Sampling and processing methods of microplastics in river sediments - A review

Occurrence and environmental fate of anti-influenza drugs in a subcatchment of the Yodo River Basin, Japan

Understanding the current situation and risk of environmental contamination by anti-influenza drugs in aquatic environments is key to prevent the unexpected emergence and spread of drug-resistant viruses. However, few reports have been focused on newer drugs that have recently been introduced in clinical settings. In this study, the behaviour of the prodrug baloxavir marboxil (BALM)-the active ingredient of Xofluza, an increasingly popular anti-influenza drug-and its pharmacologically active metabolite baloxavir (BAL) in the aquatic environment was evaluated. Additionally, their presence in urban rivers and a wastewater treatment plant (WWTP) in the Yodo River basin was investigated and compared with those of the major anti-influenza drugs used to date (favipiravir (FAV), peramivir (PER), laninamivir (LAN), and its active metabolite, laninamivir octanoate (LANO), oseltamivir (OSE), and its active metabolite, oseltamivir carboxylate (OSEC), and zanamivir (ZAN)) to comprehensively assess their environmental fate in the aquatic environment. The results clearly showed that BALM, FAV, and BAL were rapidly degraded through photolysis (2-h, 0.6-h, and 0.4-h half-lives, respectively), followed by LAN, which was gradually biodegraded (7-h half-life). In addition, BALM and BAL decreased by up to 47 % after 4 days and 34 % after 2 days of biodegradation in river water. However, the remaining conventional drugs, except for LANO (<1 % after 10 days), were persistent, being transported from the upstream to downstream sites. The LogKd values for the rates of sorption of BALM (0.5-1.6) and BAL (1.8-3.1) on river sediment were higher than those of conventional drugs (-0.5 to 1.7). Notably, all anti-influenza drugs were effectively removed by ozonation (>90-99.9 % removal) after biological treatment at a WWTP. Thus, these findings suggest the importance of introducing ozonation to reduce pollution loads in rivers and the environmental risks associated with drug-resistant viruses in aquatic environments, thereby promoting safe river environments.

Eco-toxic Risk Assessment of microplastics in water and sediment across Nigeria Offshore, Gulf of Guinea

Globally, the environmental impacts of microplastics (MPs) as emerging pollutants have drawn a lot of attention. This study aimed to assess the distribution and associated potential ecotoxic risk of MPs in the water and sediment of Nigeria's offshore waters. Water and sediment samples were collected from sixteen (16) stations in October 2023 and analysed using Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy and stereomicroscopy. For physical characterization, the composition of MPs in sediment and water was 73 particles/kg and 48 particles/L, respectively, while the ATR-FTIR composition at the Eastern Zone (EZ) was 705 particles/L and 1033 particles/kg, the Central Zone (CZ) was 212 particles/L and 338 particles/kg, and the Western Zone (WZ) was 223 particles/L and 218 particles/kg. The identified MPs shapes were filaments, plastic films, fibre, and microbeads. Polychloroprene (CR) (18.10% and 16.86%) at EZ and CZ and polyvinyl alcohol (PVA) (20.64%) at WZ were most abundant in sediment, respectively. In comparison, PVA (22.3%, 22.2%, and 21.08%) was most abundant across EZ, CZ, and WZ in water. The polymer-based plastic contamination factors (ppCf) and pollution load index (pPLI) showed low contamination and pollution load, and the polymer risk index (pRi) showed medium and low risk in water and sediment, respectively. The polymer ecological risks index (pERI) showed a high-risk level (pERI: 1,001-10,000) in water and sediment across the EZ, CZ, and WZ of the Nigerian offshore waters. In marine environments, an extensive environmental monitoring program and trend forecasting for microplastics are crucial. This study will provide theoretical and technical support for developing efficient legislation or policy on the prevention and control of plastic pollution.

Occurrence, potential sources, and ecological risk assessment of microplastics in the inland river basins in Northern China

Microplastics (MPs) are the pollutants, found widely across various environmental media. However, studies on the MP pollution in urban rivers and the necessary risk assessments remain limited. In this study, the abundance and characteristics of microplastics in a typical urban river were examined to evaluate their distribution, sources, and ecological risks. It was observed that the abundance of MPs in sediments (220-2840 items·kg-1 dry weight (DW)) was much higher than that in surface water (2.9-10.3 items·L-1), indicating that the sediment is the "sink" of river MPs. Surface water and sediment were dominated by small particle size MPs (< 0.5 mm). Fiber and debris were common shapes of MPs in rivers and sediments. The microplastics in river water and sediments were primarily white and transparent, respectively. Polypropylene (PP) and polyethylene (PE) were the major polymers found.

Microplastics from face mask impairs sperm motility

The COVID-19 pandemic has resulted in unprecedented plastic pollution from single-used personal protective equipment (PPE), especially face masks, in coastal and marine environments. The secondary pollutants, microplastics from face masks (mask MP), rise concern about their detrimental effects on marine organisms, terrestrial organisms and even human. Using a mouse model, oral exposure to mask MP at two doses, 0.1 and 1 mg MP/day for 21 days, caused no change in animal locomotion, total weight, or sperm counts, but caused damage to sperm motility with increased curvilinear velocity (VCL). The high-dose mask MP exposure caused a significant decrease in linearity (LIN) of sperm motility. Further testicular transcriptomic analysis revealed perturbed pathways related to spermatogenesis, oxidative stress, inflammation, metabolism and energy production. Collectively, our findings substantiate that microplastics from face masks yield adverse effects on mammalian reproductive capacity, highlighting the need for improved plastic waste management and development of environmentally friendly materials.

