Sorption of three synthetic musks by microplastics

Photochemically induced aging of polystyrene nanoplastics and its impact on norfloxacin adsorption behavior

The co-occurrence of nanoplastics (NPs) and antibiotics in the environment is a growing concern for ecological safety. As NPs age in natural environments, their surface properties and morphology may change, potentially affecting their interactions with co-contaminants such as antibiotics. It is crucial to understand the effect of aging on NPs adsorption of antibiotics, but detailed studies on this topic are still scarce. The study utilized the photo-Fenton-like reaction to hasten the aging of polystyrene nanoplastics (PS-NPs). The impact of aging on the adsorption behavior of norfloxacin (NOR) was then systematically examined. The results showed a time-dependent rise in surface oxygen content and functional groups in aged PS-NPs. These modifications led to noticeable physical changes, including increased surface roughness, decreased particle size, and improved specific surface area. The physicochemical changes significantly increased the adsorption capacity of aged PS-NPs for norfloxacin. Aged PS-NPs showed 5.03 times higher adsorption compared to virgin PS-NPs. The adsorption mechanism analysis revealed that in addition to the electrostatic interactions, van der Waals force, hydrogen bonding, π-π* interactions and hydrophobic interactions observed with virgin PS-NPs, aged PS-NPs played a significant role in polar interactions and pore-filling mechanisms. The study highlights the potential for aging to worsen antibiotic risk in contaminated environments. This study not only enhances the comprehension of the environmental behavior of aged NPs but also provides a valuable basis for developing risk management strategies for contaminated areas.

Hydrophobic organic contaminants affiliated with polymer-specific microplastics in urban river tributaries and estuaries

Exposure to microplastics (MPs) and hydrophobic organic contaminants (HOCs) combined at high concentrations may induce adverse effects to aquatic organisms in laboratory-scale studies. To determine environmentally relevant concentrations of HOCs in MPs, it is essential to understand the occurrence of MP-affiliated HOCs in the aquatic environment. Here we report the occurrences of HOCs affiliated with polymer-specific floating MPs from 12 tributaries and three estuaries in the Pearl River Delta, South China. Target HOCs include nine synthetic musks (SMs), 14 ultraviolet adsorbents (UVAs), 15 polycyclic aromatic hydrocarbons (PAHs), eight polybrominated diphenyl ethers (PBDEs), and 14 polychlorinated biphenyls (PCBs). Average concentrations of MP-affiliated ∑9SM, ∑14UVA, ∑15PAH, ∑8PBDE, and ∑14PCB were 1790, 5550, 1090, 412, and 107 ng g-1, respectively. The average concentrations of HOCs affiliated with MPs of different polymer types were 9790, 7220, 72,500, and 55,800 ng g-1 for polyethylene (PE), polypropylene, polystyrene, and other MPs, respectively. As the concentration of PE was the highest among all MPs at the average concentration of 0.77 mg m-3, the monthly outflow of PE-affiliated HOCs accounted for the largest proportion (46 %) in the outflow of MP-affiliated HOCs (2.8 g) to the coastal ocean via three estuaries. These results suggest that HOCs were highly concentrated in MPs and varied among different chemicals and polymer types. Due to the differences of polymer characteristics and half-life of affiliated chemicals, future toxicology studies concerning exposure to these combined pollutants may need to specify polymer types and their affiliated chemicals.

Interactions between microplastics and contaminants: A review focusing on the effect of aging process

Microplastics (MPs) in the environment are a major global concern due to their persistent nature and wide distribution. The aging of MPs is influenced by several processes including photodegradation, thermal degradation, biodegradation and mechanical fragmentation, which affect their interaction with contaminants. This comprehensive review aims to summarize the aging process of MPs and the factors that impact their aging, and to discuss the effects of aging on the interaction of MPs with contaminants. A range of characterization methods that can effectively elucidate the mechanistic processes of these interactions are outlined. The rate and extent of MPs aging are influenced by their physicochemical properties and other environmental factors, which ultimately affect the adsorption and aggregation of aged MPs with environmental contaminants. Pollutants such as heavy metals, organic matter and microorganisms have a tendency to accumulate on MPs through adsorption and the interactions between them impact their environmental behavior. Aging enhances the specific surface area and oxygen-containing functional groups of MPs, thereby affecting the mechanism of interaction between MPs and contaminants. To obtain a more comprehensive understanding of how aging affects the interactions, this review also provides an overview of the mechanisms by which MPs interact with contaminants. In the future, there should be further in-depth studies of the potential hazards of aged MPs in different environments e.g., soil, sediment, aquatic environment, and effects of their interaction with environmental pollutants on human health and ecology.

The carrier effect mechanism of butachlor in water by three typical microplastics

Butachlor (BUT) is a widely used herbicide that can cause environmental problems when used excessively. BUT has been found to exist in large quantities in the water environment so far. As an agricultural pre-emergent herbicide, BUT can enter the water environment through multiple channels and cause pollution. This study investigated the mechanism of three types of microplastics (MPs): polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC) to remove BUT from water. The adsorption behavior between MPs and BUT under different factors, namely pH, salt ion concentration, and aging, was investigated. This study further investigated the desorption and aging of BUT-adsorbed MPs. In this research, the adsorption capacity of BUT by PE, PP, and PVC are 13.65 μg/g, 14.82 μg/g, and 18.88 μg/g, respectively, and the order of carrier effect was: PVC>PP>PE. Experiments show that MPs have low adsorption performance on the microgram level for BUT. The adsorption behavior of PE, PP, and PVC on BUT conformed to pseudo-second-order kinetics, indicating the presence of physical and chemical adsorption. The Langmuir isotherm model fits well, indicating that the adsorption is a single-layer adsorption process. The pH value causes slight fluctuations in the overall carrier effect. Low concentration of salt ions can inhibit the carrier effect, and high concentration will promote the interaction between MPs and BUT. Aging experiments show that the carrier effect of the original materials was higher than the adsorption capacity of hydrogen peroxide and MPs after acid aging, and acid aging can cause the adsorption capacity to drop significantly.

Sources, distribution, and environmental effects of microplastics: a systematic review

Microplastics (MPs) are receiving increasing attention from researchers. They are environmental pollutants that do not degrade easily, are retained for prolonged periods in environmental media such as water and sediments, and are known to accumulate in aquatic organisms. The aim of this review is to show and discuss the transport and effects of microplastics in the environment. We systematically and critically review 91 articles in the field of sources, distribution, and environmental behavior of microplastics. We conclude that the spread of plastic pollution is related to a myriad of processes and that both primary and secondary MPs are prevalent in the environment. Rivers have been indicated as major pathways for the transport of MPs from terrestrial areas into the ocean, and atmospheric circulation may be an important avenue for transporting MPs between environmental compartments. Additionally, the vector effect of MPs can change the original environmental behavior of other pollutants, leading to severe compound toxicity. Further in-depth studies on the distribution and chemical and biological interactions of MPs are highly suggested to improve our understanding of how MPs behave in the environment.

Polypropylene microplastics aging under natural conditions in winter and summer and its effects on the sorption and desorption of nonylphenol

Plastics in the environment undergo various aging effects. Due to the changes in physical and chemical properties, the sorption behavior of aged microplastics (MPs) for pollutants differs from that of pristine MPs. In this paper, the most common disposable polypropylene (PP) rice box was used as the source of MPs to study the sorption and desorption behavior of nonylphenol (NP) on pristine and naturally aged PPs in summer and winter. The results show that summer-aged PP has more obvious property changes than winter-aged PP. The equilibrium sorption amount of NP on PP is summer-aged PP (477.08 μg/g) > winter-aged PP (407.14 μg/g) > pristine PP (389.29 μg/g). The sorption mechanism includes the partition effect, van der Waals forces, hydrogen bonds and hydrophobic interaction, among which chemical sorption (hydrogen bonding) dominates the sorption; moreover, partition also plays an important role in this process. Aged MPs' more robust sorption capacity is attributed to the larger specific surface area, stronger polarity and more oxygen-containing functional groups on the surface that are conducive to forming hydrogen bonds with NP. Desorption of NP in the simulated intestinal fluid is significant owning to intestinal micelles' presence: summer-aged PP (300.52 μg/g) > winter-aged PP (291.08 μg/g) > pristine PP (287.12 μg/g). Hence, aged PP presents a more vital ecological risk.

