A review of microplastics aggregation in aquatic environment: Influence factors, analytical methods, and environmental implications

Evaluation of microplastics and metal accumulation in domestic ducks (Anas platyrhynchos f. domesticus) of a contaminated reservoir in Central Mexico

We procured a total of 22 Anas platyrhynchos f. domesticus (domestic ducks) individuals around the Valsequillo Dam, Puebla, Mexico, to assess ingested plastics and accumulated metals (As, Ba, Cd, Cr, Cu, Hg, Ni, Pb, Zn). The morphometric results of all the samples presented adverse body conditions, where the females had less average body weight (1.94 ± 0.30 kg), height (53. 7 ± 2.78 cm) and wingspan length (92.6 ± 7.45 cm) compared to the male species. The coefficients of variation of all the studied elements (CV > 36 %), except Cu in feathers, demonstrated a high degree of variation, implying exogenous contamination from human activities. Nearly all the studied species presented MP ingestion, with an average of 154.9 suspected particles/ individual. The colour of the MPs was mainly blue (35 %) and transparent (32 %), while the principal forms of MPs were fragments (53 %) and filaments (36 %). The SEM-EDX characterization presented carbon and oxygen peaks and affirmed that the extracted particles are polyethylene and polypropylene. The Pollution Load Index values for MPs were found to be >1, signifying that the site is polluted by MPs, and the calculated Potential Risk Index denoted that the ducks are at low risk of exposure to Cd, Cr, Zn and Ni, and a constant exposure to Cu can be harmful. The study will contribute to establishing baseline data to elucidate the degree of accumulation of MPs and metals in domestic ducks which will be used to employ monitoring programs for the sustainable conservation of the aquatic ecosystem.

Sensitivity analysis of a one-dimensional microplastic transport model in turbulent rivers: Intrinsic properties and hydrodynamics

Since rivers are major transport routes for microplastics, developing novel modeling approaches has become a subject of research to better understand the transport behavior of these particles in river systems. This study aims to model the vertical transport of microplastics at selected sites of the Ergene River, Türkiye, simulate the concentration dynamics of these particles in water and sediment under different hydrodynamic and morphological conditions, and determine the sensitivity of the model results to parameters related to the physical characteristics of microplastics, as well as river hydrodynamics and morphology. A mechanistic model was developed using data on microplastics, river hydrodynamics and morphology. Mass-balance and hydrodynamic equations were utilized for model construction in GoldSim to predict the transport of microplastics between the water column and sediment. The model results revealed that the residence time of microplastics in water was directly related to flow characteristics and river hydraulics, while the initial concentration of particles in water dominated other parameters in influencing the settling and resuspension fluxes of microplastics. Turbulent conditions affected both flow rate and particle resuspension, suggesting that turbulence can either increase or decrease microplastic concentrations and their residence time in the water column and sediment. The model results for both compartments were most sensitive to changes in water and plastic density, whereas Nikuradse sand roughness was the least significant parameter affecting the model outcomes for both compartments.

Preliminary insights into the photosensensitivity of bio-based plastics: Release of microplastic-derived organic matter in water under UV irradiation

This is the first study to investigate the possible release of microplastic-derived dissolved organic matter (MP-DOM) in water from three major types of bio-based MPs, namely, polylactic acid (PLA), polyhydroxyalkanoate (PHA) and PLA-PHA mixtures, under ultraviolet (UV) irradiation conditions. At an initial MP concentration of approximately 5 g per liter, the release of MP-DOM from the studied MPs ranged from 1.55 to 6.68 mg of dissolved organic carbon per g of MP after 30 days of exposure. The results from the measured MP-DOM, along with changes in spectral measurements obtained from shortwave infrared spectroradiometer (SWIR) and micro Fourier-transform infrared spectrometer (μFT-IR), confirmed that the bio-based polymers appeared to be photosensitive due to the observed possible formation of carbonyl bonds with increased carbonyl index on the UV-irradiated surface. Additionally, the fluorescence excitation-emission spectra of the MP-DOM revealed narrow fluorescence peaks, suggesting the presence of organic matter with structural features similar to those of humic substances. These findings on bio-based MPs provide insights into their fate and potential impacts on water environments.

Disentangling the retention preferences of estuarine suspended particulate matter for diverse microplastic types

As a major source of microplastics (MPs) for global oceans, estuarine MPs pose challenges for numerical modeling due to their particle diversity, while hydrodynamics and suspended particulate matter (SPM) further exacerbate transport prediction uncertainties. This study employs a categorization framework to pinpoint 16 representative MPs types, precisely simulating their transport processes in the Yangtze River estuary (YRE). Furthermore, spatial links between SPM concentrations and MP types at 1800+ simulated sites were examined using ArcGIS and bivariate Local Indicators of Spatial Association (BI-LISA). Results indicate that low-density (≤0.95 g/cm³), small-diameter (<500 μm) fiber MPs are more prone to hetero-aggregation with estuarine SPM flocs, while MPs with opposite characteristics may move depending on their intrinsic properties. High-high BI-LISA clusters were observed both in river branches and at the confluence with the sea, the latter closely associated with the turbidity maximum zone that promote MP hetero-aggregation. The interaction of these currents and Yangtze (Changjiang) diluted water forms MPs clusters between 122.0°E and 122.5°E at the confluence of the South Branch, averaging over 870 μg/m3. Examining the trapping preferences of estuarine SPMs for various MPs through this classification framework can help to determine the bioavailability of environmental MPs to aquatic organisms and map the MPs baseline values for health risk quantification.

Aggregation behavior of photoaging nanoplastics in artificial sweat solutions

The aging process and aggregation behavior of nanoplastics govern their fate and ecological risk in aquatic environments. Unfortunately, the aggregation behavior of nanoplastics in sweat and the effect of aging on this process remains unknown. This study investigated the aggregation kinetics of polystyrene nanoplastics (PS-NPs) in three types of artificial sweat before and after photoaging. The aggregation rates (k) of PS-NPs before and after photoaging followed the order ofAmerican-Association-of-Textile-Chemists-and-Colorists-pH-4.3 (kaged =0.6381 nm/s, koriginal =0.4337 nm/s) > British-Standard-pH-6.5 (kaged =0.3589 nm/s, koriginal =0.1297 nm/s) >International-Standard-Organization-pH-8.0 (kaged =0 nm/s, koriginal =0 nm/s). Photoaging decreased the C-O content on the surface of PS-NPs from 4.47 % to 1.97 %, thus to promote the aggregation of PS-NPs. Moreover, decrease of the pH value of three types of artificial sweat (from 8.0 to 4.3) all increased the aggregation rate of the PS-NPs. Inorganic constituents (NaCl and Na2HPO4) promoted the aggregation of PS-NPs by increasing the positive charges on the surface of PS-NPs, while organic constituents (L-histidine, lactic acid, and urea) stabilized PS-NPs by adsorbing on the surface of PS-NPs. These findings demonstrated that the solution conditions of sweat and photoaging process together determined the transport and distribution of nanoplastics in sweat, offering new insights for assessing and predicting the skin exposure risk of nanoplastics.

Impact of polyvinyl chloride nano-plastics on the biochemical status of Oreochromis niloticus under a predicted global warming scenario

Plastic pollution and global warming are widespread issues that lead to several impacts on aquatic organisms. Despite harmful studies on both subjects, there are few studies on how temperature increases plastics' adverse effects on aquatic animals, mainly freshwater species. So, this study aims to clarify the potential impact of temperature increases on the toxicological properties of polyvinyl chloride nano-plastics (PVC-NPs) in Nile tilapia (Oreochromis niloticus) by measuring biochemical and oxidative biomarkers. The fish groups were subjected to three distinct temperatures (30, 32, and 34 °C) and subsequently separated into two groups: 0 and 10 mg/L of PVC-NPs, as it is expected that these temperatures may modify their chemical properties, which can influence their absorption and toxicity in fish. After 4 days, the biochemical response of fish exposed to PVC-NPs and elevated temperatures showed a significant increase in the levels of plasma total proteins, albumin, globulin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), creatinine, and uric acid. Additionally, the level of oxidative stress biomarkers in the liver, gills, and brain was found to have a significant increase in malondialdehyde (MDA) concentration and a decrease in glutathione reduced (GSH) concentration and catalase (CAT) activity in all studied groups. Finally, the current findings revealed a synergistic cytotoxic effect of PVC-NPs and temperatures on the metabolic and oxidative stress indices of O. niloticus.

