The occurrence and transport of microplastics: The state of the science

Estuarine plastic dynamics: Analyzing export patterns from a typical semi-enclosed bay in Asia

Semi-enclosed estuarine systems are recognized as hotspots for microplastic (MP) pollution, yet their export dynamics remain poorly understood. This study investigates the distribution of microplastics (<5 mm) and macroplastics (>5 mm) in Sanya Bay, a typical semi-enclosed bay in southern China. Based on 45 surface water samples, MP concentrations ranged from 0.298 to 4.010 items/m³ (mean: 1.628 ± 1.055), significantly higher than macroplastics (mean: 0.109 ± 0.338 items/m³). Most particles were fragments smaller than 5 mm, dominated by white, green, and transparent colors. The main polymers identified were polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET). A "dual-center" pattern was observed: low-density plastics (e.g., PP, PE) accumulated near river mouths and offshore islands, while high-density plastics (e.g., PET, PVC) settled in estuarine zones. Principal Coordinate Analysis (PCoA) revealed spatial clustering across estuarine, coastal, and offshore areas, influenced by land-based inputs, human activity, and hydrodynamic transport. This study provides new insights into plastic transport mechanisms in semi-enclosed bays and highlights the importance of integrating plastic properties with environmental forces. The findings support targeted pollution management in similar coastal environments.

Microplastic-induced alterations in growth and microecology of mulberry seedlings: Implications for sustainable forest-soil systems

This study investigated the ecotoxicological effects of polyethylene (PE) and polylactic acid (PLA) microplastics (MPs) on mulberry growth and soil-microbe interactions through controlled pot experiments (0.1 % and 1 % concentrations). PE exposure significantly increased mulberry height by 16 % (0.1 %) and 18 % (1 %) (p < 0.05), whereas PLA reduced total biomass by 12 % (0.1 %) and 66 % (1 %), highlighting polymer- and concentration-dependent responses. MPs differentially modulated soil biogeochemistry: PE decreased nitrate and ammonium nitrogen levels while enhancing nitrogen fixation (nifH) (from 0.9 × 107 to 6.1 × 107 copies/g) and denitrification (nirK) (from 1.0 × 108 to 1.9 × 108 copies/g) gene expression via Acidobacteriota enrichment, which was correlated with increased soil organic matter mobilisation and photosynthetic rates. PLA disrupted phosphorus cycling and destabilised structure of fungal communities critical for nutrient assimilation. Structural equation modelling identified direct microplastic-soil-plant linkages, with real-time polymerase chain reaction validating PE-driven suppression of nitrogen loss through microbial functional shifts. These findings illuminate the dual roles of microplastics as ecological stressors and modifiers, providing actionable insights for balancing agricultural productivity and soil health in MP-contaminated forest ecosystems.

Vertical Distribution and Multi-Source Pathways of Microplastics in Agricultural Soils: A Study of Typical Irrigation Areas in the Upper Yellow River Basin

Agricultural production inputs, irrigation water and atmospheric deposition are the primary sources of microplastics (MPs) in farmland soils. Irrigation exacerbates the vertical migration of MPs from surface soils to deeper aquifer, posing significant ecological and healthy risks to groundwater. However, most studies focused upon surface soils, with limited effort on the spatial distribution and influencing factors of MPs. This study compared forest and grassland soils in the upper Yellow River region, analyzed the vertical distribution of MPs across six soil layers (0-100 cm) under border and drip irrigation patterns. Additionally, the specific composition of MPs in atmospheric source in 1-year settling period, irrigation water, fertilizers, and seed coatings was investigated. The results showed that MPs were detected in all 0-100 cm soil layers, with significantly higher abundance in farmland soils (5,688.8 ± 609.38 items/kg) than in forest (2,387.05 ± 152.47 items/kg) and grassland (669.64 ± 131.83 items/kg) soils. The MPs abundance in farmland increased with prolonged plastic film mulching. Overall, MPs abundance decreased with soil depth, but accumulation occurred at 20-30 cm due to tillage and irrigation. The MPs abundance in the border-irrigated farmland (5,688.79 ± 1,497.11 items/kg) was twice that in the drip-irrigated farmland (2,744.44 ± 996.93 items/kg), indicating that border irrigation intensifies surface soil contamination and accelerates MPs migration to the deeper layers. The primary MPs components in farmland soils were PVC, PU, CPE, ACR, PE, EVA, FKM, PET and PTFE. PVC and PU mainly originated from fertilizers, seed coatings, irrigation water, and atmospheric deposition, while CPE, PI, PLA, and PSF were likely derived from the irrigation water and atmospheric deposition. In conclusion, the soil MPs mainly originated from atmospheric source, irrigation water and agricultural inputs. The MPs distribution was influenced by tillage intensity and irrigation practices. These findings provided a better understanding of the MPs distribution patterns and influencing factors, thereby aiding in development of effective pollution control strategies.

Microplastic distribution in the surface water and potential fish uptake in an oligotrophic lake (Lake Mainit, Philippines)

Analyzing microplastic distribution patterns in freshwater ecosystems provides critical insights into pollution sources and accumulation zones, contributing to ecosystem health and functioning. Here, the surface water of Lake Mainit, an oligotrophic body of water in the Philippines, and the potential ingestion by Glossogobius giuris (15), a local fish species inhabiting the lake, were investigated. The surface water samples collected in ten sampling sites revealed an average microplastic concentration of 313.33 ± 252.11 particles/m3, with elevated levels in the northern part of the lake, likely due to adjacent industrial and agricultural activities. Fibers were the predominant microplastic morphology (58 %), with polyamide (28 %) as the most common polymer found in the surface water, suggesting primary sources from textiles and household waste. Size analysis showed that particles under 100 μm in size were most abundant, posing increased ingestion risks for aquatic organisms. All examined fish samples contained microplastics, averaging 0.7 particles per fish, primarily from the smallest particle class, indicating a potential risk of bioaccumulation. Risk assessment using the Polymer Hazard Index (PHI) and Pollution Load Index (PLI) indicated that polyvinyl chloride (PVC) and polyamide (PA) pose moderate to high pollution risks due to their persistence and toxicity potential. The PERI value for Lake Mainit was 34.63, classifying it as a minor risk. While current contamination levels are low, continued monitoring is essential to prevent future ecological risks. These results highlight the ecological threat of microplastics in Lake Mainit, with implications for biodiversity and human health, as the lake is an important local food source. To mitigate these risks, stricter pollution control, enhanced waste management, and public awareness initiatives are recommended. This study presents foundational data on microplastic pollution in an oligotrophic Philippine lake, emphasizing the need for further research to support protective management strategies.

Current research status on the distribution and transport of micro(nano)plastics in hyporheic zones and groundwater

Micro(nano)plastics, as an emerging environmental pollutant, are gradually discovered in hyporheic zones and groundwater worldwide. Recent studies have focused on the origin and spatial/temporal distribution of micro(nano)plastics in regional groundwater, together with the influence of their properties and effects of environmental factors on their transport. However, the transport of micro(nano)plastics in the whole hyporheic zone-groundwater system and the behavior of co-existing substances still lack a complete theoretical interpretation. To provide systematic theoretical support for that, this review summarizes the current pollution status of micro(nano)plastics in the hyporheic zone-groundwater system, provides a comprehensive introduction of their sources and fate, and classifies the transport mechanisms into mechanical transport, physicochemical transport and biological processes assisted transport from the perspectives of mechanical stress, physicochemical reactions, and bioturbation, respectively. Ultimately, this review proposes to advance the understanding of the multi-dimensional hydrosphere transport of micro(nano)plastics centered on groundwater, the microorganisms-mediated synergistic transformation and co-transport involving the intertidal circulation. Overall, this review systematically dissects the presence and transport cycles of micro(nano)plastics within the hyporheic zone-groundwater system and proposes prospects for future studies based on the limitations of current studies.

