Microplastics pollution in inland freshwaters of China: A case study in urban surface waters of Wuhan, China

Wastewater plastisphere enhances antibiotic resistant elements, bacterial pathogens, and toxicological impacts in the environment

Microplastics (MPs) are plastic particles with a size <5 mm that have raised alarming concerns owing to their ecological and human health impacts. They are largely released into the environment through the dumping of plastic waste and wastewater from treatment plants, domestic sewage, agricultural runoff, and industrial sources. Conventional wastewater treatment plants (WWTPs) are unable to remove micro and nano-sized plastic particles, which end up in the natural aquatic and terrestrial environment, causing multifaceted toxic impacts. Moreover, plastics in wastewater generate biofilm that potentially enriches antibiotic resistant bacteria (ARBs), antibiotic resistant genes (ARGs), and bacterial pathogens, which can largely impact antibiotic resistance development among organisms in the environment and transfer to humans through the food chain. Therefore, the current review aims to highlight the potential role of wastewater plastisphere in the enrichment and dissemination of ARBs, ARGs, and potential bacterial pathogens through mobile genetic elements (MGEs) in the environment. Further, the interaction of wastewater MPs with organic and inorganic contaminants and the associated ecological and human health impacts have been presented. Last but not the least, control strategies and future research perspectives on wastewater plastisphere are also highlighted.

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

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

Differences, links, and roles of microbial and stoichiometric factors in microplastic distribution: A case study of five typical rice cropping regions in China

Microplastics (MPs), as new pollutants in agroecosystems, have already attracted widespread attention from scientists. However, our understanding of MP geographic distribution and its influencing factors across spatial scales remains poor. Here, a regional-scale field investigation was conducted to assess the distribution characteristic of MPs in five major rice-growing regions of China, and we explored the roles of biological and abiotic factors, especially stoichiometry and microbial influences on MP distribution. MPs were observed in all sampling sites, averaging 6,390 ± 2,031 items⋅kg^–1. Sizes less than 0.5 mm and black and transparent MPs dominated. Fiber, classified as one of the MP shapes, occurred most frequently. MP community analysis, firstly used in paddy soil, revealed more black MPs abundance in Henan (HE), more rayon, blue, and other colors MPs in Hunan (HN), more transparent MPs in Tianjing (TJ), and more PE MPs in Heilongjiang (DB). Higher MP community diversity was found in most south paddy soils of this study, due to a broader range of sources. C/N showed a positive relationship with pellet-shaped MP abundance and MPs of size between 2 and 5 mm (P < 0.05). Chao1 index of soil microbial communities was positively correlated with the MP abundance, MPs of size less than 0.5 mm, and fiber abundance. The minimum temperature was positively correlated with MP abundance (P < 0.05), implying the potential effects of the freeze-thaw process might exist. The regression analysis highlighted the important role of population quantity in determining MP abundance (R = 0.421, P = 0.02). This study confirmed the wide distribution of MPs in different soil depths of paddy lands in China and demonstrated that its distribution was influenced by population quantity and environmental variables, such as microbiology. These findings could provide a basis for the toxicological behavior of MPs and the potential risk to human health.

Microplastics distribution and possible ingestion by fish in lacustrine waters (Lake Bracciano, Italy)

Understanding the spatial distribution patterns of microplastics (plastics < 5 mm) contributes to the assessment of sources and sinks of pollution thus providing information for the management of biota safety and overall ecosystem functionality. We chose a semi-closed study area, Lake Bracciano (Italy), to assess the environmental variability of contamination, focusing on the water compartment and the exposure of biota, specifically fish, by analysing the ingestion of microplastics. The focus of this study is to evaluate the concentration of microplastics in water (surface and column) across the lake and the ingestion of microplastics by two fish species of economic interest: Atherina boyeri and Coregonus lavaretus, inhabiting demersal and pelagic habitats respectively. Results show a surface contamination of 392,000 ± 417,000 items km^-2 and a column one of 0.76 ± 1.00 items m^-3. Fragments were the most abundant in surface while fibres in the column. Microplastics were found in C. lavaretus specimens, corresponding to contamination frequency of 5% and concentration of 0.15 items/fish. The main polymer found in water was polyethylene (81%); of minor percentages, there were various other polymers, including polystyrene and acrylic, which were also found in fish. As scientific literature provides few research where water and fish are simultaneously sampled, this investigation wants to contribute filling this knowledge gap by investigating for the first time a volcanic lake.

Dietary consumption of polypropylene microplastics alter the biochemical parameters and histological response in freshwater benthic mollusc Pomacea paludosa

One of the most common environmental pollutant in aquatic ecosystems are polypropylene microplastics and their impacts on aquatic organisms are still scarce. The study aimed to prepare polypropylene microplastics using organic solvent (spherical and 11.86-44.62 μm) and then test their toxicity on the freshwater benthic mollusc grazer Pomaceae paludosa. The present study investigated chronic (28 days) exposure of polypropylene microplastics via dietary supplements (250 mg kg^-1, 500 mg kg^-1 & 750 mg kg^-1) in P. paludosa, and the toxic effect was evaluated in digestive gland tissue. The FTIR results revealed no change in polypropylene microplastics during ingestion or after egestion. On the other hand, Ingestion causes accumulation in their bodies and disrupts redox homeostasis. Meanwhile, alteration occurs in oxidative stress-related biomarkers such as increased reactive oxygen species level (ROS), impaired the biochemical parameters of antioxidant system catalase (CAT), glutathione peroxidase (GPx), reduced glutathione (GSH), and glutathione - S- transferase (GST), deterioration of oxidative stress effects in lipid peroxidation (LPO) and carbonyl protein (CP) and changed the digestive enzymes such as amylase, pepsin, esterase and alkaline phosphatase that are measured in hepatopancreas tissue. The histology results revealed that ingesting these microplastics caused severe damage to the digestive gland cells. According to the findings, ingestion of polypropylene microplastics in benthic freshwater mollusc causes more serious harm and impacts energy acquisition. This finding represents the ecological risk of polypropylene microplastic pollution in the freshwater ecosystem.

Microplastics in urban soils of Nanjing in eastern China: Occurrence, relationships, and sources

Although microplastic (MP) pollution has been defined as a new global challenge by the United Nations Environment Programme, their abundance and composition has only been studied in-depth within farmland soil, while minimal attention has been placed on urban soil contamination. Accordingly, within the current study, MP abundance and composition is investigated within urban soil from green spaces in Nanjing, eastern China. The average MP abundance in soil was 461 ± 222 items/kg and primarily comprised fibers (39.1%) and fragments (37.7%). MPs <1000 μm in size accounted for 83.7% of the total content and white MPs were the most abundant (26.5%). The dominant polymers were polyethylene glycol terephthalate (32.0%) and polypropylene (20.5%). Moreover, relationship network analysis generated three distinct MP modules based on community similarity. Indeed, the degree of similarity increased by ∼26.8% per kilometer. Furthermore, application of a forward selective optimal multiple regression model identified clay, sand, longitude, and points of interest for recycling bins (RecyclePOI) as the primary spatial and soil environmental factors affecting MP abundance and composition. Additionally, five potential sources of MPs were identified based on the MP diversity integrated index fitting results, and point of interest density (MDII-POI) source analysis (R² = 0.21-0.62; P < 0.05). In particular, the point of interest of express delivery points (ExpressPOI) were important sources of plastic emissions as they are widely distributed throughout urban and fringe areas. Collectively, the findings of this study provide novel insights regarding quantitative source appointment and regional ecological control of MPs in urban soil.