Riverine microplastics in the Mount Everest region affected by glacier meltwater

Understanding the distribution and drivers of microplastics (MPs) in remote and sensitive environments is essential for assessing their ecological impacts and devising mitigation strategies. This study investigates the distribution and characteristics of MPs in streams and sediments of the Mt. Everest region. Results show that microplastic (MP) abundance during the non-monsoon season was 2-4 times higher than in the monsoon season. MPs were predominantly fragments, composed of specific polymer types (PA, PET), and fell within the 10-30 µm size range. An ecological risk assessment was conducted to better evaluate MP pollution in the Mt. Everest region. The study found that recharge sources of streams influenced MP distribution, with streams receiving non-glacial recharge exhibiting higher MP concentrations during the monsoon season, likely due to the dilution effect of glacier meltwater. Principal component analysis highlighted correlations between MP abundance and environmental factors such as wind speed, dissolved oxygen, stream order, and elevation. These findings advance our understanding of MP pollution dynamics in high-altitude streams, establish a foundation for evaluating their ecological impacts, and offer valuable insights for developing mitigation strategies. This study provides a critical reference for further exploring MP contamination in high-elevation ecosystems and addressing its challenges.

Ocean current modulation of the spatial distribution of microplastics in the surface sediments of the Beibu Gulf, China

Microplastic pollution, a major global environmental issue, is gaining heightened attention worldwide. Marginal seas are particularly susceptible to microplastic contamination, yet data on microplastics in marine sediments remain scarce, especially in the Beibu Gulf. This study presents a large-scale investigation of microplastics in the surface sediments of the Beibu Gulf to deciphering their distribution, sources and risk to marginal seas ecosystems. The results reveal widespread microplastic contamination, with an average abundance of 391 ± 27 items/kg in sediments. The spatial variability of microplastic abundance was significant, with lower levels in the western Beibu Gulf and higher concentrations in the northeastern and southeastern regions. The spatial distribution of microplastics was largely driven by geological features, hydrodynamic conditions, and human activity, with minimal influence from local environmental factors such as water depth, sediment grain size, organic carbon content, and sediment types. The pollution load index (PLI) suggests a low level of microplastic contamination, but the polymer hazard index (PHI) identified a high ecological risk, likely due to the presence of PVC, a polymer with higher chemical toxicity. Our findings highlight the significant role of hydrodynamic processes in determining microplastic distribution in the Beibu Gulf. These insights enhance our understanding of microplastic dispersal and its governing factors in semi-enclosed marginal seas, providing foundation for targeted pollution control strategies.

Exploring Nanoplastics Bioaccumulation in Freshwater Organisms: A Study Using Gold-Doped Polymeric Nanoparticles

The evaluation of nanoplastics bioaccumulation in living organisms is still considered an emerging challenge, especially as global plastic production continues to grow, posing a significant threat to humans, animals, and the environment. The goal of this work is to advance the development of standardized methods for reliable biomonitoring in the future. It is crucial to employ sensitive techniques that can detect and measure nanoplastics effectively, while ensuring minimal impact on the environment. To understand nanoplastics retention by freshwater organisms, phyto- and zooplankton, and mussels were exposed to gold-doped polymeric nanoparticles synthesized in our laboratory. The results demonstrated that measuring gold content using inductively coupled plasma mass spectrometry (ICP-MS), along with confirmation of its presence through electron microscopy in selected exposed samples provides insight into the accumulation and release of nanoplastics by organisms playing a relevant ecological role at the early levels of aquatic food webs.

Modeling of heteroaggregation driven buoyant microplastic settling: Interaction with multiple clay particles

The ecological risk of microplastics (MPs) has received widespread attention, but understanding ecological risk starts with understanding environmental migration. Heteroaggregation is an important process that affects the vertical migration of MPs, and the mathematical model is a common tool used to project the migration behavior of MPs. However, the mathematical model based on the aggregation of MPs with one clay particle is not applicable to simulate the migration behavior of buoyant microplastic (BMP). Hence, this study developed a model for heteroaggregation of one BMP with multiple clay particles based on the Population Balance Equation, and the main factors affecting the sedimentation of BMP are clarified through parameter sensitivity analysis and scenario simulation. The results show that neglecting the interaction of one BMP with multiple clay particles in the mathematical model can underestimate the predicted settling concentration of BMP, especially in aqueous environments with higher clay concentration and salinity. The settling process of BMP is controlled by the heteroaggregation rate, which is sensitive to environmental conditions and insensitive to particle properties. This study emphasizes the importance of considering the interaction of one BMP with multiple clay particles in the future mathematical model, which will provide a more reliable prediction of the migration of MPs in aquatic environments.

Microplastics in aquatic systems: A comprehensive review of its distribution, environmental interactions, and health risks

Microplastics (MPs) have become a critical pollutant, accumulating in aquatic ecosystems and posing significant environmental and human health risks. Approximately 5.25 trillion plastic particles float in global oceans, releasing up to 23,600 metric tonnes of dissolved organic carbon annually, which disrupts microbial dynamics. MPs arise from the breakdown of larger plastics, degraded by photodegradation, thermal degradation, and biological processes, which are influenced by polymer type and environmental factors. As carriers, MPs absorb and transport contaminants such as heavy metals, per- and polyfluoroalkyl substances (PFAS), and persistent organic pollutants (POPs) across trophic levels, thereby increasing toxicity within food webs. Key aquatic organisms, including microalgae, molluscs, and fish, experience cellular toxicity, oxidative stress, and disruptions in essential functions due to MP ingestion or adhesion, raising concerns about their bioaccumulation in humans through ingestion, inhalation, and dermal contact. The complex surface chemistry of MPs enhances their pollutant adsorption, a process modulated by environmental pH, salinity, and contamination levels, while aging and structural attributes further impact their bioavailability and toxicity. This review consolidates knowledge on MPs' occurrence, transformation, pollutant interactions, and methodologies for sampling and analysis, emphasizing advancements in spectroscopy and imaging techniques to improve MP detection in aquatic environments. These insights underscore the pressing need for standardized analytical protocols and comprehensive toxicological research to fully understand MPs' effects on ecosystems and human health, informing future mitigation strategies and policy development.

Origin and intra-annual variability of vertical microplastic fluxes in Fram Strait, Arctic Ocean

Microplastic (MP) pollution has reached the remotest areas of the globe, including the polar regions. In the Arctic Ocean, MPs have been detected in ice, snow, water, sediment, and biota, but their temporal dynamics remain poorly understood. To better understand the transport pathways and drivers of MP pollution in this fragile environment, this study aims to assess MPs (≥ 11 μm) in sediment trap samples collected at the HAUSGARTEN observatory (Fram Strait) from September 2019 to July 2021. MP fluxes determined by μ-Fourier transform infrared (FTIR) imaging ranged from 0 to 2.9 MP m-2 d-1, peaking in April 2020 and April 2021, with all detected MPs being <300 μm in size. There was no strong correlation between MPs and any of the recorded biogeochemical and physical variables, as each MP flux event was associated with different variables such as biogenic matter, sea ice concentration, or origin. By providing time series data over 21 months, this study provides a baseline for future MP flux assessments in Fram Strait, Arctic.