Invisible threats in soil: Microplastic pollution and its effects on soil health and plant growth

Microplastics (MPs) are a significant environmental contaminant that increasingly threaten soil health and crop productivity in agricultural systems. This review explores the origins, migration patterns, and ecological impacts of MPs within soil environments, specifically examining their influence on soil structure, microbial communities, and nutrient cycles essential for plant growth. Despite the progress in understanding Microplastic (MP) pollution, gaps remain in assessing the long-term implications on soil stability, microbial biodiversity, and crop yield. Through bibliometric and synthesis analyses of recent studies, this paper identifies how MPs disrupt soil physical and chemical processes, alter microbial dynamics, and interfere with carbon and nitrogen cycles, resulting in reduced soil fertility and compromised crop health. Key findings reveal that MPs can infiltrate plant root systems, impair water and nutrient uptake, and even accumulate in plant tissues, causing oxidative stress, cellular dysfunction, and yield reduction. This work emphasizes the urgent need for refined environmental risk assessments and sustainable agricultural practices to mitigate MP pollution. This comprehensive synthesis offers a foundational perspective to guide future research and policy efforts in addressing MPs' environmental and agricultural impacts.

Microplastics in freshwater and marine ecosystems: Occurrence, characterization, sources, distribution dynamics, fate, transport processes, potential mitigation strategies, and policy interventions

Most of the literature on microplastics (MPs) focuses on freshwater or terrestrial ecosystems, frequently overlooking their interconnections with the marine environments. This oversight is worrying given that both ecosystems serve as primary pathways for the introduction of MPs into marine environments. This review synthesizes existing literature on MPs in both freshwater and marine ecosystems across all six continents. The most commonly produced plastic polymers in industry are polyethylene (36 %) and polypropylene (21 %), and studies revealed that these two materials are the most abundant in aquatic ecosystems. Primary and secondary MPs originate from a range of sources including land-based disposal, the ocean, airborne deposition, wastewater treatment facilities, automobiles, pharmaceuticals and personal care products, synthetic textiles, and insect repellents. Notably, secondary MPs, which are formed from the breakdown of larger plastic items comprise approximately 69-81% of marine debris, especially in urbanized, densely populated areas. The inconsistencies of the methodologies (sampling, extraction, and quantification) and the units employed for result presentations are part of the major limitations in MPs research. Environmental phenomena such as heteroaggregation, weathering, adsorption, leaching, and fragmentation are the major factors influencing the behavior, fate, and degradation process of plastic particles. The physicochemical properties of plastic polymers, such as density, crystallinity, as well as bioturbation, meteorological forces, and wind actions, including currents, waves, and tides, are responsible for biofouling, aggregation, sinking into the bottom sediment, resuspension, and the vertical, horizontal, and spatiotemporal distributions and transport of MPs. The potential solutions to mitigate plastic pollution are grounded in the 3Rs framework, which includes reducing production and consumption, advancing the biotechnological, chemical and microbial development of degradable polymers, promoting reusable plastic products with lower environmental impacts over their lifetimes, and recycling waste into new products. The regulatory policies on single-use plastics commonly involve permanent bans and financial penalties for violators. In addition, nations such as the United States, the Netherlands, and northern Europe have introduced economic incentives to encourage the return of reusable materials to reduce plastic waste and the resulting envrionmental pollution.

Developmental Toxicity of Micro(Nano)Plastics (MNPs) Exposure in Mammals: A Mini-Review

Micro(nano)plastics (MNPs) pose a significant threat to both ecological environments and human health. This review systematically examines the developmental toxicity of MNPs in mammals, with a particular focus on the impact of maternal and paternal exposure on offspring. Evidence indicates that MNPs can cross placental barriers, inducing abnormal development of embryos, fetuses, and placentas. This disruption leads to a range of adverse outcomes, including neurodevelopmental abnormalities, behavioral disorders, reproductive system damage, etc., in offspring. Through a comprehensive analysis of the existing literature, this review aims to provide a foundation for future research on the developmental toxicity of MNPs and highlight the urgent need for action to mitigate the detrimental effects of MNPs on human health and ecosystem integrity.

The impact of biodegradable plastics on methane and carbon dioxide emissions in soil ecosystems: a Fourier transform infrared spectroscopy approach

Biodegradable plastics (BPs), promising eco-friendliness, raise environmental concerns as they degrade into numerous microplastics (Bio-MPs). The impact of Bio-MPs on methane (CH4) and carbon dioxide (CO2) emissions in soil ecosystems remains largely unexplored. Utilizing Fourier transform infrared (FTIR) spectroscopy, we innovatively designed a circulating system, integrating a long optical-path gas cell with a static chamber for continuous and convenient CH4/CO2 monitoring in paddy soils with the addition of Bio-MPs (PBAT). On the 7th day of incubation, we observed a significant increase in CH4/CO2 absorption peaks due to the addition of PBAT, with enhancements of 92-fold and 213-fold, respectively. Built upon this system, we explored a quantitative method based on the main absorption peak (3010 cm-1) for CH4, and calculated cumulative emissions. Additionally, we analyzed attenuated total reflection (ATR) spectra of soil with and without Bio-MPs based on FTIR spectrometer, revealing the characteristic response in soil ATR spectra triggered by PBAT, and demonstrating ATR spectroscopy's potential for identifying soil contamination by Bio-MPs. This study aims to broaden and improve the utilization of FTIR spectroscopy for the purpose of monitoring soil GHG emissions and identifying soil contaminated by Bio-MPs, thereby offering significant insights into the influence of Bio-MPs on climate change.

Recent advances and factors affecting the adsorption of nano/microplastics by magnetic biochar

The increase in nano/microplastics (NPs/MPs) from various everyday products entering aquatic environments highlights the urgent need to develop mitigation strategies. Biochar (BC), known for its excellent adsorption capabilities, can effectively target various harmful organic and inorganic pollutants. However, traditional methods involving powdered BC necessitate centrifugation and filtration, which can lead to the desorption of pollutants and subsequent secondary pollution. Magnetic biochar (MBC) offers a solution that facilitates straightforward and rapid separation from water through magnetic techniques. This review provides the latest insights into the progress made in MBC applications for the adsorption of NPs/MPs. This review further discusses how external factors such as pH, ionic strength, temperature, competing ions, dissolved organic matter, aging time, and particle size impact the MBC adsorption efficiency of MPs. The use of machine learning (ML) for optimizing the design and properties of BC materials is also briefly addressed. Finally, this review addresses existing challenges and future research directions aimed at improving the large-scale application of MBC for NPs/MPs removal.

Environmental impact of microplastics and potential health hazards

Microscopic plastic (microplastic) pollutants threaten the earth's biodiversity and ecosystems. As a result of the progressive fragmentation of oversized plastic containers and products or manufacturing in small sizes, microplastics (particles of a diameter of 5 mm with no lower limit) are used in medicines, personal care products, and industry. The incidence of microplastics is found everywhere in the air, marine waters, land, and even food that humans and animals consume. One of the greatest concerns is the permanent damage that is created by plastic waste to our fragile ecosystem. The impossibility of the complete removal of all microplastic contamination from the oceans is one of the principal tasks of our governing body, research scientists, and individuals. Implementing the necessary measures to reduce the levels of plastic consumption is the only way to protect our environment. Cutting off the plastic flow is the key remedy to reducing waste and pollution, and such an approach could show immense significance. This review offers a comprehensive exploration of the various aspects of microplastics, encompassing their composition, types, properties, origins, health risks, and environmental impacts. Furthermore, it delves into strategies for comprehending the dynamics of microplastics within oceanic ecosystems, with a focus on averting their integration into every tier of the food chain.

Comprehensive analysis of proteomic and biochemical responses of Daphnia magna to short-term exposure to polystyrene microplastic particles

Microplastic (MP) represent a pervasive and escalating threat to aquatic ecosystems, impacting organisms from cellular to population levels. To investigate the immediate molecular impacts of MP exposure, we exposed Daphnia magna, a keystone species in freshwater ecosystems, to polystyrene microplastic particles (5 μm, 5 μg/L) for 48 h. Through proteomic and biochemical analyses, we identified extensive disruptions in key physiological pathways. Notably, proteins involved in energy metabolism, including glycolysis and the tricarboxylic acid (TCA) cycle, were downregulated, suggesting a metabolic shift away from growth-related processes. Elevated levels of oxidative stress markers such as superoxide dismutase, catalase, and glutathione reductase reflected a pronounced response to reactive oxygen species. The upregulation of endocytosis-related proteins, including caveolin-1 (CAV1) and phosphatidylinositol-4-phosphate 5-kinase (PIP5K), highlights their role in actively internalizing and compartmentalizing MP, potentially as a protective mechanism against oxidative damage. These findings reveal that short-term MP exposure triggers a complex, multi-pathway stress response in D. magna, underscoring potential vulnerabilities that could impact broader ecological dynamics. This study emphasizes the urgency of understanding MP toxicity to guide environmental policies and conservation efforts aimed at mitigating the effects of plastic pollution.