The interaction mechanisms of co-existing polybrominated diphenyl ethers and engineered nanoparticles in environmental waters: A critical review

This review focuses on the occurrence and interactions of engineered nanoparticles (ENPs) and brominated flame retardants (BFRs) such as polybrominated diphenyl ethers (PBDEs) in water systems and the generation of highly complex compounds in the environment. The release of ENPs and BFRs (e.g. PBDEs) to aquatic environments during their usage and disposal are summarised together with their key interaction mechanisms. The major interaction mechanisms including electrostatic, van der Waals, hydrophobic, molecular bridging and steric, hydrogen and π-bonding, cation bridging and ligand exchange were identified. The presence of ENPs could influence the fate and behaviour of PBDEs through the interactions as well as induced reactions under certain conditions which increases the formation of complex compounds. The interaction leads to alteration of behaviour for PBDEs and their toxic effects to ecological receptors. The intermingled compound (ENPs-BFRs) would show different behaviour from the parental ENPs or BFRs, which are currently lack of investigation. This review provided insights on the interactions of ENPs and BFRs in artificial, environmental water systems and wastewater treatment plants (WWTPs), which are important for a comprehensive risk assessment.

Sorption and desorption of bisphenols on commercial plastics and the effect of UV aging

Plastics gradually degrade in the natural environment from the effect of irradiation, which can change the surface properties of plastics and affect the migration behaviour of pollutants. Up to now, studies on the sorption/desorption behaviour of organic pollutants on aged plastics are still limited. In this study, several types of commercial plastics (polyurethane (PU), polyamide (PA), polyvinyl chloride (PVC), expanded polystyrene (EPS)) were selected to investigate the sorption and release behaviour for four kinds of bisphenols (bisphenol-F, A, B, AP). The results from Raman spectroscopy and scanning electron microscopy (SEM) analysis showed evidence of oxidization and surface cracks of plastics after irradiation. The sorption behaviour for both fresh and aged plastics were dominated by hydrophobicity. In addition, the electrostatic force, H-bonding interaction, and π-π interaction were also the important factors impacting the sorption process. The desorption kinetics behaviour indicates that desorption becomes faster after aging. Hydrophobicity is also an important factor that affects desorption behaviour. This study showed that sorption capacity for most fresh and aged plastics was enhanced by the impact of salinity and dissolved organic matter (DOM). Increased temperature could increase the desorption of bisphenols on both fresh and aged plastics, which illustrated that warm environments would promote more pollutants be released from plastics to water bodies.

Adsorption of pesticides and personal care products on pristine and weathered microplastics in the marine environment. Comparison between bio-based and conventional plastics

The hydrophobicity of persistent organic pollutants (POPs) makes them adsorb on microplastics in the marine environment, affecting their distribution, persistence, or their transfer to the trophic chain. Fragrances and non-polar pesticides can be adsorbed by microplastics in the marine environment because of their physico-chemical characteristics. In this work, the adsorption of two pesticides (α-endosulfan and chlorpyrifos) and 6 musk fragrances (musk xylene, musk ketone, musk moskene, galaxolide, tonalide, and celestolide) on polyamide (PA6) (a petroleum based polymer) and on polyhydroxybutyrate (PHB) (biopolymer) in seawater was studied, considering also the effect of water temperature and plastic weathering. Results show higher adsorption of the selected pollutants for PHB than PA, being PA more affected by the water temperature and the plastic weathering. The highest percentage of adsorption was achieved in most cases at 24 h. In addition, this process was irreversible, as it showed the leaching assays. Besides, this work revealed that plastics mitigate the degradation of α-endosulfan in aquatic media (hydrolysis), showing that plastics can act as inhibitors of degradation of POPs, increasing its persistence in the environment.

Sorption of selected pharmaceutical compounds on polyethylene microplastics: Roles of pH, aging, and competitive sorption

Microplastics (MPs) as the carrier of pharmaceuticals in aquatic environments have been concerned in recent years. However, the influences of environmental factors on the sorption of pharmaceuticals onto MPs, particularly the effect of the simultaneous sorption by MPs of different pharmaceuticals in multi-solute systems are still unclear. This study investigated the influences of pH, aging of MPs, and competition of pharmaceuticals on the sorptions of sulfamethoxazole (SMX), propranolol (PRP), and sertraline (SER) onto polyethylene MPs. In the 96 h pH-dependent experiments, the sorptions of the three pharmaceuticals were mainly driven by hydrophobic interaction. Besides, the ionization states of the three pharmaceuticals varied with the pH ranging from 2.00 to 12.00, and electrostatic interaction would affect the sorption affinities of the pharmaceuticals in different ionization states. In the aged MPs experiments, the MPs aged by UV irradiation showed a stronger sorption capacity than the pristine ones. Across the MPs under different UV irradiation durations, the 6 d aged MPs showed the highest sorption percentages of 23.0% and 17.6% for SER and PRP, respectively; for SMX, the highest sorption percentage of 5.4% was recorded with the 10 d aged MPs. In the multi-solute systems, the sorption kinetics of the three pharmaceuticals fit well with the pseudo-second-order model. The sorption quantities of the three pharmaceuticals onto MPs followed the order of SER cations (18.70 μg g^-1) > SMX anions (7.83 μg g^-1) > PRP cations (3.80 μg g^-1) at pH 7.00. The good fitting of the Freundlich model suggested a multilayer sorption of the three pharmaceuticals onto MPs. The SER with higher hydrophobicity would preferentially be adsorbed onto MPs and influenced the subsequently sorption processes of the other pharmaceuticals via electrostatic interactions. This may change the environmental fate of the contaminants, which should be carefully considered in future work.

Effects of garbage salvaging and suspended crossbar on microplastic pollution along a typical urban river

Microplastic pollution has been considered as a global environmental issue that potentially threatens human health. However, research about microplastic pollution in urban rivers is still insufficient. This study analyzed the abundance and distribution of microplastics in surface water of the Nanfei River in Hefei, China. Microplastic concentrations ranged from 0.8 to 27 items/L along the studied river. The small size (50-333 μm) (47.58-84.89%) and white (55.65-88.89%) were predominant among all samples, except that collected from the source reach. Pellet was a typical and abundant microplastic type and accounted for 60.30%. PE and PP were the major polymers, occupying 55.24% and 22.86%, respectively. The results showed that traditional environmental management practices including salvaging surface garbage regularly and setting wooden suspended crossbars at tributary confluences could significantly mitigate the pollution degree of microplastics. The polymer risk index was calculated to describe the potential risk of microplastics, and the pollution level was still at high risk under various management practices. This study provides a valuable finding for future research on microplastics in urban city rivers, which may improve the knowledge that how to control and prevent microplastic pollution.

A Novel Analytical Approach to Assessing Sorption of Trace Organic Compounds into Micro- and Nanoplastic Particles

Assessing the sorption of trace organic compounds (TOrCs) into micro- and nanoplastic particles has traditionally been performed using an aqueous phase analysis or solvent extractions from the particle. Using thermal extraction/desorption–gas chromatography/mass spectrometry (TD-Pyr-GC/MS) offers a possibility to analyze the TOrCs directly from the particle without a long sample preparation. In this study, a combination of two analytical methods is demonstrated. First, the aqueous phase is quantified for TOrC concentrations using Gerstel Twister® and TD-GC/MS. Subsequently, the TOrCs on the particles are analyzed. Different polymer types and sizes (polymethyl methacrylate (PMMA), 48 µm; polyethylene (PE), 48 µm; polystyrene (PS), 41 µm; and PS, 78 nm) were analyzed for three selected TOrCs (phenanthrene, triclosan, and α-cypermethrin). The results revealed that, over a period of 48 h, the highest and fastest sorption occurred for PS 78 nm particles. This was confirmed with a theoretical calculation of the particle surface area. It was also shown for the first time that direct quantification of TOrCs from PS 78 nm nanoparticles is possible. Furthermore, in a mixed solute solution, the three selected TOrCs were sorbed onto the particles simultaneously.