The abundance and analytical characterization of microplastics in the surface water of Haryana, India

Microplastic (MP) contamination has become a serious environmental concern that affects terrestrial environments, aquatic ecosystems, and human health. The current study assesses the presence, abundance, and morphology of MPs present in the surface water of Rohtak district, Haryana, India, which is rapidly undergoing industrialization. While the morphological studies of MPs were conducted through stereo microscopy and field emission-scanning electron microscopy (FE-SEM), the elemental composition of polymers was analyzed through attenuated total reflectance-Fourier transform infrared (ATR-FTIR). The results revealed that the surface water was significantly contaminated by polyethylene, polypropylene, and polystyrene. Moreover, the abundance of MPs was found to be 16-28 particles/L with an average value of 23 particles/L. Most of the MPs had fibrous morphology with the specifics being, fibers (43.9%), fragments (23.7%), films (17%), and pellets (15.4%). The MPs exhibited a size range of 0.61-4.87 mm, with an average size measured at 2.03 ± 0.04 mm. Also, the MP pollution load index values for the surface water bodies were found to be below 10, indicating a low risk category. Though currently designated as "low risk," it is important that mitigation strategies be brought over at this juncture to further prevent the deterioration of quality of water. Thus, this study not only intends to bring forth the impact of human activities, industrial waste, open waste dumping, and inadequate municipal waste management practices on increasing MP concentration but also highlights the sustainable alternatives and strategies to address this emerging pollutant in urban water systems. For further prevention, the implementation of stringent regulations and on-site plastic waste segregation is a critical component in preventing the disposal of plastic waste in surface water bodies. RESEARCH HIGHLIGHTS: The abundance of MPs was found to be 16-28 particles/L, with an average value of 23 particles/L. The surface water bodies in Rohtak district fall into the hazard categories of low risk with values less than 10. The overall MP concentration in water, across all five areas, based on color was in order: white/transparent (39.1%), black (15%), gray (9.1%), green (8.7%), blue (7.8%), red (7.8%), orange (6.3%), and yellow (6.1%). The dominant polymers were polyethylene (PE) (42%) and polypropylene (41%) as determined by FTIR spectroscopy.

Impacts of wind forcing on microplastics kinematic in a sensitive water area

Microplastics (MPs) have been found in different environmental department globally, and the threat to organisms posed by MPs is also widely recognized. Kinematic characteristics of low-density fiber MPs in Poyang Lake under different due-south wind were calculated by combining hydrodynamic model with particle tracking model in this study. Poyang Lake is divided into north lake and south lake for study based on its topographic and hydrodynamic characteristics, and the results are as follows: the critical wind speeds causing vertical mixing of MPs in the water column ranges from 6 to 9 m·s-1 in the north lake, while it is >9 m·s-1 in the south lake, and the MPs beaching rate decreases by 7.08 %/(m·s-1) as the due-south wind speed increases. The MPs speed is mainly affected by surface current, while the direction of the velocity is more affected by wind. The MPs velocity in the south lake is only 27.10 % of that in the north lake, and the direction is more dispersed, so the due-south wind concentrates the direction of MPs velocity more to the north in the south lake. The northern wards movement of MPs resulted in a noticeable decrease in FS in the south lake, with FS decreasing by 0.10 for every 1 m·s-1 increase in wind speed, and therefore, the due-south wind reduces the ecological risk posed by MPs through reducing the range of movement and retention time. However, since the FS in the north lake has been close to the minimum value of 1, the reduction of the FS is not significant, and the wind reduces the risk mainly by shortening the retention time of the MPs. Therefore, the ecological risk caused by MPs in Poyang Lake under no or weak wind conditions should be taken into consideration.

Optimising microplastic polyethylene terephthalate fibre extraction from sediments: Tailoring a density-separation procedure for enhanced recovery and reliability

Despite the presence of microplastics in sediments being widely acknowledged, the absence of standardised processing methods in extracting microplastics can compromise reliable and comparable results. Density separation is a predominant method for extracting microplastics from sediments. In this study, Sodium Polytungstate (ρ = 1.6 g cm-3) was selected as the density separation agent for three key factors: i) optimal density for extracting common plastic polymers, ii) low toxicity, and iii) recycling potential of the solution. It is therefore cost-effective, and the risk of solution dispersal is minimal. The solution was tested through four separation procedures, extracting PET fibres from three artificial sediment mixtures (i.e., pure sand, pure mud, and 50 % sand and 50 % mud). The results indicate that the solution employed in this work is highly effective for extracting microplastic fibres from sediments, with recovery rates up to 99 %. However, the results highlight differences in the recovery among the four procedures and in terms of the sediment characteristics. Specifically, extracting microplastics was easier in sandy sediment samples than in mud-rich ones. The complexity of extracting microplastics from mud-rich sediments results from i) the creation of microplastic-sediment aggregates forming denser structures, that settle down trapping microplastics in sediments; ii) the development of a clay sediment cap that hinders the rise of microplastics to the surface. Reducing the risk of underestimation of microplastic content in mud-rich samples can be accomplished by applying a procedure that involves placing the samples with the Sodium Polytungstate solution on a stirring plate while progressively lowering the rotation velocity. Using this method, cohesive sediments lose their ability to trap microplastics while aggregating, consequently reducing their ability to drag microplastics to the bottom. This facilitated microplastics to reach the liquid surface, thereby enabling an efficient retrieval even in mud-rich samples.

Settling and rising velocities of microplastics: Laboratory experiments and lattice Boltzmann modeling

Microplastics (MPs) have become pervasive in marine ecosystems, potentially causing environmental degradation, impacting ecological function, and posing a serious public health risk. Despite the widespread distribution of MPs, their vertical transport within a water column has limited understanding, representing a key knowledge gap in the development of water quality models to minimize these risks. In this study, 6152 individual particles of six common types of MPs were observed through water column experiments to examine a range of drivers of the vertical velocity of MPs, including particle density and size, biofilm growth, water temperature, and salinity. The experimental results revealed that the vertical velocity of MPs obeyed Stokes' law under laminar conditions; increasing salinity decreased the settling tendency of the particles. Moreover, biofilm attachment induced notable alterations in particle characteristics within 60 days, resulting in slower settling velocities (up to a 21.9% change for non-buoyant MPs) and even a reversed vertical direction (up to several times for buoyant particles). Furthermore, a lattice Boltzmann model could predict the vertical velocity of MPs with reasonable accuracy, especially for small particles. This work facilitates the development of sophisticated models/formulas that integrate particle morphology, hydrodynamics, and biological factors to enhance the understanding of MP transport through the river-to-coastal continuum.

Co-accumulation characteristics and interaction mechanism of microplastics and PFASs in a large shallow lake

Microplastics (MPs) and per- and polyfluoroalkyl substances (PFASs) coexist widely in lakes and affect ecological security. The coexistence characteristics and adsorption-desorption mechanisms between MPs and typical PFASs were explored in a typical eutrophic shallow lake (Taihu Lake). Polyvinyl chloride (PVC) and polyethylene (PE) are the primary types of MPs in Taihu Lake, with average abundances in water and sediment of 18630 n/m3 and 584 n/kg, respectively. The average concentrations of PFASs in water and sediment are 288.93 ng/L and 4.33 ng/g, with short-chain PFASs (C4-C7) being the main pollutants. Perfluorobutanoic acid (PFBA) in both water and sediment contributed 38.48 % and 44.53 %, respectively, followed by hexafluoropropylene oxide dimer acid (HFPO-DA). The morphological characteristics of MPs influence the distribution of long-chain PFAS in lake water, while the presence of HFPO-DA and perfluorohexanoic acid (PFHxA) in sediment is directly linked to the concentration and size of MPs. A combination of field investigations and indoor experiments revealed that the irreversible adsorption characteristics between MPs and HFPO-DA may promote the high cumulative flux of HFPO-DA in sediment, and the biofilm on the surface of MPs significantly accelerates this accumulation process. The results provide a new perspective on the co-transport behavior of emerging pollutants in aquatic environments.

Determination of Seasonal Microplastic pollutıon Variation in Aquatic Environments: Case Study from İskenderun Technical University Pond

Although microplastic (MP) pollution in aquatic ecosystems has been a critical issue, a significant portion of previous studies has been limited to marine environments. Few studies have evaluated MP abundance in inland waters, and those that exist often ignore seasonal variations. This study aimed to assess the seasonal variations in microplastic (MP) abundance in the İskenderun Technical University (İSTE) Pond. MP abundance ranged from 0.5 MPs/L to 10.8 MPs/L, with a mean of 3.7 MPs/L. Fiber-shaped, black-colored, small-sized (< 1000 μm) MPs were commonly found on the surface water. Statistical analysis confirmed significant variations in MP abundance across seasons. The abundance of MPs in the surface water correlated with the mean annual precipitation. Atmospheric deposition and storm water runoff were major contributors to microplastic pollution in the pond. PP and PET particles were identified. The findings of this study contains preliminary results that can be used in the development of future legislations and regulations.

