Fenton aging significantly affects the heavy metal adsorption capacity of polystyrene microplastics

Application of FTIR two-dimensional correlation spectroscopy (2D-COS) analysis in characterizing environmental behaviors of microplastics: A systematic review

Microplastics (MPs) are ubiquitous in the environment, continuously undergo aging processes and release toxic chemical substances. Understanding the environmental behaviors of MPs is critical to accurately evaluate their long-term ecological risk. Generalized two-dimensional correlation spectroscopy (2D-COS) is a powerful tool for MPs studies, which can dig more comprehensive information hiding in the conventional one-dimensional spectra, such as infrared (IR) and Raman spectra. The recent applications of 2D-COS in analyzing the behaviors and fates of MPs in the environment, including their aging processes, and interactions with natural organic matter (NOM) or other chemical substances, were summarized systematically. The main requirements and limitations of current approaches for exploring these processes are discussed, and the corresponding strategies to address these limitations and drawbacks are proposed as well. Finally, new trends of 2D-COS are prospected for analyzing the properties and behaviors of MPs in both natural and artificial environmental processes.

Microplastics in the soil-water-food nexus: Inclusive insight into global research findings

Nuisance imposed by biotic and abiotic stressors on diverse agroecosystems remains an area of focus for the scientific fraternity. However, emerging contaminants such as microplastics (MP) have imposed additional dimension (alone or in combinations with other stressors) in agroecosystems and keep escalating the challenges to achieve sustainability. MP are recognized as persistent anthropogenic contaminants, fetch global attention due to their unique chemical features that keeps themselves unresponsive to the decaying process. This review has been theorized to assess the current research trends (along with possible gap areas), widespread use of MP, enhancement of the harshness of heavy metals (HMs), complex interactions with physico-chemical constituents of arable soil, accumulation in the edible parts of field crops, dairy products, and other sources to penetrate the food web. So far, the available review articles are oriented to a certain aspect of MP and lack a totality when considered from in soil-water-food perspective. In short, a comprehensive perspective of the adverse effects of MP on human health has been assessed. Moreover, an agro-techno-socio-health prospective-oriented critical assessment of policies and remedial measures linked with MP has provided an extra edge over other similar articles in influential future courses of research.

The interaction mechanisms of algal organic matter (AOM) and various types and aging degrees of microplastics

Algal blooms can produce substantial amounts of algal organic matter (AOM). Microplastics (MPs) in aquatic environments inevitably interact with AOM. Meanwhile, the aging and type of MPs may increase the uncertainty surrounding interaction. This study focused on polyethylene (PE) and polylactic acid (PLA) to investigate their interaction with AOM before and after aging. The results shw that PLA has a stronger adsorption capacity for AOM than PE. Meanwhile, aging enhanced and weakened the adsorption of PE and PLA for AOM. Compared to unaged PE (UPE) and aged PLA (APLA), aged PE (APE) and unaged PLA (UPLA) more significantly promote the humification of AOM and alter its functional groups. 2D-IR-COS analysis reveals that the sequence of functional group changes in AOM interacting with MPs is influenced by the type and aging of MPs. After interacting with AOM, surface roughness increased for all MPs. FTIR and XPS analyses show that the addition of AOM accelerated the oxidation of MPs surfaces, especially for UPE and APLA, with oxygen content increasing by 9.32 % and 1 %. Aging enhances the interaction between PE and AOM, while weakening the interaction between PLA and AOM. These findings provide new insights into understanding the interplay between AOM and MPs.

Impact of the hydrated functional zone on the adsorption of ciprofloxacin to microplastics under the influence of UV aging

The inevitable UV aging of microplastics (MPs) is one of the key factors affecting their interaction with antibiotics. In this study, polyethylene (PE) and polystyrene (PS) MPs were aged with UV irradiation. The adsorption isotherms and kinetics of ciprofloxacin (CIP) to virgin and aged MPs were investigated through various models, and the effects of pH on the adsorption amount were explored. Characterization revealed that the surfaces of aged MPs became rougher, and the hydrophilicity increased. These aged MPs were still in the early stage of aging on the basis of their carbonyl index (CI) (<0.2) and O/C (<0.04) values. The adsorption isotherms indicated that the adsorption mechanism of aged PE was different from that of virgin PE. Compared with virgin PE, the adsorption amount of aged PE increased by 87.80-95.45%, and the adsorption rate decreased by 65.52-80.74%. However, aging did not significantly affect the equilibrium adsorption amount or adsorption rate of aged PS. The external diffusion rate (Kext) (about 2.29-0.36 h-1) was almost 30 times greater than the internal diffusion rate (Kint) in the film-pore mass transfer (FPMT) model, indicating that CIP adsorption rate was dominated by external diffusion. A hydrated functional zone is thought to form around aged MPs, thus changing the adsorption mechanism and adsorption amount of aged PE. Therefore, more attention should be given to alterations in the hydrated functional zone in the early stage of MPs aging.

Unraveling the effects of acrylonitrile butadiene styrene (ABS) microplastic ageing on the sorption and toxicity of ionic liquids with 2,4-D and glyphosate herbicides

Microplastics represent a novel category of environmental pollutants, and understanding their interactions with typical xenobiotics is crucial. In this study, we investigated the impact of ionic liquids (ILs) containing herbicidal anions, namely glyphosate [Glyph] and 2,4-dichlorophenoxyacetate [2,4-D], and the surfactant cation - dodecyltrimethylammonium [C12TMA] on acrylonitrile butadiene styrene (ABS) microplastics. The aim of the study was to assess the sorption capacity of microplastics that were present in both untreated and aged form using standard and modified Fenton methods. In addition, impact on toxicity and stress adaptation of the model soil bacterium Pseudomonas putida KT2440 was measured. Upon ageing, ABS microplastics underwent a fivefold increase in BET surface area and total pore volume (from 0.001 to 0.004 cm3/g) which lead to a dramatic increase in adsorption of the cations on ABS microplastics from 40-45% for virgin ABS to 75-80% for aged ABS. Toxicity was mainly attributed to hydrophobic cations in ILs (EC50 ∼ 60-65 mg/dm3), which was also mitigated by sorption on ABS. Furthermore, both cations and anions behaved similarly across different ILs, corresponding chlorides, and substrates used in the ILs synthesis. These findings highlight microplastics potential as hazardous sorbents, contributing to the accumulation of xenobiotics in the environment.

Intrinsic Peroxidase-like Activity of Polystyrene Nanoplastics Mediates Oxidative Stress

Nanoplastics represent a global environmental concern due to their ubiquitous presence and potential adverse impacts on public and environmental health. There is a growing need to advance the mechanistic understanding of their reactivity as they interact with biological and environmental systems. Herein, for the first time, we report that polystyrene nanoplastics (PSNPs) have intrinsic peroxidase-like activity and are able to mediate oxidative stress. The peroxidase-like activity is dependent on temperature and pH, with a maximum at pH 4.5 and 40 °C. The catalytic activity exhibits saturation kinetics, as described by the Michaelis-Menten model. The peroxidase-like activity of PSNPs is attributed to their ability to mediate electron transfer from peroxidase substrates to H2O2. Ozone-induced PSNP aging can introduce oxygen-containing groups and disrupt aromatic structures on the nanoplastic surface. While ozonation initially enhances peroxidase-like activity by increasing oxygen-containing groups without degrading many aromatic structures, extended ozonation destroys aromatic structures, significantly reducing this activity. The peroxidase-like activity of PSNPs can mediate oxidative stress, which is generally positively correlated with their aromatic structures, as suggested by the ascorbic acid assay. These results help explain the reported oxidative stress exerted by nanoplastics and provide novel insights into their environmental and public health implications.