Fugitive release and influencing factors of microplastics in urbanized watersheds: A case study of the central area of Suzhou City

Urban areas are greatly affected by human activities that may result in the release of microplastics. Fugitive release of microplastics is the unorganized discharge of microplastics produced during plastic manufacturing and use. The microplastics enter the environment in a variety of ways. To investigate fugitively released microplastics and identify the major influencing factors in urban watersheds, the central area of Suzhou city was selected as a case study. This area has a dense network of canals without sources of organized release. The results show that the microplastic abundance in the urban canal of the area ranged from 8.29 to 40.63 particles L^-1, with a mean of 14.75 ± 3.95 particles L^-1. To better understand the relationship between microplastics and human activities, the main influencing factors, including water quality, water-related activities, dwelling type, urban landscaping, trash collection and land use type, were assessed. Water quality was not correlated with microplastic distribution in the urban watershed, as it is in larger watersheds. Water-related activities caused elevated fugitive release of microplastics. The abundance of microplastics discharged into the water environment in modern communities was significantly less than that discharged in an area of traditional residences. Traffic activities contributed to microplastic release, while urban landscaping physically blocked microplastics from flowing into urban waterbodies to some extent. Trash collection did not reduce the abundance of microplastic particles in the water, despite its ability to remove other types of plastic waste. The results also suggest that the contributions of different land use types to the abundance of microplastics in urban areas from highest to lowest were as follows: tourist districts > commercial areas > public areas > residential areas > roads. Moreover, fugitive release is an important source to be considered in future research on urban microplastic management. The renewal of urban construction to mitigate the influence of human activities on water ecology may play a positive role in controlling the fugitive release of microplastics.

A systematic study of microplastic occurrence in urban water networks of a metropolis

The release of microplastics from sewage treatment works (STWs) into the oceans around coastal cities is well documented. However, there are fewer studies on the microplastic abundance in stormwater drains and their emissions into the coastal marine environment via sewage and stormwater drainage networks. Here, we comprehensively investigated microplastic abundance in 66 sewage and 18 sludge samples collected from different process stages at three typical STWs and 36 water samples taken from six major stormwater drains during the dry and wet seasons in Hong Kong, which is a metropolitan city in south China. The results showed that microplastics were detected in all the sewage and stormwater samples, with the abundance ranging from 0.07 to 91.9 and from 0.4 to 36.48 particles/L, respectively, and in all the sludge samples with the abundance ranging from 167 to 936 particles/g (d. w.). There were no significant seasonal variations in the microplastic abundance across all samples of sewage, sludge, and stormwater. For both waterborne sample types, a smaller size (0.02-0.3 mm) and fiber shape were the dominant characteristics of the microplastics. Polyethylene terephthalate (PET) and polypropylene (PP) were the most abundant polymer types in the sewage samples, while polyethylene (PE), PET, PP, and PE-PP copolymer were the most abundant polymer types in the stormwater samples. The estimated range of total daily microplastic loads in the effluent from STWs in Hong Kong is estimated to be 4.48 × 10⁹ - 2.68 × 10¹⁰ particles/day, demonstrating that STWs are major pathways of microplastics in coastal environments despite the high removal percentage of microplastics in sewage treatment processes examined. This is the first comprehensive study on microplastics in the urban waters of a coastal metropolis. However, further studies on other coastal cities will enable an accurate estimation of the microplastic contribution of stormwater drains to the world's oceans.

Fate of face masks after being discarded into seawater: Aging and microbial colonization

Billions of discarded masks have entered the oceans since the outbreak of the COVID-19 pandemic. Current reports mostly discuss the potential of masks as plastic pollution, but there has been no study on the fate of this emerging plastic waste in the marine environment. Therefore, we exposed masks in natural seawater and evaluated their aging and effects on the microbial community using a combination of physicochemical and biological techniques. After 30-day exposure in natural seawater, the masks suffered from significant aging. Microbial colonizers such as Rhodobacteraceae Flavobacteriaceae, Vibrionaceae and fouling organisms like calcareous tubeworms Hydroides elegans were massively present on the masks. The roughness and modulus of the mask fiber increased 3 and 5 times, respectively, and the molecular weight decreased 7%. The growth of biofouling organisms caused the masks negatively buoyant after 14-30 days. Our study sheds some light on the fate of discarded masks in a coastal area and provides fundamental data to manage this important plastic waste during COVID-19 pandemic.

Huge quantities of microplastics are "hidden" in the sediment of China's largest urban lake-Tangxun Lake

Microplastics (MPs) pollution in Tangxun Lake, the largest urban lake in China, was investigated. The average MPs pollution in sediment (1.81 ± 1.75 × 10⁴ items kg^-1) is at a high level, while the MPs in lakeshore water (917.77 ± 742.17 items m^-3) is in the middle to low level compared with existing studies, which is related to the government's protection. Fragments and fibers are the most common shapes in sediment and water, respectively. MPs size <1 mm dominates in the sediment, while the MPs in water has a larger size. The distribution of MPs in the inner lake shows that pellets tend to "hidden" in sediments. Suspected MPs are randomly selected for polymer detection by Micro-Raman microscopy. Polypropylene (PP), polyethylene (PE) and polyethylene terephthalate (PET) are the most common polymer types in water, sediment and atmospheric deposition MPs samples. The input of wastewater, fishery and surrounding human activities are the main sources of MPs in sediment. Atmospheric deposition has a great impact on the distribution of MPs, while the contribution of surface runoff to lake MPs is not remarkable. In addition, MPs in sediments have exceeded the environmental carrying capacity. More attention should be focused on the sediment, where huge amounts of MPs are "hidden".

Microplastics in 48 wastewater treatment plants reveal regional differences in physical characteristics and shape-dependent removal in the transition zone between North and South China

This study investigated the physical characteristics and removal efficiency of microplastics in wastewater from regions with different climatic conditions and economic development levels. Microplastics with different shapes and sizes were analyzed from the influent and effluent of 48 wastewater treatment plants in three regions of Shaanxi Province (China). Results indicated that the abundance of microplastics in the influent samples was higher in the region with less regional water resources. However, the per capita microplastics emissions was higher in the region with higher economic development level. There were less fibers and more foams and beads in the more developed region. The removal efficiency of microplastics was related to their shape and size. Particularly, the removal efficiency showed a significant negative correlation with the percentage of foams, while it had a significant positive relationship with the proportions of films and fibers. The highest removal efficiency was obtained when the size of microplastics was ranged from 0.5 to 1.0 mm. This study suggests, compared to improving the removal efficiency of microplastics, that reducing the input at source is a more scientific and promising method.

