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

Effect of surface functional groups of polystyrene micro/nano plastics on the release of NOM from flocs during the aging process

Currently, the hidden risk of microplastics in the coagulation process has attracted much attention. However, previous studies aimed at improving the removal efficiency of microplastics and ignored the importance of interactions between microplastics and natural organic matter (NOM). This study investigated how polystyrene micro/nano particles impact the release of NOM during the aging of flocs formed by aluminum-based coagulants Al13 and AlCl3. The results elucidated that nano-particles with small particle sizes and agglomerative states are more likely to interact with coagulants. After 7 years of floc aging, the DOC content of the nano system decreased by more than 40%, while the micron system did not change significantly. During coagulation, the benzene rings in polystyrene particles form complexes with electrophilic aluminum ions through π-bonding, creating new Al-O bonds. NOM tends to adsorb at micro/nano plastic interfaces due to hydrophobic interactions and conformational entropy. In the aging process, the structure of PS-Al13 or PS-AlCl3 flocs and the functional groups on the surface of micro/nano plastics control the absorption and release of organic matter through hydrophobic, van der Waals forces, hydration, and polymer bridging. In the system with the addition of nano plastics, several DBPs such as TCAA, DCAA, TBM, DBCM and nitrosamines were reduced by more than 50%. The reaction order of different morphological structures and surface functional groups of microplastics to Al13 and AlCl3 systems is aromatic C-H > C-OH > C-O > NH2 > aromatic CC > aliphatic C-H and C-O>H-CO> NH2 >C-OH> aliphatic C-H. The results provided a new sight to explore the effect of micro/nano plastics on the release of NOM during flocs aging.

Polyhydroxybutyrate (PHB) nanoparticles modulate metals toxicity in Hydra viridissima

The use of bioplastics (e.g., polyhydroxybutyrate) emerged as a solution to help reduce plastic pollution caused by conventional plastics. Nevertheless, bioplastics share many characteristics with their conventional counterparts, such as degradation to nano-sized particles and the ability to sorb environmental pollutants, like metals. This study aimed to assess the potential impacts of the interaction of metals (cadmium - Cd, copper - Cu, and zinc - Zn) with polyhydroxybutyrate nanoplastics (PHB-NPLs; ~200 nm) on the freshwater cnidarian Hydra viridissima in terms of mortality rates, morphological alterations, and feeding behavior. The metal concentrations selected for the combined exposures corresponded to concentrations causing 20 %, 50 %, and 80 % of mortality (LC20, LC50, and LC80, respectively) and the PHB-NPLs concentrations ranged from 0.01 to 1000 μg/L. H. viridissima sensitivity to the metals, based on the LC50's, can be ordered as: Zn < Cd < Cu. Combined exposure to metals and PHB-NPLs yielded distinct outcomes concerning mortality, morphological changes, and feeding behavior, uncovering metal- and dose-specific responses. The interaction between Cd-LCx and PHB-NPLs progressed from no effect at LC20,96h to an ameliorative effect at Cd-LC50,96h. Cu-LCx revealed potential mitigation effects (LC20,96h and LC50,96h) but at Cu-LC80,96h the response shifts to a potentiating effect. For Zn-LCx, response patterns across the combinations with PHB-NPLs were like those induced by the metal alone. PHB-NPLs emerged as a key factor capable of modulating the toxicity of metals. This study highlights the context-dependent interactions between metals and PHB-NPLs in freshwater environments while supporting the need for further investigation of the underlying mechanisms and ecological consequences in forthcoming research.

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.

Optimizing Antimony Speciation Analysis via Frontal Chromatography-ICP-MS to Explore the Release of PET Additives

Antimony (Sb) contamination poses significant environmental and health concerns due to its toxic nature and widespread presence, largely from anthropogenic activities. This study addresses the urgent need for an accurate speciation analysis of Sb, particularly in water sources, emphasizing its migration from polyethylene terephthalate (PET) plastic materials. Current methodologies primarily focus on total Sb content, leaving a critical knowledge gap for its speciation. Here, we present a novel analytical approach utilizing frontal chromatography coupled with inductively coupled plasma mass spectrometry (FC-ICP-MS) for the rapid speciation analysis of Sb(III) and Sb(V) in water. Systematic optimization of the FC-ICP-MS method was achieved through multivariate data analysis, resulting in a remarkably short analysis time of 150 s with a limit of detection below 1 ng kg-1. The optimized method was then applied to characterize PET leaching, revealing a marked effect of the plastic aging and manufacturing process not only on the total amount of Sb released but also on the nature of leached Sb species. This evidence demonstrates the effectiveness of the FC-ICP-MS approach in addressing such an environmental concern, benchmarking a new standard for Sb speciation analysis in consideration of its simplicity, cost effectiveness, greenness, and broad applicability in environmental and health monitoring.