Differential effects of polystyrene microplastics on the adsorption of cadmium and ciprofloxacin by tea leaf litter-derived magnetic biochar: Influencing factors and mechanisms

Water pollution involves the coexistence of microplastics (MPs) and traditional pollutants, and how can MPs influence the adsorption of other pollutants by biochar during the treatment process remains unclear. This study aimed to investigate the influence of polystyrene microplastics (PS MPs) on the adsorption of cadmium (Cd) and ciprofloxacin (CIP) by magnetic biochar (MTBC) in the single and binary systems. MTBC was prepared using tea leaf litter; the effects of time, pH, and salt ions on the adsorption behaviors were investigated; and X-ray photoelectronic spectroscopy (XPS) and density flooding theory analysis were conducted to elucidate the influence mechanisms. Results indicated that PS MPs reduced the pollutants adsorption by MTBC due to the heterogeneous aggregation between PS MPs and MTBC and the surface charge change of MTBC induced by PS MPs. The effects of PS MPs on heavy metals and antibiotics adsorption were distinctly different. PS MPs reduced Cd adsorption on MTBC, which were significantly influenced by the solution pH and salt ions contents, suggesting the participation of electrostatic interaction and ion exchange in the adsorption, whereas the effects of PS MPs on CIP adsorption were inconspicuous. In the hybrid system, PS MPs reduced pollutants adsorption by MTBC with 66.3% decrease for Cd and 12.8% decrease for CIP, and the more remarkable reduction for Cd was due to the predominated physical adsorption, and CIP adsorption was mainly a stable chemisorption. The influence of PS MPs could be resulted from the interaction between PS MPs and MTBC with changing the functional groups and electrostatic potential of MTBC. This study demonstrated that when using biochar to decontaminate wastewater, it is imperative to consider the antagonistic action of MPs, especially for heavy metal removal. PRACTITIONER POINTS: Magnetic biochar (MTBC) was prepared successfully using tea leaf litter. MTBC could be used for cadmium (Cd) and ciprofloxacin (CIP) removal. Polystyrene microplastics (Ps MPs) reduced Cd/CIP adsorption by MTBC. Ps MPs effects on Cd adsorption were more obvious than that of CIP. Ps MPs changed the functional groups and electrostatic potential of MTBC, thus influencing MTBC adsorption.

Adsorption mechanism of hexavalent chromium on electron beam-irradiated aged microplastics: Novel aging processes and environmental factors

Microplastics are widely present in the natural environment and exhibit a strong affinity for heavy metals in water, resulting in the formation of microplastics composite heavy metal pollutants. This study investigated the adsorption of heavy metals by electron beam-aged microplastics. For the first time, electron beam irradiation was employed to degrade polypropylene, demonstrating its ability to rapidly age microplastics and generate a substantial number of oxygen-containing functional groups on aged microplastics surface. Adsorption experiments revealed that the maximum adsorption equilibrium capacity of hexavalent chromium by aged microplastics reached 9.3 mg g-1. The adsorption process followed second-order kinetic model and Freundlich model, indicating that the main processes of heavy metal adsorption by aged microplastics are chemical adsorption and multilayer adsorption. The adsorption of heavy metals on aged microplastics primarily relies on the electrostatic and chelation effects of oxygen-containing functional groups. The study results demonstrate that environmental factors, such as pH, salinity, coexisting metal ions, humic acid, and water matrix, exert inhibitory effects on the adsorption of heavy metals by microplastics. Theoretical calculations confirm that the aging process of microplastics primarily relies on hydroxyl radicals breaking carbon chains and forming oxygen-containing functional groups on the surface. The results indicate that electron beam irradiation can simultaneously oxidize and degrade microplastics while reducing hexavalent chromium levels by approximately 90%, proposing a novel method for treating microplastics composite pollutants. Gas chromatography-mass spectrometry analysis reveals that electron beam irradiation can oxidatively degrade microplastics into esters, alcohols, and other small molecules. This study proposes an innovative and efficient approach to treat both microplastics composite heavy metal pollutants while elucidating the impact of environmental factors on the adsorption of heavy metals by electron beam-aged microplastics. The aim is to provide a theoretical basis and guidance for controlling microplastics composite pollution.

Distribution and effects of microplastics as carriers of heavy metals in river surface sediments

There are few studies on microplastics (MPs) in urban river sediments compared to oceans, soils, and even rivers. In this study, the seasonal abundance of MPs, as well as their influencing factors on heavy metal adsorption in river sediments of the Ancient Canal of Zhenjiang City, China, were investigated for the first time. Through on-site sampling, microscopic observation, Raman spectroscopy, scanning electron microscopy, and high-temperature digestion, the abundance, shape, color, particle size, type, and surface characteristics of MPs in Ancient Canal sediments in different seasons, as well as the influencing factors of MPs as heavy metal carriers in different seasons, were analyzed. The results showed that the average abundance of MPs is 2049.09 ± 883.78 and 2216.36 ± 826.21 items kg-1 dry sediments in summer and winter, respectively, and different sites change significantly. In addition, particle sizes, types, colors, and shapes of MPs exhibited seasonal variations. Four MPs shapes were mainly observed: fibers, fragments, particles, and films. Among them, MPs in summer sediments are mainly fiber, and MPs in winter sediments are mainly particles. In the sediment in summer and winter, transparent MPs and small-size (<0.5 mm) MPs are the main ones, where the abundance of MPs decreased with increasing MPs size. The main MPs species are polyvinyl chloride (PVC), polystyrene (PS), polypropylene (PP), polyethylene terephthalate (PET), polycarbonate (PC), and polyethylene (PE), with PP being the predominant MPs in the sediments in different seasons. Scanning electron microscopy-energy dispersive spectrometer (SEM-EDS) revealed that the surfaces of the MPs were characterized by rough, porous, cracked, and torn, with the attachment of various heavy metal elements, and all of the heavy metal elements accumulated to different degrees on the MPs. There was a significant positive correlation (p < 0.05) between the Mn content in the MPs and the Mn content in the sediments in winter, suggesting that the Mn in the MPs in winter may be derived from the sediments. In addition, the type, shape, size, and color of MPs affect the adsorption capacity of heavy metals. Most of the adsorption of MPs on Pb showed a significant negative correlation, and the adsorption of MPs on Cr, Zn, Cu, Cd, and Mn showed a significant positive correlation. MPs can be used as carriers of heavy metals, which will further enhance the hazards of living organisms and pose a potential threat to the safety of the urban river environment.

Polyethylene terephthalate (PET) microplastics as radionuclide (U-232) carriers: Surface alteration matters the most

Polyethylene terephthalate (PET) plastics find widespread use in various aspects of our daily lives but often end up in the environment as (micro)plastic waste. In this study, the adsorption efficiency of PET microplastics for U-232 has been investigated prior and after surface alteration (e.g. oxidation (PET-ox), MnO2-coating (PET/MnO2) and biofilm-formation (PET/Biofilm)) in the laboratory (at pH 4, 7 and 9) and seawater samples under ambient conditions and as a function of temperature. The results revealed a significant increase in the adsorption efficiency upon surface alteration, particularly after biofilm development on the MP's surface. Specifically, the Kd values evaluated for the adsorption of U-232 by PET, PET-ox, PET/MnO2 and PET/Biofilm are 12, 27, 73 and 363, respectively, at pH 7 and under ambient conditions. The significantly higher adsorption efficiency of the altered and particularly biofilm-coated PET, emphasizes the significance of surface alteration, which may occur under environmental conditions. In addition, according to the thermodynamic investigations the adsorption of U-232 by PET-MPs (both non-treated and modified), the adsorption is an endothermic and entropy-driven reaction. A similar behavior has been also observed using seawater solutions and assumes that surface alteration is expected to enhance the radionuclide, stability, mobility and bioavailability in environmental water systems.

Microplastics emerge as a hotspot for dibutyl phthalate sources in rivers and oceans: Leaching behavior and potential risks

Dibutyl phthalate (DBP) as a plasticizer has been widely used in the processing of plastic products. Nevertheless, these DBP additives have the potential to be released into the environment throughout the entire life cycle of plastic products. Herein, the leaching behavior of DBP from PVC microplastics (MPs) in freshwater and seawater and its potential risks were investigated. The results show that the plasticizer content, UV irradiation, and hydrochemical conditions have a great influence on the leaching of DBP from the MPs. The release of DBP into the environment increases proportionally with higher concentrations of additive DBP in MPs, particularly when it exceeds 15 %. The surface of MPs undergoes accelerated oxidation and increased hydrophilicity under UV radiation, thereby facilitating the leaching of DBP. Through 30 continuous leaching experiments, the leaching of DBP from MPs in freshwater and seawater can reach up to 12.28 and 5.42 mg g-1, respectively, indicating that MPs are a continuous source of DBP pollution in the aquatic environment. Moreover, phthalate pollution index (PPI) indicates that MPs can significantly increase DBP pollution in marine environment through land and sea transport processes. Therefore, we advocate that the management of MPs waste containing DBP be prioritized in coastal sustainable development.