Factors Influencing the Vertical Migration of Microplastics up and down the Soil Profile

Soil ecosystems are under serious threat from microplastics (MPs), and this is causing worldwide concern. The relationship between soil and MPs has become a popular research topic, and the vertical migration of soil MPs is of increasing interest. This Review summarizes the current status of research into the factors affecting the vertical migration of soil MPs. Published research shows that the characteristics of MPs and the physicochemical properties of the soil affect the infiltration process. Soil organisms play a key role in the vertical migration by acting as vectors or as a result of adsorption. Dissolved organic matter and metal oxides transfer MPs by adsorption-desorption. In addition, rainfall and dry-wet cycles alter the mobility of soil MPs, leading to changes in migration processes. Agricultural activities such as tillage and irrigation may distribute MPs throughout the topsoil. Vertical migration of soil MPs is a process influenced by a combination of factors, and the role of these factors in MP deposition needs to be explored further.

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

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

Global patterns of lake microplastic pollution: Insights from regional human development levels

Microplastics have emerged as a pervasive pollutant across various environmental media. Nevertheless, our understanding of their occurrence, sources, and drivers in global lakes still needs to be completed due to limited data. This study compiled data from 117 studies (2016-May 2024) on microplastic contamination in lake surface water and sediment, encompassing surface water samples in 351 lakes and lake sediment samples in 200 lakes across 43 countries. Using meta-analysis and statistical methods, the study reveals significant regional variability in microplastic pollution, with concentrations ranging from 0.09 to 130,000 items/m3 in surface water and from 5.41 to 18,100 items/kg in sediment. Most microplastics were under 1 mm in particle size, accounting for approximately 79 % of lake surface water and 76 % of sediment. Transparent and blue microplastics were the most common, constituting 34 % and 21 % of lake surface water and 28 % and 18 % of sediment, respectively. Fibers were the dominant shape, representing 47 % of lake surface water and 48 % of sediment. The primary identified polymer types were polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET). Countries like India, Pakistan, and China had higher contamination levels. Positive correlations were found between microplastic abundance in surface water and factors like human footprint index (r = 0.29, p < 0.01), precipitation (r = 0.21, p < 0.05), and net surface solar radiation (r = 0.43, p < 0.001). In contrast, negative correlations were observed with the human development index (r = -0.61, p < 0.01) and wind speed (r = -0.42, p < 0.001). In sediment, microplastics abundance correlated positively with the human footprint index (r = 0.45, p < 0.001). This study underscores the variability in microplastic pollution in global lakes and the role of human activities and environmental factors, offering a valuable reference for future research.

Biological hazards of micro- and nanoplastic with adsorbents and additives

With the increased worldwide production of plastics, interest in the biological hazards of microplastics (MP) and nanoplastics (NP), which are widely distributed as environmental pollutants, has also increased. This review aims to provide a comprehensive overview of the toxicological effects of MP and NP on in vitro and in vivo systems based on studies conducted over the past decade. We summarize key findings on how the type, size, and adsorbed substances of plastics, including chemical additives, impact organisms. Also, we address various exposure routes, such as ingestion, inhalation, and skin contact, and their biological effects on both aquatic and terrestrial organisms, as well as human health. Additionally, the review highlights the increased toxicity of MP and NP due to their smaller size and higher bioavailability, as well as the interactions between these particles and chemical additives. This review emphasizes the need for further research into the complex biological interactions and risks posed by the accumulation of MP and NP in the environment, while also proposing potential directions for future studies.

Microplastics in urban water cycles: Looking for a more scientific approach for sampling and characterization in wastewater and drinking water treatment plants

Specific campaigns to detect microplastics (MPs) in the urban water cycle were carried out in three drinking water plants and two wastewater treatment plants. A self-designed sampler for MPs detection in water matrices was in this study preliminary validated and then tested in long term campaigns sampling up to 1000 L. Raw drinking water and wastewater show microplastics (MPs) concentrations of 2-11 and of 480-801 MPs/m3, respectively, and MPs removals of 47-78 % and of 84-98 %, correspondingly. Specific roles of chemical and physical conventional processes in microplastics removals were investigated. Solid-liquid separation, flotation and filtration are the main processes for achieving high microplastics removal. Regarding concentrated matrices, MPs concentrations in sludge samples varied in the range of 5000-500,000 MPs/m3. Finally, shapes, size classes and polymers' typologies were investigated in the extracted MPs. The detected sizes are mainly 0.5-0.1 mm in drinking waters while 5-1 mm in wastewaters. Wastewaters were predominated by synthetic fibers (polyester type), while drinking waters were mainly characterized by fragments and the fibers were mostly of natural origin. Finally, the results of this study supported best practices and guidelines for a representative assessment of MPs in water (sampling methods, extraction procedures, characterization and quantification).

Assessment of microplastics in human stool: A pilot study investigating the potential impact of diet-associated scenarios on oral microplastics exposure

As emerging contaminants microplastic particles have become of particular relevance as they are widely present in the environment and of potential concern to human health. Humans are exposed through different routes, with oral intake and inhalation being the most significant. Dietary intake substantially contributes to oral exposure, although data is still lacking. This first-of-its-kind pilot study investigates the influence of different plastic use and food consumption scenarios (normal, low, high) on microplastic content in stool reflecting oral intake by performing an intervention study with fifteen volunteers. Stool samples were analyzed for ten different plastic types in three size fractions including 5-50 μm (qualitative), 50-500 μm and 500-5000 μm (quantitative). In all samples, microplastic particles were detected with median concentrations up to 3.5 particles/g stool in the size fraction 50-500 μm. Polyethylene was the most frequently detected polymer type. The different scenarios did not result in a consistent pattern of microplastics, however, the use of plastics for food packaging and preparation, and the consumption of highly processed food were statistically significantly associated with microplastics content in stool. These results provide initial findings that contribute to filling current knowledge gaps and pave the way for further research.

Accumulation of airborne microplastics on leaves of different tree species in the urban environment

Microplastics (MPs) are omnipresent in the environment and they are linked to ecosystem and human health problems. The atmospheric transport of MPs and the role of tree leaves in MP atmospheric deposition has not been adequately studied. MP concentrations on the leaves of different tree species in urban regions of the Netherlands and Portugal, along with related MP deposition, were investigated in this study. We collected leaves from cedar, eucalyptus, oak, pine and willow trees, together with monthly deposition of particles under the trees and in the open space in Coimbra (Portugal). In Wageningen (the Netherlands), we collected leaves from a fir and a holly tree at different heights above the ground and with dry and wet weather conditions. MPs were extracted through density separation and quantified under a microscope. Polymer types were identified using μ-FTIR. The results showed a higher number of MP particles on the needle-shaped leaves from fir (2.52 ± 2.14 particles·cm-2) and pine (0.5 ± 0.13 particles·cm-2) and significantly lower numbers of MPs per cm2 of leaf area on the bigger leaves from eucalyptus (0.038 ± 0.003 particles·cm-2) and cedar (0.037 ± 0.002 particles·cm-2). All tree leaves seemed to filter airborne MPs, especially the smallest particles. A non-significantly higher number of particles on leaves was detected on lower tree branches and after dry periods. The deposition of MPs under trees was generally higher than in the open space. Our results indicated that part of the MPs retained by the tree leaves floats down to lower branches and to the soil surface. We also saw that different tree species had different capacities to retain particles on their leaves over time. To control the transport of MPs through the atmosphere, it is essential to consider the role of different vegetation types in filtering small particles, especially in cities.