Microplastics in Asian rivers: Geographical distribution, most detected types, and inconsistency in methodologies

Microplastics pose a significant environmental threat, with potential implications for toxic chemical release, aquatic life endangerment, and human food chain contamination. In Asia, rapid economic growth coupled with inadequate waste management has escalated plastic pollution in rivers, positioning them as focal points for environmental concern. Despite Asia's rivers being considered the most polluted with plastics globally, scholarly attention to microplastics in the region's freshwater environments is a recent development. This study undertakes a systematic review of 228 scholarly articles to map microplastic hotspots in Asian freshwater systems and synthesize current research trends within the continent. Findings reveal a concentration of research in China and Japan, primarily investigating riverine and surface waters through net-based sampling methods. Polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET) emerge as the predominant microplastic types, frequently observed as fibers or fragments. However, the diversity of sampling methodologies and reporting metrics complicates data synthesis, underscoring the need for standardized analytical frameworks to facilitate comparative analysis. This paper delineates the distribution of microplastic hotspots and outlines the prevailing challenges and prospects in microplastic research within Asian freshwater contexts.

Regression analysis for the determination of microplastics in sediments using differential scanning calorimetry

This research addresses the growing need for fast and cost-efficient methods for microplastic (MP) analysis. We present a thermo-analytical method that enables the identification and quantification of different polymer types in sediment and sand composite samples based on their phase transition behavior. Differential scanning calorimetry (DSC) was performed, and the results were evaluated by using different regression models. The melting and crystallization enthalpies or the change in heat capacity at the glass transition point were measured as regression analysis data. Ten milligrams of sea sand was spiked with 0.05 to 1.5 mg of microplastic particles (size: 100 to 200 µm) of the semi-crystalline polymers LD-PE, HD-PE, PP, PA6, and PET, and the amorphous polymers PS and PVC. The results showed that a two-factorial regression enabled the unambiguous identification and robust quantification of different polymer types. The limits of quantification were 0.13 to 0.33 mg and 0.40 to 1.84 mg per measurement for semi-crystalline and amorphous polymers, respectively. Moreover, DSC is robust with regard to natural organic matrices and allows the fast and non-destructive analysis of microplastic within the analytical limits. Hence, DSC could expand the range of analytical methods for microplastics and compete with perturbation-prone chemical analyses such as thermal extraction-desorption gas chromatography-mass spectrometry or spectroscopic methods. Further work should focus on potential changes in phase transition behavior in more complex matrices and the application of DSC for MP analysis in environmental samples.

Removal of polystyrene microplastics using biochar-based continuous flow fixed-bed column

In the realm of environmental challenges, microplastics have emerged as a pressing threat, presenting risks to both individuals and ecosystems. Conventional treatment plants are presently not equipped for effectively removing these minute contaminants. This study presents an investigation into the potential of a continuous flow biochar column, utilizing biochar derived from banana peel through a nitrogen-free slow pyrolysis process for the removal of microplastics. A systematic exploration of various parameters, including bed height, flow rate, inflow microplastic concentration, and microplastic size is undertaken to discern their impact on polystyrene removal efficiency. A peak removal efficiency of 92.16% has been achieved under specific conditions: a 6-cm bed height, a 3-mL/min flow rate, an inlet concentration of 0.05 g/L, and microplastic sizes ranging from 150 to 300 µm. The removal efficiency was inversely affected by flow rate while directly influenced by bed height. To deepen the understanding of polystyrene removal on biochar, a detailed characterization of the synthesized material was carried out. The removal of microplastics by banana peel biochar (BPB) is observed to be dominated by adsorption and filtration processes. The entanglement of microplastics with minuscule biochar granules, capture between particles, and entrapment in the porous system were identified as the mechanisms of removal. Leveraging the hydrophobic nature of polystyrene microplastics, interactions with the hydrophobic functional groups in BPB result in effective adsorption. This is further complemented by self-agglomeration and filtration mechanisms that synergistically contribute to the elimination of larger agglomerates. The findings thus provide a comprehensive understanding, offering hope for a more effective strategy in mitigating the environmental impact of microplastics.

Exploring the influence of sediment motion on microplastic deposition in streambeds

Microplastics (MP) of all sizes and densities have been found deposited in streambeds. Several delivery processes were proposed to explain these observations. However, none of the previous studies explored these processes systematically, especially in cases of streambeds made of fine sediments that are regularly in motion. In this study, we quantified the effect of streambed motion on the deposition and accumulation of MP in streambed sediments using particle tracking simulations in a numerical flow and transport model. The model was run for streamwater velocities of 0.1-0.5 m s-1 and median grain sizes of 0.15-0.6 mm. Streambed morphodynamics were estimated from these input parameters using empirical relationships. MP propensity to become trapped in porous media was simulated using a filtration coefficient. For each grain size and streamwater velocity, a wide variety of filtration coefficients was used in simulations in order to predict the fate of particles in the sediment. We found that exchange due to sediment turnover leads to burial and long-term deposition of MP that originally were not expected to enter the bed due to size exclusion. The results also show that in streambeds with fine sediments, localized deposits of MP are expected to occur as a horizontal layer below the moving fraction of the bed (upper layer). However, increasing celerity reduces the depth of MP deposition in the streambed. We conclude that models that do not include the effect of bed motion on MP deposition are likely miscalculating the deposition, retention, resuspensions and long-term accumulation of MP in streambed sediments.

Microplastic pollution in urban rivers within China's Danxia landforms: Spatial distribution characteristics, migration, and risk assessment

The potential deleterious effects of microplastics on environmental integrity and human health have elicited global attention. Particularly vulnerable to microplastics are Danxia landforms, characterized by their unique topographical features and ecologically fragile milieu. Notwithstanding, empirical studies assessing the prevalence of microplastics in these unique landforms remain strikingly limited. The present investigation comprehensively examined the abundance of microplastics in surface water, sediment, and groundwater across six cities and six counties within the Danxia landforms. Comparative analysis revealed a moderate level of microplastic contamination in the urban rivers of the Danxia region relative to other freshwater rivers. Anthropogenic activities, notably urban wastewater treatment and tourism, emerged as principal contributors to microplastic pollution. Sedimentary microplastics exhibited an accumulative trend from upstream to downstream locations. The risk assessment revealed a high potential ecological risk in counties and a moderate risk in cities. Cluster analysis suggested that groundwater microplastics were a confluence of hydraulic interactions between surface and subsurface waters within the Danxia region. This investigation elucidates the microplastic contamination profile, origins, migratory patterns, and associated risks in Danxia's urban rivers, thereby furnishing scientific underpinning for health and ecological preservation strategies within urbanized Danxia landscapes.