Selection of engineered degradation method to remove microplastics from aquatic environments

Microplastics (MPs) in the aquatic environment are difficult to degrade naturally due to their hydrophobicity and structure. A variety of engineered degradation methods were developed to treat MPs contamination in the aquatic environment. Current reviews of MPs degradation methods only provided an inventory but lacked systematic comparisons and application recommendations. However, selecting suitable degradation methods for different types of MPs contamination may be more effective. This work examined the present engineered degradation methods for MPs in the aquatic environment. They were categorized into chemical degradation, biodegradation, thermal degradation and photodegradation. These degradation methods were systematically summarized in terms of degradation efficiency, technical limitations and production of environmental hazards. Also, the potential influences of different environmental factors and media on degradation were analyzed, and the selection of degradation methods were suggested from the perspectives of contamination types and degradation mechanisms. Finally, the development trend and challenges for studying MPs engineered degradation were proposed. This work will contribute to a better selection of customized degradation methods for different types of MPs contamination scenarios in aquatic environments.

Characteristics of organic matter driven by Eichhornia crassipes during co-contamination with per(poly)fluoroalkyl substances (PFASs) and microplastics (MPs)

Co-contamination with MPs and PFASs has been recorded, particularly in surface-water environments. Floating macrophyte microcosms are an important part of the surface water ecosystem, and dissolved organic matter (DOM) driven by floating macrophytes (FMDDOM) is critical for maintaining material circulation. However, knowledge gaps remain regarding the impact of MPs and PFASs co-pollution on FMDDOM. An greenhouse simulation experiment was conducted in this study to investigate the effects of four PFASs, perfluorooctanoic acid (PFOA), perfluoro-octane-sulfonic acid (PFOS), perfluoro-2-methyl-3-oxahexanoic acid (Gen X), and potassium 9-chlorohexadecafluoro-3-oxanonane-1-sulfonate (F-53B), on FMDDOM sourced from Eichhornia crassipes (E. crassipes), a typical floating macrophyte, in the presence and absence of polystyrene (PS) MPs. Four PFASs increased FMDDOM release from E. crassipes, leading to a 32.52-77.49 % increase in dissolved organic carbon (DOC) levels. PS MPs further increased this, with results ranging from -21.28 % to 26.49 %. Based on the parallel factor analysis (PARAFAC), FMDDOM was classified into three types of fluorescent components: tryptophan-like, humic-like, and tyrosine-like compounds. Contaminants of MPs and PFASs modified the relative abundance of these three components. Protein secondary structure analysis showed that fluorocarbon bonds tended to accumulate on the α-helix of proteins in FMDDOM. The relative abundance of fluorescent and chromophorous FMDDOMs varied from 0.648 ± 0.044 to 0.964 ± 0.173, indicating that the photochemical structures of the FMDDOM were modified. FMDDOM exhibits decreased humification and increased aromaticity when contaminated with MPs and PFASs, which may be detrimental to the geochemical cycling of carbon. This study offers a theoretical basis for assessing the combined ecological risks of MPs and PFASs in floating macrophyte ecosystems.

Predicting a Wide Range of Fractal Dimensions of Salt-Induced Aggregates in Water Using a Random Forest Model

Salt-induced colloidal aggregates can significantly influence contaminant fate and transport in natural and engineered systems. These aggregates' fractal dimensions (df), ranging from 1.4 to 2.2, depend on various system variables. However, the quantitative relationship between these variables and df of aggregates has not been fully explored, especially in predicting a wide range of df. Here, we developed a random forest model capable of predicting the complete range of aggregate df using just four simple physical and chemical parameters of the aggregating system as inputs. The model accurately predicts the df of aggregates formed by colloids of different sizes, ranging from nano to micro sizes, after being trained and tested on appropriate data sets. Ionic strength (IS) has the most significant influence on the df of aggregates formed by microsized particles followed by the relative hydrodynamic radius of aggregates (Rh/Rp), particle concentration (Cp), and primary particle radius (Rp). For aggregates formed by both nano- and microsized particles, IS still has a strong influence on the df, with the significance of Rp increasing. All four inputs are negatively correlated with predicting the df of aggregates. The predictions align well with the physical interpretations.

Photoaging-induced variations in heteroaggregation of nanoplastics and suspended sediments in aquatic environments: A case study on nanopolystyrene

Photoaging of nanoplastics (NPs) and heteroaggregate with suspended sediments (SS) determines transport processes and ecological risks of NPs in aquatic environments. This study investigated the disruption of photoaging on the heteroaggregation behavior of polystyrene NPs (PSNPs) and SS in different valence electrolyte solutions and deduced the interaction mechanisms by integrating aggregation kinetics and molecular dynamics (MD) simulation. Increasing the electrolyte concentration significantly enhanced the heteroaggregation between PSNPs and SS, and the divalent electrolytes induced the heteroaggregation more efficiently. MD simulation at the molecular level revealed that PS and SS could spontaneously form clusters, and photoaged PS has a stronger potential to fold into a dense state with SS. Photoaging for 30 d retarded heteroaggregation due to the steric hindrance produced by the leached organic matter in NaCl solutions, and the critical coagulation concentration (CCC) increased by >85.44 %. Contrarily, photoaging caused more oxygen-containing functional groups produced on the surface of PSNPs through Ca2+ bridging promoting heteroaggregation and thus destabilizing in CaCl2 solutions, the CCC decreased by 23.53 % ∼ 35.29 %. These findings provide mechanistic insight into the environmental process of NPs and SS and are crucial for a comprehensive understanding of the environmental fate and transport of NPs in aquatic environments.

The surface diffusivity of nanoparticles physically adsorbed at a solid-liquid interface

This work proposes an analytical model considering the effects of hydrodynamic drag and kinetic barriers induced by liquid solvation forces to predict the translational diffusivity of a nanoparticle on an adsorbing surface. Small nanoparticles physically adsorbed to a well-wetted surface can retain significant in-plane mobility through thermally activated stick-slip motion, which can result in surface diffusivities comparable to the bulk diffusivity due to free-space Brownian motion. Theoretical analysis and molecular dynamics simulations in this work show that the surface diffusivity is enhanced when (i) the Hamaker constant is smaller than a critical value prescribed by the interfacial surface energy and particle dimensions, and (ii) the nanoparticle is adsorbed at specific metastable separations of molecular dimensions away from the wall. Understanding and controlling this phenomenon can have significant implications for technical applications involving mass, charge, or energy transport by nanomaterials dispersed in liquids under micro/nanoscale confinement, such as membrane-based separation and ultrafiltration, surface electrochemistry and catalysis, and interfacial self-assembly.

Erosion of rigid plastics in turbid (sandy) water: quantitative assessment for marine environments and formation of microplastics

Mechanical degradation (erosion) of plastics in the marine environment has been reported in many literature studies but without quantitative information. This type of degradation is crucial as it accounts for most of the initial microplastic products, in marine environments (e.g., rivers and oceans). Here, we quantify the erosion of plastics by water-borne sediments under typical perpendicular water velocities and sand loads of turbid rivers and coastal oceans. Polypropylene (PP) shows the highest response to water-borne erosion, with a surface degradation rate of 5160 μm per year (4.44 mg per mm2 per year), compared with high-density polyethylene (HDPE) with a degradation rate of 1874 μm per year (1.79 mg per mm2 per year), resulting in the formation of microplastics (MPs). The rate of formation of such microplastic particles (>10 μm), as characterised by a laser direct infrared (LDIR) chemical imaging system, amounts to 669 particles per mm2 per year for PP and 187 particles per mm2 per year for HDPE, exhibiting average particle sizes of 60 μm and 23 μm in the same order. Furthermore, surface microscopy provided valuable insights into the dominant erosion mechanisms, revealing three distinct zones and the surface features reveal the brittle erosion behaviours. These results will enable a better assessment of degradation and lifetime prediction of plastics in turbid rivers and coastal oceans, allowing precise estimation of the rate of formation of MPs.

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.