Effects of Polyester Microfibers on the Growth and Toxicity Production of Bloom-Forming Cyanobacterium Microcystis aeruginosa

The global pollution of microplastics (MPs) has attracted wide attention, and many studies have been conducted on the effects of MP qualities or types and particle sizes on aquatic organisms. However, few studies on the impact of polyethylene terephthalate microplastic (mPET) with different colors on phytoplankton in aquatic ecosystems have been carried out. In this study, mPET of three common colors (green, black, and white) in different concentrations (0, 10, 50, 100, and 200 mg/L) were selected to explore effects on a bloom-forming cyanobacterium Microcystis aeruginosa. The growth, photosynthesis, the number and size of colony, and MC-LR production of M. aeruginosa were studied within a 25-days exposure experiment. The results showed that colors of mPET had significant effects on the growth and photosynthesis of this species but the concentration of mPET had no significant effect. The low concentration of green mPET group promoted algal growth, photosynthesis, and the M. aeruginosa exposed to it was easier to agglomerate into colonies. Moreover, both mPET colors and concentrations have a significant impact on the microcystin production of M. aeruginosa. The low concentration of the green mPET group significantly inhibited the production throughout the experiment, while the white and black mPET significantly increased the concentration of extracellular microcystin (MC-LR). Our results provided new insights into the effects of MPs with different colors and concentrations on the growth and physiology of cyanobacteria and provide basic data for the ecological risk assessment and pollution prevention of MPs.

Elimination of Microplastics at Different Stages in Wastewater Treatment Plants

Microplastic pollution has been widely studied as a global issue due to increased plastic usage and its effect on human and aquatic life. Microplastics originate from domestic and industrial activities. Wastewater treatment plants (WWTPs) play an important role in removing a significant amount of microplastics; otherwise, they end up in bioaccumulation. This study provides knowledge about the characteristics of microplastics, removal efficiency, and the correlation between wastewater quality and microplastic concentrations from three different WWTPs that differ in the type of biological and advanced wastewater treatment techniques that are believed to play an important role in microplastic removal. Microplastics of different types, such as fragments, fibers, and beads, are identified by using an optical microscope before and after the treatment process at each stage to assess the effect of different treatment techniques. In the screening unit and primary clarifier unit, WWTP-B shows the highest removal efficiency with 74.76% due to a distribution flow system installed before the primary clarifier to ensure a constant flow of wastewater. WWTP-B uses a bioreactor consisting of a filter plate coated with activated carbon (BSTS II) that can enhance the adaptability and adhesion of microorganisms and showed that 91.04% of the microplastic was removed. Furthermore, only WWTP-A and WWTP-B were applied coagulation, followed by the disc filter; they showed significant results in microplastic removal, compared to WWTP-C, which only used a disc filter. In conclusion, from all WWTP, WWTP-B shows good treatment series for removing microplastic in wastewater; however, WWTP-B showed a high rate of microplastic removal; unfortunately, large amounts of microplastics are still released into rivers.

Assessment of microplastic contamination in the urban lower Chao Phraya River of Bangkok city, Thailand

Rivers are one of the major pathways for the transportation of microplastics (MPs) from land-based sources to the ocean. However, there are only a few studies on MPs in freshwater environments, particularly in Asian countries. In this study, MP contamination in the Chao Phraya River in selected locations distributed throughout Bangkok, Thailand was investigated. MPs were collected using a Manta net with a mesh size of 335 μm. After digestion and distinction based on density, MPs were observed using a stereomicroscope, and polymer types were identified using Fourier Transform Infrared Spectroscopy. MP concentrations detected in the five sampling locations of the river water from upstream to downstream were 11, 35, 40, 15, and 4 particles/m³, with an average concentration of 21±16 particles/m³. Most MPs were identified as either fragments or sheets/films. Polypropylene was the dominant polymer type. The number of MPs increases as their size decreases. Potential sources of MPs may include the degradation of single-use plastic products, especially containers and plastic packaging. MP concentrations and characteristics varied for different locations, indicating different sources and pathways of MPs in urban contexts. Further investigation on the different pathways of the transportation of MPs to river water from land-based sources is required.

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

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

Combined ingestion of polystyrene microplastics and epoxiconazole increases health risk to mice: Based on their synergistic bioaccumulation in vivo

Microplastic and pesticide are two common environmental pollutants whose adverse effects have been widely reported, but it is unclear whether they cause combined toxicity in mammals. In this study, polystyrene microplastics (5 µm, 0.012 or 0.120 mg/kg) or/and epoxiconazole (0.080 mg/kg) were administered orally to mice for 6 weeks, their toxicity to liver and kidney was assessed from changes in histopathology, tissue function, oxidative defense system and metabolic profile. In addition, mechanism of combined toxicity was explored in terms of bioaccumulation levels, intestinal barrier, gut microbiota. Results showed that combined ingestion of polystyrene (0.120 mg/kg) and epoxiconazole caused more severe tissue damage, dysfunction, oxidative stress, and metabolic disorders compared to single exposure sources. Interestingly, occurrence of combined toxicity was associated with their increased accumulation in tissues. In-depth exploration found that epoxiconazole caused intestinal barrier damage by targeting the gut microbiota, leading to massive invasion and accumulation of polystyrene, which in turn interfered with the metabolic clearance of epoxiconazole in liver. In all, findings highlighted that polystyrene and epoxiconazole could cause combined toxicity in mice through the synergistic effect of their bioaccumulation in vivo, which provided new reference for understanding the health risks of microplastics and pesticides and sheds light on the potential risk to humans of their combined ingestion.

A review of microplastics in soil: Occurrence, analytical methods, combined contamination and risks

Microplastics (MPs) pollution is becoming a serious environmental issue of global concern. Currently, the effects of MPs on aquatic ecosystems have been studied in detail and in depth from species to communities. However, soils, the largest reservoir of MPs, have been less studied, and little is known about the occurrence, environmental fate and ecological impacts of MPs. Therefore, based on the existing knowledge, this paper firstly focused specifically on the main sources of soil MPs pollution and explored the main reasons for their strong heterogeneity in spatial distribution. Secondly, as a primary prerequisite for evaluating MPs contamination, we systematically summarized the analytical methods for soil MPs and critically compared the advantages and disadvantages of the different methods in the various operational steps. Furthermore, this review highlighted the combined contamination of MPs with complex chemical contaminants, the sorption mechanisms and the associated factors in the soil. Finally, the risks posed by MPs to soil, plants, the food chain and even humans were outlined, and future directions for soil MPs research were proposed, while the urgent need for a unified approach to MPs extraction and identification was emphasized. This study provides a theoretical reference for a comprehensive understanding of the separation of soil MPs and their ecological risk as carriers of pollution.

Distribution Patterns of Microplastics Pollution in Urban Fresh Waters: A Case Study of Rivers in Chengdu, China

Microplastics are widely found in oceans and rivers. In China, the research on microplastic pollution in inland urban fresh waters of China is insufficient. We studied microplastics in the surface waters of urban rivers in Chengdu, which is the largest city in western China. The concentration of microplastics in the analysis environment ranged from 5.00 to 10.5 items/L, and the average quantity was 8.82 items/L. The majority of the microplastics were transparent and took the form of fragments, particles, and fibers. Polyethylene terephthalate (PET) and polyamide (PA) were the dominant polymer types of the microplastics analyzed. Plastic particles ≤ 500 μm accounted for 69.8% of the total. This large proportion of small transparent microplastics in urban rivers in Chengdu is a potential threat to the growth of aquatic organisms and birds foraging from the river and may pose hazards to human health. Additionally, the correlation of microplastic content with population quantity and economic level was calculated by the Pearson coefficient method (p < 0.05), and the results showed that both have an important effect on the number of microplastics in rivers. This research provides a reference for understanding the level of microplastics in urban rivers in Chengdu and pollution control.