Accelerated aging behavior of degradable and non-degradable microplastics via advanced oxidation and their adsorption characteristics towards tetracycline

The increasing global utilization of biodegradable plastics due to stringent regulations on traditional plastics has caused a significant rise in microplastic (MPs) pollution in aquatic ecosystems from biodegradable products. However, the environmental behavior of biodegradable MPs remains inadequately elucidated. This study explored the aging processes of polylactic acid (PLA) and polystyrene (PS) under a heat-activated potassium persulfate (K2S2O8) system, as well as their adsorption characteristics towards tetracycline (TCs). In comparison to PS, the surface structure of PLA experienced more pronounced changes over aging, exhibiting evident pits, cracks, and fragmentation. The carbonyl index (CI) and oxygen/carbon ratio (O/C) of PS displayed exponential growth over time, whereas the values for PLA showed linear and exponential increases, respectively. The adsorption capacity of TCs by PS and PLA aged for 6 days increased from 0.312 mg‧g-1 and 0.457 mg‧g-1for original PS and PLA, respectively, to 0.372 mg‧g-1 and 0.649 mg‧g-1. Meanwhile, the adsorption rate (k2 values) for TCs decreased by 42.03 % for PS and 79.64 % for PLA compared to their initial values. The findings indicated that biodegradable PLA-MPs may exhibit higher tetracycline carrying capacities than PS, potentially increasing environmental and organismal risks, particularly in view of aging effects.

Microplastics and Co-pollutants in soil and marine environments: Sorption and desorption dynamics in unveiling invisible danger and key to ecotoxicological risk assessment

Microplastics (MPs) and their co-pollutants pose significant threats to soil and marine environments, necessitating understanding of their colonization processes to combat the plastic pandemic and protect ecosystems. MPs can act as invisible carriers, concentrating and transporting pollutants, leading to a more widespread and potentially toxic impact than the presence of either MPs or the pollutants alone. Analyzing the sorption and desorption dynamics of MPs is crucial for understanding pollutants amplification and predicting the fate and transport of pollutants in soil and marine environments. This review provides an in-depth analysis of the sorption and desorption dynamics of MPs, highlighting the importance of considering these dynamics in ecotoxicological risk assessment of MPs pollution. The review identifies limitations of current frameworks that neglect these interactions and proposes incorporating sorption and desorption data into robust frameworks to improve the ability to predict ecological risks posed by MPs and co-pollutants in soil and marine environments. However, failure to address the interplay between sorption and desorption can result in underestimation of the true impact of MPs and co-pollutants, affecting livelihoods and agro-employments, and exacerbate poverty and community disputes (SDGs 1, 2, 3, 8, 9, and 16). It can also affect food production and security (SDG 2), life below water and life on land (DSGs 14 and 15), cultural practices, and natural heritage (SDG 11.4). Hence, it is necessary to develop new approaches to ecotoxicological risk assessment that consider sorption and desorption processes in the interactions between the components in the framework to address the identified limitations.

Aged polystyrene microplastics cause reproductive impairment via DNA-damage induced apoptosis in Caenorhabditis elegans

Although polystyrene microplastics (PS-MPs) could induce toxic effects on environmental organisms, the toxicity of aged PS-MPs with H2O2 on soil organisms remains unclear. Our study utilized Caenorhabditis elegans as model organism to examine the reproductive toxicity of pristine PS-MPs (pPS-MPs) and aged PS-MPs (aPS-MPs) at environmentally relevant concentrations (0.1-100 μg/L). Acute exposure to aPS-MPs could induce greater reproductive impairment compared to pPS-MPs, as evidenced by changes in brood size and egg release. Assessment of gonad development using the number of mitotic cells, length of gonad arm, and relative area of gonad arm as parameters revealed a high reproductive toxicity caused by aPS-MPs exposure. Furthermore, aPS-MPs exposure promoted substantial germline apoptosis. Additionally, exposure to aPS-MPs (100 μg/L) markedly altered the expression of DNA damage-induced apoptosis-related genes (e.g., egl-1, cep-1, clk-2, ced-3, -4, and -9). Alterations in germline apoptosis caused by aPS-MPs were observed in mutants of cep-1, hus-1, egl-1, ced-3, -4, and -9. Consequently, the augmentation of reproductive toxicity resulting from aPS-MPs exposure was attributed to DNA damage-triggered cellular apoptosis. Additionally, the EGL-1-CEP-1-HUS-1-CED-3-CED-4-CED-9 signaling pathway was identified as a key regulator of germline apoptosis in nematodes. Our study provides insights into potential environmental risk of aPS-MPs with H2O2 on environmental organisms.

Adsorption behavior and mechanism of heavy metals onto microplastics: A meta-analysis assisted by machine learning

Microplastics (MPs) have the potential to adsorb heavy metals (HMs), resulting in a combined pollution threat in aquatic and terrestrial environments. However, due to the complexity of MP/HM properties and experimental conditions, research on the adsorption of HMs onto MPs often yields inconsistent findings. To address this issue, we conducted a comprehensive meta-analysis assisted with machine learning by analyzing a dataset comprising 3340 records from 134 references. The results indicated that polyamide (PA) (ES = -1.26) exhibited the highest adsorption capacity for commonly studied HMs (such as Pb, Cd, Cu, and Cr), which can be primarily attributed to the presence of C=O and N-H groups. In contrast, polyvinyl chloride (PVC) demonstrated a lower adsorption capacity, but the strongest adsorption strength resulting from the halogen atom on its surface. In terms of HMs, metal cations were more readily adsorbed by MPs compared with metalloids and metal oxyanions, with Pb (ES = -0.78) exhibiting the most significant adsorption. As the pH and temperature increased, the adsorption of HMs initially increased and subsequently decreased. Using a random forest model, we accurately predicted the adsorption capacity of MPs based on MP/HM properties and experimental conditions. The main factors affecting HM adsorption onto MPs were HM and MP concentrations, specific surface area of MP, and pH. Additionally, surface complexation and electrostatic interaction were the predominant mechanisms in the adsorption of Pb and Cd, with surface functional groups being the primary factors affecting the mechanism of MPs. These findings provide a quantitative summary of the interactions between MPs and HMs, contributing to our understanding of the environmental behavior and ecological risks associated with their correlation.

Natural and simulated weathering of polystyrene: A molecular view of the polymeric interface

This work presents the changing abundance of surface functional groups (SFGs) on polystyrene (PS) upon weathering within one or a few molecular monolayers from a molecular point of view. PS particles were aged by exposing it to a gas flow of typically (5 %) O3 in O2 (PSO3), UV radiation using a solar simulator under controlled conditions in the laboratory (PSSS) and to the water/air interface immerged in a freshwater lake for 2 months (PSL). The chemical composition of the interface of weathered, compared to pristine (virgin or PSV) material was established using a titration technique that probed the chemical composition of the molecular interface of the polymer. The main conclusions of this exploratory study are: (a) The interface of PS changes significantly compared to ATR-FTIR spectra that do not show additional absorptions in the mid-IR spectrum over a penetration depth of more than hundred monolayers at 10 μm; (b) The average surface functionalization of the gas-solid interface, corresponding to the sum of all examined types of SFG, increases from 20 % of a monolayer for PSV to 40, 50 and 84 % for PSL, PSO3 and PSSS, respectively; (c) in all cases the most important SFG was surface -OH ranging from 11.2 to 64 % for PSV and PSSS, respectively; (d) each PS sample shows a characteristic SFG pattern or fingerprint using several probe gases; (e) O3 interaction led to interface acidification; (f) UV treatment leads to the highest degree of surface -OH functionalization compared to PSO3 and PSL. The accumulation of SFG's renders the interface more reactive towards adsorption of probe gases.

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.

Activating Adsorption Sites of Waste Crayfish Shells via Chemical Decalcification for Efficient Capturing of Nanoplastics

The property of being stubborn and degradation resistant makes nanoplastic (NP) pollution a long-standing remaining challenge. Here, we apply a designed top-down strategy to leverage the natural hierarchical structure of waste crayfish shells with exposed functional groups for efficient NP capture. The crayfish shell-based organic skeleton with improved flexibility, strength (14.37 to 60.13 MPa), and toughness (24.61 to 278.98 MJ m-3) was prepared by purposefully removing the inorganic components of crayfish shells through a simple two-step acid-alkali treatment. Due to the activated functional groups (e.g., -NH2, -CONH-, and -OH) and ordered architectures with macropores and nanofibers, this porous crayfish shell exhibited effective removal capability of NPs (72.92 mg g-1) by physical interception and hydrogen bond/electrostatic interactions. Moreover, the sustainability and stability of this porous crayfish shell were demonstrated by the maintained high-capture performance after five cycles. Finally, we provided a postprocessing approach that could convert both porous crayfish shell and NPs into a tough flat sheet. Thus, our feasible top-down engineering strategy combined with promising posttreatment is a powerful contender for a recycling approach with broad application scenarios and clear economic advantages for simultaneously addressing both waste biomass and NP pollutants.