The triple exposure nexus of microplastic particles, plastic-associated chemicals, and environmental pollutants from a human health perspective

The presence of microplastics (MPs) is increasing at a dramatic rate globally, posing risks for exposure and subsequent potential adverse effects on human health. Apart from being physical objects, MP particles contain thousands of plastic-associated chemicals (i.e., monomers, chemical additives, and non-intentionally added substances) captured within the polymer matrix. These chemicals are often migrating from MPs and can be found in various environmental matrices and human food chains; increasing the risks for exposure and health effects. In addition to the physical and chemical attributes of MPs, plastic surfaces effectively bind exogenous chemicals, including environmental pollutants (e.g., heavy metals, persistent organic pollutants). Therefore, MPs can act as vectors of environmental pollution across air, drinking water, and food, further amplifying health risks posed by MP exposure. Critically, fragmentation of plastics in the environment increases the risk for interactions with cells, increases the presence of available surfaces to leach plastic-associated chemicals, and adsorb and transfer environmental pollutants. Hence, this review proposes the so-called triple exposure nexus approach to comprehensively map existing knowledge on interconnected health effects of MP particles, plastic-associated chemicals, and environmental pollutants. Based on the available data, there is a large knowledge gap in regard to the interactions and cumulative health effects of the triple exposure nexus. Each component of the triple nexus is known to induce genotoxicity, inflammation, and endocrine disruption, but knowledge about long-term and inter-individual health effects is lacking. Furthermore, MPs are not readily excreted from organisms after ingestion and they have been found accumulated in human blood, cardiac tissue, placenta, etc. Even though the number of studies on MPs-associated health impacts is increasing rapidly, this review underscores that there is a pressing necessity to achieve an integrated assessment of MPs' effects on human health in order to address existing and future knowledge gaps.

Insights into Plastic Degradation Processes in Marine Environment by X-ray Photoelectron Spectroscopy Study

The present study employs X-ray photoelectron spectroscopy (XPS) to analyze plastic samples subjected to degradation processes with the aim to gain insight on the relevant chemical processes and disclose fragmentation mechanisms. Two model plastics, namely polystyrene (PS) and polyethylene (PE), are selected and analyzed before and after artificial UV radiation-triggered weathering, under simulated environmental hydrodynamic conditions, in fresh and marine water for different time intervals. The object of the study is to identify and quantify chemical groups possibly evidencing the occurrence of hydrolysis and oxidation reactions, which are the basis of degradation processes in the environment, determining macroplastic fragmentation. Artificially weathered plastic samples are analyzed also by Raman and FT-IR spectroscopy. Changes in surface chemistry with weathering are revealed by XPS, involving the increase in chemical moieties (hydroxyl, carbonyl, and carboxyl functionalities) which can be correlated with the degradation processes responsible for macroplastic fragmentation. On the other hand, the absence of significant modifications upon plastics weathering evidenced by Raman and FT-IR spectroscopy confirms the importance of investigating plastics surface, which represents the very first part of the materials exposed to degradation agents, thus revealing the power of XPS studies for this purpose. The XPS data on experimentally weathered particles are compared with ones obtained on microplastics collected from real marine environment for investigating the occurring degradation processes.

Effect of microplastics used in agronomic practices on agricultural soil properties and plant functions: Potential contribution to the circular economy of rural areas

The extensive use of plastic materials and their improper disposal results in high amounts of plastic waste in the environment. Aging of plastics leads to their breakdown into smaller particles, such as microplastics (MPs) and nanoplastics. This research investigates plastics used in agricultural practices as they contribute to MP pollution in agricultural soils. The distribution and characteristics of MPs in agricultural soils were evaluated. In addition, the effect of MPs on soil properties, the relationship between MPs and metals in soil, the effect of MPs on the fate of pesticides in agricultural soils and the influence of MPs on plant growth were analysed, discussing legume, cereal and vegetable crops. Finally, a brief description of the main methods of chemical analysis and identification of MPs is presented. This study will contribute to a better understanding of MPs in agricultural soils and their effect on the soil-plant system. The changes induced by MPs in soil parameters can lead to potential benefits as it is possible to increase the availability of micronutrients and reduce plant uptake of toxic elements. Furthermore, although plastic pollution remains an emerging threat to soil ecosystems, their presence may result in benefits to agricultural soils, highlighting the principles of the circular economy.