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.

Microplastics and potentially toxic elements: A review of interactions, fate and bioavailability in the environment

In recent years, microplastics (MPs) have obtained growing public concern due to widespread distribution and harmful impacts. Their distinctive features including porous structure, small size, as well as large specific surface area render MPs to be carriers for transporting other pollutants in the environment, especially potentially toxic elements (PTEs). Considering the hot topic of MPs, it is of great significance to comb the reported literature on environmental behaviors of co-occurrence of MPs and PTEs, and systematically discuss their co-mobility, transportation and biotoxicity to different living organisms in diverse environmental media. Therefore, the aim of this work is to systematically review and summarize recent advances on interactions and co-toxicity of MPs and PTEs, in order to provide in-depth understanding on the transport behaviors as well as environmental impacts. Electrostatic attraction and surface complexation mainly govern the interactions between MPs and PTEs, which are subordinated by other physical sorption processes. Besides, the adsorption behaviors are mainly determined by physicochemical properties regarding to different MPs types and various condition factors (e.g., ageing and PTEs concentrations, presence of substances). Generally speaking, recently published papers make a great progress in elucidating the mechanisms, impact factors, as well as thermodynamic and kinetic studies. Bioavailability and bioaccumulation by plant, microbes, and other organisms in both aquatic and terrestrial environment have also been under investigation. This review will shed novel perspectives on future research to meet the sustainable development goals, and obtain critical insights on revealing comprehensive mechanisms. It is crucial to promote efficient approaches on environmental quality improvement as well as management strategies towards the challenge of MPs-PTEs.

Identification and quantification of polystyrene microplastics in marine sediments facing a river mouth through NMR spectroscopy

Accurate identification and quantification of microplastic pollution in marine sediments are crucial for assessing their ecological impact. In this study, we explored the potential of Nuclear Magnetic Resonance (NMR) spectroscopy as an analytical tool for the analysis of microplastics in complex environmental matrices such as marine sediments. Two common plastic polymers, polystyrene (PS) and acrylonitrile butadiene styrene (ABS), were investigated. The marine sediments facing the Tiber River mouth (Italy) were collected according to a bathymetric gradient. Results demonstrated the successful detection and quantification of PS in all sediment samples (within a range of 12.3-64.6 μg/L), while no ABS significant signals were found. An increment trend with depth was observed in the PS signal, relatable to its physicochemical properties and the Tiber River plume hydrodynamic characteristics. The NMR's non-destructive nature and minimal sample preparation represent a promising avenue for standardizing protocols to assess the microplastic distribution and impact in marine sediments.

Effects of near-bed turbulence on microplastics fate and transport in streams

Quantifying the impact of hyporheic exchange is crucial for understanding the transport and fate of microplastics in streams. In this study, we conducted several Computational Fluid Dynamics (CFD) simulations to investigate near-bed turbulence and analyze vertical hyporheic exchange. Different arranged spheres were used to represent rough and permeable sediment beds in natural rivers. The velocities associated with vertical hyporheic flux and the gravitational force were compared to quantify the susceptibility of microplastics to hyporheic exchange. Four scenario cases representing different channel characteristics were studied and their effects on microplastics movements through hyporheic exchange were quantitatively studied. Results show that hyporheic exchange flow can significantly influence the fate and transport of microplastics of small and light-weighted microplastics. Under certain conditions, hyporheic exchange flow can dominate the behavior of microplastics with sizes up to around 800 μm. This dominance is particularly evident near the sediment-water interface, especially at the top layer of sediments. Higher bed porosity enhances the exchange of microplastics between water and sediment, while increased flow conditions extend the vertical exchange zone into deeper layers of the bed. Changes in the bedform lead to the most pronounced vertical hyporheic exchange, emphasizing the control of morphological features on microplastics transport. Furthermore, it is found that sweep-ejection events are prevailing near the bed surface, serving as a mechanism for microplastics transport in rivers. As moving from the water column to deeper layers in the sediment bed, there's a shift from sweeps dominance to ejections dominance, indicating changes of direction in microplastics movement at different locations.

A critical review on remediation of microplastics using microalgae from aqueous system

Microplastics (MPs) are deemed to be a global concern due to their harmful negative effects on the aquatic environment and human beings. MPs have a significant impact on both fresh and marine water ecosystems. In many countries, there is concern about the deleterious consequences of MPs on human health due to the presence of MPs in aquatic life for higher intake of marine food (fish and shellfish). Exposure to MPs causes fish to suffer from growth retardation, neurotoxicity, and behavioural abnormalities and it affects human as well. It causes oxidative stress, neurotoxicity, cytotoxicity, and immune system disruption after being ingested to these contaminated fish in human body. Due to these reasons, it has become imperative to find ways to resolve this problem. This review paper represents a pioneering endeavor by consolidating comprehensive information on microplastic-polluted Indian riverine ecosystems and effective MPs removal methods into a single, cohesive document. It meticulously evaluates the principles, removal efficiency, benefits, and drawbacks of various techniques, aiming to identify the most optimal solution. Furthermore, this paper provides a comprehensive exploration of the interesting interactions between MPs and microalgae, delving into the intricate processes of hetero-aggregation. Additionally, it shines a spotlight on the latest advancements in understanding the efficacy of microalgae in removing MPs, showcasing recent breakthroughs in this field of research. Moreover, the work goes beyond conventional assessments by elucidating the characteristics of MPs and exploring diverse influencing parameters that impact MPs removal by microalgae and also addresses the potential future aspects. This thorough investigation uncovers important factors that could significantly contribute to the development of more efficient and sustainable remediation strategies.

A review on constructive classification framework of research trends in analytical instrumentation for secondary micro(nano)plastics: What is new and what needs next?