Evaluation of the migration behaviour of microplastics as emerging pollutants in freshwater environments

Microplastics, as an emerging pollutant, are widely distributed in freshwater environments such as rivers and lakes, posing immeasurable potential risks to aquatic ecosystems and human health. The migration behaviour of microplastics can exacerbate the degree or scope of risk. A complete understanding of the migration behaviour of microplastics in freshwater environments, such as rivers and lakes, can help assess the state of occurrence and environmental risk of microplastics and provide a theoretical basis for microplastic pollution control. Firstly, this review presents the hazards of microplastics in freshwater environments and the current research focus. Then, this review systematically describes the migration behaviours of microplastics, such as aggregation, horizontal transport, sedimentation, infiltration, stranding, resuspension, bed load, and the affecting factors. These migration behaviours are influenced by the nature of the microplastics themselves (shape, size, density, surface modifications, ageing), environmental conditions (ionic strength, cation type, pH, co-existing pollutants, rainfall, flow regime), biology (vegetation, microbes, fish), etc. They can occur cyclically or can end spontaneously. Finally, an outlook for future research is given.

Inter-annual variation in the microplastics abundance in feces of the Baird's tapir (Tapirus bairdii) from the Selva Maya, México

Microplastics (MPs) are found in a wide range of ecosystems, from the Arctic to the deep ocean. However, there is no data on their presence in terrestrial mammals that inhabit the Selva Maya. The aim of this study is to detect the presence of MPs in the feces of the Baird's tapir (Tapirus bairdii) from the region of Calakmul, located in the Yucatan Peninsula, Mexico. We analyzed 129 fecal samples collected during 2017 and 2018, obtaining 57 and 72 samples during the rainy and dry seasons respectively. Sixty-eight percent of the samples contained 743 MPs with a mean of 19.3 ± 28.1 MPs/kg of dry weight (DW) feces in both years. An inter-annual variation in the average abundance of microplastic was observed during the two-year period (2017-2018), with a 72 % increase in these plastic particles in feces. Fourteen polymers were identified, with ethylene vinyl acetate (EVA), polypropylene (PP) and polyester (PES) being the most abundant during both years. Although the effects of MPs on the health of tapirs are not known, their presence is cause for concern. There is an urgent need for the implementation of appropriate plastic waste management programs in communities of the Selva Maya to diminish the consumption of MPs in species including humans where they pose a significant risk to health. ENVIRONMENTAL IMPLICATIONS: The use of plastics worldwide is increasing every day, so the presence of microplastics is and will continue to be a major environmental problem. It is known that contaminants can adhere to plastics, making them hazardous materials. Microplastics can contaminate remote areas such as Biosphere Reserves. Terrestrial species such as the tapir can ingest microplastics, putting their health at risk. Knowing the dispersion of microplastics is very important in order to manage them properly, taking into account their emission sources and type of polymer.

Plastic litter is a part of the carbon cycle in an urban river: Microplastic and macroplastic accumulate with organic matter in floating debris rafts

Watershed models of plastic export from rivers to oceans have large uncertainties, and improvements require direct measurements of riverine macroplastic (>5 mm) and microplastic (<5 mm). Also, plastic represents allochthonous carbon inputs to rivers but is rarely measured as carbon mass. We quantified plastic and organic matter within floating debris rafts and open water in an urban river. Macroplastics only occurred in debris rafts. Microplastics had higher concentrations in debris rafts relative to open water. Across sites, organic matter was positively correlated with microplastics and macroplastics. Last, carbon in plastic was 40% of the carbon mass in coarse particulate organic matter in debris rafts. Floating plastic litter accumulates with particulate organic matter in debris rafts. Plastic is an overlooked and ecological meaningful component of carbon standing stocks in urban rivers. Results will inform improved carbon budget calculation in rivers and watershed models of plastic export. PRACTITIONER POINTS: Plastic particles floating on the surface of an urban river accumulate in debris rafts compared to open water in terms of count and mass. Abundance and composition of plastic particles in debris rafts were distinct from those in open water areas. Plastic litter as units of carbon mass was in the same order of magnitude as carbon mass in course particulate organic matter. Plastic litter moves in similar ways to naturally occurring organic particles and should be measured as a part of the riverine carbon cycle.

Unseen riverine risk: Spatio-temporal shifts of microplastic pollution and its bioavailability in freshwater fish within the Ikopa River urban system

Growing concern over microplastic pollution, driven by their widespread accumulation in the environment, stresses the need for comprehensive assessments. This study investigates the spatial and temporal distribution of microplastics in the Ikopa River (Antananarivo - Madagascar), which flows through a densely populated area, and examines their correlation with contamination levels in local fish species. By analyzing upstream and downstream stations across wet and dry seasons, only a notable increase in microplastic concentration downstream during the wet season was observed, ranging from 138.6 ± 9.0 to 222.0 ± 24.5 particles m-3, with polyethylene-co-vinyl acetate being the predominant polymer at 62.3 ± 5.13% of the total sampled polymers. This distribution underlines the impact of urban activities on pollution levels. Fish species, gambusia and Nile tilapia, were assessed for microplastic occurrence in gills and gastrointestinal tracts. Higher contamination rates were found in gambusia, enlightening the influence of feeding behaviour and fish habitat on microplastics contamination. Ingestion of microplastics directly from the water column was evident in both species, with the detection of high-density plastics such as polytetrafluoroethylene and polyvinyl chloride suggesting likely sediment contamination. This research highlights the widespread contamination of aquatic environments and its direct impact on local wildlife, pointing to a clear requirement for effective pollution management strategies.

Microplastics in Hong Kong's marine waters: Impact of rainfall and Pearl River discharge

This study provided a systematic investigation of microplastics in Hong Kong's surface marine waters during the pandemic from 2019 to 2021. Microplastics (2.07 ± 4.00 particles/m3) exhibited significant temporal variations with higher abundance in the wet season, without a consistent trend after the mandatory mask-wearing requirement was announced. The impact of pandemic restrictions on microplastic distribution was found to be relatively minor. However, significant correlations between microplastic abundances and rainfall highlighted the substantial contribution of local emissions through surface runoff. Notably, sites in closer proximity to the Pearl River Delta exhibited higher microplastic abundances, indicating their association with emission sources. The influence of rainfall and adverse weather on marine microplastic loads demonstrated different sensitivities among various locations but can generally last for one month. These results revealed the impact of seasonal rainfall on coastal microplastics and emphasized the need for efforts to reduce microplastic discharge from land-based sources.

The Potential Mechanisms Involved in the Disruption of Spermatogenesis in Mice by Nanoplastics and Microplastics

BACKGROUND

Plastic-based products are ubiquitous due to their tremendous utility in our daily lives. Nanoplastic (NP) and microplastic (MP) pollution has become a severe threat to the planet and is a growing concern. It has been widely reported that polystyrene (PS) MPs are severely toxic to the male reproduction system, with effects including decreased sperm parameters, impaired spermatogenesis, and damaged testicular structures. However, the molecular mechanisms for impaired spermatogenesis remain poorly understood.

METHODS

C57BL/6 male mice were treated with PS-NPs (80 nm) and PS-MPs (5 μm) by oral gavage every day for 60 days. A series of morphological analyses were completed to explore the influence of PS-NP and PS-MP exposure on the testes. Compared to other cell types in the seminiferous tubule, PS-NP and PS-MP exposure can lead to decreased spermatocytes. Then, more refined molecular typing was further performed based on gene expression profiles to better understand the common and specific molecular characteristics after exposure to PS-NPs and PS-MPs.

RESULTS

There were 1794 common DEGs across the PS-NP groups at three different doses and 1433 common DEGs across the PS-MP groups at three different doses. GO and KEGG analyses of the common DEGs in the PS-NP and PS-MP groups were performed to enrich the common and specific functional progress and signaling pathways, including 349 co-enriched GO entries and 13 co-enriched pathways. Moreover, 348 GO entries and 33 pathways were specifically enriched in the PS-NP group, while 526 GO entries and 15 pathways were specifically enriched in the PS-MPs group.