Riverine Plastic Pollution in Asia: Results from a Bibliometric Assessment

Rivers are important ecosystems, vital to the livelihoods of hundreds of millions of humans and other species. Despite their environmental, social, and economic importance, current use of rivers is unsustainable, due to a combination of solid waste and high levels of pollutants. Plastic materials are among the most predominant of such pollutants. Based on the need for additional research in this area, this study examines pressures put to rivers and explores trends related to riverine plastic pollution, with a focus on Asia. Apart from the bibliometric analysis, and relying on the collected information, examples describing the drivers of riverine plastic pollution in a sample of Asian countries are described, outlining the specific problem and its scope. Among some of the results obtained from it, mention can be made to the fact that much of the literature focuses on plastic pollution as a whole and less on one of its most significant ramifications, namely microplastics. Additionally, there is a need related to data availability on riverine plastic data and improving the understanding of transport mechanisms in relation to riverine plastic emission into the ocean. The results from this study illustrate the significance of the problems posed by plastic waste to Asian rivers and point out the fact that there are still significant gaps in respect of regulations and standards, which prevent improvements that are highlighted in this study. Based on the results of this bibliometric assessment, specific measures via which levels of riverine plastic pollution may be reduced are presented, bringing relevant new insights on this topic beyond the existing reviews.

Microplastic load in the surface water and Tilapia sparrmanii (Smith, 1840) of the river systems of Okavango Delta, Botswana

Microplastics are 'emerging' contaminants that threatens freshwaters and may have negative impact on the aquatic organisms. However, Botswana has no information on the status of microplastics, including freshwater like the Okavango Delta- the largest, inland wetland hosting wildlife, tourism, and supporting the socio-economic lifestyle of inhabitants. This study assessed the spatial distribution and characterization of microplastics in surface water and in the digestive organs of fish (Tilapia sparrmanii) from the Okavango delta. Surface water samples (156) and whole intact fish (15) were collected and analysed for microplastic contents by wet peroxide oxidation, potassium hydroxide (fish only), density separation, extraction, and stereomicroscope identification. The weight of microplastics for surface water samples varied from 138.18 to 381.67 µg m^-3 and abundance ranged from 10.18 to 22.67 items L^-1 with significant difference observed between sites in both variables. In tilapia, the highest microplastic abundance were found in the intestines then the stomach and the gills from the fish samples. Most prevailing size ranges of microplastics in fish and water samples were 1-2 mm and 2-3 mm while the most abundant shapes were fragments and fibres, respectively. Translucent microplastics were dominant in all samples. The results indicate the presence of microplastics in the Okavango delta even though they are very low (µg m^-3). This baseline information will provide insights on the loads of microplastics in surface water and the quantities ingested by fish in the Okavango delta hence the need for monitoring. It would also guide on the need for effective policies addressing plastic and microplastic pollution.

The Occurrence of Microplastics and the Formation of Biofilms by Pathogenic and Opportunistic Bacteria as Threats in Aquaculture

Aquaculture is the most rapidly growing branch of animal production. The efficiency and quality of the produced food depends on sustainable management, water quality, feed prices and the incidence of diseases. Micro- (MP < 5 mm) and nanoplastic (NP < 1000 nm) particles are among the current factors causing serious water pollution. This substance comes solely from products manufactured by humans. MP particles migrate from the terrestrial to the aquatic environment and adversely affect, especially, the health of animals and humans by being a favorable habitat and vector for microbial pathogens and opportunists. More than 30 taxa of pathogens of humans, aquacutural animals and plants, along with opportunistic bacteria, have been detected in plastic-covering biofilm to date. The mobility and durability of the substance, combined with the relatively closed conditions in aquacultural habitats and pathogens’ affinity to the material, make plastic particles a microbiological medium threatening the industry of aquaculture. For this reason, in addition to the fact of plastic accumulation in living organisms, urgent measures should be taken to reduce its influx into the environment. The phenomenon and its implications are related to the concept of one health, wherein the environment, animals and humans affect each other’s fitness.

Surface water, sediment, and biota: The first multi-compartment analysis of microplastics in the Karnafully river, Bangladesh

The Karnafullly River, which flows through Chattogram and falls into the Bay of Bengal, Bangladesh, is vulnerable to microplastic contamination. In this study, we looked at microplastics in the Karnafully River's surface water (5 sites), sediment (9 sites), and biota (4 species). Microplastic concentrations ranged from 0.57 ± 0.07 to 6.63 ± 0.52 items/L in surface water, 143.33 ± 3.33 to 1240 ± 5.77 items/kg dry weight in sediment, and 5.93 ± 0.62 to 13.17 ± 0.76 items/species in biota. A significant difference (P < 0.05) was found in the concentration of MPs in the Karnafully River's sediment, biota, and surface water. High percentage of fiber-shaped and small-sized MPs (<1 mm) were detected throughout the samples. Water and sediment MPs were often transparent/white and blue, whereas biota MPs were mostly black and red, indicating a color preference during biological uptake. The Bay of Bengal received 61.3 × 10⁹ microplastic items per day. The feeding zone of biota influenced the level of microplastics, with a trend of pelagic > demersal > benthic > benthopelagic. Polyethylene and polyethylene terephthalate were the most abundant polymer. Using the average fish intake rate in Bangladesh, we computed a possible consumption of 4015-7665 items of MPs/person/year.

Occurrence of Microplastics in Borehole Drinking Water and Sediments in Lagos, Nigeria

We investigated the occurrence of microplastics in samples of borehole drinking water and sediments obtained from borehole sites in Lagos Island, Nigeria. The samples were digested with hydrogen peroxide, pretreated, and filtered through a polytetrafluoroethylene membrane. The filtered microplastics were examined/analyzed under an attenuated total reflection Fourier-transformed infrared device, to quantify the microplastics. The results showed the presence of microplastics in drinking water and sediments from the sites, with plastic concentrations ranging from 206 to 1691 items m^-3 and 9-47 items kg^-1 for drinking water and sediments, respectively; polypropylene was the most common and was approximately 61.9% for borehole drinking water. In terms of shape distribution, plastic fragments were the highest, at 73.02%. The detected microplastics had a size range of 0.02-0.5 mm. In addition, sites with a lower percentage of microplastics had lower population densities and lower industrial activity, whereas areas of high industrial activity had high amounts of microplastics. Environ Toxicol Chem 2022;41:1721-1731. © 2022 SETAC.