Microplastic properties and their interaction with hydrophobic organic contaminants: a review

Microplastics (MPs) have been defined as particles of size < 5 mm and are characterized by hydrophobicity and large surface areas. MPs interact with co-occurring hydrophobic organic contaminants (HOCs) via sorption-desorption processes in aquatic and terrestrial environments. Ingestion of MPs by living organisms may increase exposure to HOC levels. The key mechanisms for the sorption of HOCs onto MPs are hydrophobic interaction, electrostatic interaction, π-π interactions, hydrogen bonding, and Van der Waals forces (vdW). Polymer type, UV-light-induced surface modifications, and the formation of oxygen-containing functional groups have a greater influence on electrostatic and hydrogen bonding interactions. In contrast, the formation of oxygen-containing functional groups negatively influences hydrophobic interaction. MP characteristics such as crystallinity, weathering, and surface morphology affect sorption capacity. Matrix properties such as pH, ionic strength, and dissolved organic matter (DOM) also influence sorption capacity by exerting synergistic/antagonistic effects. We reviewed the mechanisms of HOC sorption onto MPs and the polymer and matrix properties that influence the HOC sorption. Knowledge gaps and future research directions are outlined.

Removal of polystyrene nanoplastics from water by CuNi carbon material: The role of adsorption

Nanoplastics have attracted wide attention worldwide as a new potentially threatening pollutant, and they can cause harm to the organisms and pose threat to the water environment. Therefore, efficient removal techniques for nanoplastics are urgently needed. In this study, CuNi carbon material (CuNi@C) was prepared by hydrothermal method for the removal of polystyrene (PS) nanoplastics from water. CuNi@C was effectively adsorbed on PS nanoplastics. When the CuNi@C dosage increased from 0.1 g/L to 0.3 g/L, the removal efficiency of PS nanoplastics (10 mg/L) elevated from 32.72% to 99.18%. The images of the scanning electron microscope (SEM) and the Fourier transform infrared spectroscopy (FTIR) spectra of CuNi@C confirmed the adsorption of PS nanoplastics on the CuNi@C. The fitting results of adsorption kinetic models and isotherms equations demonstrated that physical adsorption and monolayer coverage were the predominant mechanisms of the PS nanoplastics adsorption on CuNi@C. Thermodynamics analysis illustrated the adsorption of PS nanoplastics on CuNi@C was a spontaneous and endothermic process. The electrostatic attraction occurred in adsorption progress, and the removal efficiency of PS nanoplastics in the acidic system was generally higher than that in the alkaline system. CuNi@C can be recycled via washing and drying treatment and these CuNi@C comparable PS nanoplastics removal performance to the original ones. After four times cycles, CuNi@C can still remove ~75% of total PS nanoplastics from water. This study reveals that CuNi@C can be used as promising techniques for the removal of PS nanoplastics from the aqueous environment.

Post COVID-19 pandemic: Disposable face masks as a potential vector of antibiotics in freshwater and seawater

With the outbreak and widespread of the COVID-19 pandemic, large numbers of disposable face masks (DFMs) were abandoned in the environment. This study first investigated the sorption and desorption behaviors of four antibiotics (tetracycline (TC), ciprofloxacin (CIP), sulfamethoxazole (SMX), and triclosan (TCS)) on DFMs in the freshwater and seawater. It was found that the antibiotics in the freshwater exhibited relatively higher sorption and desorption capacities on the DFMs than those in the seawater. Here the antibiotics sorption processes were greatly related to their zwitterion species while the effect of salinity on the sorption processes was negligible. However, the desorption processes were jointly dominated by solution pH and salinity, with greater desorption capacities at lower pH values and salinity. Interestingly, we found that the distribution coefficient (K_d) of TCS (0.3947 L/g) and SMX (0.0399 L/g) on DFMs was higher than those on some microplastics in freshwater systems. The sorption affinity of the antibiotics onto the DFMs followed the order of TCS > SMX > CIP > TC, which was positively correlated with octanol-water partition coefficient (log K_ow) of the antibiotics. Besides, the sorption processes of the antibiotics onto the DFMs were mainly predominated by film diffusion and partitioning mechanism. Overall, hydrophobic interaction regulated the antibiotics sorption processes. These findings would help to evaluate the environmental behavior of DFMs and to provide the analytical framework of their role in the transport of other pollutants.

Microplastic Pollution Focused on Sources, Distribution, Contaminant Interactions, Analytical Methods, and Wastewater Removal Strategies: A Review

Plastics have been one of the most useful materials in the world, due to their distinguishing characteristics: light weight, strength, flexibility, and good durability. In recent years, the growing consumption of plastics in industries and domestic applications has revealed a serious problem in plastic waste treatments. Pollution by microplastics has been recognized as a serious threat since it may contaminate all ecosystems, including oceans, terrestrial compartments, and the atmosphere. This micropollutant is spread in all types of environments and is serving as a “minor but efficient” vector for carrier contaminants such as pesticides, pharmaceuticals, metals, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs). The need to deeply study and update the evolution of microplastic sources, toxicology, extraction and analysis, and behavior is imperative. This review presents an actual state of microplastics, addressing their presence in the environment, the toxicological effects and the need to understand their extent, their interactions with toxic pollutants, the problems that arise in the definition of analytical methods, and the possible alternatives of treatments.

Microplastics and nanoplastics: Recent literature studies and patents on their removal from aqueous environment

The presence of microplastics (MP) and nanoplastics (NP) in the environment poses significant hazards towards microorganisms, humans, animals and plants. This paper is focused on recent literature studies and patents discussing the removal process of these plastic pollutants. Microplastics and nanoplastics can be quantified by counting, weighing, absorbance and turbidity and can be further analyzed using scanning electron microscopy (SEM), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, surface-enhanced Raman spectroscopy and Raman tweezers. Mitigation methods reported are categorized depending on the removal characteristics: (i) Filtration and separation method: Filtration and separation, electrospun nanofiber membrane, constructed wetlands; (ii) Capture and surface attachment method: coagulation, flocculation and sedimentation (CFS), electrocoagulation, adsorption, magnetization, micromachines, superhydrophobic materials and microorganism aggregation; and (iii) Degradation method: photocatalytic degradation, microorganism degradation and thermal degradation; where removal efficiency between 58 and 100% were reported. As these methods are significantly distinctive, the parameters which affect the MP/NP removal performance e.g., pH, type of plastics, presence of interfering chemicals or ions, surface charges etc. are also discussed. 42 granted international patents related to microplastics and nanoplastics removal are also reviewed where the majority of these patents are focused on separation or filtration devices. These devices are efficient for microplastics up to 20 μm but may be ineffective for nanoplastics or fibrous plastics. Several patents were found to focus on methods similar to literature studies e.g., magnetization, CFS, biofilm and microorganism aggregation; with the addition of another method: thermal degradation.

Seeking for a perfect (non-spherical) microplastic particle - The most comprehensive review on microplastic laboratory research

In recent decades, much attention has been paid to microplastic pollution, and research on microplastics has begun to grow exponentially. However, microplastics research still suffers from the lack of standardized protocols and methods for investigation of microplastics under laboratory conditions. Therefore, in this review, we summarize and critically discuss the results of 715 laboratory studies published on microplastics in the last five years to provide recommendations for future laboratory research. Analysis of the data revealed that the majority of microplastic particles used in laboratory studies are manufactured spheres of polystyrene ranging in size from 1 to 50 µm, that half of the studies did not characterize the particles used, and that a minority of studies used aged particles, investigated leaching of chemicals from microplastics, or used natural particles as a control. There is a large discrepancy between microplastics used in laboratory research and those found in the environment, and many laboratory studies suffer from a lack of environmental relevance and provide incomplete information on the microplastics used. We have summarized and discussed these issues and provided recommendations for future laboratory research on microplastics focusing on (i) microplastic selection, (ii) microplastic characterization, and (iii) test design of laboratory research on microplastics.