Secondary micro(nano)plastics generated from the degradation of plastics pose a major threat to environmental and human health. Amid the growing research on microplastics to date, the detection of secondary micro(nano)plastics is hampered by inadequate analytical instrumentation in terms of accuracy, validation, and repeatability. Given that, the current review provides a critical evaluation of the research trends in instrumental methods developed so far for the qualitative and quantitative determination of micro(nano)plastics with an emphasis on the evolution, new trends, missing links, and future directions. We conducted a meta-analysis of the growing literature surveying over 800 journal articles published from 2004 to 2022 based on the Web of Science database. The significance of this review is associated with the proposed novel classification framework to identify three main research trends, viz. (i) preliminary investigations, (ii) current progression, and (iii) novel advances in sampling, characterization, and quantification targeting both micro- and nano-sized plastics. Field Flow Fractionation (FFF) and Hydrodynamic Chromatography (HDC) were found to be the latest techniques for sampling and extraction of microplastics. Fluorescent Molecular Rotor (FMR) and Thermal Desorption-Proton Transfer Reaction-Mass Spectrometry (TD-PTR-MS) were recognized as the modern developments in the identification and quantification of polymer units in micro(nano)plastics. Powerful imaging techniques, viz. Digital Holographic Imaging (DHI) and Fluorescence Lifetime Imaging Microscopy (FLIM) offered nanoscale analysis of the surface topography of nanoplastics. Machine learning provided fast and less labor-intensive analytical protocols for accurate classification of plastic types in environmental samples. Although the existing analytical methods are justifiable merely for microplastics, they are not fully standardized for nanoplastics. Future research needs to be more inclined towards secondary nanoplastics for their effective and selective analysis targeting a broad range of environmental and biological matrices.

Hydro-geomorphic perspectives on microplastic distribution in freshwater river systems: A critical review

Freshwater river systems are commonly defined as the main transport paths of microplastics (MP) from land into the seas. A shift in research interest from oceans to rivers can be observed, as a large number of i) case studies, ii) review papers and iii) experimental studies in this field have been published recently. Still, studies often lack an in-depth consideration of quantification, as units are mostly based on item numbers. Spatiotemporal aspects are often neglected. Transport paths linking MP sources and sinks in the environment are insufficiently understood and only recently the awareness increased that sustainable management of the MP pollution cannot be addressed without a sound knowledge of water- and sediment-driven MP transport. Within this review paper, we therefore i) reviewed 92 MP case-studies, with a special focus on spatiotemporal aspects and ii) gathered and compared global load-estimation data from these studies. We then outlined the key processes determining MP movement in rivers on the basis of existing laboratory experiments and theoretical approaches. A procedure to effectively compare units of MP in the water column and in riverine sediments was developed on the basis of i) an extensive MP-dataset in German waterways and ii) suspended sediment concentrations (SSC) of nearest monitoring stations of the German water and shipping authority. Our analysis indicates that relating MP in water samples to SSC reduces the often stated large difference between MP concentrations in the water column and bed sediments and therefore relativizes the importance of river beds as a major "MP sink". As for a quantification of MP fluxes, the use of MP masses as unit is crucial, we applied an approach to convert MP items to masses with the help of i) a power-law distribution of MP-particle size, triangular distributions of ii) form-ratios and iii) polymer densities. An evaluation with an own, extensive dataset of MP-particles showed reasonable results. Therefore, we translated global load data from item numbers to mass values for further analysis. Values were within a reasonable range, especially when considering the respective catchment size of each river at the sampling site.

Characterization and removal efficiencies of microplastics discharged from sewage treatment plants in Southeast Spain

Microplastics (MPs) are ubiquitous pollutants that can effectively harm different ecosystems. The information on the relative contribution of wastewater treatment plants (WWTPs) to the surrounding environment is important, in order to understand ecological health risks and implement measures to reduce their presence. This focus article presents a quantitative assessment on the relative concentration and types of MPs delivered from four WWTPs located at the Southeast of Spain. Samples from WWTPs were collected throughout a four-year period, comprising more than 1,200 L of analyzed wastewater and 3,215 microparticles isolated. Density extraction with 1.08 g/mL NaCl salt solution was systematically used as the main separation method, in a simple and reliable manner, and repeat extraction cycles did not play any significant impact on the study outcomes. The four WWTPs had removal efficiencies between 64.3% and 89.2% after primary, secondary, and tertiary treatment phases, without diurnal or daily variations. Advanced treatment methods displayed a lower removal rate for fibers than for particulate MPs. The abundance of MPs was always higher and with a lower mean size in wastewater samples collected in Autumn than for the rest of seasons. MPs dumped from WWTPs in large quantities into the environment are meant to be regarded as an important point source for aquatic and terrestrial environments.

Effects of microplastics and arsenic on plants: Interactions, toxicity and environmental implications

Microplastics are emerging pollutants that are ubiquitously present in environment. Occurrence and dispersion of microplastics in the soil can pose a considerable risk to soil health and biodiversity, including the plants grown in the soil. Uptake and bioaccumulation of microplastics can have detrimental effects on different plant species. Additionally, the co-presence of microplastics and arsenic can cause synergistic, antagonistic, or potentiating toxic impacts on plants. However, limited studies are available on the combined effects of microplastics and arsenic on plants. This paper elucidates both the individual and synergistic effects of microplastics and arsenic on plants. At the outset, the paper highlighted the presence and degradation of microplastics in soil. Subsequently, the interactions between microplastics and plants, accumulation, and influences of microplastics on plant growth and metabolism were explained with underlying mechanisms. Combined effects of microplastics and arsenic on plant growth, metabolism, and toxicity were discussed thereafter. Combined toxic effects of microplastics and arsenic on plants can have detrimental implications on environment, ecosystems and biodiversity. Further investigations on food chain and human health are needed in the context of microplastic-arsenic interactions.

