Exposure Pathway (AEP), a conceptual framework originally proposed for chemical exposure assessment, to facilitate organization, visualization and evaluation of existing information generated from microplastic research, and to efficiently identify future knowledge and regulatory needs. A putative microplastic AEP network (mpAEP) was developed to demonstrate the concept and model development strategies. Two mpAEP case studies, with polyethylene (PE) as a prototype, were then presented based on existing environmental exposure data collected from the Changjiang Estuary and the East China Sea (Case I), and the Oslo Fjord (Case II), respectively. Weight of evidence (WoE) assessment of the mpAEPs were performed for evaluating the essentiality, theoretical plausibility, empirical evidence and quantitative understanding of the evidence and relationships in the AEPs. Both cases showed moderate/high WoE to support the strength of the models, whereas also displayed clear knowledge gaps, thus providing guidance for future investigations and regulations. The mpAEP framework introduced herein presents a novel strategy for organizing fragmented information from diverse types of microplastic research, enhancing mechanistic understanding of causal relationships and facilitating the development of quantitative prediction models for research and regulation in the future.

Microplastics in China Sea: Analysis, status, source, and fate

Microplastics (MPs) in marine environments have raised increasing concerns worldwide in recent years. China is one of the largest plastic producers in the world. In this review, available information on MPs in China Sea was reviewed, including studies on seawater, sediment, and biota. The status and limits of sampling methods of MPs were summarized, such as sampling tools, sampling volume, and depth of sampling. The analytical methods of MPs were outlined, such as sieving, density separation, purification, filtration, and visual sorting. The characteristics of MPs, such as abundances, sizes, shapes, polymer types, sources, and fates were analyzed. The abundances of MPs in China Sea varied from 0.1 to 27,840.0 items m^-3 in seawater, and from 13.0 to 14,712.0 items kg^-1 d.w. in sediments. Furthermore, MPs were mainly featured with sizes ranging from 0.001 to 0.5 mm, with colors of transparent and black, and polymer types of polypropylene and polyethylene. To promote research on MPs in China Sea, the sampling and analytical methods were insufficiently standardized and should be improved. As for microplastic (MP) pollution in China Sea, laws and regulations have already been established to manage and control plastic waste. Furthermore, several suggestions to control plastic pollution were as follows: (1) control marine plastic pollution at the source; (2) strengthen technological innovations; (3) urge people to minimize disposable plastic products in their daily lives; (4) strengthen international cooperation in the treatment of marine plastic waste.

Critical review of environmental impacts of microfibers in different environmental matrices

Microfibers, as globally emerging environmental pollutants, have received increasing attention over recent years. In ecosystems, natural textile microfibers are the predominant fibers. The inadvertent ingestion of microplastics by organisms in an ecosystem provides a channel for microfibers to enter biological webs. Based on existing research on microfibers, this review summarizes the potential adverse impacts of microfibers on organisms living in marine, freshwater, and soil ecosystems, and provides a brief introduction to the source of microfibers, as well as the related current status and future challenges. Although previous studies have recorded the adverse effects of microfibers on ecosystems, there remains a lack of evidence on the toxic effects of microfibers on the primary producer level in food chains (e.g., phytoplankton). This is essential, as the long-term effects of microfiber toxicity on different ecosystems ultimately affect human health. The analysis of microfiber toxicity paves the way for the field of environmental research and provides future perspectives for researchers in the fields of ecotoxicology and microplastics.

Microplastics pollution and risk assessment in water bodies of two nature reserves in Jilin Province: Correlation analysis with the degree of human activity