Microplastics: A review of analytical methods, occurrence and characteristics in food, and potential toxicities to biota

Microplastics (MPs) are ubiquitous in various environment compartments, including food. Here, we collected research reports of MPs in food published during 2010-2020, and summarized the analytical methods developed and utilized by researchers (e.g., digestion, separation and identification, as well as related QA/QC measures implemented), the occurrence, and the characteristics of MPs in six kinds of food. The potential effects on biota from exposure to MPs were also reviewed. The results showed that most researchers digested food samples using chemical solutions such as HNO₃, H₂O₂, KOH, or NaOH. FT-IR and Raman spectroscopy were the main technique for identifying MPs, and microscopes were used to count MP particles. The abundances MPs were in the ranges of 0-5860, 2.00-1100, 0-698, 4.00-18.7, 0-5.68 × 10⁴ and 900-3000 particles/kg in beverages, condiments, honey, meat, seafood and vegetables, respectively. The "maximum" annual human intake of MPs from these foods is approximately 1.42 × 10⁵-1.54 × 10⁵ particles/capita, equivalent to the consumption of 50 plastic bags (size: 0.04 mm × 250 mm × 400 mm, density: 0.98 g/cm³) each year. Blue-colored and fiber-shaped MP particles were the most commonly observed in food, predominated by PA, PE, PES, PET and PP types. Toxicity studies indicated that MPs, additives of MPs and adsorbents or microorganisms on the surfaces of MPs were all somewhat toxic to cells or biota. Exposure to MPs may induce oxidative stress, inflammation, neurotoxicity, and reproductive toxicity, and change the structure of intestinal microflora in cells or biota. Therefore, we call for more investigation into the residual, excretion and bioavailability of MPs or related absorbents/additives in biota and humans.

Removal of microplastics from water by magnetic nano-Fe3O4

Microplastics (MPs) have been widely detected in aquatic environments, and become emerging contaminants of growing concern. It is urgently needed to explore how to effectively remove MPs from water. This study first established an alternative method of removing MPs by magnetic nano-Fe₃O₄. Results showed that 1.3 g·L^-1 nano-Fe₃O₄ and 150 min treatments caused optimal magnetization of MPs via surface absorption. Then, magnetized MPs in water can be conveniently removed by suction of the magnet. The average removal rate of four common types of MPs including polyethylene, polypropylene, polystyrene and polyethylene terephthalate in size of approximately 200-900 μm was 86.87 ± 6.92%, 85.05 ± 4.70%, 86.11 ± 6.21%, and 62.83 ± 8.34%, respectively. The removal rate varied among polymer- and size-different MPs, and was positively related to the density of nano-Fe₃O₄ absorbed on MP surfaces. In addition, the removal rate of MPs in artificial seawater was relatively high in comparison to pure water. Furthermore, the established approach was effectively applied to remove MPs in environmental water bodies including river water, domestic sewage, and natural seawater, with the removal rate of higher than 80%. Altogether, this study provided a novel and simple removal approach to remove MPs in water, which has a certain application prospect.

Adsorption of micropollutants onto realistic microplastics: Role of microplastic nature, size, age, and NOM fouling

This work aims at evaluating the role of nature, size, age, and natural organic matter (NOM) fouling of realistic microplastics (MPs) on the adsorption of two persistent micropollutants (diclofenac (DCF) and metronidazole (MNZ)). For such goal, four representative polymer types (polystyrene (PS), polyethylene terephthalate (PET), polypropylene (PP) and high-density polyethylene (HDPE)) were tested. MPs were obtained by cryogenic milling of different commercial materials (disposable bottles, containers, and trays), and fully characterized (optical microscopic and SEM images, FTIR, elemental analysis, water contact angle and pH_slurry). The micropollutants hydrophobicity determined to a high extent their removal yield from water. Regardless of the MP's nature, the adsorption capacity for DCF was considerably higher than the achieved for MNZ, which can be related to its stronger hydrophobic properties and aromatic character. In fact, aromatic MPs (PS and PET) showed the highest adsorption capacity values with DCF (~100 μg g^-1). The MP size also played a key role on its adsorption capacity, which was found to increase with decreasing the particle size (20-1000 μm). MPs aging (simulated by Fenton oxidation) led also to substantial changes on their sorption behavior. Oxidized MPs exhibited acidic surface properties which led to a strong decrease on the adsorption of the hydrophobic micropollutant (DCF) but to an increase with the hydrophilic one (MNZ). NOM fouling (WWTP effluent, river water, humic acid solution) led to a dramatic decrease on the MPs sorption capacity due to sorption sites blocking. Finally, the increase of pH or salinity of the aqueous medium increased the micropollutants desorption.

Sorption of organochlorine pesticides on polyethylene microplastics in soil suspension

As a new type of environmental pollutant, microplastics (MPs) can adsorb residual organochlorine pesticides (OCPs) in the soil and pose a severe threat to the soil ecosystems. To understand the interaction between soil MPs and OCPs, the sorption of two kinds of OCPs, including hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs), on polyethylene (PE) microplastics in soil suspension was studied through sorption kinetics and isotherm models. The effects of solution/soil ratio and MPs diameter on sorption were examined. The kinetic experiment results show that the sorption equilibrium was 12 h， and the sorption process of OCPs on MPs can be well described by a pseudo-second-order model. The Freundlich model (R² = 0.942-0.997) provides a better fit to the sorption isotherm data than the Langmuir model (R² = 0.062-0.634), indicating that the sorption process takes place on the nonuniform surface of MPs. The MPs had a good sorption effect on OCPs when the solution/soil ratio was from 75:1 to 100:1. As the diameter of MPs increases, the sorption capacity decreases. These results provide support for further research on microplastic pollution in soil.

Microplastics: An overview on separation, identification and characterization of microplastics

At present plastic residues has become grave threat to the environment. Microplastics are plastic residues with a size <5 mm, due to their small size it is very difficult to remove them from water bodies, sediments and air with available techniques. Nanoplastics are different in size range as nanoplastics are smaller than 1 μm in size. This review is an attempt to gather an insight towards microplastic and its associated point of concerns. The review will highlight some of the methods appropriate for microplastics sampling and techniques for its identification in environmental samples. Some of the sampling methods include sieving, filtration, visual sorting, digestion, density separation. While, identification techniques in practice are SEM-EDS, FTIR, NIR, Raman, NMR spectroscopy, etc. Still there is a need and scope for development of more economical and portable techniques in this direction.

Ecotoxicological effects of microplastics on aquatic organisms: a review

Microplastics   ( <5 mm), which are classified based on primary or secondary sources, are widely distributed in the environment and exert significant effects on aquatic life forms; however, evidence regarding the ecotoxicological effects of microplastics on aquatic organisms is still limited. This research aims at filling a knowledge gap regarding generation sources, distribution, physicochemical properties, and biological behavior of microplastics (MP) in aquatic environments and their interaction with aquatic organisms. The literature indicates that concentrations of MPs observed in such environments are higher than the threshold for safe concentration (6650 buoyant particles/m³). MPs having large specific surface area, low polarity, and hydrophobic properties have been shown to absorb dichlorodiphenyltrichloroethane (DDT), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbon (PAHs), bisphenol A (BPA), polyfluoroalkyl substances (PFAS), antibiotics, and heavy metals. MPs adsorb large amounts of toxic organic chemicals (18,700 ng/g PCBs; 24,000 ng/g PAHs) and heavy metals (0.21-430 μg/g Cr; 0.0029-930 μg/g Cd; 0.35-2.89 μg/g As; 0.26-698,000 μg/g Pb). MPs originating from polystyrene (PS), polypropylene (PP), and polyvinylchloride (PVC) show greater toxicity toward aquatic organisms, with effects on the immune system, reproductive system, nervous system, and endocrine system. Thus, elucidating the cumulative toxic expression of MPs in different polluted environments is critical.