Abundance, characteristics, and ecological risks of microplastics in the riverbed sediments around Dhaka city

Microplastic (MP) pollution has become an escalating problem in Bangladesh due to its rapid urbanization, economic growth, and excessive use of plastics; however, data on MP pollution from fresh water resources in this country are limited. This study investigated microplastics pollution in riverbed sediments in the peripheral rivers of Dhaka, the capital of Bangladesh. Twenty-eight sediment samples were collected from the selected stations of the Buriganga, Turag, and Balu Rivers. Density separation and wet-peroxidation methods were employed to extract MP particles. Attenuated total reflectance-Fourier transform infrared spectroscopy was used to identify the polymers. The results indicated a medium-level abundance of MPs in riverbed sediment in comparison with the findings of other studies in freshwater sediments worldwide. Film shape, white and transparent color, and large-size (1-5 mm) MPs were dominant in the riverbed sediment. The most abundant polymers were polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET). Pollution load index (PLI) values greater than 1 were observed, indicating that all sampling sites were polluted with MPs. An assessment of ecological risks, using the abundance, polymer types, and toxicity of MPs in the sediment samples, suggested a medium to very high ecological risk of MP pollution of the rivers. The increased abundance of MPs and the presence of highly hazardous polymers, namely; polyurethane, acrylonitrile butadiene styrene, polyvinyl chloride, epoxy resin, and polyphenylene sulfide, were associated with higher ecological risks. Scanning electron microscopy (SEM) analysis indicated that the MPs were subjected to weathering actions, reducing the size of MPs, which caused additional potential ecological hazards in these river ecosystems. This investigation provides baseline information on MP pollution in riverine freshwater ecosystems for further in-depth studies of risk assessment and developing strategies for controlling MP pollution in Bangladesh.

Mission Tara Microplastics: a holistic set of protocols and data resources for the field investigation of plastic pollution along the land-sea continuum in Europe

The Tara Microplastics mission was conducted for 7 months to investigate plastic pollution along nine major rivers in Europe-Thames, Elbe, Rhine, Seine, Loire, Garonne, Ebro, Rhone, and Tiber. An extensive suite of sampling protocols was applied at four to five sites on each river along a salinity gradient from the sea and the outer estuary to downstream and upstream of the first heavily populated city. Biophysicochemical parameters including salinity, temperature, irradiance, particulate matter, large and small microplastics (MPs) concentration and composition, prokaryote and microeukaryote richness, and diversity on MPs and in the surrounding waters were routinely measured onboard the French research vessel Tara or from a semi-rigid boat in shallow waters. In addition, macroplastic and microplastic concentrations and composition were determined on river banks and beaches. Finally, cages containing either pristine pieces of plastics in the form of films or granules, and others containing mussels were immersed at each sampling site, 1 month prior to sampling in order to study the metabolic activity of the plastisphere by meta-OMICS and to run toxicity tests and pollutants analyses. Here, we fully described the holistic set of protocols designed for the Mission Tara Microplastics and promoted standard procedures to achieve its ambitious goals: (1) compare traits of plastic pollution among European rivers, (2) provide a baseline of the state of plastic pollution in the Anthropocene, (3) predict their evolution in the frame of the current European initiatives, (4) shed light on the toxicological effects of plastic on aquatic life, (5) model the transport of microplastics from land towards the sea, and (6) investigate the potential impact of pathogen or invasive species rafting on drifting plastics from the land to the sea through riverine systems.

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

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

Pretreatment methods for monitoring microplastics in soil and freshwater sediment samples: A comprehensive review

This paper reviews the currently used pretreatment methods for microplastics (MPs) analysis in soil and freshwater sediments, primarily sample processing, pretreatment, and characterization methods for MPs analysis. In addition, analytical tools (e.g., lab instruments), MPs characteristics, and MPs quantity, are included in this review. Prior to pretreatment, soil and sediment samples are typically processed using sieving and drying methods, and a sample quantity of <50 g was mostly used for the pretreatment. Density separation was commonly performed before organic matter removal. Sodium chloride (NaCl) and zinc chloride (ZnCl₂) were most often used for density separation, and hydrogen peroxide (H₂O₂) oxidation was most frequently used to remove organic matter. Although advantages of each pretreatment method have been investigated, it is still challenging to determine a universal pretreatment method due to sample variability (e.g., sample characteristics). Furthermore, it is highly required to establish standard pretreatment methods that can be used for various environmental matrices, including air, water, and wastes as well as soil and sediment.

Research status and prospects of microplastic pollution in lakes

As an emerging pollutant, microplastics have attracted widespread concern around the world. Research on microplastics was first conducted in oceans, and in recent years, inland water, especially lakes, has gradually become a hot spot. This paper systematically reviews the sampling, separation, purification, and identification technologies used to assess microplastics in lakes and summarizes the occurrence of lake microplastics worldwide. The results show that microplastics are widespread in lake water and sediment. There are obvious geographical differences in the occurrence of microplastics. The abundance of microplastics in different lakes varies greatly. The forms are mostly fibrous and fragments, and the main polymers are polypropylene (PP) and polyethylene (PE). Previous papers have failed to comment in as much detail on the microplastic sampling techniques employed within lake systems. The sampling and analysis methods are critical to accurately evaluating contamination results. Due to the widespread presence of microplastics and the lack of uniform standards, there are various sampling methods. Trawls and grabs are most widely used in the sampling of lake water bodies and sediment, and sodium chloride and hydrogen peroxide are the most widely used media for flotation and digestion, respectively. In the future, it will be critical to establish unified standards for lake microplastic sampling and analysis technology, further explore the migration mechanism of microplastics in lake systems, and pay attention to the impact of microplastics on lake ecosystems.

Assessment of pollution and risks associated with microplastics in the riverine sediments of the Western Ghats: a heritage site in southern India