Navigating the difference of riverine microplastic movement footprint into the sea: Particle properties influence

As a critical source of marine microplastics (MPs), estuarine MPs community varied in movement due to particle diversity, while tide and runoff further complicated their transport. In this study, a particle mass gradient that represents MPs in the surface layer of the Yangtze River estuary was established. This was done by calculating the masses of 16 particle types using the particle size probability density function (PDF), with typical shapes and polymers as classifiers. Further, Aschenbrenner shape factor and polymer density were embedded into drag coefficients to categorically trace MP movement footprints. Results revealed that the MPs in North Branch moved northward and the MPs in South Branch moved southeastward in a spiral oscillation until they left the model boundary under Changjiang Diluted Water front and the northward coastal currents. Low-density fibrous MPs are more likely to move into the open ocean and oscillate more than films, with a single PE fiber trajectory that reached a maximum oscillatory width of 16.7 km. Over 95 % of the PVC fiber particles settled in nearshore waters west of 122.5°E. Elucidating the aggregation and retention of different MPs types can provide more accurate environmental baseline reference for more precise MP exposure levels and risk dose of ingestion for marine organisms.

Combined toxicity of pristine or artificially aged tire wear particles and bisphenols to Tigriopus japonicus

Tire wear particles (TWPs) are considered an important component of microplastic pollution in the marine environment and occur together with a variety of aquatic pollutants, including frequently detected bisphenols. The adverse effects of TWPs or bisphenols on aquatic organisms have been widely reported. However, the combined toxicity of TWPs and bisphenols is still unknown. In this study, the combined toxicity of both pristine (p-) and aged TWPs (a-TWPs) and four bisphenols ((bisphenol A (BPA), bisphenol F (BPF), bisphenol S (BPS), and bisphenol AF (BPAF)) to Tigriopus japonicus was evaluated. TWPs increased the toxicity of BPA and BPF but decreased the toxicity of BPAF. For BPS, there was synergistic toxic effect in the presence of p-TWPs, but slightly antagonistic effect was observed in the presence of a-TWPs. This adsorption of BPAF by TWPs resulted in a reduction of its toxicity to the copepod. A-TWPs could release more Zn than p-TWPs, and the released Zn contributed to the synergistic effect of TWPs and BPA or BPF. The aggregation formed by TWPs in certain sizes (e.g., 90-110 μm) could cause intestinal damage and lipid peroxidation in T. japonicus. The synergistic effect of p-TWPs and BPS might be due to the aggregation size of the binary mixture. The results of the current study will be important to understand the combined toxic effect of TWPs and bisphenols and the potential toxic mechanisms of the binary mixture.

Ecotoxicological Effects of Microplastics Combined With Antibiotics in the Aquatic Environment: Recent Developments and Prospects

Both microplastics and antibiotics are commonly found contaminants in aquatic ecosystems. Microplastics have the ability to absorb antibiotic pollutants in water, but the specific adsorption behavior and mechanism are not fully understood, particularly in relation to the impact of microplastics on toxicity in aquatic environments. We review the interaction, mechanism, and transport of microplastics and antibiotics in water environments, with a focus on the main physical characteristics and environmental factors affecting adsorption behavior in water. We also analyze the effects of microplastic carriers on antibiotic transport and long-distance transport in the water environment. The toxic effects of microplastics combined with antibiotics on aquatic organisms are systematically explained, as well as the effect of the adsorption behavior of microplastics on the spread of antibiotic resistance genes. Finally, the scientific knowledge gap and future research directions related to the interactions between microplastics and antibiotics in the water environment are summarized to provide basic information for preventing and treating environmental risks. Environ Toxicol Chem 2024;43:1950-1961. © 2024 SETAC.

Enhancing microplastic removal from natural water using coagulant aids

Microplastic (MP) pollution poses a significant environmental challenge, underscoring the need for improved water treatment methods. This study investigates the effectiveness of coagulation, flocculation, and sedimentation processes for removing microbeads, focusing on key factors that influence removal efficiency. Among the coagulants tested, polyaluminium chloride (PAC) demonstrated superior performance by enhancing the aggregation of microplastics with flocs. Optimal treatment conditions were determined to be 0.4 mmol/L PAC and 3 mg/L polyacrylamide (PAM) at pH 8 (before adding PAC), with rapid stirring at 240 rpm for 1 min, followed by slow stirring at 35 rpm for 13 min, and a sedimentation period of 25 min. Under these conditions, removal efficiencies exceeded 95 % for a range of microbeads (10-1000 μm: Polystyrene (PS), Polypropylene (PP), Polyvinyl chloride (PVC), Polyamide (PA), Polyethylene (PE), and Polyurethane (PU)) from natural water samples. Without PAM, PAC alone achieved a 97 % removal rate for PS microbeads. The addition of PAM maintained high removal efficiency, while aluminium sulphate and ferric chloride were less effective, with removal rates of 67 % and 48 % for PS microbeads, respectively. PAM enhanced MP removal across various coagulants and microbead types, with maximum efficiency observed at PAM concentrations of ≥3 mg/L. The treatment also demonstrated that organic matter in Regent's Park pond water could further improve MP removal. Size significantly impacts removal efficiency: larger microbeads (1 mm to >250 μm) were removed more effectively (95 %) compared to smaller ones (10 to <250 μm), which had a lower removal rate of 49 %. Denser microbeads like PVC (density 1.38 g/cm³) settled more efficiently than lighter microbeads such as PE (density 0.97 g/cm³). These findings suggest a need for advanced technologies to better remove lighter, smaller MPs from water.

Co-photoaging inhibited the heteroaggregation between polystyrene nanoplastics and different titanium dioxide nanoparticles

Heteroaggregation between nanoplastics (NPs) and titanium dioxide nanoparticles (TiO2NPs) determines their environmental fates and ecological risks in aquatic environments. However, the co-photoaging scenario of NPs and TiO2NPs, interaction mechanisms of TiO2NPs with (aged) NPs, as well as the dependence of their heteroaggregation on TiO2NPs facets remain elusive. We found the critical coagulation concentration (CCC) of polystyrene nanoplastics (PSNPs) with coexisting RTiO2NPs was 1.9 - 2.2 times larger than that with coexisting ATiO2NPs, suggesting a better suspension stability of PSNPs+RTiO2NPs. In addition, CCC of TiO2NPs with coexisting photoaged PSNPs (APSNPs) was larger 1.7 - 2.2 times than that with PSNPs coexisting, indicating photoaging inhibited their heteroaggregation due to increasing electrostatic repulsion derived from increased negative charges on APSNPs and the polymer-derived dissolved organic carbon. Coexisted TiO2NPs promoted oxidation of PSNPs with the action of HO· and O2·- under UV light, leading to inhibited heteroaggregation. Moreover, Van der Waals and Lewis-acid interaction dominated the formation of primary heteroaggregates of PSNPs-TiO2NPs (ESE = ‒2.20 ∼ ‒2.78 eV) and APSNPs-TiO2NPs (ESE = ‒3.29 ∼ ‒3.67 eV), respectively. The findings provide a mechanistic insight into the environmental process of NPs and TiO2NPs, and are significant for better understanding their environmental risks in aquatic environments.

New Insights into the Formation of Aggregates of Bidisperse Nano- and Microplastics in Water Based on the Analysis of In Situ Microscopy and Molecular Simulation

Microplastics (MPs) and nanoplastics (NPs) in water pose a global threat to human health and the environment. To develop efficient removal strategies, it is crucial to understand how these particles behave as they aggregate. However, our knowledge of the process of aggregate formation from primary particles of different sizes is limited. In this study, we analyzed the growth kinetics and structures of aggregates formed by polystyrene MPs in mono- and bidisperse systems using in situ microscopy and image analysis. Our findings show that the scaling behavior of aggregate growth remains unaffected by the primary particle size distribution, but it does delay the onset of rapid aggregation. We also performed a structural analysis that reveals the power law dependence of aggregate fractal dimension (df) in both mono- and bidisperse systems, with mean df consistent with diffusion-limited cluster aggregation (DLCA) aggregates. Our results also suggest that the df of aggregates is insensitive to the shape anisotropy. We simulated molecular forces driving aggregation of polystyrene NPs of different sizes under high ionic strength conditions. These conditions represent salt concentration in ocean water and wastewater, where the DLVO theory does not apply. Our simulation results show that the aggregation tendency of the NPs increases with the ionic strength. The increase in the aggregation is caused by the depletion of clusters of ions from the NPs surface.