CONCLUSIONS

PS-NPs were predominantly involved in regulating retinoic acid metabolism, whereas PS-MPs primarily influenced pyruvate metabolism and thyroid hormone metabolism. Our results highlight the different molecular mechanisms of PS-NPs and PS-MPs in the impairment of spermatogenesis in male mammals for the first time, providing valuable insights into the precise mechanisms of PS-NPs and PS-MPs in male reproduction.

Research priorities on microplastics in marine and coastal environments: An Australian perspective to advance global action

Plastic and microplastic contamination in the environment receive global attention, with calls for the synthesis of scientific evidence to inform actionable strategies and policy-relevant practices. We provide a systematic literature review on microplastic research across Australian coastal environments in water, sediment and biota, highlighting the main research foci and gaps in information. At the same time, we conducted surveys and workshops to gather expert opinions from multiple stakeholders (including researchers, industry, and government) to identify critical research directions to meet stakeholder needs across sectors. Through this consultation and engagement process, we created a platform for knowledge exchange and identified three major priorities to support evidence-based policy, regulation, and management. These include a need for (i) method harmonisation in microplastic assessments, (ii) information on the presence, sources, and pathways of plastic pollution, and (iii) advancing our understanding of the risk of harm to individuals and ecosystems.

Airborne transboundary microplastics-A Swirl around the globe

Microplastics are persistent pollutants discovered and extensively researched in marine, freshwater, and terrestrial ecosystems but have yet to receive attention in an atmospheric context. Although recent reports stated the presence of microplastics in the air, their global existence and distribution are not critically discussed to date. This review aimed to investigate the current status of research on atmospheric microplastics through bibliometric analysis and by comparing and summarising published research on global distribution. The review also provides a summary of methods that have been used to collect samples, identify microplastics, quantify their occurrence, and determine their transport mechanisms. The bibliometric analysis revealed that atmospheric microplastic studies predominantly originated in China. Clothing, vehicle, and tire materials were the major primary sources while house furniture, construction materials, landfills, urban dust, plastic recycling processes, and agricultural sludge were precursor secondary sources. Polyethylene, polypropylene, and polyethylene terephthalate microfibres have most frequently found in indoor and outdoor atmospheres. Level of urbanization and temporal or spatial distributions governs the fate of airborne microplastics, however, the knowledge gap in the retention and circulation of microplastics through the atmosphere is still large. Many challenges and limitations were identified in the methods used, presentation of data, aerodynamic processes facilitating atmospheric transport, and scarcity of research in spatially and temporally diverse contexts. The review concluded that there was a greater need for globalization of research, methods and data standardization, and emphasizes the potential for future research with atmospheric transportation modelling and thermochemical analysis.

Navigating the nexus: climate dynamics and microplastics pollution in coastal ecosystems

Microplastics (MPs) pollution is an emerging environmental health concern, impacting soil, plants, animals, and humans through their entry into the food chain via bioaccumulation. Human activities such as improper solid waste dumping are significant sources that ultimately transport MPs into the water bodies of the coastal areas. Moreover, there is a complex interplay between the coastal climate dynamics, environmental factors, the burgeoning issue of MPs pollution and the complex web of coastal pollution. We embark on a comprehensive journey, synthesizing the latest research across multiple disciplines to provide a holistic understanding of how these inter-connected factors shape and reshape the coastal ecosystems. The comprehensive review also explores the impact of the current climatic patterns on coastal regions, the intricate pathways through which MPs can infiltrate marine environments, and the cascading effects of coastal pollution on ecosystems and human societies in terms of health and socio-economic impacts in coastal regions. The novelty of this review concludes the changes in climate patterns have crucial effects on coastal regions, proceeding MPs as more prevalent, deteriorating coastal ecosystems, and hastening the transfer of MPs. The continuous rising sea levels, ocean acidification, and strong storms result in habitat loss, decline in biodiversity, and economic repercussion. Feedback mechanisms intensify pollution effects, underlying the urgent demand for environmental conservation contribution. In addition, the complex interaction between human, industry, and biodiversity demanding cutting edge strategies, innovative approaches such as remote sensing with artificial intelligence for monitoring, biobased remediation techniques, global cooperation in governance, policies to lessen the negative socioeconomic and environmental effects of coastal pollution.

Toxicological review of micro- and nano-plastics in aquatic environments: Risks to ecosystems, food web dynamics and human health

The increase of micro- and nano-plastics (MNPs) in aquatic environments has become a significant concern due to their potential toxicological effects on ecosystems, food web dynamics, and human health. These plastic particles emerge from a range of sources, such as the breakdown of larger plastic waste, consumer products, and industrial outputs. This review provides a detailed report of the transmission and dangers of MNPs in aquatic ecosystems, environmental behavior, and interactions within aquatic food webs, emphasizing their toxic impact on marine life. It explores the relationship between particle size and toxicity, their distribution in different tissues, and the process of trophic transfer through the food web. MNPs, once consumed, can be found in various organs, including the digestive system, gills, and liver. Their consumption by lower trophic level organisms facilitates their progression up the food chain, potentially leading to bioaccumulation and biomagnification, thereby posing substantial risks to the health, reproduction, and behavior of aquatic species. This work also explores how MNPs, through their persistence and bioaccumulation, pose risks to aquatic biodiversity and disrupt trophic relationships. The review also addresses the implications of MNPs for human health, particularly through the consumption of contaminated seafood, highlighting the direct and indirect pathways through which humans are exposed to these pollutants. Furthermore, the review highlights the recommendations for future research directions, emphasizing the integration of ecological, toxicological, and human health studies to inform risk assessments and develop mitigation strategies to address the global challenge of plastic pollution in aquatic environments.

Multi-method analysis of microplastic distribution by flood frequency and local topography in Rhine floodplains

Rivers are important transport pathways for microplastics into the ocean, but they can also be potential sinks due to microplastic deposition in the sediments of the river bed and adjacent floodplains. In particular, floods can (re)mobilise microplastics from sediments and floodplains, (re)deposit and relocate them depending on the floodplain topography. The knowledge about fluvial microplastic input to floodplains, their spatial distribution and their fate in floodplain soils is limited. To investigate this topic, we sampled soil at a depth of 5-20 cm along three transects in three different Rhine floodplains. We analysed the soil samples in tandem with pyrolysis GC/MS and ATR- & μ-FPA-FTIR for their microplastic abundance and mass concentrations. To study the influence of flood frequency on the microplastic abundance in the three floodplains, we fitted a hydrodynamic flood model (MIKE 21, DHI, Hørsholm, Denmark) and related the results to the respective spatial microplastic distribution. We found similar microplastic distribution patterns in each floodplain. The highest microplastic abundance (8516-70,124 microplastics kg-1) and mass concentration (46.2-141.6 mg kg-1) were consistently found in the farthest transects from the Rhine in a topographical depression. This microplastic distribution pattern is detectable with both, pyrolysis GC/MS and FTIR. The strongest correlation between the results of both methods was found for small, abundant microplastic particles. Our results suggest that the spatial distribution of microplastics in floodplains is related to the combination of flood frequency and local topography, that ought to be explicitly considered in future studies conducted in floodplains. Finally, our results indicate that pyrolysis GC/MS and FTIR data are comparable under certain conditions, which may help in the decision for the analytical method and sampling design in future studies.

Simulation of the dynamic processes of microplastic suspension and deposition in a lake sediment-water system

The occurrence of microplastics in aquatic environments has attracted increasing interest from both the public and scientists, especially their migration behaviors. Although several environmental behaviors of microplastics have been studied, the issue of microplastic suspension and deposition in lake sediment-water systems remains to be elucidated. In this study, we built an indoor sediment-water system with input and output rivers that simulated the actual situations in lakes, and aimed to explore the suspension and deposition behavior of microplastics using eight group experiments. The abundance of microplastics in overlying water and sediments in different periods was analyzed, and the characteristics of hydrodynamic disturbance on microplastic suspension and deposition were identified. Importantly, the exchange of microplastics in sediments and water under dynamic flow conditions was assessed. The results showed that the middle-scale experiment designed in this study effectively simulated the dynamic transport process of microplastics in lakes, and the hydrodynamic force had a significant impact on the suspension and deposition behaviors of microplastics. The average abundance of polystyrene, polyethylene terephthalate and polyamide microplastics was 1.07, 0.60 and 0.83 particles/L in overlying water during the suspension experiments, respectively. This showed a pattern of first rising and then falling with the extension of suspension time. Even in the environment with the maximum input water volume (8000 ml/min) in this study, only microplastics at a depth of 0 to 2 cm from the sediment were suspended. The average abundance of microplastics was 313.02 particles/kg during the deposition experiments, which gradually increased with the extension of deposition time in sediments. Finally, microplastic sizes in water of the suspension experiments and in sediments of the deposition experiments were concentrated in the range of 500 to 1500 μm and 300 to 1000 μm, respectively.