There is very little knowledge on microplastic pollution in the Western Ghats (WG), a heritage site in southwest India. To address this, we have studied the spatiotemporal variations of sedimentary microplastics (MPs) from the River Sharavathi, a pristine river in the Western Ghats (WG), southern India. The rich biodiversity in the region makes it relevant to analyse the distribution of this emerging pollutant that is causing harm to the biota and the ecosystem. We analysed the sedimentological and carbon content (organic and inorganic) of these sediments and explored their relationship with MPs. Finally, risk assessment indices such as the Pollution Load Index (PLI), the Polymer Hazard Index (PHI), and the Potential Ecological Risk Index (PERI) were calculated to detect the levels of plastic pollution. The concentration of MPs ranged from 2.5 to 57.5 pieces/kg and 0 to 15 pieces/kg during the pre-monsoon and post-monsoon seasons, respectively. The dip in the MPs' abundance during the post-monsoon season was due to the extremely high rainfall in the river basin during July-August 2019, which would have entrained the sedimentary MPs and transported them to the coast/Arabian Sea. Smaller MPs (0.3-1 mm) were more abundant than the larger MPs (1-5 mm), mainly due to the breakdown of sedimentary plastics by physical processes. Fragments, films, foams, and fibres were the main categories of MPs, and the main polymers were polyethylene, polyethylene terephthalate, and polypropylene. No significant relationship was observed between the sedimentological properties and microplastics, which may be due to the different physical properties of sediments and microplastics. The PLI, PHI, and PERI indices suggest different contamination levels in the river basin. Based on the PLI scores, all the samples belong to the hazardous level I suggesting minor risk category, and the risk of microplastic pollution falls under the high to hazardous risk category based on the PHI values. The PERI value ranged from 160 to 440 and 40 to 2240 during the pre-monsoon and post-monsoon seasons, respectively. The risk assessment in a region known for its rich biodiversity is crucial, as the data can be used by the district administration to mitigate plastic pollution.

Spatial and temporal variability of microplastic abundance in estuarine intertidal sediments: Implications for sampling frequency

Microplastics (<5 mm) are well documented across shorelines worldwide; however, high variability in microplastic abundance is often observed within and among field studies. The majority of microplastic surveys to date consist of single sampling events that do not consider spatiotemporal variability as a potential confounding factor in the interpretation of their results. Therefore, these surveys may not accurately capture or reflect levels of microplastic contamination in the environment. Here, we provide the first investigation of small-scale spatial and temporal variability of microplastic abundance, distribution, and composition in the intertidal zone of an urbanized US estuary to better understand the short-term, daily spatiotemporal variability of microplastics in dynamic coastal environments. Intertidal sediment was collected from both the low and high intertidal zones of a sandy estuarine beach located in South Carolina, southeastern US every 1 to 2 days at low tide over 17 days (12 sampling events; total n = 72). Study-wide, microplastic abundance ranged from 44 to 912 microplastics/m² and consisted primarily of polyethylene, nylon, polyester, and tire (or tyre) wear particles. High temporal variability was observed, with microplastic abundance differing significantly among sampling events (p = 0.00025), as well as among some consecutive tidal cycles occurring within 12 h of each other (p = 0.007). By contrast, low spatial variability was observed throughout the study with no significant differences in microplastic abundance detected between the low and high intertidal zones (p = 0.76). Of the environmental factors investigated, wind direction on the day of sampling had the greatest effect on temporal microplastic variability. Our results demonstrate that there can be significant temporal variability of microplastic abundance in estuarine intertidal sediments and are important for informing the methods and interpretation of future microplastic surveys in dynamic coastal environments worldwide.

Microplastics pollution in freshwater sediments: The pollution status assessment and sustainable management measures

Microplastics (MPs) pollution in freshwater sediments has brought hidden dangers to food and drinking water supply. Implementing sustainable management measures for MPs pollution in freshwater sediments has become an inevitable trend for sustainable development of society. Existing studies still lacked sufficient discussion in sustainable management of MPs pollution in freshwater sediments. This makes it difficult to formulate sustainable management measures for MPs pollution in freshwater sediments. This study analyzed the pollution status of MPs in freshwater sediments from 84 study areas. The results showed that current studies on MPs pollution in freshwater sediments were mainly concentrated in densely populated and economically developed areas. The average abundance of MPs in freshwater sediments from collected study areas was 1290.88 items/kg, this brought a potential threat to sustainable development in surrounding areas. The pollution load level and potential ecological risk level of MPs in freshwater sediments from these study areas were low. Reducing MPs discharge and restricting the use of high-risk polymers are effective ways to prevent the deterioration of MPs pollution status in freshwater sediments. The abundance and types of MPs in freshwater sediments from these study areas were affected by human activities. Sustainable management of MPs pollution in freshwater sediments from collected study areas requires establishing a lifecycle management system for plastic products, and the industrial structures should be optimized. In addition, legislation and market regulation are effective ways to restrict the discharge of plastic wastes. Sustainable management of MPs in freshwater sediments requires the synergy of legislation and market regulation.

A Production and Fractionation Protocol for Polyvinyl Chloride Microplastics

Concerns about the presence of microplastics in the environment has increased in recent years, prompting more attention from scientists. Thorough exposure studies using artificially produced microplastics containing additives are required to assess their potentially hazardous effects. Therefore, an efficient microplastic production and fractionation protocol was established using a cryogenic grinding and wet-sieving approach. The developed cryogenic grinding method was able to produce (20-40 g/h) polyvinyl chloride (PVC) microplastics having a volume-weighted mean particle size of 391 µm and a span of 2.12. Performing a second grinding cycle on the same particles resulted in microplastics which were smaller (volume-weighted mean size = 219 μm) and had a narrower particle size distribution (span = 1.59). In addition, the microplastics were also fractionated into different particle size ranges using a vibrating wet-sieving tower. The latter technique allowed separating 10 g of PVC microplastics into seven different fractions using six sieves (Ø 200 mm) for 30 min while shaking. By using the developed method, PVC microplastics could easily be made and fractionated into desired particle-size ranges. The proposed protocol could also be adjusted to produce and fractionate microplastics of other plastics.