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

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

Effect of cascade damming on microplastics transport in rivers: A large-scale investigation in Wujiang River, Southwest China

Rivers are the important channels for transporting microplastics into the ocean from land. Prosperous dam construction changed the connectivity of rivers, thereby reducing the flux of microplastics to the ocean. However, this process currently lacks verification for the large-scale watersheds. In this study, we investigated the Wujiang River in China to evaluate the interception of cascade dams on microplastics. The results showed that: 1) The midstream exhibits a high abundance of microplastics (606.6-1046.2 items·kg^-1) while the upstream and downstream reach exhibits relatively low pollution levels. The small-sized microplastics of 0-0.5 mm are easily migrated into downstream while the large-sized microplastics of 0.5-5 mm tend to deposit. 2) Ten kinds of plastic materials were found, in which polyethylene and polypropylene, originated from the developed tourism and fishery, account for 74.2% in all samples. 3) The earliest microplastics were found in the sediments of 1962. The abundance of microplastics in the sediments in seven reservoirs increased over time, impling the contribution of increasing human activities. 4) Positive correlations between the abundance of microplastics in sediments and local gross domestic product (GDP) (n = 33, R² = 0.89, p < 0.05) and negative correlations between microplastics abundance and reservoir basin area (n = 33, R² = 0.42, p < 0.05) revealed that GDP and watershed area are the key factors that control the distribution of microplastics. Our results help to understand the migration of microplastics between terrestrial and marine ecosystems.

Comparative analysis of microplastic organization and pollution risk before and after thawing in an urban river in Beijing, China

Urban rivers are potential sinks for microplastic (MP) contamination in the environment. However, the footprint of MPs in urban rivers is not well understood because it is influenced by natural and anthropogenic factors. This study focused on the occurrence, pollution risk, and potential sources of MPs in surface water and sediments before and after thawing in Shahe River, Beijing. The size distribution, morphological characteristics and polymer types of MPs were analyzed using a micro-Raman spectroscopy. The results showed that the average abundance of MP obviously increased after river thawing, from 1772 ± 1668 items·m^-3 to 3877 ± 2517 items·m^-3 in surface water and 4776 ± 4817 items·kg^-1 to 14,004 ± 5371 items·kg^-1 in sediments. The MP polymer types were more diverse after thawing. The main MP type in surface water changed from polyethylene terephthalate (PET) to polypropylene (PP). Moreover, PP was the most common type in sediments. Small-sized MPs (SMPs, 10-300 μm) were dominant in Shahe River, with the proportion increasing from 48.5% to 83.3% in surface water and from 84.3% to 94.4% in sediments after thawing. Although the MP pollution risk increased after thawing, it was still low in the Shahe River. Unfortunately, changes in polymer types caused by thawing and the emergence of toxic polymers increased the ecological risk in the urban river. These results revealed the information of MP contamination before and after thawing, and highlighted the barrier influence of river icing on the migration of MPs. Overall, the results presented a new perspective on the environmental behavior of microplastics in urban rivers, suggesting that the occurrence and dominance of SMPs and the emergence of toxic polymers in urban environmental media require close attention in the future.

A review of analytical methods and models used in atmospheric microplastic research

Microplastic pollution in the environment has become a source of concern in recent years. The transport and deposition of suspended atmospheric microplastics play an important role in the global linkage of microplastic sources and sinks. In this review, we summarized recent research progress on sampling devices, pretreatments, and identification methods for atmospheric microplastics. The total suspended particles and atmospheric deposition, including dust, rainfall, and snow samples, are the environmental carriers for atmospheric microplastic studies. There are active and passive sampling methods. Pretreatment depends on sample types and identification methods and includes sieving, digestion, density separation, filtration, and drying. The measured features for atmospheric microplastics include particle size distributions, shapes, colors, surface morphology, and polymer compositions, using stereomicroscopes, Fourier transform infrared spectroscopy, scanning electron microscopy, Raman spectroscopy, and liquid chromatography-tandem mass spectrometry. Laser direct infrared spectroscopy and thermochemical methods coupled with mass spectrometry are potential methods for identifying atmospheric microplastics. Currently, models for estimating the fluxes of atmospheric microplastic emission, transport, and deposition are in the initial stages of development; their implementation will enhance our understanding of the "microplastic cycle" globally based on simulated and observed data.

Ingestion and characterization of plastic debris by loggerhead sea turtle, Caretta caretta, in the Balearic Islands

Plastic waste has become ubiquitous pollutants in seas and oceans and can affect a wide range of species. For some marine species, plastic debris could pose a considerable threat through entanglement, ingestion, and habitat degradation and loss. Sea turtles are one of the most sensitive species, as their migratory behaviour and multifaceted life cycles make these reptiles especially vulnerable to the negative effects of plastic debris. The present study aimed to assess the amount and composition of plastic debris ingested by loggerhead turtles (Caretta caretta, Linnaeus, 1758) in the Balearic Islands Sea, thusly providing new information to complete the knowledge for this topic. In this work, 45 stranded dead C. caretta specimens were necropsied, and their digestive tract content analysed for the presence of plastic debris. Plastic objects were observed in 27 individuals (60.0%), with an average of 12.7 ± 4.7 plastic items per turtle. Litter in the faecal pellet was also monitored in 67 living individuals, observing plastic elements in 46 (68.7%) of the specimens, reporting an average of 9.7 ± 3.3 plastic elements per individual. Overall, 785 plastic items were found, measured, weighed and categorized according to size, colour, shape, and type of polymer. The main elements ingested were plastic sheets that were found in 65.3% of the turtles analysed, being white (42.7%) and transparent (29.2%) the most predominant colours. Most elements were macroplastics (59.3%), while microplastics were not found. Fourier Transform Infrared Spectrometry (FT-IR) analysis showed that high-density polyethylene and polypropylene were the main polymer plastics, representing 42.3% and 33.8% of the total, respectively. In conclusion, the high occurrence of plastic debris determined in the present study evidenced for the first time plastic ingestion in loggerhead turtles in the Balearic Islands, and highlights C. caretta as a bioindicator organism for marine pollution.

Toxicity evaluation of the combination of emerging pollutants with polyethylene microplastics in zebrafish: Perspective study of genotoxicity, mutagenicity, and redox unbalance

Despite the toxicity of microplastics (MPs) in freshwater fish has been demonstrated in previous studies, their effects when mixed with other pollutants (organic and inorganic) are poorly understood. Thus, we aimed to test the hypothesis that the association of polyethylene MPs (PE-MPs) to a mix of emerging pollutants induces more adverse genotoxic, mutagenic, and redox unbalance effects in adult zebrafish (Danio rerio), after 15 days of exposure. Although the accumulation of MPs in animals was greater in animals exposed to PE-MPs alone, erythrocyte DNA damage (comet assay) and the frequency of erythrocytic nuclear abnormalities (ENAs) evidenced in zebrafish exposed to PE-MPs alone were as pronounced as those observed in animals exposed to the mix of pollutant (alone or in combination with MPs), which constitutes the big picture of the current study. Moreover, we noticed that such effects were associated with an imbalance between pro-and antioxidant metabolism in animals, whose activity of superoxide dismutase (SOD) and catalase (CAT) was assessed in different organs which were not sufficient to counterbalance the production of reactive oxygen species [hydrogen peroxide (H₂O₂)] and nitrogen [nitric oxide (NO)] evaluated. The principal component analysis (PCA) also revealed that while the antioxidant activity was more pronounced in the brain and liver of animals, the highest production of H₂O₂ was perceived in the gills and muscles, suggesting that the biochemical response of the animals was organ-dependent. Thus, the present study did not demonstrate antagonistic, synergistic, or additive effects on animals exposed to the combination between PE-MPs and a mix of pollutants in the zebrafish, which reinforces the theory that interactions between pollutants in aquatic ecosystems may be as complex as their effects on freshwater ichthyofauna.