Impacts of microplastic and seawater acidification on unicellular red algae: Growth response, photosynthesis, antioxidant enzymes, and extracellular polymer substances

Microplastics (MPs) pollution and seawater acidification have increasingly become huge threats to the ocean ecosystem. Their impacts on microalgae are of great importance, since microalgae are the main primary producers and play a critical role in marine ecosystems. However, the impact of microplastics and acidification on unicellular red algae, which have a unique phycobiliprotein antenna system, remains unclear. Therefore, the impacts of polystyrene-MPs alone and the combined effects of MPs and seawater acidification on the typical unicellular marine red algae Porphyridium purpureum were investigated in the current study. The result showed that, under normal seawater condition, microalgae densities were increased by 17.75-41.67 % compared to the control when microalgae were exposed to small-sized MPs (0.1 μm) at concentrations of 5-100 mg L-1. In addition, the photosystem II and antioxidant enzyme system were not subjected to negative effects. The large-sized MPs (1 μm) boosted microalgae growth at a low concentration of MPs (5 mg L-1). However, it was observed that microalgae growth was significantly inhibited when MPs concentration increased up to 50 and 100 mg L-1, accompanied by the remarkably reduced Fv/Fm value and the elevated levels of SOD, CAT enzymes, phycoerythrin (PE), and extracellular polysaccharide (EPS). Compared to the normal seawater condition, microalgae densities were enhanced by 52.11-332.56 % under seawater acidification, depending on MPs sizes and concentrations, due to the formed CO2-enrichment condition and appropriate pH range. PE content in microalgal cells was significantly enhanced, but SOD and CAT activities as well as EPS content markedly decreased under acidification conditions. Overall, the impacts of seawater acidification were more pronounced than MPs impacts on microalgae growth and physiological responses. These findings will contribute to a substantial understanding of the effects of MPs on marine unicellular red microalgae, especially in future seawater acidification scenarios.

Molecular dynamics simulations of anisotropic particles accelerated by neural-net predicted interactions

Rigid bodies, made of smaller composite beads, are commonly used to simulate anisotropic particles with molecular dynamics or Monte Carlo methods. To accurately represent the particle shape and to obtain smooth and realistic effective pair interactions between two rigid bodies, each body may need to contain hundreds of spherical beads. Given an interacting pair of particles, traditional molecular dynamics methods calculate all the inter-body distances between the beads of the rigid bodies within a certain distance. For a system containing many anisotropic particles, these distance calculations are computationally costly and limit the attainable system size and simulation time. However, the effective interaction between two rigid particles should only depend on the distance between their center of masses and their relative orientation. Therefore, a function capable of directly mapping the center of mass distance and orientation to the interaction energy between the two rigid bodies would completely bypass inter-bead distance calculations. It is challenging to derive such a general function analytically for almost any non-spherical rigid body. In this study, we have trained neural nets, powerful tools to fit nonlinear functions to complex datasets, to achieve this task. The pair configuration (center of mass distance and relative orientation) is taken as an input, and the energy, forces, and torques between two rigid particles are predicted directly. We show that molecular dynamics simulations of cubes and cylinders performed with forces and torques obtained from the gradients of the energy neural-nets quantitatively match traditional simulations that use composite rigid bodies. Both structural quantities and dynamic measures are in agreement, while achieving up to 23 times speedup over traditional molecular dynamics, depending on hardware and system size. The method presented here can, in principle, be applied to any irregular concave or convex shape with any pair interaction, provided that sufficient training data can be obtained.

Aerosolization of micro- and nanoplastics via sea spray: Investigating the role of polymer type, size, and concentration, and potential implications for human exposure

Micro- and nanoplastics (MNPs) can enter the atmosphere via sea spray aerosols (SSAs), but the effects of plastic characteristics on the aerosolization process are unclear. Furthermore, the importance of the transport of MNPs via these SSAs as a possible new exposure route for human health remains unknown. The aim of this study was two-fold: (1) to examine if a selection of factors affects aerosolization processes of MNPs, and (2) to estimate human exposure to MNPs via aerosols inhalation. A laboratory-based bubble bursting mechanism, simulating the aerosolization process at sea, was used to investigate the influence of MNP as well as seawater characteristics. To determine the potential human exposure to microplastics via inhalation of SSAs, the results of the laboratory experiments were extrapolated to the field based on sea surface microplastic concentrations and the volume of inhaled aerosols. Enrichment seemed to be influenced by MNP size, concentration and polymer type. With higher enrichment for smaller particles and denser polymers. Experiments with different concentrations showed a larger range of variability but nonetheless lower concentrations seemed to result in higher enrichment, presumably due to lower aggregation. In addition to the MNP characteristics, the type of seawater used seemed to influence the aerosolization process. Our human exposure estimate to microplastic via inhalation of sea spray aerosols shows that in comparison with reported inhaled concentrations in urban and indoor environments, this exposure route seems negligible for microplastics. Following the business-as-usual scenario on plastic production, the daily plastic inhalation in coastal areas in 2100 is estimated to increase but remain far below 1 particle per day. This study shows that aerosolization of MNPs is a new plastic transport pathway to be considered, but in terms of human exposure it seems negligible compared to other more important sources of MNPs, based on current reported environmental concentrations.

When antibiotics encounter microplastics in aquatic environments: Interaction, combined toxicity, and risk assessments

Antibiotics and microplastics (MPs), known as emerging pollutants, are bound to coexist in aquatic environments due to their widespread distribution and prolonged persistence. To date, few systematic summaries are available for the interaction between MPs and antibiotics in aquatic ecosystems, and a comprehensive reanalysis of their combined toxicity is also needed. Based on the collected published data, we have analyzed the source and distribution of MPs and antibiotics in global aquatic environments, finding their coexistence occurs in a lot of study sites. Accordingly, the presence of MPs can directly alter the environmental behavior of antibiotics. The main influencing factors of interaction between antibiotics and MPs have been summarized in terms of the characteristics of MPs and antibiotics, as well as the environmental factors. Then, we have conducted a meta-analysis to evaluate the combined toxicity of antibiotics and MPs on aquatic organisms and the related toxicity indicators, suggesting a significant adverse effect on algae, and inapparent on fish and daphnia. Finally, the environmental risk assessments for antibiotics and MPs were discussed, but unfortunately the standardized methodology for the risk assessment of MPs is still challenging, let alone assessment for their combined toxicity. This review provides insights into the interactions and environment risks of antibiotics and MPs in the aquatic environment, and suggests perspectives for future research.

Acceleration a yeast-based biodegradation process of polyethylene terephthalate microplastics by Tween 20: Efficiency, by-product analysis, and metabolic pathway Prediction

Polyethylene terephthalate is a widely produced plastic polymer that exhibits considerable biodegradation resistance, making its derived microplastics ubiquitous environmental pollutants. In this study, a new yeast strain (Vanrija sp. SlgEBL5) was isolated and found to have lipase and esterase-positive capabilities for degrading polyethylene terephthalate microplastics. This isolate changed the microplastic surface charge from -19.3 to +31.0 mV and reduced more than 150 μm of its size in addition to reducing the intensity of the terephthalate, methylene, and ester bond functional groups of the polymer in 30 days. Tween 20 as a chemical auxiliary treatment combined with biodegradation increased the microplastic degradation rate from 10 to 16.6% and the thermal degradation rate from 85 to 89%. Releasing less potentially hazardous by-products like 1,2 diethyl-benzene despite the higher abundance of long-chain n-alkanes, including octadecane and tetracosane was also the result of the bio + chemical treatment. Altogether, the findings showed that Vanrija sp. SlgEBL5 has the potential as a biological treating agent for polyethylene terephthalate microplastics, and the simultaneous bio + chemical treatment enhanced the biodegradation rate and efficiency.