The retention of plastic particles by macrophytes in the Amazon River, Brazil

This study evaluated the presence of plastics and microplastics in macrophytes in an urbanized sector of the Amazon River. A total of 77 quadrats in 23 macrophyte banks were sampled during the dry (September 2020) and rainy (June 2021) season. Five species were identified: Paspalum repens, Pontederia rotundifolia, Pistia stratiotes, Salvinia auriculata and Limnobium laevigatum, with P. repens being dominant during the dry season (47.54%) and P. rotundifolia during the rainy season (78.96%). Most of the plastic particles accumulated in Paspalum repens (49.3%) and P. rotundifolia (32.4%), likely due to their morphological structure and volume. The dry season showed a higher accumulation of plastic particles than the rainy season. Microplastics were found in most samples, during both the dry (75.98%) and rainy seasons (74.03%). The upstream macrophyte banks retained more plastic particles compared to the downstream banks. A moderate positive correlation was observed between the presence of plastic particles and macrophyte biomass, and a weak positive correlation between the occurrence of microplastics and mesoplastics. White and blue fragments, ranging from 1 to 5 mm were the most common microplastics found in the macrophyte banks. Green fragments and green and blue fibers were identified as polypropylene, blue and red fragments as polyethylene, and white fragments as polystyrene. Therefore, the results of this study highlight the first evidence of the retention of plastic particles in macrophytes of the Amazon and highlight a significant risk due to the harmful effects that this type of plastic can cause to the fauna and flora of aquatic ecosystems.

Characteristics and adsorption behavior of typical microplastics in long-term accelerated weathering simulation

Microplastics can function as carriers in the environment, absorbing various toxins and spreading to diverse ecosystems. Toxins accumulated in microplastics have the potential to be re-released, posing a threat. In this study, two typical plastics, namely polyethylene (PE) and polystyrene (PS), along with the degradable plastic poly(butylene adipate-co-terephthalate) (PBAT), were subjected to a long-term ultraviolet alternating weathering experiment. The study investigated the variations in the weathering process and pollutant adsorption of microplastics of different particle sizes. Furthermore, the adsorption capacity of microplastics for various pollutants was assessed. The findings indicate that particle size significantly influences weathering, leading to variations in adsorption capacity. The weathered PE displays a higher adsorption capacity for azo dyes. Additionally, the adsorption capacity of PBAT for neutral red is double that of antibiotics. Importantly, the maximum adsorption capacity of PBAT for pollutants after aging is approximately 10 times greater than that of PE. Consequently, degradable plastics undergoing weathering in the natural environment may pose a higher ecological risk than traditional plastics.

Recent advances in microplastic removal from drinking water by coagulation: Removal mechanisms and influencing factors

Microplastics (MPs) are emerging contaminants that are widely detected in drinking water and pose a potential risk to humans. Therefore, the MP removal from drinking water is a critical challenge. Recent studies have shown that MPs can be removed by coagulation. However, the coagulation removal of MPs from drinking water remains inadequately understood. Herein, the efficiency, mechanisms, and influencing factors of coagulation for removing MPs from drinking water are critically reviewed. First, the efficiency of MP removal by coagulation in drinking water treatment plants (DWTPs) and laboratories was comprehensively summarized, which indicated that coagulation plays an important role in MP removal from drinking water. The difference in removal effectiveness between the DWTPs and laboratory was mainly due to variations in treatment conditions and limitations of the detection techniques. Several dominant coagulation mechanisms for removing MPs and their research methods are thoroughly discussed. Charge neutralization is more relevant for small-sized MPs, whereas large-sized MPs are more dependent on adsorption bridging and sweeping. Furthermore, the factors influencing the efficiency of MP removal were jointly analyzed using meta-analysis and a random forest model. The meta-analysis was used to quantify the individual effects of each factor on coagulation removal efficiency by performing subgroup analysis. The random forest model quantified the relative importance of the influencing factors on removal efficiency, the results of which were ordered as follows: MPs shape > Coagulant type > Coagulant dosage > MPs concentration > MPs size > MPs type > pH. Finally, knowledge gaps and potential future directions are proposed. This review assists in the understanding of the coagulation removal of MPs, and provides novel insight into the challenges posed by MPs in drinking water.

How do polystyrene microplastics affect the adsorption of copper in soil?

Microplastics (MPs) commonly coexist with heavy metals in the soil environment. MPs can influence the activity of heavy metals, and the specific mechanisms need to be further explored. Here, different contents of polystyrene (PS) MPs were added to soil to explore their effects on the adsorption and desorption characteristics of copper (Cu2+) in soil. The adsorption process was mainly chemical adsorption and belonged to a spontaneous, endothermic reaction. The hydrophobicity of MPs slowed down the adsorption and desorption rates. The main adsorption mechanisms included complexation by oxygen-containing functional groups, ion exchange (accounting for 33.97-36.04 % of the total adsorption amounts), and electrostatic interactions. MPs lacked oxygen-containing functional groups and were predominantly engaged in ion exchange and electrostatic interactions. MPs diluted, blocked the soil, and covered the active sites of soil, which reduced adsorption (3.56-16.18 %) and increased desorption (0.90-2.07 %) of Cu2+ in soil samples, thus increasing the activity and mobility of Cu2+. These findings provide new insights into the effects of MPs on the fate and risk of heavy metals in soil. ENVIRONMENTAL IMPLICATION: The existing literature concerning the effects of microplastics on the adsorption of heavy metals in soil is insufficient. Our investigation unveiled that the main adsorption mechanisms of different soil samples included complexation by oxygen-containing functional groups, ion exchange (accounting for 33.97-36.04 % of the total adsorption amounts), and electrostatic interactions. MPs lacked oxygen-containing functional groups and were predominantly engaged in ion exchange and electrostatic interactions. MPs diluted, blocked the soil, and covered the active sites of soil, which reduced adsorption (3.56-16.18 %) and increased desorption (0.90-2.07 %) of Cu2+ in soil samples, thus increasing the activity and mobility of Cu2+.

Probing the molecular interaction between photoaged polystyrene microplastics and fulvic acid

As emerging contaminants, microplastics (MPs) are becoming a matter of global concern, and they have complex interactions with dissolved organic matter (DOM) widely present in aqueous environments. Here, we investigate the molecular interactions between aged polystyrene microplastics (PS-MPs) and fulvic acid (FA) under neutral conditions using a series of analytical techniques. The structural changes of FA and the binding interactions of PS-MPs with FA at a molecular level were explored by fluorescence and FT-IR combined with two-dimensional correlation spectroscopy (2D-COS). Results showed that photoaging of PS-MPs changed the sequence of structural variations with FA. Atomic force microscopy-infrared spectroscopy (AFM-IR) strongly demonstrated that the surface roughness of both pristine and aged PS-MPs greatly increased after FA addition. Meanwhile, AFM-IR and Raman spectroscopy revealed a stronger interaction between aged PS-MPs and FA. The content of oxygen-containing functional groups in PS-MPs increased after aging and after binding with FA, and surface distribution of these functional groups also changed. XPS analyses indicated that the oxygen content in PS-MPs increased after the interaction with FA and the increase in oxygen content was even greater in aged PS-MPs. Overall, these research findings are useful to understand the environmental impacts of DOM-MPs interactions and to address the uncertainty of MPs aging effect on their environmental behavior in aquatic ecosystems.