Sorption of tetracycline onto hexabromocyclododecane/polystyrene composite and polystyrene microplastics: Statistical physics models, influencing factors, and interaction mechanisms

Microplastics (MPs) are becoming a major concern due to their great potential to sorb and transport pollutants in the aquatic environment; hexabromocyclododecane (HBCD) is a common chemical additive in polystyrene (PS) MPs. However, the underlying mechanisms for the interaction of tetracycline (TC) onto HBCD-PS composites MPs (HBCD-PS MPs) are still not well documented. Our findings showed that the addition of HBCD resulted in a relatively higher hydrophobicity of PS MPs, and significantly enhanced the sorption ability of HBCD-PS MPs for TC. The kinetic models suggested that the sorption of TC onto PS and HBCD-PS MPs were mainly controlled by film diffusion and intra-particle diffusion, respectively. The statistical physics models were used to elucidate the sorption of TC onto PS and HBCD-PS MPs was associated with the formation of the monolayer, and the results indicated the TC was sorbed onto the two MPs by both multi-molecular and non-parallel processes. The TC sorption was solution pH-dependent while the effect of NaCl content on TC sorption was negligible. The presence of Cu(Ⅱ), Pb(Ⅱ), Cd(Ⅱ), and Zn(Ⅱ) ions had different influences on the TC sorption onto both the MPs. Overall, various mechanisms including π-π and hydrophobic interactions jointly regulated the sorption of TC onto both the MPs. Our results provided new insights into the sorption behavior and interaction mechanisms of TC onto both the MPs and highlighted that the addition of HBCD likely increased the enrichment capacity of MPs for pollutants in the environment.

Post COVID-19 pandemic: Biofragmentation and soil ecotoxicological effects of microplastics derived from face masks

Because of the COVID-19 pandemic, used face masks have increasingly littered the environment and are causes for concern since they are commonly made of plastics such as polypropylene. Understanding production of microplastics from face masks is essential for predicting the post COVID-19 pandemic impact on the soil ecosystem. We investigated the generation of nanofibers from meltblown face mask filters (MB filters) and their adverse effects on soil species, particularly the earthworm and springtail. Results of MB filter soil bioassays at a high concentration (1000 mg/kg dry soil) suggest inhibited reproduction and stunted growth in springtails, decreased intracellular esterase activity in earthworm coelomocytes, and inhibited spermatogenesis in male earthworm reproductive tissues. Moreover, it was estimated that generation of nanofibers from microfibers and fragments of MB filters might occur in the soil ecosystem post COVID-19. This study does not oppose the use of face masks but aims to encourage appropriate disposal of the masks. Preservation of human health and the ecosystem should be prioritized even amidst the COVID-19 pandemic.

Current Progress on Marine Microplastics Pollution Research: A Review on Pollution Occurrence, Detection, and Environmental Effects

Recently, microplastics pollution has attracted much attention in the environmental field, as researchers have found traces of microplastics in both marine and terrestrial ecological environments. Here, we reviewed and discussed the current progress on microplastics pollution in the marine environment from three main aspects including their identification and qualification methods, source and distribution, and fate and toxicity in a marine ecosystem. Microplastics in the marine environment originate from a variety of sources and distribute broadly all around the world, but their quantitative information is still lacking. Up to now, there have been no adequate and standard methods to identify and quantify the various types of microplastics, which need to be developed and unified. The fate of microplastics in the environment is particularly important as they may be transferred or accumulated in the biological chain. Meanwhile, microplastics may have a high adsorption capacity to pollutants, which is the basic research to further study their fate and joint toxicity in the environment. Therefore, all the findings are expected to fill the knowledge gaps in microplastics pollution and promote the development of relative regulations.

Interactions Between Microplastics and Heavy Metals in Aquatic Environments: A Review

Microplastics (MPs), tiny particles broken down from larger pieces of plastics, have accumulated everywhere on the earth. As an inert carbon stream in aquatic environment, they have been reported as carriers for heavy metals and exhibit diverse interactive effects. However, these interactions are still poorly understood, especially mechanisms driving these interactions and how they pose risks on living organisms. In this mini review, a bibliometric analysis in this field was conducted and then the mechanisms driving these interactions were examined, especially emphasizing the important roles of microorganisms on the interactions. Their combined toxic effects and the potential hazards to human health were also discussed. Finally, the future research directions in this field were suggested. This review summarized the recent research progress in this field and highlighted the essential roles of the microbes on the interactions between MPs and heavy metals with the hope to promote more studies to unveil action mechanisms and reduce/eliminate the risks associated with MP presence.

Interactions between microplastics, pharmaceuticals and personal care products: Implications for vector transport

Microplastics are well known for vector transport of hydrophobic organic contaminants, and there are growing concerns regarding their potential adverse effects on ecosystems and human health. However, recent studies focussing on hydrophilic compounds, such as pharmaceuticals and personal care products (PPCPs), have shown that the compounds ability to be adsorbed onto plastic surfaces. The extensive use of PPCPs has led to their ubiquitous presence in the environment resulting in their cooccurrence with microplastics. The partitioning between plastics and PPCPs and their fate through vector transport are determined by various physicochemical characteristics and environmental conditions of specific matrices. Although the sorption capacities of microplastics for different PPCP compounds have been investigated extensively, these findings have not yet been synthesized and analyzed critically. The specific objectives of this review were to synthesize and critically assess the various factors that affect the adsorption of hydrophilic compounds such as PPCPs on microplastic surfaces and their fate and transport in the environment. The review also focuses on environmental factors such as pH, salinity, and dissolved organics, and properties of polymers and PPCP compounds, and the relationships with sorption dynamics and mechanisms. Furthermore, the ecotoxicological effects of PPCP-sorbed microplastics on biota and human health are also discussed.

Nanoplastics in aquatic systems - are they more hazardous than microplastics?

The fragmentation of plastic materials into nanoparticles of less than 1000 nm (secondary nanoplastics) and their possible accumulation in the environment is a recent matter of concern. There are still no suitable standard methods for determining the concentrations and chemical makeup of these particles in aquatic systems and the fate and effect of nanoplastics in the aquatic environment has been little explored, although there has been research using engineered nanoparticles as models. In this review, we give a summary of the (mainly laboratory-based) studies on the influences of nanoplastics. We aim to provide an updated overview of this emerging topic, reviewing the literature mainly from 2018 onwards and considering the effects of nanoplastics on ecosystems, their uptake and transport of polluting molecules, and the challenges that are faced by workers in this area. The review includes 119 references.

Sorption of chemical contaminants on degradable and non-degradable microplastics: Recent progress and research trends

Microplastics (<5 mm) are ubiquitous contaminants of growing concern. These have been found in multiple environmental compartments, including remote sites where anthropogenic activity is null. Once released, microplastics interact with multiple chemicals in the environment, many of which are classified as organic contaminants or heavy metals. Some contaminants have an affinity for microplastics, attributed to certain sorption mechanisms, and thus become vectors of hazardous chemicals. Here, we focused on the sorption behavior of degradable and non-degradable microplastics, including field and laboratory experiments. We reviewed the sorption mechanisms, namely hydrophobic interactions, electrostatic interactions, pore-filling, Van der Waals forces, hydrogen bonding, and π-π interactions, and the factors strengthening or weakening these mechanisms. Then, we analyzed the literature investigating the sorption behavior of a wide range of chemicals contaminants on microplastics, and the current knowledge regarding the occurrence of organic contaminants and heavy metals on microplastics extracted from the environment. The future perspectives and research priorities were discussed. It is apparent that degradable microplastics, such as polylactic acid or polybutylene succinate, have a greater affinity for hydrophobic contaminants than conventional synthetic non-degradable microplastics according to recent studies. However, studies assessing degradable microplastics are scarce and much research is required to further prove this point. We stated several knowledge gaps in this new line of research and suggest the future studies to follow an integrative approach, allowing to comprehend the multiple factors involved, such as ecotoxicity, bioaccumulation, and fate of the chemical contaminants.