Occurrence, distribution and sources of microplastics in beach sediments of Miri coast, NW Borneo

Microplastics (MPs) pollution has gained a lot of global interests due to its toxicity to the surrounding ecosystems. The aim of this study is to identify the abundances, physical characteristics, polymer type and elemental composition of MPs in beach sediments of Miri coast, located in Sarawak State, East Malaysia. A total of 1553 particles from 24 sediment samples, collected from eight different beaches along Miri coastline were identified. MPs from the sediments were extracted using density separation method and analyzed through stereoscopic microscope, ATR-FTIR and SEM-EDX. MPs were present most abundant in Lutong Beach, which is the hotspot for the recreational activities. Fragments were identified as the highest abundance type of MPs, followed by fiber, foam and pellet. MPs of size of <1 mm were predominantly present in the samples. Varieties of colors were distinguished in which transparent or no color MPs were the highest quantity studied in the samples. Polymers identified were mainly polyethylene (PE), polyester (PET), polystyrene (PS) and polypropylene (PP), derived from primary and secondary MPs. Carbon and oxygen were dominant and have the highest concentration identified with other elements such as Ca, Al, Ti and Cl. The primary use of these elements as additives are associated with the manufacturing process as they are used to enhance the quality during plastic production. The outcome of this study is to be the first report to identify and characterize the MPs in beach sediments of Miri coast. The occurrence of MPs in Miri beaches may negatively impact marine organisms as this affects their food chain. As consumers, humans are most likely to be affected by the presence of MPs due to their consumption of marine animals, particularly fish present in this region.

First evidence of microplastics isolated in European citizens' lower airway

Microplastics (MPs) have been detected in all environmental locations, including the atmosphere. However, few studies have investigated the presence of airborne MPs in the human respiratory system. Our research purpose was to investigate these pollutants in the lower human airways of 44 adult European citizens, using bronchoalveolar lavage fluid (BALF) collection as a minimally invasive method, that enables the detection of these pollutants in living patients. We studied the relationship between the patients' life habits and physiological parameters, based on background information and medical and occupational history, and the concentration of MPs isolated from their respiratory systems. Our results indicate that most MPs were in the form of microfibers (MFs) (97.06%), with an average concentration of 9.18 ± 2.45 items/100 mL BALF, and only 5.88% (0.57 ± 0.27 items/100 mL BALF) were particulate MPs, without a significant relationship with environmental, physiological, or clinical factors. The average size was 1.73 ± 0.15 mm, with the longest dimension (9.96 mm) corresponding to a polyacrylic fiber. Taken together, the results demonstrated the occurrence of MPs in the lower human airway, although more studies are necessary to elucidate the negative effects these pollutants could induce in the human respiratory system and its associated diseases.

An Insight into the Sorption Behavior of 2,3,7,8-Tetrachlorodibenzothiophene on the Sediments and Paddy Soil from Chaohu Lake Basin

Considering the frequent detection of polychlorinated dibenzothiophenes (PCDTs) in various environmental matrices and the potential ecological health risks, the environmental behavior of such compounds needs to be elucidated further. In this work, the sorption behavior of 2,3,7,8-tetrachlorodibenzothiophene (2,3,7,8-TCDT) onto three sediments and paddy soil from Chaohu Lake were investigated via batch equilibration experiments. From the perspective of sorption kinetics and isotherms, the sorption characteristics and mechanism of 2,3,7,8-TCDT on the above four carriers were compared, and the relationship between their structural characteristics and soil sorption capacity was discussed. Results suggested that rapid sorption played the primary role during the sorption process of 2,3,7,8-TCDT and the corresponding sorption isotherms were well fitted using the Freundlich logarithmic model. Moreover, the effects of pH and dissolved organic matter (DOM) on the sorption of 2,3,7,8-TCDT were investigated. The maximum sorption capacity of 2,3,7,8-TCDT on sediment was under acidic pH condition (pH = 4.0). Meanwhile, DOM at a low level promoted the sorption capacity of sediment toward 2,3,7,8-TCDT, while the high concentration of DOM inhibited this effect. In addition, the values of logK_oc were obtained using high-performance liquid chromatography (HPLC) and did not show any significant correlation with organic carbon (OC) contents, thereby indicating that the partition effect was the dominating influencing factor for the sorption of 2,3,7,8-TCDT both on sediments and soil. This work provides useful data to understand the sorption behavior of 2,3,7,8-TCDT on sediments and soil and assess its potential environmental risk.

Critical effect of biodegradation on long-term microplastic weathering in sediment environments: A systematic review

Microplastic (MP) pollution in global sediment has been intensely studied and recognized as the ultimate sink for residual MPs in terrestrial and aquatic ecosystems. During MP long-term retention in sediments, plastic-degrading bacteria (i.e., Flavobacteriaceae, Bacillus, Rhodobacteraceae, and Desulfobacteraceae) can utilize those MPs as their carbon and energy sources through enzyme (hydrolase and oxidoreductase) reactions, which further alter or transform high molecular weight MP polymers into lower molecular weight biodegradation byproducts (i.e., monomers and oligomers) and release toxic additives. In other words, MPs can act as durable substrates for plastic-degrading bacteria in sediments. However, to date, the biodegradation rates of MPs in sediment environments are still poorly understood due to their limited degradation efficiency. Herein, we review the enzyme-induced biodegradation processes of MPs in sediment environments, which is important for accessing the alteration of MP properties and their potential ecological risks after undergoing long-term weathering processes. In addition, the factors associated with the MP properties (polymer type, molecular weight, crystallinity, and hydrophobicity) and sediment conditions (sediment type, temperature, pH, salinity, and oxygen content) that influence plastic degradation processes are also reviewed. The mechanisms may relate to the MP properties and sediment conditions that can influence microbial abundance, enzyme concentrations, and enzyme activities, thus altering MP biodegradation ratios. We anticipate that the observations reviewed in this study will pose a new issue to better understand the formation process, fate, and potential ecological risks associated with aged MPs in sediment environments.

Hidden problems in geological heritage sites: The microplastic issue on Saint Mary's Island, India, Southeast Arabian Sea

Microplastics (MPs) have become a dominant constituent of several oceanic islands. This study focuses on the occurrence and distribution of MPs present in the beach sediments of Saint Mary's Island (SMI), a geological heritage site located in the south-eastern part of the Arabian Sea. The average (standard deviation) abundance of MPs on this island was 97.18 (80.49) particles/kg. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy revealed that MPs are composed of high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyamide (PA). Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS) highlighted the presence of Cr, As, Pb, and Cd (harmful pollutants) on MP surfaces. The MPs in the SMI are largely contributed by the nearby fishing harbour, touristic beaches and estuaries. The results of this study, act as a starting point for continuous environmental monitoring in this unique region of the world.

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

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

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.