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

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

Adsorption characteristics of ciprofloxacin hydrochloride on polystyrene microplastics in freshwater

In order to reveal the adsorption mechanism of microplastics (MPs) on antibiotics, polystyrene (PS) was chosen as a typical microplastic, Fenton and high-temperature aging methods were used to obtain aged MPs particles. The adsorption behavior and mechanism of ciprofloxacin hydrochloride (CIP) on PS before and after aging were studied by batch adsorption experiments, and other influencing environmental conditions were evaluated concurrently. The results showed that the adsorption of CIP on PS was an exothermic reaction, the pseudo-second-order model and Freundlich isothermal models could fit the adsorption of CIP on PS. Aging treatment enhanced the adsorption capacity of PS to CIP, and Fenton aging for 7 days had the best effect. The highest adsorption was observed when the solution pH was 6. The adsorption capacity of microplastics gradually decreased with increasing ionic strength and the concentration of fulvic acid, while the aging microplastics changed little with the concentration of fulvic acid. The presence of both Cu (II) and CIP inhibits the adsorption of each other on microplastics. Based on the above findings, the adsorption of CIP on PS is dominated by physical adsorption, and electrostatic interactions and hydrogen bonding interactions are also important mechanisms for the adsorption of CIP on microplastics.

Effects of tire-road wear particles on the adsorption of tetracycline by aquatic sediments

Tire-road wear particles (TRWPs) are formed by friction between the tire and the road. TRWPs are ubiquitous across the globe, especially in sediments. However, the possible effects of TRWPs on tetracycline (TC) in aquatic sediments are unknown. To investigate the potential role of TRWPs as carriers of co-pollutants, this study investigated the pore surface properties and TC adsorption behavior of TRWP-contaminated sediments and explored the TC behavior in water sediments, as well as the role of aging processes and TRWPs abundance. The results showed that the surface morphology of TRWP-contaminated sediments changed and the adsorption capacity of sediments to TC increased. The TC adsorption capacity of sediments contaminated by 2% TRWPs increased from 3.15 to 3.48 mg/g. Moreover, the surface physical and chemical properties of TRWPs after UV aging changed, which further increased the TC adsorption capacity. The TC adsorption capacity of the sediments contaminated by aged TRWPs increased from 3.48 to 3.65 mg/g. Changing the proportion of aged TRWPs, we found that the adsorption capacity of sediments contaminated by different proportions of TRWPs for TC was 2% > 1% > 0.5% > 4% > blank sediment. These results may contribute to predicting the potential environmental risks of TRWPs in aquatic sediments.

Interaction of microplastics with heavy metals in soil: Mechanisms, influencing factors and biological effects

Microplastics (MPs) and heavy metals (HMs) in soil contamination are considered an emerging global problem that poses environmental and health risks. However, their interaction and potential biological effects remain unclear. Here, we reviewed the interaction of MPs with HMs in soil, including its mechanisms, influencing factors and biological effects. Specifically, the interactions between HMs and MPs mainly involve sorption and desorption. The type, aging, concentration, size of MPs, and the physicochemical properties of HMs and soil have significant impacts on the interaction. In particular, MP aging affects specific surface areas and functional groups. Due to the small size and resistance to decomposition characteristics of MPs, they are easily transported through the food chain and exhibit combined biological effects with HMs on soil organisms, thus accumulating in the human body. To comprehensively understand the effect of MPs and HMs in soil, we propose combining traditional experiments with emerging technologies and encouraging more coordinated efforts.

Investigation of the adsorption behavior and adsorption mechanism of pollutants onto electron beam-aged microplastics

Microplastics, as an emerging pollutant, are widely distributed worldwide. Extensive research has been conducted to address the issue of microplastic pollution; however, effective methods for microplastic treatment are still lacking. This study innovatively utilizes electron beam technology to age and degrade microplastics. Compared to other treatment methods, electron beam technology can effectively promote the aging and degradation of microplastics. The Oxygen - carbon ratio of aged microplastics reached 0.071, with a mass loss of 48 % and a carbonyl index value of 0.69, making it the most effective method for short-term aging treatment in current research efforts. Theoretical calculations and experimental results demonstrate that a large number of oxygen-containing functional groups are generated on the surface of microplastics after electron beam irradiation, changing their adsorption performance for pollutants. Theoretical calculations show that an increase in oxygen-containing functional groups on the surface leads to a gradual decrease in hydrophobic pollutant adsorption capacity while increasing hydrophilic pollutant adsorption capacity for aged microplastics. Experimental studies were conducted to investigate the adsorption behavior and process of typical pollutants by aged microplastics which conform to pseudo-second-order kinetics and Henry model during the adsorption process, and the adsorption results are consistent with theoretical calculations. The results show that the degradation of microplastics is mainly due to hydroxyl radicals generated by electron beam irradiation, which can break the carbon chain of microplastics and gradually degrade them into small molecular esters and alcohols. Furthermore, studies have shown that microplastics can desorb pollutants in pure water and simulated gastric fluid. Overall, electron beam irradiation is currently the most effective method for degrading microplastics. These results also clearly elucidate the characteristics and mechanisms of the interaction between aged microplastics and organic pollutants, providing further insights for assessing microplastic pollution in real-world environments.

Insight into the adsorption behaviors and bioaccessibility of three altered microplastics through three types of advanced oxidation processes

Advanced oxidation processes (AOPs) can significantly alter the structural properties, environmental behaviors and human exposure level of microplastics in aquatic environments. Three typical microplastics (Polyethylene (PE), polypropylene (PP), and polystyrene (PS)) and three AOPs (Heat-K2S2O8 (PDS), UV-H2O2, UV-peracetic acid (PAA)) were adopted to simulate the process when microplastics exposed to the sewage disposal system. 2-Nitrofluorene (2-NFlu) adsorption experiments found the equilibrium time decreased to 24 hours and the capacity increased up to 610 μg g-1, which means the adsorption efficiency has been greatly improved. The fitting results indicate the adsorption mechanism shifted from the partition dominant on pristine microplastic to the physical adsorption (pore filling) dominant. The alteration of specific surface area (21 to 152 m2 g-1), pore volume (0.003 to 0.148 cm3 g-1) and the particle size (123 to 16 μm) of microplastics after AOPs are implying the improvement for pore filling. Besides, the investigation of bioaccessibility is more complex, AOPs alter microplastic with more oxygen-containing functional groups and lower hydrophobicity detected by XPS and water contact angle, those modifications have increased the sorption concentration, especially in the human intestinal tract. Therefore, this indicates the actual exposure of organic compounds loaded in microplastic may be higher than in the pristine microplastic. This study can help to assess the human health risk of microplastic pollution in actual environments.

Adsorption of Pb(II) by UV-aged microplastics and cotransport in homogeneous and heterogeneous porous media

To investigate the adsorption effects of aged microplastics (MPs) on Pb(II) and their co-transport properties in homogeneous (quartz sand) and heterogeneous (quartz sand with apple branches biochar) porous media, we explored the co-transport of UV-irradiated aged MPs and coexisting Pb(II) along with their interaction mechanisms. The UV aging process increased the binding sites and electronegativity of the aged MPs' surface, enhancing its adsorption capacity for Pb(II). Aged MPs significantly improved Pb(II) transport through homogeneous media, while Pb(II) hindered the transport of aged MPs by reducing electrostatic repulsion between these particles and the quartz sand. When biochar, with its loose and porous structure, was used as a porous medium, it effectively inhibited the transport capacity of both contaminants. In addition, since the aged MPs cannot penetrate the column, a portion of Pb(II) adsorbed by the aged MPs will be co-deposited with the aged MPs, hindering Pb(II) transport to a greater extent. The transport experiments were simulated and interpreted using two-point kinetic modeling and the DLVO theory. The study results elucidate disparities in the capacity of MPs and aged MPs to transport Pb(II), underscoring the potential of biochar application as an effective strategy to impede the dispersion of composite environmental pollutants.

Microplastics' toxic effects and influencing factors on microorganisms in biological wastewater treatment units

Prior to entering the water body, microplastics (MPs) are mostly collected at the sewage treatment plant and the biological treatment unit is the sewage treatment facility's central processing unit. This review aims to present a comprehensive analysis of the detrimental impacts of MPs on the biological treatment unit of a sewage treatment plant and it covers how MPs harm the effluent quality of biological treatment processes. The structure of microbial communities is altered by MPs presence and additive release, which reduces functional microbial activity. Extracellular polymers, oxidative stress, and enzyme activity are explored as micro views on the harmful mechanism of MPs on microorganisms, examining the toxicity of additives released by MPs and the harm caused to microorganisms by harmful compounds that have been adsorbed in the aqueous environment. This article offers a theoretical framework for a thorough understanding of the potential problems posed by MPs in sewage treatment plants and suggests countermeasures to mitigate those risks to the aquatic environment.