Organic Contaminants and Interactions with Micro- and Nano-Plastics in the Aqueous Environment: Review of Analytical Methods

Micro- and nanoplastic particles are increasingly seen not only as contaminants themselves, but also as potential vectors for trace organic chemicals (TOrCs) that might sorb onto these particles. An analysis of the sorbed TOrCs can either be performed directly from the particle or TOrCs can be extracted from the particle with a solvent. Another possibility is to analyze the remaining concentration in the aqueous phase by a differential approach. In this review, the focus is on analytical methods that are suitable for identifying and quantifying sorbed TOrCs on micro- and nano-plastics. Specific gas chromatography (GC), liquid chromatography (LC) and ultraviolet-visible spectroscopy (UV-VIS) methods are considered. The respective advantages of each method are explained in detail. In addition, influencing factors for sorption in the first place are being discussed including particle size and shape (especially micro and nanoparticles) and the type of polymer, as well as methods for determining sorption kinetics. Since the particles are not present in the environment in a virgin state, the influence of aging on sorption is also considered.

Removal of polystyrene and polyethylene microplastics using PAC and FeCl3 coagulation: Performance and mechanism

As a new type of potentially threatening pollutant, microplastics are widely distributed in water and may come into contact with the humans through tap water. The removal behaviors of microplastics in water treatment plants coagulation are not completely clear. In this paper, the removal performance and mechanism of polystyrene (PS) and polyethylene (PE) microplastics using PAC and FeCl₃ coagulation were studied. Results showed that PAC was better than FeCl₃ in removal efficiency of PS and PE microplastics. Charge neutralization occurred in the coagulation process. The figures of scanning electron microscope (SEM) illustrate that agglomeration adsorption occurred in PS system, and the Fourier transform infrared spectroscope (FTIR) spectra demonstrates that new bonds were formed during the interaction between PS microplastics and coagulants. In addition, the hydrolysis products of coagulants played a major role rather than the hydrolysis process in both PS system and PE system. The removal efficiency of microplastics in alkaline conditions was higher than that in acidic conditions. Cl^- had little effect on the removal efficiency of microplastics, while SO₄^2- and CO₃^2- had inhibitory and promoting effects respectively. The increase of stirring speed could improve the removal efficiency of microplastics. This paper can provide a reference for the study of microplastics treated by coagulation.

Role of Structural Morphology of Commodity Polymers in Microplastics and Nanoplastics Formation: Fragmentation, Effects and Associated Toxicity in the Aquatic Environment

With the continued growth in plastic production, its ubiquitous use and insufficient waste management and disposal, the increased levels of plastics in the environment have led to growing ecological concerns. The breakdown of these plastic macromolecules to smaller micro and nanosized particles and their detection in the aerial, aquatic, marine and terrestrial environments has been reviewed extensively, especially for thermoplastics. However, the formation of micro and nanoplastics has typically been explained as a physical abrasion process, largely overlooking the underlying chemical structure-morphology correlations to the degradation mechanisms of the plastics. This is particularly true for the common commodity thermosets. This review focuses on the degradation pathways for the most widely produced commodity thermoplastics and thermosets into microplastics (MP)s and nanoplastics (NP)s, as well as their behaviour and associated toxicity. Special emphasis is placed on NPs, which are associated with greater risks for toxicity compared to MPs, due to their higher surface area to volume ratios. This review also assesses the current state of standardized detection and quantification methods as well as comprehensive regulations for these fragments in the aquatic environment.

Effect of cadmium on the sorption of tylosin by polystyrene microplastics

Microplastics are widespread in the environment and might transport readily by ocean currents, wind and atmospheric deposition. Simultaneously, antibiotics and heavy metals could often be detected in the environment. They are both positively charged, it is necessary to clarify the interactions of these pollutants with microplastics when they were coexist. In this study, the most commonly used polystyrene (PS) was selected as a representative microplastic. This study investigated the effect of Cd(II) on the sorption of TYL by PS in different coexistence systems. The results showed that: in the composite system, when TYL and Cd(II) coexist, the presence of Cd(II) could inhibit the sorption of TYL by PS, and the inhibitory effect increases with the increase of the concentration of Cd(II), indicating that competitive sorption dominates the sorption. When PS adsorbed Cd(II) first and then adsorbed TYL, the presence of Cd(II) was conducive to the sorption of TYL, and the sorption strengthened with the increase of Cd(II) concentration, indicating that the complexation between TYL and Cd(II) enhanced the sorption of TYL. In addition, initial pH values and ionic strength were essential in the sorption process. Therefore, this study could provide an important basis for evaluating the environmental behavior and ecological risk of microplastics in the process of compound pollution.

Interactions between microplastics and organic pollutants: Effects on toxicity, bioaccumulation, degradation, and transport

Microplastics (MPs), defined as particles with diameters <5 mm and including nanoplastics (NPs), with diameters <1 μm, are characterized by large specific surface areas and hydrophobicity. In aquatic and terrestrial environments, MPs interact with co-occurring organic pollutants through sorption and desorption, which alters the environmental behavior of the pollutants, such as their toxicity, bioaccumulation, degradation, and transport. In this review, we summarize the results of current studies of the interactions between MPs and organic contaminants, and focus on the different mechanisms and subsequent ecological risks of contaminant transfer among environmental media, MPs and organisms. The sorption/desorption of organic pollutants on/from MPs is discussed with respect to solution conditions and the properties of both the MPs and the pollutants. More importantly, the ability of MPs to alter the toxicity, bioaccumulation, degradation, and transport of organic pollutants through these interactions is considered as well. We then examine the interrelationships of the different environmental behaviors of MPs and organic pollutants and the roles played by environmental processes. Finally, we identify the remaining knowledge gaps that must be filled in further studies in order to accurately evaluate the environmental risks of MPs and their associated organic pollutants.

Equilibrium, kinetics and molecular dynamic modeling of Sr2+ sorption onto microplastics

Microplastics (MPs) are becoming ubiquitous pollutants in the global environments, which can potentially sorb metals ions in aquatic environments, causing adverse consequences. The interaction between Sr²⁺ and MPs, and the involved mechanisms have not been studied. Here we investigated the sorption behaviors of Sr²⁺ by polyamide (PA), polystyrene (PS), and polypropylene (PP). Three phenomenological mathematical models were developed and applied to describe the rate-limiting step in the sorption process. The molecular dynamic (MD) simulation was also conducted to investigate the sorption mechanism. The results showed that the optimum isotherm was presented by the nonlinear Temkin model. The maximum sorption capacities of Sr²⁺ by PA, PS and PP were 31.8, 51.4 and 52.4 μg g^-1, respectively, with the initial Sr²⁺concentration of 3400 μg L^-1. The phenomenological models adequately described the sorption kinetics data, concluding that the internal diffusion was the limiting step for Sr²⁺ sorption onto PS; while the external and internal diffusion were the slowest steps in the case of PA and PP. The MD study revealed that the main sorption mechanism was electrostatic interaction. The interaction energies of PA-SrCl₂, PS-SrCl₂, and PP-SrCl₂ were -5.638, -6.418, and -13.05 kcal mol^-1.

Strong sorption of two fungicides onto biodegradable microplastics with emphasis on the negligible role of environmental factors

Microplastics have attracted much attention in recent years because they are able to interact with other pollutants including pesticides, with implications for the potential risks to biota. However, the sorption behavior of pesticides on microplastics, especially on biodegradable microplastics which are promising alternatives to conventional polymers, has been insufficiently studied. In this study, triadimefon and difenoconazole were selected as model triazole fungicides, and their sorption behavior on a typical biodegradable microplastics (PBS: polybutylene succinate) and two conventional polyethylene (PE) and polyvinyl chloride (PVC) microplastics was investigated with batch experiments in an aqueous solution. PBS presented the highest sorption capacity for triadimefon (104.2 ± 4.8 μg g^-1) and difenoconazole (192.8 ± 2.3 μg g^-1), which was 1.8- and 1.3-fold that on PE and 4.4- and 7.4-fold that of PVC, respectively. The results of sorption kinetic and isotherm modeling were better fit by a pseudo-second order model and linear model, respectively. More importantly, the effects of environmental factors (pH, salinity and dissolved organic matter) on the sorption behavior were investigated. Fungicide sorption on PBS was generally not affected by salinity, pH or dissolved organic matter. However, in contrast, salinity and dissolved organic matter both significantly decreased sorption on PE and PVC. The results showed that not only the sorption capacities of biodegradable microplastics but also their responses to environmental factors are quite different from those of conventional microplastics. This finding highlights the importance of the role played by biodegradable microplastics in the accumulation and transportation of organic pollutants.