Plastic Interactions with Pollutants and Consequences to Aquatic Ecosystems: What We Know and What We Do Not Know

Plastics are a group of synthetic materials made of organic polymers and some additives with special characteristics. Plastics have become part of our daily life due to their many applications and uses. However, inappropriately managed plastic waste has raised concern regarding their ecotoxicological and human health risks in the long term. Due to the non-biodegradable nature of plastics, their waste may take several thousands of years to partially degrade in natural environments. Plastic fragments/particles can be very minute in size and are mistaken easily for prey or food by aquatic organisms (e.g., invertebrates, fishes). The surface properties of plastic particles, including large surface area, functional groups, surface topography, point zero charge, influence the sorption of various contaminants, including heavy metals, oil spills, PAHs, PCBs and DDT. Despite the fact that the number of studies on the biological effects of plastic particles on biota and humans has been increasing in recent years, studies on mixtures of plastics and other chemical contaminants in the aquatic environment are still limited. This review aims to gather information about the main characteristics of plastic particles that allow different types of contaminants to adsorb on their surfaces, the consequences of this adsorption, and the interactions of plastic particles with aquatic biota. Additionally, some missing links and potential solutions are presented to boost more research on this topic and achieve a holistic view on the effects of micro- and nanoplastics to biological systems in aquatic environments. It is urgent to implement measures to deal with plastic pollution that include improving waste management, monitoring key plastic particles, their hotspots, and developing their assessment techniques, using alternative products, determining concentrations of micro- and nanoplastics and the contaminants in freshwater and marine food-species consumed by humans, applying clean-up and remediation strategies, and biodegradation strategies.

Microplastic concentration, distribution and dynamics along one of the largest Mediterranean-climate rivers: A whole watershed approach

Microplastics (MPs) have been recognized as one of the most ubiquitous environmental pollutants globally. They have been found in all ecosystems studied to date, threatening biological diversity, ecosystem functioning and human health. The present study aimed to elucidate the environmental and anthropogenic drivers of MP dynamics in the whole catchment of the Biobío river, one of the largest rivers in South America. MP concentration and characteristics were analysed in 18 sites subjected to different sources of pollution and other human-related impacts. The sampling sites were classified in relation to altitudinal zones (highland, midland and lowland) and ecosystem types (fluvial and reservoir), and different water and territorial environmental variables were further collated and considered for analysis. Seven types of microplastic polymers were identified in the samples analysed, with a catchment mean (±SE) MP concentration of 22 ± 0.4 particles m^-3, and MP presence being significantly higher in lowlands (26 ± 2 particle m^-3) and in reservoirs (42 ± 14 particle m^-3). The most abundant type of MP was fragments (84%), with a mean concentration of 37 ± 6 particles m^-3. Overall, MP concentrations were low compared to those found in other studies, with a strong influence of human population size.

Microplastic pollution in urban Lake Phewa, Nepal: the first report on abundance and composition in surface water of lake in different seasons

Microplastics are man-made pollutants which have been detected in surface water and groundwater. Research on microplastic concentration in aquatic environment is attracting scientists from developing countries, but in Nepal no information regarding microplastic in freshwater system is available. Therefore, this study investigates the presence and abundance of microplastic in lake surface water of Phewa Lake, the second largest lake in Nepal. The average concentration of microplastic for surface water was 2.96 ± 1.83 particles/L in winter (dry) season and 1.51 ± 0.62 particles/L in rainy (wet) season. Significant difference with t = 4.687 (p < 0.01) in microplastic concentration was observed in two different seasons. Fibers (93.04% for winter and 96.69% for rainy season) were the commonly found microplastic type in lake water and transparent as the dominant color for the two seasons. Almost all the detected microplastic were found to be < 1 mm in size. Due to the small size of microplastic and unavailability of micro-Fourier transform infrared spectroscopy (μ-FTIR) and Raman spectroscopy in Nepal, polymer identification was not done. The findings from this study can provide a valuable baseline data on microplastics for the first time in Nepal's freshwater lake environment.

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.

Transmission of nanoplastics from Culex quinquefasciatus to Pardosa pseudoannulata and its impact on predators

Many studies have explored the effects of plastic particles on aquatic organisms. To date, however, few studies have reported on the effects of plastic particles on terrestrial invertebrates. Here, Culex quinquefasciatus (southern house mosquito, prey) and Pardosa pseudoannulata (wolf spider, predator) were used to explore the transmission of nanoplastics (NPs) from aquatic to terrestrial invertebrates and to verify the effects of NPs in prey on predators. Mosquito larvae were exposed to 0, 200, and 1000 NPs mL^-1 polystyrene, respectively, and then fed to spiders when they matured. Results showed that ingestion of NP-exposed mosquitoes affected the growth, development, and behavior of P. pseudoannulata, and the intestinal tissue structure, intestinal flora composition, and related enzymatic activities were also impacted. These results indicate that after spiders ingested NP-exposed mosquitoes, their growth, development, and predation ability were affected. This may prolong time to maturation and decrease the ability of spiders to survive and reproduce in the environment. Thus, plastic particles likely have a wide range of effects on organisms as well as the whole ecosystem.

An enhanced risk assessment framework for microplastics occurring in the Westerscheldt estuary

Microplastics (MPs) pollution in the aquatic environment raises considerable concerns. Freshwater system is generally considered as an important source for MPs transformation into the marine environment, however, only limited data on the MPs pollution in global freshwater systems is available at this time. In this study, we explored the abundance, characteristics and distribution of microplastics in the Scheldt River. The investigation results indicated that the abundance of microplastics in sediments (15-413 items/kg dry weight (DW)) was much higher than that in surface water (0-113 items/m³), and small size MPs (less than 500 μm) frequently appeared in sediments. Industrial activities were regarded as the major cause of MP discharging. Risk assessment models with using data of the concentration of MPs, polymer types and toxicity of MPs exposure were developed to assess the risk of MPs pollution in both surface water and sediment of the Westerscheldt estuary. Risk assessment results revealed that MPs exposure have potentially adverse effects on the aquatic ecosystem and human health. MPs tend to be transported from "Hotspots", such as urban or industries area, to remote areas. The risk assessment of MPs serves as a baseline for better understanding the distribution and characteristics of MPs and highlights the need of intensively monitoring to limit MPs release by intensively monitoring. This research provides a perspective on the risk of MPs that could be used in future studies.

A Meta-Analysis of the Characterisations of Plastic Ingested by Fish Globally

Plastic contamination in the environment is common but the characterisation of plastic ingested by fish in different environments is lacking. Hence, a meta-analysis was conducted to identify the prevalence of plastic ingested by fish globally. Based on a qualitative analysis of plastic size, it was determined that small microplastics (<1 mm) are predominantly ingested by fish globally. Furthermore, our meta-analysis revealed that plastic fibres (70.6%) and fragments (19.3%) were the most prevalent plastic components ingested by fish, while blue (24.2%) and black (18.0%) coloured plastic were the most abundant. Polyethylene (15.7%) and polyester (11.6%) were the most abundant polymers. Mixed-effect models were employed to identify the effects of the moderators (sampling environment, plastic size, digestive organs examined, and sampling continents) on the prevalence of plastic shape, colour, and polymer type. Among the moderators, only the sampling environment and continent contributed to a significant difference between subgroups in plastic shape and polymer type.