Critical evaluation of the performance of rhamnolipids as surfactants for (phyto)extraction of Cd, Cu, Fe, Pb and Zn from copper smelter-affected soil

Rhamnolipids are biosurfactants produced by bacteria belonging to the Pseudomonas genus. They are discussed to complex heavy metal cations stronger than cations of Fe, Ca, Mg. It is therefore suggested to employ rhamnolipids in phytoextraction where their addition to soil should result in preferential complexation of heavy metals that can be taken up by plants, thus enabling rapid and ecological clean-up of contaminated soil. In order to test this concept, we evaluated the rhamnolipid-mediated phytoextraction of heavy metal from soil collected from the vicinity of a copper smelter. The following aspects were investigated: i) selectivity of rhamnolipids towards Cu, Zn, Pb, Cd and Fe during soil washing; ii) phytoextraction efficiency of each ion with respect to the effective concentration of rhamnolipids; iii) possible phytotoxic effects; iv) effect of micro-sized polystyrene amendment. The experiments evaluated soil washing efficiency, BCR (Community Bureau of Reference) sequential extraction to determine the impact of rhamnolipids on the mobility of metal ions, phytoextraction with maize (Zea mays L.) and phytotoxic effects based on dry matter, chlorophyll fluorescence and content. The obtained results indicated that rhamnolipids lack desired selectivity towards heavy metal ions as Fe was complexed more efficiently by 80 % of the available rhamnolipids compared to priority pollutants like Zn, Cu, Pb, which were complexed by only 20 % of the tested rhamnolipids. With increased concentration of rhamnolipids, the soil washing efficiency increased and shifted in favour of Fe, reaching values of approx. 469 mg for Fe and only 118 mg in total of all tested heavy metals. Phytoextraction also favoured the accumulation of Fe, while Cd was not removed from the soil even at the highest applied rhamnolipid concentrations. Considering the selectivity of rhamnolipids and the costs associated with their production, our results suggest the need to search for other alternative (bio)surfactants with better selectivity and lower price.

Comparison of three digestion methods for microplastic extraction from aquaculture feeds

Microplastics (MPs) are ubiquitous pollutants found in aquaculture animals that may threaten human health through the food chain. However, there is a lack of effective methods for extracting MPs from aquaculture feeds containing complex components such as organic matter and fish bones. Therefore, in the present study, the extraction efficiency of three digestion methods using 30 % H2O2, Fenton reagent, and 30 % H2O2 + HNO3 for different particle sizes and types of MPs in aquaculture feeds was investigated and compared. The total digestion efficiency of the aquaculture feeds by 30 % H2O2 was 97.3 ± 0.1 %, while the recovery efficiency of MPs was 91.3 ± 1.1 % -103.1 ± 0.9 %. However, there was a large deviation in the extraction efficiency of MPs from aquaculture feeds by the Fenton reagent and 30 % H2O2 + HNO3. Notably, the surface morphology, particle size distribution, and oxidation degree of MPs hardly changed after 30 % H2O2 digestion. More importantly, the changes in the spectral features and carbonyl index of MPs after 30 % H2O2 digestion were smaller than those of the Fenton reagent and 30 % H2O2 + HNO3, which did not affect the identification of MPs. Overall, 30 % H2O2 was more efficient in extracting MPs from aquaculture feeds, and no significant effect on the characteristics of MPs was observed. This work provides novel insights into the effect of chemical pretreatment on the extraction of MPs in aquaculture feeds and provides an optimal protocol for the detection of MPs in aquaculture feeds.

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

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

Intracellular Protein Adsorption Behavior and Biological Effects of Polystyrene Nanoplastics in THP-1 Cells

Micro(nano)plastics (MNPs) are emerging pollutants that can adsorb pollutants in the environment and biological molecules and ultimately affect human health. However, the aspects of adsorption of intracellular proteins onto MNPs and its biological effects in cells have not been investigated to date. The present study revealed that 100 nm polystyrene nanoplastics (NPs) could be internalized by THP-1 cells and specifically adsorbed intracellular proteins. In total, 773 proteins adsorbed onto NPs with high reliability were identified using the proteomics approach and analyzed via bioinformatics to predict the route and distribution of NPs following cellular internalization. The representative proteins identified via the Kyoto Encyclopedia of Genes and Genomes pathway analysis were further investigated to characterize protein adsorption onto NPs and its biological effects. The analysis revealed that NPs affect glycolysis through pyruvate kinase M (PKM) adsorption, trigger the unfolded protein response through the adsorption of ribophorin 1 (RPN1) and heat shock 70 protein 8 (HSPA8), and are chiefly internalized into cells through clathrin-mediated endocytosis with concomitant clathrin heavy chain (CLTC) adsorption. Therefore, this work provides new insights and research strategies for the study of the biological effects caused by NPs.

Mineralization characteristics and behavior of polyethylene microplastics through ozone-based treatment

The elimination of microplastics (MPs) has become an urgent issue due to their large quantities and imperfect treatment technologies. In this work, polyethylene (PE), which is ubiquitous in the environment, was selected to study its removal by ozone-based treatment. Catalysts including α-MnO2 and α-FeOOH were synthesized for catalytic ozonation to improve efficiency. The study focused on simulating the conversion of CO2 in the off-gas via the detection of inorganic carbon produced. The morphology and structure of the remaining PE MPs were characterized using scanning electron microscope and Fourier-transform infrared spectroscopy-attenuated total reflection. Our results confirmed that fragmentation and oxidation occurred in the remaining PE MPs, which enhanced the adsorption capacity of ofloxacin (OF). Besides, the 20 mM α-FeOOH could better improve the mineralization efficiency by 3.27 folds with more production of •OH (1.09*10-12 M). Moreover, possible products identified by liquid chromatography-time-of-flight mass spectrometer confirmed the decomposition of main chains of MPs into low-molecular-weight organic compounds with functional groups such as C-OH, C-O-C, and CO. The finding that photoaged PE MPs could be efficiently mineralized under the attack of O3/•OH provides a solid foundation for the removal of natural MPs in the environment.

The adsorption and release mechanism of different aged microplastics toward Hg(II) via batch experiment and the deep learning method

Aged microplastics are ubiquitous in the aquatic environment, which inevitably accumulate metals, and then alter their migration. Whereas, the synergistic behavior and effect of microplastics and Hg(II) were rarely reported. In this context, the adsorptive behavior of Hg(II) by pristine/aged microplastics involving polystyrene, polyethylene, polylactic acid, and tire microplastics were investigated via kinetic (pseudo-first and second-order dynamics, the internal diffusion model), Langmuir, and Freundlich isothermal models; the adsorption and desorption behavior was also explored under different conditions. Microplastics aged by ozone exhibited a rougher surface attached with abundant oxygen-containing groups to enhance hydrophilicity and negative surface charge, those promoted adsorption capacity of 4-20 times increment compared with the pristine microplastics. The process (except for aged tire microplastics) was dominated by a monolayer chemical reaction, which was significantly impacted by pH, salinity, fulvic acid, and co-existing ions. Furthermore, the adsorbed Hg(II) could be effectively eluted in 0.04% HCl, simulated gastric liquids, and seawater with a maximum desorption amount of 23.26 mg/g. An artificial neural network model was used to predict the performance of microplastics in complex media and accurately capture the main influencing factors and their contributions. This finding revealed that aged microplastics had the affinity to trap Hg(II) from freshwater, whereafter it released the Hg(II) once transported into the acidic medium, the organism's gastrointestinal system, or the estuary area. These indicated that aged microplastics could be the sink or the source of Hg(II) depending on the surrounding environment, meaning that aged microplastics could be the vital carrier to Hg(II).

Co-exposure to UV-aged microplastics and cadmium induces intestinal toxicity and metabolic responses in earthworms

Aged microplastics (MPs) alter the interaction with heavy metals due to changes in surface properties. However, the combined toxicological effects of aged MPs on heavy metals in soil remain poorly understood. In this study, earthworms were employed as model animals to investigate the effects of aged MPs on the biotoxicity of cadmium (Cd) by simulating the exposure patterns of original and UV-aged MPs (polylactic acid (PLA) and polyethylene (PE)) with Cd. The results showed that UV-aging decreased the zeta potential and increased the specific surface area of the MPs, which enhanced the bioaccumulation of Cd and caused more severe oxidative stress to earthworms. Meanwhile, the earthworm intestines exhibited increased tissue damage, including chloragogenous tissue congestion lesions, and typhlosole damage. Furthermore, the combined exposure to UV-aged MPs and Cd enhanced the complexity of the microbial network in the earthworm gut and interfered with endocrine disruption, membrane structure, and energy metabolic pathways in earthworms. The results emphasized the need to consider the degradation of MPs in the environment. Hence, we recommend that future toxicological studies use aged MPs that are more representative of the actual environmental conditions, with the results being important for the risk assessment and management of MPs.