Abiotic weathering of plastic: Experimental contributions towards understanding the formation of microplastics and other plastic related particulate pollutants

The increasing use of plastic (synthetic polymers) results in the release of uncontrollable amounts of synthetic materials into the environment through waste, infrastructure, and essential goods. As plastic materials undergo weathering, a complex process unfolds, leading to the formation of pollutants, notably microplastics. This study employs multiple instrumental methods to explore the intricate abiotic degradation of the five most commonly used synthetic polymers in environmentally relevant conditions. An extensive set of analytical techniques, along with chemometric analysis of the results of Raman spectroscopy, was used to characterize the materials and evaluate the nature and extent of degradation caused by artificial weathering under temperature, humidity, and solar-like irradiation cycles. Investigation focuses on the link between abiotic weathering and the generation of micro- and nanoplastics, accompanied by molecular and surface adhesion changes, and the release of additives such as metals and metal oxides. Research reveals that microplastics may exhibit varied physical properties due to the incorporation of significant quantities of high-density additives from the parent plastic, which might influence the extraction methods and the transportation models' accuracy. At the molecular and microscopic scales, non-homogeneous pathways through which plastic decomposes during weathering were observed. The formation of additive-polymer combinations might play a pivotal role in the monitoring approaches for microplastics, presenting unique challenges in assessing the environmental impact of different plastic types. These findings offer complex insight into abiotic weathering, microplastics' generation, and the influence of additives that were previously overlooked in toxicity and health assessment studies. As plastic pollution continues to escalate, understanding these complex processes is crucial for microplastic monitoring development and adopting effective preventative measures.

Green direct ultrasonic slurry sampling and electrothermal atomic absorption spectrometry method for metal analysis of solid plastics samples

This work presents a "green" analytical method developed for the determination of potentially toxic metals such as aluminium, barium and chromium in solid plastics samples using the slurry sampling technique in conjunction with electrothermal atomic absorption spectrometry. The development of the slurry sampling technique in conjunction with electrothermal atomic absorption spectrometry entailed optimisation of the measuring conditions, which included optimisation of the temperature programme, selection of an appropriate liquid medium for slurry preparation, optimisation of the concentration and volume of the liquid medium and optimisation of the mass of the solid plastics sample. The following conditions were determined: the optimal pyrolysis temperature for aluminium, barium and chromium was in the range of 1300 °C to 1700 °C and the optimal atomisation temperature was in the range of 2100 °C to 2400 °C. The optimal liquid media for solid plastics samples were H2O, 0.2% (v/v) HNO3 and 0.2% (v/v) HCl. The optimal volume of liquid medium was in the range from 5 to 15 mL and the mass of the solid plastics samples was in the range from 30 to 100 mg. The limit of detection and limit of quantification were estimated as 0.06-0.52 ng g-1 and 0.22-1.69 ng g-1 for aluminium, 0.11-0.94 ng g-1 and 0.37-3.14 ng g-1 for barium and 0.07-0.31 ng g-1 and 0.25-1.04 ng g-1 for chromium. Relative standard deviation was below 5% for all plastic samples analysed. Based on the established validation parameters, the slurry sampling technique in conjunction with electrothermal atomic absorption spectrometry represents a viable technique for metal analysis of a variety of plastic materials. The concentrations of analytes in individual solid plastic samples were in the range of 1.36 ± 0.06 μg g-1 to 22.65 ± 0.66 μg g-1 for aluminium, 1.13 ± 0.03 μg g-1 to 6.01 ± 0.22 μg g-1 for barium and 0.60 ± 0.03 μg g-1 to 10.48 ± 0.46 μg g-1 for chromium.

Insights into adsorption behavior and mechanism of Cu(II) onto biodegradable and conventional microplastics: Effect of aging process and environmental factors