As a new type of environmental pollutant, microplastics (MPs) are widely present in freshwater systems. The ecological risks of MPs pollution in nature reserves and the correlation between human activities and the abundance of MPs are still unclear. This is the first survey of MPs in freshwater systems in Northeast China. The content and composition of MPs in 19 water samples were investigated in Chagan lake and Xianghai. The abundance of MPs samples in Chagan Lake averages 3.61 ± 2.23 particles/L, and in Xianghai averages 0.29 ± 0.11 particles/L. The main types of MPs in Chagan Lake are PA (23.7%) and PS (53.2%); while in Xianghai are PP (56%) and PS (32.7%). Foam, white and <1 mm are the main shapes, colors and sizes of Chagan Lake MPs, while of Xianghai are film, transparent and <1 mm. This may be related to the well-developed tourism and fishing industry (foam and fishing line) in Chagan Lake and aquaculture in Xianghai (foam and plastic film). The hazard index (HI) indicated a Hazard Level III for MPs pollution in Chagan Lake and Xianghai. Pollution load index (PLI) and potential ecological risk index (RI) indicate that the pollution risk of MPs polymers in the two places is relatively small. The degree of human activity is quantified to analyze the correlation of MPs abundance. The quantified scores are positively correlated with the abundance of MPs at different sampling points (Chagan lake: P < 0.05, 95% Cl; Xianghai: P < 0.05, 95% Cl).

Microplastic pollution characteristic in surface water and freshwater fish of Gehu Lake, China

Much more attention has been poured into microplastic pollution in freshwater systems recently. In the present study, the pollution of microplastics (MPs) in surface water and freshwater fish (crucian carp, etc.) were investigated from Gehu Lake, which is the second largest lake in southern Jiangsu after Taihu Lake. The result manifested that the average abundance of MPs was respectively 6.33±2.67 n/L for surface water and 10.7 items per individual for freshwater fish. The distribution of MPs in Gehu Lake varied from place to place, with the highest abundance of MPs was observed in the two estuaries of the eastern part of the lake. It was speculated that topographical factors and human factors were the main factors affecting the abundance and distribution of MPs. Transparent fibers were the main type of MPs in water samples, accounting for 69.70% of all detected particles. Meanwhile, most of the MPs ingested by freshwater fish were fibers, and the main colors were transparent and blue. In addition, the dominant size of the MPs was between 0.1 to 0.5 mm in water and fish samples. Moreover, PES, man-made fiber, and PP were the dominant polymer types in the surface water and fish samples. The results of this investigation can provide basic data for the research and management of MPs in freshwater systems.

Plastic microbeads: small yet mighty concerning

The net use of plastic has increased and this augmentation in plastic usage results in ever- growing accumulation of plastic waste in our ecosystems. Regrettably, a portion of this waste is the microplastics including microbeads, which are tiny plastic particles <5 mm in diameter. Microbeads are used in our personal care products. Although, legislative ban of microbeads in some developed countries has proven effective, but many countries do not take any legal action. Hence, microbead-containing products are openly sold in international market and entered into the food chain and disturb it. In human beings and animals, plastic when ingested causes internal bleeding, abrasion, ulcers and blockage of the digestive tract. The present review highlighted the bioaccumulation of microbeads via the food chain and its adverse effect on environment health. Moreover, different scientific views and suggestions for eradication of the problem and present scenario of the use of microbeads in some Asian countries have also been discussed.

What You Net Depends on if You Grab: A Meta-analysis of Sampling Method's Impact on Measured Aquatic Microplastic Concentration

Microplastic pollution is measured with a variety of sampling methods. Field experiments indicate that commonly used sampling methods, including net, pump, and grab samples, do not always result in equivalent measured concentration. We investigate the comparability of these methods through a meta-analysis of 121 surface water microplastic studies. We find systematic relationships between measured concentration and sampled volume, method of collection, mesh size used for filtration, and waterbody sampled. Most significantly, a strong log-linear relationship exists between sample volume and measured concentration, with small-volume grab samples measuring up to 10⁴ particles/L higher concentrations than larger volume net samples, even when sampled concurrently. Potential biasing factors explored included filtration size (±10² particles/L), net volume overestimation (±10¹ particles/L), fiber loss through net mesh (unknown magnitude), intersample variability (±10¹ particles/L), and contamination, the potential factor with an effect large enough (±10³ particles/L) to explain the observed differences. On the basis of these results, we caution against comparing concentrations across multiple studies or combining multiple study results to identify regional patterns. Additionally, we emphasize the importance of contamination reduction and quantification strategies, namely that blank samples from all stages of field sampling be collected and reported as a matter of course for all studies.