Critical review of microplastics removal from the environment

Globally, microplastics pollution has become a serious environmental threat due to their multitude sources, widespread occurrence, persistence, and adverse effects to ecosystem and the human health. Addressing this multifaceted threat requires innovative technologies that can efficiently remove microplastics from the environment. In this review, we first overviewed the source, occurrence, and potential adverse impacts of microplastics to human health. We then identified promising technologies for microplastics removal, including physical, chemical, and biological approaches. A detailed analysis of the advantages and limitations of different techniques was provided. We concluded this review with the current challenges and future research priorities, which will guide us through the path addressing microplastics contamination.

Microplastics in copepods reflects the manmade flow restrictions in the Kochi backwaters, along the southwest coast of India

This baseline study on microplastics (MPs) in calanoid copepods in the Kochi backwaters (KBW), India's largest estuary system on the west coast, focuses on (a) the spatiotemporal variations of MPs with the seasonal hydrography setting, and (b) how man-made flow restrictions of a large saltwater barrage contribute to MPs in copepods and their potential to transfer to higher trophic levels. This study found that MPs in copepods in the KBW ranged from av. 0.01 ± 0.014 to 0.11 ± 0.03 no./ind. seasonally. When the saltwater barrage shutters were fully/partially closed during the Pre-monsoon/Northeast Monsoon, MPs in copepods were considerably larger (av. 0.11 ± 0.03 no./ind., and av. 0.075 ± 0.02 no./ind., respectively) as compared to the Southwest Monsoon (av. 0.03 ± 0.01 no./ind.), when the barrage shutters were fully open. This shows the potential of man-made flow restrictions to increase the bioconcentration of MPs in copepods and their possible transfer to higher trophic levels through the food chain, adding to the region's previous discovery that much higher trophic level resources are polluted with a high concentration of MPs.

Are We Underestimating Anthropogenic Microfiber Pollution? A Critical Review of Occurrence, Methods, and Reporting

Anthropogenic microfibers, a ubiquitous environmental contaminant, can be categorized as synthetic, semisynthetic, or natural according to material of origin and production process. Although natural fibers, such as cotton and wool, originated from natural sources, they often contain chemical additives, including colorants (e.g., dyes, pigments) and finishes (e.g., flame retardants, antimicrobial agents, ultraviolet light stabilizers). These additives are applied to textiles during production to give textiles desired properties like enhanced durability. Anthropogenically modified "natural" and semisynthetic fibers are sufficiently persistent to undergo long-range transport and accumulate in the environment, where they are ingested by biota. Although most research and communication on microfibers have focused on the sources, pathways, and effects of synthetic fibers in the environment, natural and semisynthetic fibers warrant further investigation because of their abundance. Because of the challenges in enumerating and identifying natural and semisynthetic fibers in environmental samples and the focus on microplastic or synthetic fibers, reports of anthropogenic microfibers in the environment may be underestimated. In this critical review, we 1) report that natural and semisynthetic microfibers are abundant, 2) highlight that some environmental compartments are relatively understudied in the microfiber literature, and 3) report which methods are suitable to enumerate and characterize the full suite of anthropogenic microfibers. We then use these findings to 4) recommend best practices to assess the abundance of anthropogenic microfibers in the environment, including natural and semisynthetic fibers. By focusing exclusively on synthetic fibers in the environment, we are neglecting a major component of anthropogenic microfiber pollution. Environ Toxicol Chem 2022;41:822-837. © 2021 SETAC.

Occurrence, spatial distribution, and main source identification of ten bisphenol analogues in the dry season of the Pearl River, South China

Bisphenol analogues (BPs) including bisphenol a (BPA) have been broadly utilized as industrial feedstocks and unavoidably discharged into water bodies. However, there is little published data on the occurrence, distribution, and environmental risks of other BPs in surface water. In this study, ten BPs besides BPA were analyzed in surface water from the Pearl River, South China. Among these detected BPs, BPA, bisphenol F (BPF), bisphenol AF (BPAF), and bisphenol S (BPS) were the most frequently detected compounds. The median concentrations of the measured BPs were ranked in the order of BPA (34.9 ng/L) > BPS (24.8 ng/L) > BPAF (10.1 ng/L) > bisphenol F (BPF) (9.0 ng/L) > bisphenol B (BPB) (7.6 ng/L) > bisphenol C (BPC) (1.2 ng/L). Among them, BPA and BPS were predominant BPs, contributing 68% of the total ten BPs in surface water of the Pearl River. These results demonstrated that BPA and BPS were the most extensively utilized and manufactured BPs in this region. The source analysis of BPs suggested that the BPs may be originated from domestic wastewater, wastewater treatment plant (WWTP) effluent, and the leaching of microplastic in surface water of the Pearl River. The calculated BP-derived estrogenic activity exhibited low to medium risks in surface water, but their combined estrogenic effects with other endocrine disrupting compounds should not be ignored.

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.

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

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

Occurrence and Quantification of Natural and Microplastic Items in Urban Streams: The Case of Mugnone Creek (Florence, Italy)

The terrestrial environment is an important contributor of microplastics (MPs) to the oceans. Urban streams, strictly interwoven in the city network and to the MPs’ terrestrial source, have a relevant impact on the MP budget of large rivers and, in turn, marine areas. We investigated the fluxes (items/day) of MPs and natural fibers of Mugnone Creek, a small stream crossing the highly urbanized landscape of Florence (Italy) and ending in the Arno River (and eventually to the Tyrrhenian Sea). Measurements were done in dry and wet seasons for two years (2019–2020); stream sediments were also collected in 2019. The highest loads of anthropogenic particles were observed in the 2019 wet season (10⁹ items/day) at the creek outlet. The number of items in sediments increased from upstream (500 items/kg) to urban sites (1540 items/kg). Fibers were the dominant shape class; they were mostly cellulosic in composition. Among synthetic items, fragments of butadiene-styrene (SBR), indicative of tire wear, were observed. Domestic wastewater discharge and vehicular traffic are important sources of pollution for Mugnone Creek, especially during rain events. The study of small creeks is of pivotal importance to limit the availability of MPs in the environment.

Plastic mulch film induced soil microplastic enrichment and its impact on wind-blown sand and dust

Microplastics (MPs) pollution is being increasingly recognized as a global concern in all environments. Wind-blown sand and dust contaminated by MPs are an important pathway of MPs transport across different environments, which can result in on-site and off-site potential MP pollution. Here, we designed field experiments to detect MPs in surface soil and wind-blown sand and dust in farmlands with and without film mulch in a semi-arid region of northern China. This study provides the first insights into MPs enrichment in wind-blown sand and dust deposited by natural storms. The results reveal that fibers, fragments, and films constitute the major types of MPs in farmland soil and wind-blown sand and dust. The MPs abundances of 1-3 mm, <1 mm, and 3-5 mm items kg^-1 successively decrease. The enrichment of MPs in wind-blown dust is one to two orders of magnitude higher than that in wind-blown sand. For the farmlands with (without) film mulch, the MPs enrichment ratios ranged from 0.22 (0.29) to 1.35 (2.26) in the wind-blown sand and that varied from 1.79 (1.01) to 16.6 (25.79) in the wind-blown dust. Fibers are preferentially transported by wind erosion compared to fragments and films. Soil aggregating processes, wind speed, and MPs shape may influence enrichment in wind-blown sand and dust. Film mulch debris and the application of manure may be the primary sources of MPs in farmland soils. This study further highlights the importance of the transport of airborne MPs from surface soil into the atmosphere. Future research is required to establish the quantitative relationships between the MPs shape, wind speed, and surface soil properties and the MPs enrichment in wind-blown sand and dust.