The widespread promotion attempt of biodegradable plastics is considered as an effective solution to address conventional plastic pollution. However, the interaction of microplastics (MPs) easily broken down from biodegradable plastics with the coexisting pollutants in aquatic environments has gained less attention. Herein, we investigated the effects of the aging process and environmental factors on copper (Cu(II)) adsorption behavior by biodegradable polylactic acid and conventional polystyrene MPs. Results demonstrated that the aging process significantly altered physicochemical properties of both types of MPs, and PLA showed less resistance to aging. The aged polylactic acid MPs (aged-PLA) exhibited the far highest Cu(II) maximum adsorption capacity (7.13 mg/g) mainly due to its abundant oxygen-containing functional groups (OCFGs), followed by pristine polylactic acid (PLA, 6.08 mg/g), aged polystyrene (aged-PS, 0.489 mg/g) and pristine polystyrene (PS, 0.365 mg/g). The adsorption kinetics of Cu(II) on PLA MPs were controlled by film and intraparticle diffusion, while film diffusion governed the Cu(II) adsorption onto PS MPs. In addition to roles of rougher surface structure, greater surface area and pore filling, the complexation of OCFGs and electrostatic interaction were critical to the adsorption mechanism of aged-PLA and aged-PS, and cation-π interaction was associated with adsorption of aged-PS. Moreover, the adsorption capacity of Cu(II) on aged MPs gradually grew with the increasing pH from 4 to 7. Besides, humic acid significantly promoted the adsorption of Cu(II) at a low concentration (0-20 mg/L) due to the formation of binary mixtures of MPs-HA but inhibited the adsorption at a high concentration (50 mg/L) because of its competitive effect, suggesting the dual roles of humic acid in the adsorption process. Overall, our findings provide a better understanding of the adsorption behavior of metals on biodegradable MPs and emphasize their non-negligible risk as carriers of contaminant.

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

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

Freshwater Lacustrine Zooplankton and Microplastic: An Issue to Be Still Explored

Lakes are essentially interlinked to humans as they provide water for drinking, agriculture, industrial and domestic purposes. The upsurge of plastic usage, its persistence, and potential detrimental effects on organisms cause impacts on the trophic food web of freshwater ecosystems; this issue, however, still needs to be explored. Zooplankton worldwide is commonly studied as an indicator of environmental risk in aquatic ecosystems for several pollutants. The aim of the review is to link the existing knowledge of microplastic pollution in zooplankton to assess the potential risks linked to these organisms which are at the first level of the lacustrine trophic web. A database search was conducted through the main databases to gather the relevant literature over the course of time. The sensitivity of zooplankton organisms is evident from laboratory studies, whereas several knowledge gaps exist in the understanding of mechanisms causing toxicity. This review also highlights insufficient data on field studies hampering the understanding of the pollution extent in lakes, as well as unclear trends on ecosystem-level cascading effects of microplastics (MPs) and mechanisms of toxicity (especially in combination with other pollutants). Therefore, this review provides insight into understanding the overlooked issues of microplastic in lake ecosystems to gain an accurate ecological risk assessment.

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.

Influence of UV exposure time and simulated marine environment on different microplastic degradation

This study investigated the influence of environmental factors (UV radiation and salinity) in the degradative process of microplastics (MPs). MPs derived from polypropylene (PP), polystyrene (PS), and ethylene-vinyl acetate (EVA) were subjected to accelerated photodegradation while being submerged in distilled water or artificial seawater. Depending on the polymer, changes in surface properties, new functional chemical group formation and oxidative index, and thermal characteristics of samples were observed. After photodegradation experiments, EVA-MPs samples showed an increase in their thermal resistance, besides the changes in their surface. PP-MPs crystallinity index increased upon exposure to UV radiation. PS samples showed a higher carbonyl and hydroxyl index after 30 h of UV exposure. The methodology exploited applies to any location in the world and can be comparable once considering the total ultraviolet index (UVI). The saline medium increases the crystallinity index of PP and EVA-MPs samples and intensifies the formation of new carbonyl and hydroxyl bonds in EVA-MPs samples. The results showed that several environmental factors should be considered in interpreting MPs photodegradation.

The bioadhesion and effects of microplastics and natural particles on growth, cell viability, physiology, and elemental content of an aquatic macrophyte Elodea canadensis

Microplastics in the aquatic environment can interact with aquatic plants, but the consequences of these interactions are poorly understood. Therefore, the aim of this study was to investigate the effects of microplastics commonly found in the environment, namely polyethylene (PE) fragments, polyacrylonitrile (PAN) fibres, tire wear (TW) particles under a relevant environmental concentration (5000 particles/L) on the growth, cell viability, physiology, and elemental content of the aquatic macrophyte Elodea canadensis. The effects of microplastics were compared to those of natural wood particles. The results showed that all types of microplastics adhered to plant tissues, but the effect on leaves (leaf damage area) was greatest at PE > PAN > TW, while the effect of natural particles was comparable to that of the control. None of the microplastics studied affected plant growth, lipid, carbohydrate, or protein content. Electron transport system activity was significantly higher in plants exposed to PAN fibres and PE fragments, but also when exposed to natural particles, while chlorophyll a content was negatively affected only by PE fragments and TW particles. Elemental analysis of plant tissue showed that in some cases PAN fibres and TW particles caused increased metal content. The results of this study indicated that aquatic macrophytes may respond differently to exposure to microplastics than to natural particles, likely through the combined effects of mechanical damage and chemical stress.