Towards better predicting the settling velocity of film-shaped microplastics based on experiment and simulation data

The properties of microplastics determine their settling velocities and affect the fates and migration pathways of microplastics. This paper has simulated the settling velocities of film-shaped microplastics, which are present in natural aquatic environments. The numerical results provided more data to fit the terminal settling velocities of film-shaped microplastics. Comparison between the particle definition and the equivalent spherical diameter confirmed that the particle definition is more suitable for film-shaped microplastics. In the transitional flow regime, CD decreases linearly with Re. As Re further increases, CD gradually converges at approximately 1.20. By integrating the experimental and simulated data, a new explicit formula for predicting the settling velocity of film-shaped microplastics has been presented with the optimal shape parameter f. The presented formula achieves better performance (MAPE = 6.6 %, RMSE = 16.8 %, and R2 = 0.99) than the existing formulas for settling velocity for film-shaped microplastics, closely rivaling that of the ensemble learning algorithm.

Microplastics contamination in water supply system and treatment processes

Due to global demand, millions of tons of plastics have been widely consumed, resulting in the widespread entry of vast amounts of microplastic particles into the environment. The presence of microplastics (MPs) in water supplies, including bottled water, has undergone systematic review, assessing the potential impacts of MPs on humans through exposure assessment. The main challenges associated with current technologies lie in their ability to effectively treat and completely remove MPs from drinking and supply water. While the risks posed by MPs upon entering the human body have not yet been fully revealed, there is a predicted certainty of negative impacts. This review encompasses a range of current technologies, spanning from basic to advanced treatments and varying in scale. However, given the frequent detection of MPs in drinking and bottled water, it becomes imperative to implement comprehensive management strategies to address this issue effectively. Consequently, integrating current technologies with management options such as life-cycle assessment, circular economy principles, and machine learning is crucial to eliminating this pervasive problem.

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.

Anthropogenic particle abundance and characteristics in seawater and intertidal sediments of the Tonkin Bay Coast (North Vietnam)

Microplastics (MPs, plastic items from 1 µm to 5 mm in size) are present in all environmental compartments. The evaluation of their concentration, fate, and spatial distribution is still a challenge for the scientific community. This concern is just debuting in developing countries, (i.e., Asia, South America, and Africa). This study deals with the MP contamination in the abiotic marine compartments of Northern Vietnam: seawater and intertidal sediments. Four sites located in the intertidal zone or near the coastline in Tonkin Bay, Vietnam were studied. A total of 16 samples (eight for each compartment) were collected in July 2020 (rainy season) and January 2021 (dry season). Anthropogenic particles (total observed fibers and fragments) were found at levels ranging from 3 to 303 particles/m3 in seawater and from 63 to 955 particles/kg dry weight in sediments. Most of these were fibers less than 300-µm long. Higher levels of seawater at the Nam Dinh site were found in the rainy season compared to the dry one. As the river flow was estimated six times higher during the rainy season than during the dry season, these results suggest the river discharge is a potential source of contamination for the coastal zone. The temporal variability was lower for the sediments than for the seawater, suggesting the long-term integration of the anthropogenic particles in this compartment. A small portion of sorted particles were analyzed by µFTIR (8.35%), and this sub-sample was only composed of fragments. Still, fragments were mostly composed of polypropylene (PP, 82%), polyethylene (PE, 9%), and polystyrene (PS, 9%). The fragment size was similar in the two studied compartments, but it was dependent on polymer types since PS fragments (140 ± 17 µm) were smaller than those made of PE (622 ± 123 µm) and PP (869 ± 905 µm). Future works should investigate the smallest fraction of MP (even nanoplastics) as well as find solutions in order to mitigate MP contamination in the marine environment.

Altitudinal variation of microplastic abundance in lakeshore sediments from Italian lakes

Microplastic (MP) contamination represents an issue of global concern for both aquatic and terrestrial ecosystems, but only in recent years, the study of MPs has been focused on freshwaters. Several monitoring surveys have detected the presence of a wide array of MPs differing in size, shape, and polymer composition in rivers and lakes worldwide. Because of their role of sink for plastic particles, the abundance of MPs was investigated in waters, and deep and shoreline sediments from diverse lakes, confirming the ubiquity of this contamination. Although diverse factors, including those concerning anthropogenic activities and physical characteristics of lakes, have been supposed to affect MP abundances, very few studies have directly addressed these links. Thus, the aim of the present study was to explore the levels of MP contamination in mountain and subalpine lakes from Northern Italy. Fourteen lakes dislocated at different altitudes and characterized by dissimilar anthropic pressures were visited. Lakeshore sediments were collected close to the drift line to assess MPs contamination. Our results showed the presence of MPs in lakeshore sediments from all the lakes, with a mean (± standard deviation) expressed as MPs/Kg dry sediment accounting to 14.42 ± 13.31 (range 1.57-61.53), while expressed as MPs/m2, it was 176.07 ± 172.83 (range 25.00-666.67). The MP abundance measured for Garda Lake was significantly higher compared to all the other ones (F1,13 = 7.344; P < 0.001). The pattern of contamination was dominated by fibers in all the lakes, but they were the main contributors in mountain lakes. These findings showed that the MP abundance varied according to the altitude of the lakes, with higher levels measured in subalpine lakes located at low altitudes and surrounded by populated areas.

Research advances on production and application of algal biochar in environmental remediation

Algae, comprising microalgae and macroalgae, have emerged as a promising feedstock for the production of functional biochar. Recently, the application of algal biochar in environmental remediation gains increasing attention. This review summarizes research advancements in the synthesis and application of algal biochar, a versatile and sustainable material for environmental remediation ranging from wastewater treatment to soil improvement. Algal biochar can be prepared by pyrolysis, microwave-assisted pyrolysis, and hydrothermal carbonization. Physical and chemical modifications have proven to be effective for improving biochar properties. Algal biochar is promising for removing diverse pollutants including heavy metals, organic pollutants, and microplastics. The role in soil improvement signifies a sustainable approach to enhancing soil structure, nutrient retention, and microbial activity. Research gaps are identified based on current understanding, necessitating further exploration into variations in biochar characteristics, the performance improvement, large-scale applications, and the long-term evaluation for environmental application. This review provides a better understanding of algal biochar as a sustainable and effective tool in environmental remediation.

Adsorption properties and mechanism of Cu(II) on virgin and aged microplastics in the aquatic environment

Microplastics (MPs) migrate by adsorbing heavy metals in aquatic environments and act as their carriers. However, the aging mechanisms of MPs in the environment and the interactions between MPs and heavy metals in aquatic environments require further study. In this study, two kinds of materials, polyamide (PA) and polylactic acid (PLA) were used as target MPs, and the effects of UV irradiation on the physical and chemical properties of the MPs and the adsorption behavior of Cu(II) were investigated. The results showed that after UV irradiation, pits, folds and pores appeared on the surface of aged MPs, the specific surface area (SSA) increased, the content of oxygen-containing functional groups increased, and the crystallinity decreased. These changes enhanced the adsorption capacity of aged MPs for Cu(II) pollutants. The adsorption behavior of the PA and PLA MPs for Cu(II) conformed to the pseudo-second-order model and Langmuir isotherm model, indicating that the monolayer chemical adsorption was dominant. The maximum amounts of aged PA and PLA reached 1.415 and 1.398 mg/g, respectively, which were 1.59 and 1.76 times of virgin MPs, respectively. The effects of pH and salinity on the adsorption of Cu(II) by the MPs were significant. Moreover, factors such as pH, salinity and dosage had significant effects on the adsorption of Cu(II) by MPs. Oxidative complexation between the oxygen-containing groups of the MPs and Cu(II) is an important adsorption mechanism. These findings reveal that the UV irradiation aging of MPs can enhance the adsorption of Cu(II) and increase their role as pollutant carriers, which is crucial for assessing the ecological risk of MPs and heavy metals coexisting in aquatic environments.