Nitrogen supply neutralizes the nanoplastic-plant interaction in a coastal wetland

The presence of nanoplastics posed a potential threat to coastal saline-alkaline wetlands where nitrogen (N) fertilizer is being implemented as an important ecological restoration measure. Notwithstanding, the effects of N inputs on plant community in polypropylene-nanoplastics (PP-NPs) coexistence environments are largely unknown. To address this, we investigated the effects of PP-NPs addition alone or combined N supply on community aboveground biomass, morphological traits, diversity, composition, niche differentiation, interspecific interactions, and assembly. Our results showed that the PP-NPs addition alone reduced community aboveground biomass and morphological traits. However, the addition of high concentration (0.5%) PP-NPs alone favored community α-diversity and reduced community stability, which could be weakened through combined N supply. Overall, the effect of PP-NPs addition alone on plant community composition was greater than that of combined N supply. We also demonstrated PP-NPs addition alone and combined N supply reduced the niche breadth of the plant community and affected the niche overlap of dominant species. In the assembly of plant communities, stochastic processes played a dominant role. We conclude that N fertilization can amend the terrestrial nanoplastics pollution, thus mitigating the effects of PP-NPs on the plant community.

Impact of heteroaggregation between microplastics and algae on particle vertical transport

Understanding the impacts of microplastics (MPs) on aqueous environments requires understanding their transport dynamics and how their presence affects other natural processes and cycles. In this context, one aspect to consider is how MPs interact with freshwater snow (FWS), a mixture of algae and natural particles. FWS is one of the primary drivers of the flux of organic matter from the water surface to the bottom sediment, where zooplankton, diurnal migration, fish faecal pellets settling and turbulent mixing can also play prominent roles. Understanding how MPs and FWS heteroaggregation affects their respective settling velocities is important to assess not only MPs fate and transport but also their ecological impacts by altering FWS deposition and thereby nutrient cycling. In this present study, we obtained a mechanistic understanding of the processes controlling MPs settling dynamics and heteroaggregation with FWS and the subsequent impacts on the settling rates of both MPs and ballasted FWS. Here we used a plexiglass column equipped with a stereoscopic camera system to track the settling velocities of (1) MPs of various compositions, densities and morphologies, (2) FWS flocs and (3) MP-FWS agglomerates. For each experimental set, thousands of particles were tracked over a series of image sequences. We found that agglomerates with high-density MPs settled at least twofold faster than FWS alone, implying a much smaller residence time in the water column, except for cases with MP fibres or low-density plastics. These findings will help to refine MP fate models and, while contingent on MPs number, may impact biogeochemical cycles by changing the flux of nutrients contained in FWS to the sediment.

Microplastics and environmental effects: investigating the effects of microplastics on aquatic habitats and their impact on human health

Microplastics (MPs) are particles with a diameter of <5 mm. The disposal of plastic waste into the environment poses a significant and pressing issue concern globally. Growing worry has been expressed in recent years over the impact of MPs on both human health and the entire natural ecosystem. MPs impact the feeding and digestive capabilities of marine organisms, as well as hinder the development of plant roots and leaves. Numerous studies have shown that the majority of individuals consume substantial quantities of MPs either through their dietary intake or by inhaling them. MPs have been identified in various human biological samples, such as lungs, stool, placenta, sputum, breast milk, liver, and blood. MPs can cause various illnesses in humans, depending on how they enter the body. Healthy and sustainable ecosystems depend on the proper functioning of microbiota, however, MPs disrupt the balance of microbiota. Also, due to their high surface area compared to their volume and chemical characteristics, MPs act as pollutant absorbers in different environments. Multiple policies and initiatives exist at both the domestic and global levels to mitigate pollution caused by MPs. Various techniques are currently employed to remove MPs, such as biodegradation, filtration systems, incineration, landfill disposal, and recycling, among others. In this review, we will discuss the sources and types of MPs, the presence of MPs in different environments and food, the impact of MPs on human health and microbiota, mechanisms of pollutant adsorption on MPs, and the methods of removing MPs with algae and microbes.

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.

Impact of nano- and micro-sized polystyrene beads on larval survival and growth of the Pacific oyster Crassostrea gigas

This study successionally monitored how nano- and micro-sized polystyrene beads (MNPs) influence larval mortality, growth, and attachment behavior of the Pacific oyster Crassostrea gigas related to MNP diameter and concentration. D-shaped larvae were sequentially exposed to three-diameter MNPs (0.55, 3.00, 6.00 µm) at five concentrations (0, 0.1, 1.0, 10, 20 μg/mL), and their mortality, growth stages and attachment were observed daily until they die. In addition, MNP intake and accumulation in larvae at each growth stage were determined using fluorescent beads. Deterioration in larval growth and survival was observed under all the exposure conditions, while significant negative effects on the growth parameters were defined with smaller MNPs at lower concentrations. Fluorescent signals were detected in larval digestive tracts at all except D-shaped larval stage, and on the mantle and foot in pediveligers. Therefore, MNP intake adversely affects larval physiological conditions by the synchronal effects of MNP size and concentration. Our findings highlight the implications of MNP characteristics on Pacific oyster larvae, emphasizing the interplay between size, concentration, and physiological responses, crucial for mitigating nanoparticle pollution in marine ecosystems.

Unveiling the Tiny Invaders: A deep dive into microplastics in shrimp - Occurrence, detection and unraveling the ripple effects

Aquaculture is a rapidly expanding food sector worldwide; it is the farming of fish, shellfish, and other marine organisms. Microplastics (MPs) are small pieces of plastic with a diameter of less than 5 mm that end up in the marine environment. MPs are fragments of large plastics that take years to degrade but can frustrate into small pieces, and some commercially available MPs are used in the production of toothpaste, cosmetics, and aircraft. MPs are emerging contaminants; they are ingested by marine species. These MPs have effects on marine species such as growth retardation and particle translocation to other parts of the body. Recently, MPs accumulation has been observed in shrimps, as well as in a wide range of other scientific reports. So, in this study, we review the presence, accumulation, and causes of MPs in shrimp. These plastics can trophic transfer to other organisms, changes in plastic count, effects on the marine environment, and impacts of MPs on human health were also discussed. It also improves our understanding of the importance of efficient plastic waste management in the ocean, as well as the impact of MPs on marine biota and human health.

Microplastics weaken the exoskeletal mechanical properties of Pacific whiteleg shrimp Litopenaeus vannamei

The ubiquitous presence of microplastics (MPs) in aquatic environments poses a significant threat to crustaceans. Although exoskeleton quality is critical for crustacean survival, the impact of MPs on crustacean exoskeletons remains elusive. Our study represents a pioneering effort to characterize the effects of MPs exposure on crustacean exoskeletons. In this study, the mechanical properties of whiteleg shrimp Litopenaeus vannamei exoskeletons were analyzed after exposure to environmentally realistic levels of MPs. Nanoindentation data demonstrated that MPs exposure significantly increased the hardness and modulus of both the carapace and abdominal segments of L. vannamei. Moreover, fractures and embedded MPs were detected on the exoskeleton surface using SEM-EDS analysis. Further analysis demonstrated that the degree of chitin acetylation (DA) in the shrimp exoskeleton, as indicated by FTIR peaks, was reduced by MPs exposure. In addition, exposure to MPs significantly inhibited the muscle Ca2+-ATPase activity and hemolymph calcium levels. Transcriptome and metabolome analyses revealed that the expression levels of genes encoding key enzymes and metabolites in the chitin biosynthetic pathway were significantly affected by MPs exposure. In conclusion, MPs at environmentally relevant concentrations may affect the exoskeletal mechanical properties of L. vannamei through a comprehensive mechanism involving the disruption of the crystalline structure of chitin, assimilation into the exoskeleton, and dysregulation of exoskeleton biosynthesis-related pathways.

Kinetic trapping of nanoparticles by solvent-induced interactions

Theoretical analysis based on mean field theory indicates that solvent-induced interactions (i.e. structural forces due to the rearrangement of wetting solvent molecules) not considered in DLVO theory can induce the kinetic trapping of nanoparticles at finite nanoscale separations from a well-wetted surface, under a range of ubiquitous physicochemical conditions for inorganic nanoparticles of common materials (e.g., metal oxides) in water or simple molecular solvents. This work proposes a simple analytical model that is applicable to arbitrary materials and simple solvents to determine the conditions for direct particle-surface contact or kinetic trapping at finite separations, by using experimentally measurable properties (e.g., Hamaker constants, interfacial free energies, and nanoparticle size) as input parameters. Analytical predictions of the proposed model are verified by molecular dynamics simulations and numerical solution of the Smoluchowski diffusion equation.