Physicochemical properties of environmental media can affect the adsorption of arsenic (As) by microplastics

Microplastics are emerging pollutants that can adsorb heavy metals and threaten human health through food chain. Recently, there has been increasing interest in understanding the adsorption behavior of heavy metals by microplastics in farmland soil. In particular, arsenic (As), as a carcinogen, has the potential to be adsorbed by soil microplastics. However, the mechanisms and controlling factors of As adsorption by microplastics in farmland soil under natural conditions are still unknown. Here, microplastics and As were respectively added to farmland soils with different physicochemical properties from twelve provinces of China for adsorption experiment. We performed surface analysis of microplastics, quantified As accumulation through quasi-first-order kinetic equation and developed regression models to screen the factors controlling As adsorption. The results showed that the adsorption of As by soil microplastics was a chemical process accompanied by the loss of electrons from oxygen-containing functional groups. Soil cation exchange capacity (CEC) was the main factor controlling the adsorption rate, while soil organic matter (SOM), total nitrogen (TN) and CEC mainly influenced the equilibrium adsorption capacity. This is the first report on microplastic-As adsorption in natural soil, which allows deeper insights into risk assessment, prediction and control of microplastic-As pollution in agricultural soil.

Research progress on the role of biofilm in heavy metals adsorption-desorption characteristics of microplastics: A review

Microplastics (MPs) have been found to be widely distributed in aquatic environments, where they will interact with toxic heavy metals and result in more serious adverse effects on the aquatic environments and organisms. However, after entering the aquatic environments, MPs are quickly covered by biofilms, which significantly modify MPs properties and relevant heavy metals adsorption-desorption characteristics In order to better understand the adsorption behavior of heavy metals on biofilm developed MPs (BMPs), we comprehensively reviewed representative studies in this area. First, we summarized the formation process of biofilms on MPs. Subsequently, we reviewed the current understanding on the influence of biofilm formation on the properties of MPs and discussed the metal adsorption-desorption characteristics of MPs affected by these changes. Finally, based on the systematic literature review, some future research needs and strategies were proposed to further understand the interactions between MPs and heavy metals.

Occurrence and risk associated with urban road-deposited microplastics

An in-depth understanding of urban road-deposited MPs is important for the accurate prediction of the risk posed by MPs in different exposure scenarios. This study provides new insights into the intrinsic/extrinsic factors in terms of the variability of concentration and species in urban road-deposited MPs. The study results confirmed that a considerable abundance of road-deposited MPs can be identified with the average concentration ranging from 0.33 to 3.64 g m-2. Land use types and sediment particle size are the important factors that contribute to MPs abundance. The majority of detected MPs including polyethylene (PE), polypropylene (PP), polystyrene (PS) and polyethylene terephthalate (PET) are mainly derived from anthropogenic activities in commercial and residential land uses while rubber MP particles in urban road surfaces are mainly derived from tyre wear. The significant correlation (p < 0.05) between MPs and fine dust particles (< 150 µm) indicated the high affinity of small dust particles for MPs. The risk scores from MPs varied greatly from 10 to 11,000 among the study sites, which indicated the significant spatial variation of potential environmental risks posed by road-deposited MPs. The hotspots of risks posed by MPs were in areas with a high fraction of industrial, commercial and residential land uses. Specifically, the highest risk from MPs was found in mixed industrial and residential areas.

Interactions between titanium dioxide nanoparticles and polyethylene microplastics: Adsorption kinetics, photocatalytic properties, and ecotoxicity

The present study investigated the adsorption mechanism of titanium dioxide nanoparticles (nTiO₂) on polyethylene microplastics (MPs) and the resulting photocatalytic properties. This effort was supported by ecotoxicological assessments of MPs with adsorbed nTiO₂ on the immobility and behaviour of Daphnia magna in presence and absence of UV irradiation. The results showed that nTiO₂ were rapidly adsorbed on the surface of MPs (72% of nTiO₂ in 9 h). The experimental data fit well with the pseudo-second order kinetic model. Both suspended nTiO₂ and nTiO₂ immobilized on MPs exhibited comparable photocatalytic properties, with the latter showing a lower effect on Daphnia mobility. A likely explanation is that the suspended nTiO₂ acted as a homogeneous catalyst under UV irradiation and generated hydroxyl radicals throughout the test vessel, whereas the nTiO₂ adsorbed on MPs acted as a heterogeneous catalyst and generated hydroxyl radicals only locally and thus near the air-water interface. Consequently, Daphnia, which were hiding at the bottom of the test vessel, actively avoided exposure to hydroxyl radicals. These results suggest that the presence of MPs can modulate the phototoxicity of nTiO₂ - at least the location at which it is active - under the studied conditions.