Microplastics and nanoplastics: Source, behavior, remediation, and multi-level environmental impact

Plastics introduced into the natural environment persist, degrade, and fragment into smaller particles due to various environmental factors. Microplastics (MPs) (ranging from 1 μm to 5 mm) and nanoplastics (NPs) (less than 1 μm) have emerged as pollutants posing a significant threat to all life forms on Earth. Easily ingested by living organisms, they lead to ongoing bioaccumulation and biomagnification. This review summarizes existing studies on the sources of MPs and NPs in various environments, highlighting their widespread presence in air, water, and soil. It primarily focuses on the sources, fate, degradation, fragmentation, transport, and ecotoxicity of MPs and NPs. The aim is to elucidate their harmful effects on marine organisms, soil biota, plants, mammals, and humans, thereby enhancing the understanding of the complex impacts of plastic particles on the environment. Additionally, this review highlights remediation technologies and global legislative and institutional measures for managing waste associated with MPs and NPs. It also shows that effectively combating plastic pollution requires the synergization of diverse management, monitoring strategies, and regulatory measures into a comprehensive policy framework.

Anthropogenic particle concentrations and fluxes in an urban river are temporally variable and impacted by storm events

Anthropogenic particles (AP), which include microplastics and other synthetic, semisynthetic, and anthropogenically modified materials, are pollutants of concern in aquatic ecosystems worldwide. Rivers are important conduits and retention sites for AP, and time series data on the movement of these particles in lotic ecosystems are needed to assess the role of rivers in the global AP cycle. Much research assessing AP pollution extrapolates stream loads based on single time point measurements, but lotic ecosystems are highly variable over time (e.g., seasonality and storm events). The accuracy of models describing AP dynamics in rivers is constrained by the limited studies that examine how frequent changes in discharge drive particle retention and transport. This study addressed this knowledge gap by using automated, high-resolution sampling to track AP concentrations and fluxes during multiple storm events in an urban river (Milwaukee River) and comparing these measurements to commonly monitored water quality metrics. AP concentrations and fluxes varied significantly across four storm events, highlighting the temporal variability of AP dynamics. When data from the sampling periods were pooled, there were increases in particle concentration and flux during the early phases of the storms, suggesting that floods may flush AP into the river and/or resuspend particles from the benthic zone. AP flux was closely linked to river discharge, suggesting large loads of AP are delivered downstream during storms. Unexpectedly, AP concentrations were not correlated with other simultaneously measured water quality metrics, including total suspended solids, fecal coliforms, chloride, nitrate, and sulfate, indicating that these metrics cannot be used to estimate AP. These data will contribute to more accurate models of particle dynamics in rivers and global plastic export to oceans. PRACTITIONER POINTS: Anthropogenic particle (AP) concentrations and fluxes in an urban river varied across four storm events. AP concentrations and fluxes were the highest during the early phases of the storms. Storms increased AP transport downstream compared with baseflow. AP concentrations did not correlate with other water quality metrics during storms.

Mechanistic interpretation of the sorption of terbuthylazine pesticide onto aged microplastics

Microplastics (MPs) pose a global concern due to their ubiquitous distribution. Once in the environment, they are subject to aging, which changes their chemical-physical properties and ability to interact with organic pollutants, such as pesticides. Therefore, this study investigated the interaction of the hydrophobic herbicide terbuthylazine (TBA), which is widely used in agriculture, with artificially aged polyethylene (PE) MP (PE-MP) to understand how aging affects its sorption. PE was aged by an accelerated weathering process including UV irradiation, hydrogen peroxide, and ultrasonic treatment, and aged particles were characterized in comparison to pristine particles. Sorption kinetics were performed for aged and pristine materials, while further sorption studies with aged PE-MP included determining environmental factors such as pH, temperature, and TBA concentration. Sorption of TBA was found to be significantly lower on aged PE-MP compared to pristine particles because aging led to the formation of oxygen-containing functional groups, resulting in a reduction in hydrophobicity and the formation of negatively charged sites on oxidized surfaces. For pristine PE-MP, sorption kinetics were best described by the pseudo-second-order model, while it was intra-particle diffusion for aged PE-MP as a result of crack and pore formation. Sorption followed a decreasing trend with increasing pH, while it became less favorable at higher temperatures. The isotherm data revealed a complex sorption process on altered, heterogeneous surfaces involving hydrophobic interactions, hydrogen bonding, and π-π interactions, and the process was best described by the Sips adsorption isotherm model. Desorption was found to be low, confirming a strong interaction. However, thermodynamic results imply that increased temperatures, such as those resulting from climate change, could promote the re-release of TBA from aged PE-MP into the environment. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) confirmed TBA sorption onto PE.

Size- and concentration-dependent effects of microplastics on soil aggregate formation and properties

Plastics fragment and threaten soil ecosystems. Degradation of soil structure is one of the risks. Despite this, data on impacts of different sized microplastics (MPs) on soil aggregates is lacking. This study systematically investigated the effects of pristine polyethylene powders of different sizes (< 35, < 125, < 500 µm) and concentrations (0, 0.1, 1.0, 10 wt%) on aggregate formation and their properties for two contrasting soils (woodland soil, WS; agricultural soil, AS). 75 day wet-dry cycles produced newly-formed aggregates in all treatments. MP size and concentration impacted the incorporation of MPs in aggregates and this varied with aggregate size; the size distribution of aggregates also varied with MP size and concentration. Aggregates produced in soil containing 10 wt% < 35 µm MPs had significantly lower MWDs (mean weight diameters) than controls. The wettability of aggregates (> 4 mm) reduced with increasing MP exposure concentration and decreasing MP exposure size. MP incorporation decreased the water stability of aggregates (1-2 mm) in WS but increased it in AS. The particle density of aggregates (> 4 mm) significantly decreased with increasing MP concentration, whereas MP size had no effect. As MPs breakdown, fragment and become smaller over time, their potential risk to the aggregated structure of soil increases.

Science-based evidence on pathways and effects of human exposure to micro- and nanoplastics

Human exposure to plastic particles has raised great concern among all relevant stakeholders involved in the protection of human health due to the contamination of the food chain, surface waters, and even drinking water as well as due to their persistence and bioaccumulation. Now more than ever, it is critical that we understand the biological fate of plastics and their interaction with different biological systems. Because of the ubiquity of plastic materials in the environment and their toxic potential, it is imperative to gain reliable, regulatory-relevant, science-based data on the effects of plastic micro- and nanoparticles (PMNPs) on human health in order to implement reliable risk assessment and management strategies in the circular economy of plastics. This review presents current knowledge of human-relevant PMNP exposure doses, pathways, and toxic effects. It addresses difficulties in properly assessing plastic exposure and current knowledge gaps and proposes steps that can be taken to underpin health risk perception, assessment, and mitigation through rigorous science-based evidence. Based on the existing scientific data on PMNP adverse health effects, this review brings recommendations on the development of PMNP-specific adverse outcome pathways (AOPs) following the AOP Users' Handbook of the Organisation for Economic Cooperation and Development (OECD).

Occurrence of microplastics in edible tissues of livestock (cow and sheep)

Plastic contamination is widely recognized as a major environmental concern due to the entry of small plastic particles into the food chain, thereby posing potential hazards to human health. However, the current understanding of microplastic (MP; < 5 mm) particles in livestock, which serve as an important food source, is limited. This study aims to investigate the concentration and characteristics of MPs in edible tissues of cow and sheep, namely liver, meat, and tripe, obtained from butcher shops in five areas of Bushehr port, Iran. The mean concentration of MPs in different tissues of cow and sheep were 0.14 and 0.13 items/g, respectively. Among the examined tissues, cow meat exhibited the highest concentration of MPs, with a concentration of 0.19 items/g. Nylon and fiber were identified as the predominant polymer types and shapes of MPs found in cow and sheep tissues, respectively. Furthermore, no statistically significant difference was observed in MP concentration across different tissues of cow and sheep. Significantly, this study highlights the elevated hazards associated with exposure to MPs through the consumption of edible cow and sheep tissues, particularly for children who consume meat. The results underscore the potential transfer of MPs from the environment to livestock bodies through their food, contamination during meat processing, and subsequent health hazards for consumers.