Fat on plastic: Metabolic consequences of an LDPE diet in the fat body of the greater wax moth larvae (Galleria mellonella)

The caterpillar larvae of the greater wax moth (Galleria mellonella) are avid plastivores, as when provided a diet of low-density polyethylene (LDPE) they actively feed on it. Recent work has highlighted the importance of their microbiome in the putative biodegradation of this plastic polymer, though the impact of plastic metabolism on the insect host is less clear. In the present study, we undertook an integrative approach spanning all levels of biological organization to explore the effects of a plastic diet on the metabolic physiology of this animal model of plastic biodegradation. We demonstrate that an LDPE diet is not sufficient to maintain optimal larval growth and survival. In addition, we confirm that plastic fed waxworms retain their fat body lipid stores in a manner proportional to their individual polyethylene consumption suggesting a direct effect of LDPE biodegradation. At the functional level, the oxidative capacity of the fat body of LDPE-fed larvae is maintained reflecting unaltered metabolic function of the tissue. Finally, metabolomic analyses confirmed fat body lipid stores maintenance in LDPE-fed worms, but uncovered various other nutritional deficiencies. Overall, this work unveils novel insights in the complex interplay between LDPE biodegradation and the metabolic physiology of this model plastivore.

The contamination of microplastics in China's aquatic environment: Occurrence, detection and implications for ecological risk

The widespread occurrence of microplastics in aquatic ecosystems that resulted in environmental contamination has attracted worldwide attention. Microplastics pose a potential threat to the growth and health of aquatic organisms, thereby affecting the function of the ecosystems. As one of the top ten countries producing and consuming plastic products globally, China's aquatic ecosystems have been profoundly affected by microplastics. In this review, we have summarized the microplastics contamination in three typical water environments (marine environment, freshwater environment, and wastewater treatment plants) in China, elaborated on the adverse impacts of microplastics on the ecological environment, and evaluated the potential ecological risks exposed to the ecosystem. In addition, the progress of microplastics extraction methods, as the important basis of microplastics related research, in aquatic ecosystems was introduced, especially the difference between the extraction of microplastics from wastewater and sludge samples. At present, most of the research on microplastics focuses on "one point", such as a certain river or wastewater treatment plant. Research on the mitigation and transfer of microplastics among different connected water environments is still lacking. Also, the microscale ecotoxicity caused by microplastics is poorly understood. In the end, we proposed suggestions and perspectives for future research regarding microplastics in the aquatic ecosystems in China.

Investigation of microplastics release behavior from ozone-exposed plastic pipe materials

Microplastics (MPs) are detected in drinking water and plastic used during water treatment and distribution is one of the possible sources of MPs. This work aimed to investigate the MPs release behavior from ozone-exposed plastic pipe materials. The changes on physicochemical properties of the plastic materials were analyzed. The carbonyl groups introduction, the oxidation induction time variation, and the surface topography altering were detected after ozone exposure. The MPs release behavior varied between different plastic materials. As the ozone exposure duration of plastic materials prolonged, the released MPs abundance from the materials sharply increased, especially for LDPE, HDPE and PP. PVC was an exception where the released MPs abundance had little changes (p > 0.05). The total released MPs concentration from 20 h-aged samples could be ranked in order as follows: LDPE (656 ± 20 MP L^-1) > PP (349 ± 20 MP L^-1) > HDPE (337 ± 22 MP L^-1) > PVC (63 ± 13 MP L^-1). MPs release behavior was more likely to occur for LDPE, which was possibly related to the low oxidation resistance and weak stability of LDPE under ozone exposure. There was a more dominant contribution to MPs abundance increase caused by MPs release from aged plastic pipe materials than secondary MPs generation from original plastic particles. The generated MPs from 20 h-aged LDPE, HDPE, and PP accounted for 88.4%, 82.2%, and 88.3% of the total released MPs, respectively. For ozone-exposed plastic materials, the surface crack propagation and fragmentation posed an entry point for MPs generation. The proportion of generated MPs with polymer composition consistent with pipe materials (PE/PP) increased as the ozone exposure proceeded. Small-sized particles, especially 1-10 μm, were released more predominantly. This study provides an implication that possible MPs release from long-term aged plastic pipe materials under proper conditions could not be ignored.

Detection in influx sources and estimation of microplastics abundance in surface waters of Rawal Lake, Pakistan

The ever-growing production, usage and poor waste management practices of plastics are causing microplastics intrusion in freshwater environments all over the world. The identification of inflow processes and sources is equally important as the assessment of microplastic concentrations in freshwater. This study reports microplastic presence in the influx sources and provides an overall estimation of microplastic concentration in the surface water of a freshwater reservoir, Rawal Lake, Islamabad. In the current study, six major tributaries of Rawal lake were assessed for microplastic presence, out of which four tributaries showed microplastic contamination. Microplastics concentration in the lake ranged from 6.4 ± 0.5 particles/m³ to 8.8 ± 0.5 particles/m³. All the identified microplastics in tributaries and lake were secondary except granules. The prominent shape of microplastics among the studied waters was film, with transparent being the most frequent plastic-type according to color. Polyethylene (LDPE and HDPE) were the dominant type of microplastics found in the lake and the tributaries. More than 72% of microplastics had a size of 0.3-0.1 mm. This study provides a better understanding of the extent of microplastic pollution assessment in a freshwater lake with equal emphasis on microplastic presence in influx sources and the relationship of microplastics with fundamental water quality indicators (pH, temperature, dissolved oxygen, and biological oxygen demand), which may be beneficial in impeding the introduction of microplastics at sources.

Microplastics in the high-altitude Himalayas: Assessment of microplastic contamination in freshwater lake sediments, Northwest Himalaya (India)

In this study, we assess the magnitude, type, and sources of microplastic (MP) in lake bottom sediments collected from freshwater Anchar Lake, located in the Kashmir Valley, Northwest Himalaya. The MP identification was done on twenty-four lake bottom sediment samples under a stereo-microscope, and their polymer compositions were characterized using an Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy. The study reveals that 606 ± 360 (average ± SD, n = 24) numbers of MP were present per kilogram of dry sediment samples, with fibers (91%), fragments/films (8%), and pellets (1%) dominating the shape groups. Polyamide (PA, 96%) was the dominant polymer composition present in the sediment samples, followed by polyethylene terephthalate (PET, 1.4%), polystyrene (PS, 1.4%), polyvinyl chloride (PVC, 0.9%), and polypropylene (PP, 0.7%). Polymer Hazard Index (PHI) and Pollution Load Index (PLI) were used to evaluate the quality of sediments. It was noted that high PHI values (>1000) were due to the presence of PVC polymer. According to PLI values, sediments in the Anchar lake are less contaminated with MP. We conclude that MP in the Anchar Lake have a complex source derived mostly from the automobile, textile, and packaging industries.

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

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