Ultrasensitive photoelectrochemical biosensor amplified by target induced assembly of cruciform DNA nanostructure for the detection of dibutyl phthalate

In this work, an ultra-sensitive signal quenched photoelectrochemical (PEC) aptasensor for dibutyl phthalate (DBP) detection was constructed by using a target induced cruciform DNA structure as signal amplifier and g-C₃N₄/SnO₂ composite as signal indicator. Impressively, the designed cruciform DNA structure shows high signal amplification efficiency due to the reduced reaction steric hindrance because of its mutually separated and repelled tails, multiple recognition domains, and a fixed direction for the sequential identification of the target. Therefore, the fabricated PEC biosensor demonstrated a low detection limit of 0.3 fM for DBP in a wide linear range of 1 fM to 1 nM. This work offered a novel nucleic acid signal amplification approach for enhancing the sensitivity of PEC sensing platforms for the detection of phthalates (PAEs)-based plasticizer, laying the foundation for its utilization in the determine of real environmental pollutants.

Selection of the optimal extraction protocol to investigate the interaction between trace elements and environmental plastic

The interaction between environmental plastic and trace elements is an issue of concern. Understanding their interaction mechanisms is key to evaluate the potential threats for the environment. To this regard, consolidating confidence in extraction protocols can help in understanding the amount of different species present on plastic surface, as well as the potential mobility of trace elements present inside the plastic matrix (e.g., additives). Here we tested the efficacy of different reagents to mimic the elemental phases bonded to meso- and microplastic in the environment, in relation to the grade of ageing and the polymer composition. Results showed that a relatively high portion of trace elements is bonded in a weak phase and that other phases abundant in other matrices (e.g., oxides and bonded to organic matter) are only present to a limited degree in the plastic samples. The comparison of different sample types highlighted the important role of plastic ageing in governing interactions with trace elements, while the polymer composition has a limited influence on this process. Finally, the future steps toward a tailored extraction scheme for environmental plastic are proposed.

Plastic-associated metal(loid)s in the urban river environments of Mongolia

The widespread distribution of plastic debris in riverine environment is one of the major concerns of environmental pollution because of its potential impact on the aquatic ecosystem. In this study, we investigated the accumulation of metal(loid)s on polystyrene foam (PSF) plastics collected from the floodplain of the Tuul River of Mongolia. The metal(loid)s sorbed on plastics were extracted from the collected PSF via sonication after peroxide oxidation. The size-dependent association of metal(loid)s with plastics indicates that PSFs act as vectors for pollutants in the urban river environment. The mean concentrations of metal(loid)s (i.e., B, Cr, Cu, Na, and Pb) indicate a higher accumulation of the metal(loid)s on meso-sized PSFs compared with macro- and micro-sized PSFs. In addition, the images from scanning electron microscopy (SEM) indicated not only the degraded surface of plastics showing fractures, holes, and pits but also the adhered mineral particles and microorganisms on the PSFs. The interaction of metal(loid)s with plastics was probably facilitated by the physical and chemical properties of altered surface of plastics through photodegradation, followed by an increase in surface area by size reduction and/or biofilm development in the aquatic environment. The enrichment ratio (ER) of metals on PSF samples suggested the continuous accumulation of heavy metals on plastics. Our results demonstrate that the widespread plastic debris could be a carrier of hazardous chemicals in the environment. Considering that the negative impacts of plastic debris on environmental health are major concerns to be addressed, the fate and behavior of the plastics especially their interaction with pollutants in aquatic environments should be further studied.