Polystyrene micro- and nanoplastics induce gastric toxicity through ROS mediated oxidative stress and P62/Keap1/Nrf2 pathway

Microplastics (MPs) exist widely in the environment and can enter the human body indirectly through the food chain or directly through inhalation or ingestion. The primary organ that MPs contaminated food or water enters the human body through the digestive tract is the stomach. However, at present, the effects of MPs on the stomach and the related mechanism remain unclear. In this study, our results indicated that 50 nm and 250 nm polystyrene MPs (PS-MPs) at environmental related dose significantly decreased stomach organ coefficient, inhibited gastric juice secretion and mucus secretion, disrupted gastric barrier function and suppressed antioxidant ability in mice. In vitro experiments showed that PS-MPs inhibited cell viability, increased ROS generation, and induced apoptosis through mitochondria-dependent pathway. Simultaneously, PS-MPs also decreased mitochondrial membrane potential, ATP level, disrupted mitochondrial kinetic homeostasis, and activated P62 / Nrf2 / Keap1 pathway. Furthermore, blocking ROS (NAC) partially alleviated ROS and apoptosis caused by PS-MPs. Based on above findings, the potential adverse outcome pathway (AOP) of PS-MPs-caused gastric toxicity was proposed which provides a new insight into the risk assessment of MP related gastric damage. Our study unveils the gastric injury induced by PS MPs is dependent on ROS - mediated P62 / Nrf2 / Keap1 signaling pathway, and provides scientific basis for further exploration the mechanism of gastric toxicity of PS MPs.

Microplastics as carriers of toxic pollutants: Source, transport, and toxicological effects

Microplastic pollution has emerged as a new environmental concern due to our reliance on plastic. Recent years have seen an upward trend in scholarly interest in the topic of microplastics carrying contaminants; however, the available review studies have largely focused on specific aspects of this issue, such as sorption, transport, and toxicological effects. Consequently, this review synthesizes the state-of-the-art knowledge on these topics by presenting key findings to guide better policy action toward microplastic management. Microplastics have been reported to absorb pollutants such as persistent organic pollutants, heavy metals, and antibiotics, leading to their bioaccumulation in marine and terrestrial ecosystems. Hydrophobic interactions are found to be the predominant sorption mechanism, especially for organic pollutants, although electrostatic forces, van der Waals forces, hydrogen bonding, and pi-pi interactions are also noteworthy. This review reveals that physicochemical properties of microplastics, such as size, structure, and functional groups, and environmental compartment properties, such as pH, temperature, and salinity, influence the sorption of pollutants by microplastic. It has been found that microplastics influence the growth and metabolism of organisms. Inadequate methods for collection and analysis of environmental samples, lack of replication of real-world settings in laboratories, and a lack of understanding of the sorption mechanism and toxicity of microplastics impede current microplastic research. Therefore, future research should focus on filling in these knowledge gaps.

Assessment of microplastic abundance and impact on recreational beaches along the western Algerian coastline

Microplastics (MPs) have attracted global attention due to their ubiquity and potential impact on the environment. However, MPs are poorly documented along the Algerian coast. To address this data gap, this study investigated the presence of MPs on three recreational beaches in western Algeria (Stidia, Sablettes and Mersat El Hadjaj). The mean MP abundance for the three beaches was estimated at 55.47 ± 48.01 items/m2. Characterization of MPs shape revealed that fragments (79.81 %) were dominant, followed by pellets (10.58 %), filaments (5.57 %), and foam (3.85 %). An assessment of the Microplastic Pollution Index, the Pellet Pollution Index, and the Coefficient of Microplastic Impact, revealed the presence of very low to moderate levels of MPs on the beaches. This presence was associated with minimal beach pollution and moderate overall impact. The sector analysis approach results confirm that there are two different magnitudes of MPs presence that can negatively impact on the environmental quality of the studied beaches.

Microplastics in Ecuador: A review of environmental and health-risk assessment challenges

Pollution from plastic debris and microplastics (MPs) is a worldwide issue. Classified as emerging contaminants, MPs have become widespread and have been found not only in terrestrial and aquatic ecosystems but also within the food chain, which affects both the environment and human health. Since the outbreak of COVID-19, the consumption of single-use plastics has drastically increased, intensifying mismanaged plastic waste in countries such as Ecuador. Therefore, the aim of this review is to 1) summarize the state of MP-related knowledge, focusing on studies conducted with environmental matrices, biota, and food, and 2) analyze the efforts by different national authorities and entities in Ecuador to control MP contamination. Results showed a limited number of studies have been done in Ecuador, which have mainly focused on the surface water of coastal areas, followed by studies on sediment and food. MPs were identified in all samples, indicating the lack of wastewater management policies, deficient management of solid wastes, and the contribution of anthropogenic activities such as artisanal fishing and aquaculture to water ecosystem pollution, which affects food webs. Moreover, studies have shown that food contamination can occur through atmospheric deposition of MPs; however, ingredients and inputs from food production, processing, and packaging, as well as food containers, contribute to MP occurrence in food. Further research is needed to develop more sensitive, precise, and reliable detection methods and assess MPs' impact on terrestrial and aquatic ecosystems, biota, and human health. In Ecuador specifically, implementing wastewater treatment plants in major cities, continuously monitoring MP coastal contamination, and establishing environmental and food safety regulations are crucial. Additionally, national authorities need to develop programs to raise public awareness of plastic use and its environmental effects, as well as MP exposure's effects on human health.

Effects of microplastics pollution on plant and soil phosphorus: A meta-analysis

The widespread use of microplastics leads to environmental pollution, which threatens ecosystem functions (i.e., nutrient cycling). Some studies have focused on the impacts of microplastics on phosphorus from plants and soils. However, inconsistent responses of plant and soil phosphorus to microplastics have been observed. This work synthesized the results of 781 paired observations from 73 publications to explore the overall effects of microplastics on plant and soil phosphorus and whether the impacts depended on microplastics properties and experimental variables. We found the overall negative effects of microplastics on plant phosphorus and soil available phosphorus. Additionally, microplastics significantly inhibited neutral phosphatase activity but increased soil phosphorus leaching. Furthermore, the impacts of microplastics on plant and soil phosphorus varied depending on microplastics types, sizes, concentrations, and experimental durations. Soil total phosphorus and available phosphorus exhibited stronger negative responses to biodegradable than conventional microplastics. Acid phosphatase was more sensitive to biodegradable than conventional microplastics. In addition, soil total phosphorus, available phosphorus, and alkaline phosphatase were significantly correlated with microplastic concentrations and exposure time. Overall, our findings suggest that microplastics potentially threaten soil fertility and plant productivity. This work provides an important reference for predicting ecosystem functions in the context of microplastics pollution.

Nano- and micro-plastic transport in soil and groundwater environments: Sources, behaviors, theories, and models

With the increasing use of plastics, nano- and micro-plastic (NMP) pollution has become a hot topic in the scientific community. Ubiquitous NMPs, as emerging contaminants, are becoming a global issue owing to their persistence and potential toxicity. Compared with studies of marine and freshwater environments, investigations into the sources, transport properties, and fate of NMPs in soil and groundwater environments remain at a primary stage. Hence, the promotion of such research is critically important. Here, we integrate existing information and recent advancements to compile a comprehensive evaluation of the sources and transport properties of NMPs in soil and groundwater environments. We first provide a systematic description of the various sources and transport behaviors of NMPs. We then discuss the theories (e.g., clean-bed filtration and Derjaguin-Landau-Verwey-Overbeek theories) and models (e.g., single-site and dual-site kinetic retention and transport models) of NMP transport through saturated porous media. Finally, we outline the potential limitations of current research and suggest directions for future research. Overall, this review intends to assimilate and outline current knowledge and provide a useful reference frame to determine the sources and transport properties of NMPs in soil and groundwater environments.