Systematic Development of a Simultaneous Determination of Plastic Particle Identity and Adsorbed Organic Compounds by Thermodesorption-Pyrolysis GC/MS (TD-Pyr-GC/MS)

Micro-, submicro- and nanoplastic particles are increasingly regarded as vectors for trace organic chemicals. In order to determine adsorbed trace organic chemicals on polymers, it has usually been necessary to carry out complex extraction steps. With the help of a newly designed thermal desorption pyrolysis gas chromatography mass spectrometry (TD-Pyr-GC/MS) method, it is possible to identify adsorbed trace organic chemicals on micro-, submicro- and nanoparticles as well as the particle short chain polymers in one analytical setup without any transfers. This ensures a high sample throughput for the qualitative analysis of trace substances and polymer type. Since the measuring time per sample is only 2 h, a high sample throughput is possible. It is one of the few analytical methods which can be used also for the investigation of nanoplastic particles. Initially adsorbed substances are desorbed from the particle by thermal desorption (TD); subsequently, the polymer is fragmented by pyrolysis (PYR). Both particle treatment techniques are directly coupled with the same GC-MS system analyzing desorbed molecules and pyrolysis products, respectively. In this study, we developed a systematic and optimized method for this application. For method development, the trace organic chemicals phenanthrene, α-cypermethrin and triclosan were tested on reference polymers polystyrene (PS), polymethyl methacrylate (PMMA) and polyethylene (PE). Well-defined particle fractions were used, including polystyrene (sub)micro- (41 and 40 µm) and nanoparticles (78 nm) as well as 48-µm sized PE and PMMA particles, respectively. The sorption of phenanthrene (PMMA << PS 40 µm < 41 µm < PE < PS 78 nm) and α-cypermethrin (PS 41 µm < PS 40 µm < PE < PMMA < PS 78 nm) to the particles was strongly polymer-dependent. Triclosan adsorbed only on PE and on the nanoparticles of PS (PE < PS78).

Strong influence of surfactants on virgin hydrophobic microplastics adsorbing ionic organic pollutants

Microplastic (MP) pollution has become an area of increasing concern because MPs accumulate various types of pollutants. Many previous studies have explored the interactions between MPs and hydrophobic pollutants. However, little research has been conducted on hydrophilic pollutants, which are of much higher concentration and ubiquitous in environment. Surfactants cause hydrophobic MPs to become hydrophilic, which may significantly enhance their capacities to adsorb hydrophilic pollutants. This study explored the influence of co-existing surfactants on the adsorption of ionic organic pollutants by MPs, and found that the presence of an ionic surfactant could significantly enhance the capacity of polyvinyl chloride (PVC, 0.2 mm) MPs to adsorb pollutants with opposite charges. The Langmuir methylene blue adsorption capacity of PVC could be increased from 172 to 4417 ppm in the presence of a sodium dodecyl benzene sulfonate surfactant. Nonionic surfactants impeded the adsorption of both cationic and anionic pollutants due to the steric resistance of the hydrophilic polyethelene glycol chains. The electrostatic interaction mechanism dominated the interfacial behaviors of ionic pollutants on surfactant-adsorbed MP interfaces. The effects of the surfactants were further verified using four different model pollutants and six surfactants. The adsorption capacities of real environmental MPs, including PVC, polyethylene (PE), polypropylene (PP), and polystyrene (PS), increased by three to twenty-six times. The adsorption properties of MPs may be determined by the presence of co-existing surfactants, rather than their polymer species or additives.

QSPR models for predicting the adsorption capacity for microplastics of polyethylene, polypropylene and polystyrene

Microplastics have become an emerging concerned global environmental pollution problem. Their strong adsorption towards the coexisting organic pollutants can cause additional environmental risks. Therefore, the adsorption capacity and mechanisms are necessary information for the comprehensive environmental assessments of both microplastics and organic pollutants. To overcome the lack of adsorption information, five quantitative structure–property relationship (QSPR) models were developed for predicting the microplastic/water partition coefficients (log K_d) of organics between polyethylene/seawater, polyethylene/freshwater, polyethylene/pure water, polypropylene/seawater, and polystyrene/seawater. All the QSPR models show good fitting ability (R² = 0.811–0.939), predictive ability (Q²_ext = 0.835–0.910, RMSE_ext = 0.369–0.752), and robustness (Q_cv² = 0.882–0.957). They can be used to predict the K_d values of organic pollutants (such as polychlorinated biphenyls, chlorobenzene, polycyclic aromatic hydrocarbons, antibiotics perfluorinated compounds, etc.) under different pH conditions. The hydrophobic interaction has been indicated as an important mechanism for the adsorption of organic pollutants to microplastics. In sea waters, the role of hydrogen bond interaction in adsorption is considerable. For polystyrene, π–π interaction contributes to the partitioning. The developed models can be used to quickly estimate the adsorption capacity of organic pollutants on microplastics in different types of water, providing necessary information for ecological risk studies of microplastics.

Effects of the UV filter, oxybenzone, adsorbed to microplastics in the clam Scrobicularia plana

Microplastics (MPs) lipophilic nature and widespread distribution raises concerns due to their increasing presence in the marine environment and their ability to adsorb organic contaminants, as being potential vehicles for transport and potential source of accumulation of organic contaminants by marine organisms. The organic UV-filter, oxybenzone (BP-3) is a constituent of sunscreens and personal care products, entering the marine environment either by direct contact with swimmers or by wastewater effluents. In this study the ecotoxicological effects of exposure to low-density polyethylene (LDPE) microplastics with and without adsorbed BP-3 were investigated in the peppery furrow shell clam, Scrobicularia plana. LDPE microplastics with a size range of 11-13 μm were previously contaminated with an environmentally relevant concentration of BP-3 (82 ng g^-1). S. plana individuals were exposed to a concentration of 1 mg L^-1 of microplastics with and without BP-3 adsorbed in a water-sediment exposure system for 14 days. Clams were sampled at the beginning of the experiment and after 3, 7, and 14 days of exposure. Multiple biomarkers were analysed to investigate the effect of exposure in different clam tissues, gills, digestive gland, and haemolymph. Antioxidant (superoxide dismutase, catalase, glutathione peroxidase) and biotransformation (glutathione-S-transferases) enzyme activities, oxidative damage (lipid peroxidation), genotoxicity (single and double strand DNA breaks), and neurotoxicity (acetylcholinesterase activity) were assessed along with two biomarker indexes to assess the overall health status. Results indicate that after 7 days of exposure MPs with adsorbed BP-3 induced oxidative stress and damage, when compared to exposure to virgin MPs and control treatments. Neurotoxic effects were also noted in MPs with adsorbed BP-3 after 14 days exposure, while some evidence points to increased genotoxicity with exposure time. Overall results indicate that gills were more affected by exposure to microplastics than digestive gland and that biomarkers alterations are apparently more related to the toxicity of BP-3 adsorbed than virgin MPs alone.