Sorbed environmental contaminants increase the harmful effects of microplastics in adult zebrafish, Danio rerio

Aquatic animals ingest Microplastics (MPs) which have the potential to affect the uptake and bioavailability of sorbed co-contaminants. However, the effects on living organisms still need to be properly understood. The present study was designed to assess the combined effects of MPs and environmental contaminants on zebrafish (Danio rerio) health and behavior. Adult specimens were fed according to three different protocols: 1) untreated food (Control group); 2) food supplemented with 0.4 mg/L pristine polyethylene-MPs (PE-MPs; 0.1-0.3 mm diameter) (PEv group); 3) food supplemented with 0.4 mg/L PE-MPs previously incubated (PEi group) for 2 months in seawater. Analysis of contaminants in PEi detected trace elements, such as lead and copper. After 15 days of exposure, zebrafish underwent behavioral analysis and were then dissected to sample gills and intestine for histology, and the latter also for microbiome analysis. Occurrence of PEv and PEi in the intestine and contaminants in the fish carcass were analyzed. Both PEv- and PEi-administered fish differed from controls in the assays performed, but PEi produced more harmful effects in most instances. Overall, MPs after environmental exposure revealed higher potential to alter fish health through combined effects (e.g. proportion of microplastics, pollutants and/or microorganisms).

Investigation of microplastic ingestion in commercial fish from Surabaya river, Indonesia

Microplastics (MPs) were recognized as emerging environmental contaminants and ubiquitously distributed in aquatic environments, including in commercial biota. Fish are estimated as one of the most susceptible aquatic biota to ingesting microplastic (MP). Commercial fish cultivation is commonly developed in urban rivers. This situation may lead to food web safety and human health risks because most fish products are commercially available for consumption. Surabaya River, one of the main rivers in Indonesia, has been polluted by MPs. This river takes essential parts for providing clean water for Surabaya City and fishery. This study aimed to investigate: (1) MP ingestion, abundance, characteristics in commercial fish species in Surabaya River, and (2) potential influencing factors to MP ingestion in the fish. The MP ingestion was found in gills and gastrointestinal tracts (GITs) of seven commercial fish species from the Surabaya River. The highest MP abundance was found in the gill of Trichopodus trichopterus (280.73 ± 162.25 particles/g WW), in the GIT of Rasbora argyrotaenia (358.75 ± 121.98 particles/g WW), and in Notopterus notopterus (186 ± 130.81 particles/individual). The MP abundance was positively correlated to fish body size. The predominant MP polymer in both fish organs was cellophane. These MPs were mostly fiber-shaped, large-sized, and black-colored. The MP ingestion in the fish might be influenced by active/passive uptake routes, specific feeding habits, preference habitats, fish size, and MP characteristics. This investigation reveals the occurrence of MP ingestion in commercial fish, which is closely associated with human health risks via trophic transfer by accidental consumption.

Microalgae colonization and trace element accumulation on the plastisphere of marine plastic debris in Monastir Bay (Eastern Tunisia)

In this study, we examined the toxicity potential of the epiplastic microalgal community that developed on low-density polyethylene (LD-PE) plastic debris found in two distinct regions of the Monastir Bay (Tunisia): the coast exposed to anthropogenic discharges and the open sea in front of the Kuriat Islands. Concentrations of potentially toxic elements (PTEs) accumulated in sediments and plastisphere were compared in order to determine their toxicity potential to biological life. The collected plastispheres were predominantly composed of cyanobacteria, chlorophytes, and diatoms. Diatoms display a relatively high diversity (25 species). At all stations, potentially harmful microalgae (PHM) were more abundant in the plastisphere than in seawater and the coastal zone seems to harbour increased number of potentially harmful cyanobacteria within the plastisphere. At the offshore station S1, the PHM community was dominated by the potentially harmful diatoms belonging to the genus Pseudo-nitzschia. Phormidium sp. was the main potentially harmful cyanobacterium identified in the plastisphere of S1. PTEs concentration in the plastisphere was higher than in sediment and ranking with very high contamination factors at all sites according to the sequence Pb > Cu > Cd > Ni > Zn. The highest accumulation of PTEs in the plastisphere was recorded near harbors and industrial zones with important human interference. This work shows that plastisphere can be a threat to vulnerable species not only because it can contain PHM but also because it can accumulate PTEs.