Microplastic pollution in terrestrial ecosystems: Global implications and sustainable solutions

Microplastic (MPs) pollution has become a global environmental concern with significant impacts on ecosystems and human health. Although MPs have been widely detected in aquatic environments, their presence in terrestrial ecosystems remains largely unexplored. This review examines the multifaceted issues of MPs pollution in terrestrial ecosystem, covering various aspects from additives in plastics to global legislation and sustainable solutions. The study explores the widespread distribution of MPs worldwide and their potential antagonistic interactions with co-occurring contaminants, emphasizing the need for a holistic understanding of their environmental implications. The influence of MPs on soil and plants is discussed, shedding light on the potential consequences for terrestrial ecosystems and agricultural productivity. The aging mechanisms of MPs, including photo and thermal aging, are elucidated, along with the factors influencing their aging process. Furthermore, the review provides an overview of global legislation addressing plastic waste, including bans on specific plastic items and levies on single-use plastics. Sustainable solutions for MPs pollution are proposed, encompassing upstream approaches such as bioplastics, improved waste management practices, and wastewater treatment technologies, as well as downstream methods like physical and biological removal of MPs. The importance of international collaboration, comprehensive legislation, and global agreements is underscored as crucial in tackling this pervasive environmental challenge. This review may serve as a valuable resource for researchers, policymakers, and stakeholders, providing a comprehensive assessment of the environmental impact and potential risks associated with MPs.

Environmental fate, aging, toxicity and potential remediation strategies of microplastics in soil environment: Current progress and future perspectives

Microplastics (MPs) are small plastic debris (<5 mm) that result from the fragmentation of plastic due to physical and physiochemical processes. MPs are emerging pollutants that pose a significant threat to the environment and human health, primarily due to their pervasive presence and potential bioaccumulation within the food web. Despite their importance, there is a lack of comprehensive studies on the fate, toxicity, and aging behavior of MPs. Therefore, this review aims to address this gap by providing a cohesive understanding of several key aspects. Firstly, it summarizes the sources and fate of MPs, highlighting their ubiquitous presence and the potential pathways through which they enter ecosystems. Secondly, it evaluates the aging process of MPs and the factors influencing it, including the morphological and physiological changes observed in crops and the release of pollutants from aged MPs, which can have detrimental effects on the environment and human health. Furthermore, the impacts of aging MPs on various processes are discussed, such as the mobilization of other pollutants in the environment. The influence of aged MPs on the soil environment, particularly their effect on heavy metal adsorption, is examined. Finally, the review explores strategies for the prevention technologies and remediation of MPs, highlighting the importance of developing effective approaches to tackle this issue. Overall, this review aims to contribute to our understanding of MPs, their aging process, and their impacts on the environment and human health. It underscores the urgency of addressing the issue of MPs and promoting research and remediation efforts to mitigate their adverse effects.

Oxidative stress and energy metabolic response of Isochrysis galbana induced by different types of pristine and aging microplastics and their leachates

The aging process and leachate composition of different types of MPs (PS, PS-NH2, PS-COOH and PMMA) with a particle size of 1.0 μm were characterized, and marine microalgae Isochrysis galbana OA3011(I. galbana) was used as test organism to investigate the 96 h toxic effects of MPs before and after aging as well as leachate exposure. Except for polymethyl methacrylate (PMMA), all other tested microplastics showed significant aggregation in seawater, which increased with the presence of surface amino and carboxyl groups, in addition, the increase in polymer dispersibility index (PDI) values after aging reflected more severe aggregation. Fourier transform infrared spectrometer (FTIR) showed that the surface amino groups were shed during the aging of PS-NH2, which can likewise be demonstrated by the change in surface electric potential from positive to negative before and after aging. PMMA, due to the addition of plasticizers (HEHP and DIBP detected in high concentration) and its own structure, has stronger resistance to aging than the other three microplastics, and no significant aging phenomenon occurs. As for I. galbana, growth inhibition, oxidative stress and energy metabolism were tested after exposure to different microplastics and their leachate. It was found that high concentrations of A-PS had a greater negative impact on I. galbana, while the toxic effects of PS-NH2 and PS-COOH on I. galbana behaved in a diametrically opposite way before and after aging compared to PS with the inhibitory effect decreasing after aging, which was caused by the shedding of surface groups. As for PMMA, the differences in the toxic effects on microalgae before and after aging were not significant. The inhibitory effect of low concentrations of PAEs (Phthalate acid esters) in the leachate of PS-COOH on I. galbana was not significant, and the stronger inhibitory effect of 4 d L-PS-NH2 was presumed to be the shedding of positively charged groups.

Characterization and risk assessment of microplastics in laver from the Yueqing Bay

Microplastics (MPs) pollution is regarded as a global challenge for ocean. As an important food source of human, macroalgae could suffer MP pollution and transmit MPs into human via food web. However, few studies have revealed the relationship of MP pollution between macroalgae and its habitat. In order to evaluate the trapping and accumulation of MPs in macroalgae and surface water, the present study investigated MP pollution in a typical aquaculture macroalgae species, laver (Porphyra haitanensis) in the Yueqing Bay. The results indicated MP abundance in laver (1.45 ± 0.26 items/g) was at a medium level while MP abundance in surface water (0.21 ± 0.15 item/m3) was at a relatively low level worldwide. Distribution trend and characteristics of MPs in laver and surface water showed highly similarity. Besides, heavy metal elements (Fe and Zr) were detected on the surface of MPs trapped by laver. Pollution load index (PLI) in surface water of the whole bay was low, indicating MP pollution was not serious in the Yueqing Bay. Due to the discharging of domestic sewage in recent years, fiber-shaped, textile MPs accounted for most in laver and surface water of the Yueqing Bay. These results indicated that MPs in surface water could be trapped by P. haitanensis, thus macroalgae cultivation might be a potential way to alleviate seawater MP pollution in the nearshore areas.

In-situ retention of nitrogen, phosphorus in agricultural drainage and soil nutrients by biochar at different temperatures and the effects on soil microbial response

This study conducted a two-year experiment to investigate the impacts of biochar with various temperatures (350 °C, 500 °C, and 650 °C), on the reduction of pollutants in agricultural runoff and the enhancement of soil fertility. The results showed that the biochar significantly reduced the concentrations of total nitrogen and total phosphorus in farmland runoff. Moreover, higher-temperature biochar demonstrated greater efficacy in decreasing pollutants in farmland drainage. Treatment with RB650 resulted in a reduction of the total nitrogen and total phosphorus output load by 29.31-30.67 % and 21.92-25.21 %, respectively, compared to RB350. Furthermore, biochar exhibited substantial enhancements in soil fertility. This was supported by heightened soil organic matter content, increased availability of nutrients, and a noteworthy (P < 0.05) upsurge in pH, organic matter, total nitrogen, and total phosphorus content observed in the second year following the application of biochar. Biochar has the potential to enhance soil enzyme activity and affect microbial community composition, thereby facilitating nutrient cycling. The findings illustrated the regenerative and recyclable characteristics of biochar's adsorption activity throughout crop growth. This process enables sustained improvement in soil nutrient retention capacity and fertility. Thus, it emphasizes the potential of biochar as an in-situ model for nutrient retention and recycling, offering an effective approach to mitigate agricultural non-point source (NPS) pollution and enhance soil fertility.