Widespread microplastic pollution in mangrove soils of Todos os Santos Bay, northern Brazil

Microplastics have been studied in sediments from coastal and aquatic environments, but contamination of mangrove soils is still relatively unknown in most mangroves around the world. In this study, the presence of microplastics was investigated in six mangrove soils around the Todos Santos Bay (TSB), the largest and most important navigable bay on the Brazilian coast. Samples were collected at three depths (surface, 10 cm, and 30 cm) at three different distances from the lower tidal area. Ten grams of soil were sieved in a 150 μm mesh and centrifuged with ZnCl₂ solution (density of 1.5 kg dm^-3) for the extraction of microplastics. The microplastics were quantified, measured, and described using a systematic photographic method and the ImageJ program. Microplastics were abundant in all samples, with a mean of 10,782 ± 7,671 items kg^-1 (max.: 31,087 items kg^-1, only one sample <2,000 items kg^-1), higher than any other value reported worldwide. The abundances varied among the six mangroves studied, with a predominance of fibers and mean size of 196 μm. Even remote mangroves were highly polluted, reflecting a large dispersion of the pollutants. The abundance did not differ significantly between soil depths, evidencing a continuous input and burial of microplastics in the soil up to 30 cm. The investigation of the source of microplastics and their presence in water and biota is urgent in this Brazilian region, and these results emphasize the need for global actions to protect coastal ecosystems.

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.

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.

Emerging investigator series: microplastic sources, fate, toxicity, detection, and interactions with micropollutants in aquatic ecosystems - a review of reviews

Hundreds of review studies have been published focusing on microplastics (MPs) and their environmental impacts. With the microbiota colonization of MPs being firmly established, MPs became an important carrier for contaminants to step inside the food web all the way up to humans. Thus, the continuous feed of MPs into the ecosystem has sparked a multitude of scientific concerns about their toxicity, characterization, and interactions with microorganisms and other contaminants. The reports of common subthemes have agreed about many findings and research gaps but also showed contradictions about others. To unravel these equivocal conflicts, we herein compile all the major findings and analyze the paramount discrepancies among these review papers. Furthermore, we systematically reviewed all the highlights, research gaps, concerns, and future needs. The covered focus areas of MPs' literature include the sources, occurrence, fate, existence, and removal in wastewater treatment plants (WWTPs), toxicity, interaction with microbiota, sampling, characterization, data quality, and interaction with other co-contaminants. This study reveals that many mechanisms of MPs' behavior in aquatic environments like degradation and interaction with microbiota are yet to be comprehended. Furthermore, we emphasize the critical need to standardize methods and parameters for MP characterization to improve the comparability and reproducibility of the incoming research.

Unfolding the interaction between microplastics and (trace) elements in water: A critical review

Plastic and microplastic pollution is an environmental and societal concern. The interaction of plastic with organic chemicals in the environment has attracted scientific interest. New evidences have highlighted an unexpectedly high affinity of environmental plastics also for metal ions. The degree and typology of plastic ageing (including from mechanical, UV and biological degradations) appear as a pivotal factor determining such an interaction. These earlier evidences recently opened a new research avenue in the plastic pollution area. This review is the first to organize and critically discuss knowledge developed so far. Results from field and laboratory studies of metal accumulation on plastic are presented and the environmental factors most likely to control such an interaction are discussed. On the light of this knowledge, a generalist conceptual model useful for building hypotheses on the mechanisms at stake and directing future studies was elaborated and presented here. Furthermore, all available data on the thermodynamics of the plastic-metal interaction obtained from laboratory experiments are inventoried and discussed here, highlighting methodological and technical challenges that can potentially affect cross-comparability of data and their relevance for environmental settings. Finally, insights and recommendations on experimental approaches and analytical techniques that can help overtaking current limitations and knowledge gaps are proposed.

Microplastics pollution in the Brahmaputra River and the Indus River of the Indian Himalaya

Rivers act as temporary sinks of microplastics and a key medium allowing microplastics to enter the ocean. In this study, microplastics pollution in river shore sediment of the Indian Himalaya, including the Brahmaputra River and the Indus River was discussed. Sampling campaigns were performed in years 2018 and 2019. Sample pretreatment was performed using Na₂WO₄·2H₂O for density separation and H₂O₂ for oxidation of organic material. Microplastics analysis was performed by using FTIR microscope. The smaller size of microplastics 20-150 μm were more abundant (531-3485 MP/kg in the Brahmaputra River and 525-1752 MP/kg in the Indus River) than microplastics in size range between 150 μm and 5 mm (20-240 MP/kg in the Brahmaputra River and 60-340 MP/kg in the Indus River). Microplastics were found in sediments of all sampling sites. Fragmented, secondary microplastics were dominant in the river shore sediment of the Indian Himalaya. This study contributes towards filling research gap of microplastics in India's freshwater source and highlights the importance of in-depth complete studies of microplastics in the rivers that act as pathways and sinks for microplastics.

Microplastics pollution on Colombian Central Caribbean beaches

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

The extraction of microplastics from sediments: An overview of existing methods and the proposal of a new and green alternative

Microplastics (MPs) contamination is an existing and concerning environmental issue. Plastic particles have been observed worldwide in every natural matrix, with water environments being the final sink of dispersed MPs. Microplastic distribution in water ecosystems varies as a function of multiple factors, including polymer properties (e.g., density and wettability) and environmental conditions (e.g., water currents and temperature). Because of the tendency of MPs to settle, sediment is known to be one of the most impacted environmental matrices. Despite the increasing awareness of their diffusion in sediments, a proper quantification of dispersed particles is still difficult, due to the lack of standard protocols, which avoid a proper comparison of different sites. This hampers the current knowledge on environmental implications and toxicological effects of MPs in sediments. In this work, we examined 49 studies carried out from 2004 to 2020 to describe the different extraction methods applied, and to highlight pros and cons, with the aim of evaluating the more promising protocols. Therefore, we evaluated each proposed method by considering precision, reproducibility, economic viability and greenness (in term of used reagents). Finally, we proposed a valid alternative procedure in term of reliability and costs, which can attract increasing interest for future studies.