Effects of the UV filter, oxybenzone, adsorbed to microplastics in the clam Scrobicularia plana

Microplastics (MPs) lipophilic nature and widespread distribution raises concerns due to their increasing presence in the marine environment and their ability to adsorb organic contaminants, as being potential vehicles for transport and potential source of accumulation of organic contaminants by marine organisms. The organic UV-filter, oxybenzone (BP-3) is a constituent of sunscreens and personal care products, entering the marine environment either by direct contact with swimmers or by wastewater effluents. In this study the ecotoxicological effects of exposure to low-density polyethylene (LDPE) microplastics with and without adsorbed BP-3 were investigated in the peppery furrow shell clam, Scrobicularia plana. LDPE microplastics with a size range of 11-13 μm were previously contaminated with an environmentally relevant concentration of BP-3 (82 ng g^-1). S. plana individuals were exposed to a concentration of 1 mg L^-1 of microplastics with and without BP-3 adsorbed in a water-sediment exposure system for 14 days. Clams were sampled at the beginning of the experiment and after 3, 7, and 14 days of exposure. Multiple biomarkers were analysed to investigate the effect of exposure in different clam tissues, gills, digestive gland, and haemolymph. Antioxidant (superoxide dismutase, catalase, glutathione peroxidase) and biotransformation (glutathione-S-transferases) enzyme activities, oxidative damage (lipid peroxidation), genotoxicity (single and double strand DNA breaks), and neurotoxicity (acetylcholinesterase activity) were assessed along with two biomarker indexes to assess the overall health status. Results indicate that after 7 days of exposure MPs with adsorbed BP-3 induced oxidative stress and damage, when compared to exposure to virgin MPs and control treatments. Neurotoxic effects were also noted in MPs with adsorbed BP-3 after 14 days exposure, while some evidence points to increased genotoxicity with exposure time. Overall results indicate that gills were more affected by exposure to microplastics than digestive gland and that biomarkers alterations are apparently more related to the toxicity of BP-3 adsorbed than virgin MPs alone.

The sorption behaviour of amine micropollutants on polyethylene microplastics - impact of aging and interactions with green seaweed

Microplastics are ubiquitous in the environment. Due to still rising global production, the emission of polymers into the environment and the abundance of microplastics have increased accordingly. Due to the long mineralization processes of microplastics, distribution in all compartments can be found. The hydrophobic surfaces of the particles can sorb chemical pollutants, therefore providing a potential pathway to accumulation by organisms within the food web. However, little is known about how long-term aging and degradation processes of microplastics can affect the sorption behaviours of organic pollutants on the particles. In this study, important industrial additives of emerging environmental concern, such as hydrophobic aromatic amines, were studied in relation to their sorption behaviour on high-density polyethylene and low-density polyethylene microplastics. Diphenylamine (log POW (logarithmic octanol-water partition coefficient) = 3.5) showed strong sorption, carbamazepine (log POW = 2.5) showed moderate sorption, and aniline (log POW = 0.9) showed no detectable sorption behaviour. Artificially aged particles exposed to photochemical aging and long-term mechanical treatment in water were compared to pristine microplastics. While mechanically aged microplastics promoted the sorption of aromatic amines, photochemically aged particles showed a decrease in sorption capacity due to changed surface chemistry. Importantly, the sorption capacity increased with increasing salinity, leading to strong implications for ocean systems, as an elevated uptake of pollutants could occur under marine conditions. Moreover, our study demonstrates that the ecotoxicological effects of diphenylamine on the growth of the seaweed Ulva (sea lettuce, Chlorophyta) were reduced in the presence of microplastics. As the plastic particles withdrew enough contaminants from solution, even toxic levels of diphenylamine (c = 10-4 M) became tolerable for the algae. However, the pollutants initially sorbed on the microplastics can be released again at a later point in the ageing process, thus having delayed pollution potential.

Microplastics in Salt of Tuticorin, Southeast Coast of India

Microplastics (< 5 mm) are considered to be global environmental pollutants. This study investigates the occurrence, physical properties, polymer composition and surface morphology, and element composition of MPs present in food-grade salts produced from seawater and bore-well water in Tuticorin, Tamil Nadu, Southeast coast of India. Fourteen different brands of sea salts and bore-well salts were collected from the salt manufacturing units. The mean abundance of microplastics was 35 ± 15 to 72 ± 40 items/kg in sea salt and 2 ± 1 to 29 ± 11 items/kg in bore-well salt. Four types of polymers viz. polyethylene (51.6%), polypropylene (25%), polyester (21.8%), and polyamide (1.6%) were found in salt. Polyethylene fibers of size ranging from 100 to 500 µm were observed commonly. Being manufactured from seawater, sea salt had the highest quantities of different microplastic particles. The study reveals that people consume approximately 216 particles of MPs per year via sea salt and 48 items per year via bore-well salt if the average person has a daily salt intake of 5 g. The surface morphology of MPs as exhibited in the SEM-EDAX images obtained in the study revealed the different weathering features of MPs, such as pits, cracks, and particles adhering to the surface. The presence of the elements Fe, As, and Ni on the surfaces as identified by energy-dispersive x-ray spectroscopy indicates that these elements exist in the environment as contaminants and have become associated with the MPs. The trace metals adsorbed onto MPs increase the risks of human exposure and may cause some adverse effects in humans.

Sorption Behavior and Mechanisms of Organic Contaminants to Nano and Microplastics

Nano and microplastics (NPs/MPs) have received widespread attention in recent years. Because of their large specific surface area and hydrophobicity, NPs/MPs can adsorb various organic contaminants. This article gives a brief review of the sorption behavior of organic contaminants to NPs/MPs, summarizes the possible sorption mechanisms, and analyzes the influencing factors in the environment on the sorption behavior and mechanisms of NPs/MPs. The main mechanisms of sorption of organic contaminants to NPs/MPs are partitioning, surface sorption (hydrogen bonding, π-π interaction, electrostatic interaction, and van der Waals force), and pore filling. The sorption behavior of organic contaminants to NPs/MPs is not only affected by the properties of the NPs/MPs and the organic contaminants, but also by the solution chemistry, such as the pH, ionic strength, and dissolved organic matter.

Adsorption behavior and mechanism of 9-Nitroanthracene on typical microplastics in aqueous solutions

Microplastics and Nitropolycyclic aromatic hydrocarbons (NPAHs) are two types of emerging pollutants that are strong potential threats to aquatic ecosystems and organisms. The adsorption of NPAHs on microplastics may explain the fate and effects of NPAHs in natural environments. In this study, the adsorption behavior of 9-Nitroanthrene (9-NAnt) on polyethylene (PE), polypropylene (PP) and polystyrene (PS) was investigated. Kinetic experiments revealed that 9-NAnt was inclined to be adsorbed onto microplastics, especially PE, which had a large adsorption amount of 734 μg g^-1. A linear isothermal model better described the isothermal adsorption process for 9-NAnt, which indicated that a hydrophobic distribution may be the main adsorption mechanism in an aqueous solution. Water environment factors, such as the pH and ionic strength, had negligible effects on the adsorption for PE. In contrast, alkaline and high ionic strength conditions resulted in the inhibition of adsorption of PP and PS. In addition, the particle size of microplastics was negatively correlated with the log K_d of 9-NAnt, and the performance of transient aging treatments on microplastics reduced their affinity for 9-NAnt, due to the addition of oxygen-containing functional groups. Above all, hydrophobic and electrostatic processes were the main adsorption mechanisms between microplastics and 9-NAnt.

Sorption properties of cadmium on microplastics: The common practice experiment and A two-dimensional correlation spectroscopic study

Microplastics (MPs) that have accumulated in the environment are emerging as contaminating pollutants due to their interactions with metal ions. MPs change the migration and transformation of metal ions in the environment and afterward impact their environmental presence. Therefore, it is necessary to evaluate the interaction characteristics and mechanisms between Cd²⁺and MPs for assessing the ecological impacts of MPs. The traditional sequencing batch equilibrium test demonstrated that the sorption of Cd²⁺ onto MPs was related to the type of MPs present, the pH value of the solution, the ionic strength of the participants and the presence of humic acid. The sorption dynamics and isotherm experiment illustrated that the interactions were controlled by surface sorption and distribution effects. The specific surface area and surface charge were the main factors in managing the sorption process. FTIR spectra and a 2D-COS analysis showed that different functional groups played an important role in the sorption of Cd²⁺onto MPs. The results from this work afford new insights on how MPs may play an important role in the fate and transport of heavy metals and present a new analysis method for evaluating the environmental behavior of MPs and their role in transporting other contaminants.