Competitive adsorption behaviors and mechanisms of Cd, Ni, and Cu by biochar when coexisting with microplastics under single, binary, and ternary systems

In this study, the effects of coexistence with microplastics and co-ageing with the soil on adsorption behaviors and mechanisms of biochar for heavy metals were investigated. Adsorption experiments of Cd, Ni, and Cu by microplastics, biochar, and their combination were conducted in single, binary, and ternary systems. The results indicated that the heavy metal adsorption by microplastics was ranked as Ni > Cd > Cu, which increased with decreasing particle size, and the adsorption capacity of microplastics was enhanced after dry-wet and freeze-thaw ageing. Biochar preferentially adsorbed Cd in the single system, while the maximum adsorption of Cu was observed in the binary and ternary systems due to the minimizing impact of competition on the Cu adsorption by biochar. The heavy metal adsorption by the combination of microplastics and biochar was less than that by single biochar, and the smaller the particle size of microplastics, the greater the negative effects on heavy metal adsorption. Coexistence with microplastics reduced Cd adsorption of biochar by 0.72 %-50.35 %, Ni adsorption by 1.17 %-30.43 %, and Cu adsorption by 5.78 %-47.88 %, respectively. Moreover, coexistence with microplastics exacerbated the adverse impacts of competition on biochar adsorption for heavy metals. The contribution percentages of biochar mineral mechanisms for heavy metal adsorption were ranked as Cu > Cd > Ni. When coexisting with microplastics or after ageing, the mineral mechanisms of heavy metal adsorption by biochar significantly decreased. This study investigated the competitive adsorption behaviors and mechanisms of heavy metals by biochar when coexisting with microplastics, which highlighted that the application of biochar for the remediation of heavy metal pollution should be concerned with the impacts of microplastics.

Adsorption of azoxystrobin and pyraclostrobin onto degradable and non-degradable microplastics: Performance and mechanism

Microplastics (MPs) exist after agricultural operations and thus present potential hazards to the environment and human health. However, the ecological risks posed by MPs carrying pesticides remain unclear. In this study, the adsorption and desorption behaviors of two pesticides, azoxystrobin and pyraclostrobin, on degradable and non-degradable MPs of poly(butylene adipate-co-terephthalate) (PBAT) and polyethylene (PE) were compared before and after UV aging. Additionally, the bioaccessibility of MPs carrying pesticides within a condition simulating gastrointestinal fluids was evaluated. The results showed that, after UV aging, the adsorption capacity of PBAT for pesticides decreased, while that of PE increased. Moreover, PBAT possessed higher adsorption ability towards both the pesticides due to its higher specific surface area, pore volume, contact angle, and lower crystallinity, as well as stronger van der Waals forces, electrostatic interactions, and hydrogen bonding indicated by theoretical calculation. Bioaccessibility experiments showed that azoxystrobin and pyraclostrobin had a higher risk of desorption from PBAT than PE, which is mainly dependent on the LogKow of pesticides according to the random forest analysis. In brief, the study highlights the potential risks of degradable MPs carrying pesticides to human health and the ecosystem, especially when compared to their non-degradable counterparts, manifesting that the ecological risk posed by degradable MPs should not be ignored.

Various additive release from microplastics and their toxicity in aquatic environments

Additives may be present in amounts higher than 50% within plastic objects. Additives in plastics can be gradually released from microplastics (MPs) into the aquatic environment during their aging and fragmentation because most of them do not chemically react with the polymers. Some are known to be hazardous substances, which can cause toxicity effects on organisms and pose ecological risks. In this paper, the application of functional additives in MPs and their leaching in the environment are first summarized followed by their release mechanisms including photooxidation, chemical oxidation, biochemical degradation, and physical abrasion. Important factors affecting the additive release from MPs are also reviewed. Generally, smaller particle size, light irradiation, high temperature, dissolved organic matter (DOM) existence and alkaline conditions can promote the release of chemicals from MPs. In addition, the release of additives is also influenced by the polymer's structure, electrolyte types, as well as salinity. These additives may transfer into the organisms after ingestion and disrupt various biological processes, leading to developmental malformations and toxicity in offspring. Nonetheless, challenges on the toxicity of chemicals in MPs remain hindering the risk assessment on human health from MPs in the environment. Future research is suggested to strengthen research on the leaching experiment in the actual environment, develop more techniques and analysis methods to identify leaching products, and evaluate the toxicity effects of additives from MPs based on more model organisms. The work gives a comprehensive overview of current process for MP additive release in natural waters, summarizes their toxicity effects on organisms, and provides recommendations for future research.

A Latest Review on Micro- and Nanoplastics in the Aquatic Environment: The Comparative Impact of Size on Environmental Behavior and Toxic Effect

Micro and nanoplastics (MNPs) have attracted growing global research attention due to their distinct environmental impacts, addressing escalating concerns. The diverse materials, sizes, and shapes of MNPs result in a range of environmental impacts. Size, a crucial characteristic of MNPs, influences their environmental behavior, affecting processes like migration, sedimentation, aggregation, and adsorption. Moreover, size modulates the biodistribution and toxicity of MNPs in aquatic organisms. This review delves into the comprehensive impacts of plastic size, with a primary focus on environmental behavior and toxic effects. Ultimately, this review emphasizes the ecological implications of MNP size, laying a foundation for future research in this field.

Comprehensive understanding of the aging and biodegradation of polystyrene-based plastics

The extensive utilization and inadequate handling of plastics have resulted in severe environmental ramifications. In particular, plastics composed solely of a carbon-carbon (C-C) backbone exhibit limited degradation due to the absence of hydrolyzable functional groups. Plastics with enduring longevity in the natural environment are susceptible to environmental factors and their intrinsic properties, subsequently undergoing a series of aging processes that culminate in biodegradation. This article focuses on polystyrene (PS), which constitutes 20% of total plastic waste, as a case study. Initially, the application of PS in life and the impacts it poses are introduced. Following that, the key factors influencing the aging of PS are discussed, primarily encompassing its properties (e.g., surface characteristics, additives) and environmental factors (e.g., water matrices, biofilms). Lastly, an overview of microbial degradation of PS is provided, including potential microorganisms involved in PS degradation (bacteria, fungi, algae, and insects), four processes of microbial degradation (colonization, bio-fragmentation, assimilation, and mineralization), and potential mechanisms of microbial degradation. This study provides a comprehensive understanding of the multifaceted influences affecting the aging and biodegradation mechanisms of PS, thereby contributing valuable insights for the future management of plastic pollution.

Aggregation behavior of polystyrene nanoplastics: Role of surface functional groups and protein and electrolyte variation

Aggregation kinetics of plastics are affected by the surface functional groups and exposure orders (electrolyte and protein) with kinds of mechanisms in aquatic environment. This study investigates the aggregation of polystyrene nanoplastics (PSNPs) with varying surface functional groups in the presence of common electrolytes (NaCl, CaCl2, Na2SO4) and bovine serum albumin (BSA). It also examines the impact of different exposure orders, namely BSA + NaCl (adding them together), BSA → NaCl (adding BSA firstly and then NaCl), and NaCl → BSA (adding NaCl firstly and then BSA), on PSNPs aggregation. The presence of BSA decreased the critical coagulation concentration in NaCl (CCCNa+) of the non-modified PS-Bare from 222.17 to 142.81 mM (35.72%), but increased that of the carboxyl-modified PS-COOH from 157.34 to 160.03 mM (1.71%). This might be ascribed to the thicker absorbed layer of BSA onto the PS-Bare surface, known from Ohshima's soft particle theory. Their aggregation in CaCl2 was both increased because of Ca2+ bridging. Different from the monotonous effects of BSA on PS-Bare and PS-COOH, BSA initially facilitated PS-NH2 aggregation via patch-charge attraction, then inhibited it at higher salt levels through steric repulsion. Furthermore, exposure orders had no significant effect on PS-Bare and PS-COOH, but had a NaCl concentration-dependent impact on PS-NH2. At the low NaCl concentrations (10 and 100 mM), no obvious influence could be observed. While, at 300 mM NaCl, the high concentrations of BSA could not totally stabilize the salt-induced aggregates in NaCl → BSA, but could achieve it in the other two orders. These might be attributed to the electrical double layer compression by NaCl, "patch-charge" force and steric hindrance by BSA. These experimental findings shed light on the potential fate and transport of nanoparticles in aquatic environments.