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.

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.

Quantification and composition of microplastics in the Raritan Hudson Estuary: Comparison to pathways of entry and implications for fate

Comprehensive approaches are needed to understand accumulation patterns and the relative importance of pathways of entry for microplastics in the marine environment. Here, a highly urbanized estuarine environment was sampled along a salinity gradient from the mouth of the Raritan River, (New Jersey, USA) and into the Raritan Bay and the coastal ocean which are further influenced by discharge from the larger Hudson River. Polymers were characterized in two size classes by FTIR and/or Raman spectroscopy. The highest concentration of 500-2000 μm microplastic particles were observed in the mouth of the Raritan during summer low flow conditions, whereas the 250-500 μm microplastic particles were more prevalent in the bay and coastal ocean samples. These results were interpreted using fragmentation and mixing models to provide insight into the sources and fate of microplastics in this estuarine/coastal region. To investigate the potential pathways of entry into the system, samples were collected from various hydraulically connected storm water outfalls and the influent and effluent of wastewater treatment plants and polymer concentrations and types were compared to the estuarine samples. The concentrations of microplastics (500-2000 μm) ranged from 400 to 600 microplastics/m³ in storm water compared to <1-2.75 microplastics/m³ across the estuary. Of interest for analysis is the observed linear correlation between the total concentration of particles in a sample following oxidation and density separation and its microplastic concentration. Overall, the results presented reveal potentially important sources of microplastics in the estuarine environment and have implications for understanding the behavior, transport, and fate of microplastics under varying flow conditions and from estuaries with variable flushing times.

Microplastics Environmental Effect and Risk Assessment on the Aquaculture Systems from South China

The small size of microplastics and their wide distribution in water environments have attracted worldwide attention and heated discussion, because of their ingestion by aquatic organisms. At present, there are few studies on microplastics pollution in freshwater aquaculture ponds, especially shrimp ponds. In this study, the aquaculture ponds in the Pearl River Estuary were investigated. The abundance and composition of microplastics in different environmental media were studied to explore the potential sources and risk levels of microplastics, so as to provide basic data for the study of microplastics pollution in aquaculture ponds. Microplastics were observed in water and sediment samples at all sampling sites, with the abundance of 6.6 × 10³-263.6 × 10³ items/m³ (surface water) and 566.67-2500 items/kg (sediment), respectively. Thirty-seven individuals collected in six ponds belong to four species. Microplastics were observed in the gastrointestinal tract (GIT) of all fishes and shrimps, with the abundance ranging from 3-92 items/individual (fish) and 4-21 items/individual (shrimp). Among all samples, microplastics with the size range of <1 mm and fiber shape were the most common. The main microplastic components were cellulose, polypropylene (PP), and polyethylene (PE). The results of potential risk assessment showed that the pollution investigation of microplastics should not only consider the abundance. Low abundance does not mean low risk. Taking the toxicity score and abundance of microplastics as evaluation indexes to reflect the pollution status of microplastics may make the results more reliable.

Spatial and temporal distribution of microplastic in surface water of tropical estuary: Case study in Benoa Bay, Bali, Indonesia

In 2010, Indonesia estimated as the second-largest country in the world that donates plastic to the sea. This study aims to investigate the spatial and temporal distribution of microplastics in tropical estuaries. The sampling was carried out in Benoa Bay with four repetitions representing the wet and dry seasons. Spatially it was found that the highest microplastic abundance around the Suwung landfill, while the lowest at Badung River Estuary, middle, and an inlet of the Benoa Bay. The highest percentage to the lowest microplastic based on the size was 500-1000 μm (37.9%), >1000 μm (35.7%), 300-500 μm (22.1%), and <300 μm (4.3%), while based on the shape were fragments (73.19%), foam (17.02%), fiber (6.38%), and granule (3.40%). No significant differences were found between the wet and dry seasons based on the abundance, but significantly varied based on size and shape. Polymers of microplastics were dominated by polystyrene, polypropylene, and polyethylene.