Surface functional groups and biofilm formation on microplastics: Environmental implications

Microplastics (MPs) contamination is becoming a significant environmental issue, as the widespread omnipresence of MPs can cause many adverse consequences for both ecological systems and humans. Contrary to what is commonly thought, the toxicity-inducing MPs are not the original pristine plastics; rather, they are completely transformed through various surface functional groups and aggressive biofilm formation on MPs via aging or weathering processes. Therefore, understanding the impacts of MPs' surface functional groups and biofilm formation on biogeochemical processes, such as environmental fate, transport, and toxicity, is crucial. In this review, we present a comprehensive summary of the distinctive impact that surface functional groups and biofilm formation of MPs have on their significant biogeochemical behavior in various environmental media, as well as their toxicity and biological effects. We place emphasis on the role of surface functional groups and biofilm formation as a means of influencing the biogeochemical processes of MPs. This includes their effects on pollutant fate and element cycling, which in turn impacts the aggregation, transport, and toxicity of MPs. Ultimately, future research studies and tactics are needed to improve our understanding of the biogeochemical processes that are influenced by the surface functional groups and biofilm formation of MPs.

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.

Adsorption-desorption behaviors of ciprofloxacin onto aged polystyrene fragments in aquatic environments

As two emerging pollutants of great concern, microplastics (MPs) and antibiotics inevitably cooccur in various aquatic environments and interact with each other, impacting the fate and ecological risks. Aging obviously complicates their interaction and deserves further study. Therefore, the adsorption-desorption behaviors of ciprofloxacin (CIP) onto polystyrene (PS) fragments with various aging extent were investigated, and the key physiochemical properties influencing the interaction and the interaction mechanisms were clarified by redundancy analysis, FTIR and XPS spectra. The physicochemical properties of PS MPs were significantly changed with aging time, and the morphological and chemical changes seemed to occur asynchronously. The adsorption of CIP onto the pristine PS MPs relied on physisorption, especially the ion-involving electrostatic and cation-π interaction. Due to the hydrogen bonding formed by the C-OH, CO, and O-CO groups of PS and CIP, the adsorption capacities of the aged PS MPs were greatly increased. The desorption efficiency of CIP from MPs in the gastric fluid was closely related to the solution ionic strengths, C-OH and CO groups of MPs, while that in the intestinal fluid was associated with O-CO groups of MPs. The different impact factors could be well described by the differences in the chemical components and pHs of the simulated gastric and intestinal fluids. This study gives a comprehensive understanding of the adsorption-desorption behaviors of antibiotics onto MPs at a molecular level and indicates that MPs could act as Trojan horses to transport antibiotics into aquatic organisms.

Effect of Polymer Aging on Uptake/Release Kinetics of Metal Ions and Organic Molecules by Micro- and Nanoplastics: Implications for the Bioavailability of the Associated Compounds

The main driver of the potential toxicity of micro- and nanoplastics toward biota is often the release of compounds initially present in the plastic, i.e., polymer additives, as well as environmentally acquired metals and/or organic contaminants. Plastic particles degrade in the environment via various mechanisms and at different rates depending on the particle size/geometry, polymer type, and the prevailing physical and chemical conditions. The rate and extent of polymer degradation have obvious consequences for the uptake/release kinetics and, thus, the bioavailability of compounds associated with plastic particles. Herein, we develop a theoretical framework to describe the uptake and release kinetics of metal ions and organic compounds by plastic particles and apply it to the analysis of experimental data for pristine and aged micro- and nanoplastics. In particular, we elucidate the contribution of transient processes to the overall kinetics of plastic reactivity toward aquatic contaminants and demonstrate the paramount importance of intraparticulate contaminant diffusion.

Long-term aged fibrous polypropylene microplastics promotes nitrous oxide, carbon dioxide, and methane emissions from a coastal wetland soil

Microplastics (MPs) has been suggested that it can greatly affect soil greenhouse gases (GHGs) emissions via altering soil physical, chemical, and biological properties. However, the difference in GHGs emissions, especially for those from coastal wetland soils, between varied aged MPs was rarely explored and the underlying mechanisms of GHGs emissions affected by the aged MPs were poorly understood. Therefore, the implications of fibrous polypropylene MPs (FPP-MPs) exposure on N2O, CO2, and CH4 emissions were examined by a 60-day soil incubation experiment. Compared with the control, the additions of un-aged FPP-MPs with both two rates (0.2 and 2 %) and aged FPP-MPs with a low rate (0.2 %) showed an insignificant effect on N2O emission, while the aged FPP-MPs added with a high rate (2 %) resulted in a remarkably increase in N2O emission, especially for those of the 30-day-aged FPP-MPs. A significant increase in CO2 emission was only observed in the 30-day-aged FPP-MPs treatments, compared with the control, and a higher addition rate produced a higher increase of CO2 emission. Regarding CH4 emission, it was significantly increased by adding aged FPP-MPs, and a longer aging period or/and a higher addition rate generated a higher degree of promotion of CH4 emission. However, compared with the CO2 emission, the quantity of CH4 emission was extremely low. These increased GHGs emissions can be ascribed to the improvements in soil physical structure and other chemical properties (e.g., pH and contents of soil organic matter and dissolved organic carbon) and enhancements in the abundances of denitrification- and carbon mineralization-related microorganisms. Overall, our results highlight the risk of elevated GHGs emissions from the soil polluted with 30-day-aged FPP-MPs, which should not be ignored as long-term aged FPP-MPs continue to increase in coastal wetland soils.

Naturally aged polylactic acid microplastics stunted pakchoi (Brassica rapa subsp. chinensis) growth with cadmium in soil

Biodegradable microplastics (BMPs) and cadmium (Cd) are posing threats to agro-systems especially to plants and current studies mostly used virgin BMPs to explore their ecological effects. However, effects of naturally aged BMPs and their combined effects with Cd on pakchoi are yet to be unraveled. Therefore, this study incubated naturally aged polylactic acid (PLA) MPs through soil aging process and investigated the single and combined effects of Cd and PLA MPs (virgin and aged) on pakchoi (Brassica rapa subsp. chinensis) morphology, antioxidant systems and soil microbial activities. Our results found that after being deposited in soil for six months, aged PLA (PLAa) MPs formed with a fractured surface, demonstrating more detrimental effects on pakchoi than virgin ones. PLA/PLAa MPs and Cd stunted pakchoi growth, caused oxidative stress and altered the biophysical environment in soil, separately. Moreover, co-existence of PLA/PLAa MPs and Cd caused greater damages to pakchoi than applied alone. The co-presence of PLAa MPs and Cd inhibited pakchoi biomass accumulation rate by 92.2 % compared with the no-addition group. The results unraveled here emphasized BMPs, especially aged BMPs, could trigger negative effects on agro-systems with heavy metals. These findings will give reference to future holistic assessments of BMPs' ecological effects.

Scavenging microplastics and heavy metals from water using jujube waste-derived biochar in fixed-bed column trials

Extensive production and utilization of plastic products have resulted in the generation of microplastics (MPs), subsequently polluting the environment. The efficiency of biochars (BCs) derived from jujube (Ziziphus jujube L.) biomass (300 °C and 700 °C) for nylon (NYL) and polyethylene (PE) removal from contaminated water was explored in fixed-bed column trials. The optimum pH for the removal of both MPs was found 7. Both of the produced biochars demonstrated >99% removal of the MPs, while the sand filter exhibited a maximum of 78% removal of MPs. BC produced at 700 °C (BC700) showed 33-fold higher MPs retention, while BC produced at 300 °C (BC300) exhibited 20-fold higher retention, as compared to sand filters, indicating the higher efficiency of BC produced at higher pyrolysis temperature. Entrapment into the pores, entanglement with flaky structures of the BCs, and electrostatics interactions were the major mechanism for MPs retention in BCs. The efficiency of MPs-amended BCs was further explored for the removal of Pb(II) and Cd(II) in fixed-bed column trials. BC700 amended with PE and NYL exhibited the highest 50% breakthrough time (2114.23 and 2024.61 min, respectively, for Pb(II) removal and 2107.92 and 1965.19 min, respectively, for Cd(II) removal), as compared to sand filters (38.07 and 60.49 min for Pb(II) and Cd(II) removal, respectively). Thomas model predicted highest adsorption capacity was exhibited by BC700 amended with PE (584.34 and 552.80 mg g-1, for Pb(II) and Cd(II) removal, respectively), followed by BC700 amended with NYL (557.65 and 210.59 mg g-1 for Pb(II) and Cd(II) removal, respectively). Therefore, jujube waste-derived BCs could be used as efficient adsorbents to remove PE and NYL from contaminated water, while MPs-loaded BCs can further be utilized for higher adsorption of Pb(II) and Cd(II) from contaminated aqueous media. These findings suggest that BC could be used as an efficient adsorbent to remove the co-existing MPs-metals ions from the environment on a sustainable basis.