UV and chemical aging alter the adsorption behavior of microplastics for tetracycline

This study evaluates the "vector" effects of different microplastics (MPs) on coexisting pollutants. The adsorption of tetracycline was studied on biodegradable plastics poly(butylene adipate-co-terephthalate) (PBAT) and non-biodegradable plastics polystyrene (PS), polypropylene (PP), and polyethylene (PE) after UV aging and chemical aging. The physicochemical properties of PBAT changed more obviously after UV radiation and chemical aging comparing to PS, PP and PE. Pores and cracks appear on the surface of aged PBAT. The crystallinity increased from 29.2% to 52.62%. In adsorption experiments, pristine and aged PBAT had strong vector effects on the adsorption of tetracycline than PS, PP and PE. The adsorption capacity of tetracycline on PBAT was increased from 0.7980 mg g^-1 to 1.2669 mg g^-1 after chemical aging. The adsorption mechanism indicated that electrostatic interactions and hydrogen bonds contribute to the adsorption process. In addition, for the adsorption of tetracycline on PS, π-π interaction was the main cause, and the adsorption mechanism was not considerably changed by aging. In conclusion, this study demonstrates that biodegradable plastics have substantial vector effect on coexisting pollutants at the end of their life cycle, this contributes to assessment of the risk from microplastic pollution.

Physicochemical and biological ageing processes of (micro)plastics in the environment: a multi-tiered study on polyethylene

Pollution by plastic and microplastic impacts the environment globally. Knowledge on the ageing mechanisms of plastics in natural settings is needed to understand their environmental fate and their reactivity in the ecosystems. Accordingly, the study of ageing processes is gaining focus in the context of the environmental sciences. However, laboratory-based experimental research has typically assessed individual ageing processes, limiting environmental applicability. In this study, we propose a multi-tiered approach to study the environmental ageing of polyethylene plastic fragments focusing on the combined assessment of physical and biological processes in sequence. The ageing protocol included ultraviolet irradiation in air and in a range of water solutions, followed by a biofouling test. Changes in surface characteristics were assessed by Fourier transform infrared spectroscopy, scanning electron microscopy, and water contact angle. UV radiation both in air and water caused a significant increase in the density of oxidized groups (i.e., hydroxyl and carbonyl) on the plastic surface, whereby water solution chemistry influenced the process both by modulating surface oxidation and morphology. Biofouling, too, was a strong determinant of surface alterations, regardless of the prior irradiation treatments. All biofouled samples present (i) specific infrared bands of new surface functional groups (e.g., amides and polysaccharides), (ii) a further increase in hydroxyl and carbonyl groups, (iii) the diffuse presence of algal biofilm on the plastic surface, and (iv) a significant decrease in surface hydrophobicity. This suggests that biological-driven alterations are not affected by the level of physicochemical ageing and may represent, in real settings, the main driver of alteration of both weathered and pristine plastics. This work highlights the potentially pivotal role of biofouling as the main process of plastic ageing, providing useful technical insights for future experimental works. These results also confirm that a multi-tiered laboratory approach permits a realistic simulation of plastic environmental ageing in controlled conditions.

Comprehensive analysis of spatial distribution of microplastics in Rawal Lake, Pakistan using trawl net and sieve sampling methods

Occurrence of microplastics (MPs) in freshwater environments, particularly reservoir and lakes, is an emerging concern. There are limited studies in Pakistan on microplastic pollution in the lacustrine environments and those that exist do not provide sufficient information on the spatial distribution of MPs in offshore surface water. The aims of this study were to determine microplastic abundance in Rawal Lake, Pakistan and to ascertain if sampling methodology influences microplastic counts. Surface water samples were collected from 10 sites; 5 tributaries, 2 human settlement and 3 fishing and boating areas using two different sampling techniques: 100 μm mesh trawl and 20 L sample through a 45 μm mesh sieve. A significant difference was observed in the abundance of MPs across two methods with the sieve method yielding 2.8 ± 1.44 particles/L and trawl yielding 0.025 ± 0.024 particles/L. Tributaries and boating/fishing area had higher microplastic abundance than the residential area regardless of sampling method. Filaments were the dominant shape of MPs in both type of samples followed by fragments in trawl samples and films in sieved samples. Microbeads were only detected in trawl samples. MPs within size range 0.1-0.9 mm were mostly fragments (82%). MPs were diverse in colors with white/transparent and black MPs common. Polypropylene was the main type of microplastic in Rawal Lake (40-74%). Scanning Electron Microscopy (SEM) of MPs showed cracks, roughness and striations on the particles. Energy Dispersive Spectroscopy (EDS) detected heavy metals (Fe, Cu, Ni, Pb, Zn, Co and Cr) in MPs. Findings suggest that microplastic pollution in Rawal Lake may pose great risk to aquatic and human life through leaching of inherent/adsorbed heavy metals and therefore requires future investigation.

Sulfide modifies physicochemical properties and mercury adsorption of microplastics

Microplastics (MPs) tend to accumulate and undergo a sulfur weathering process that leads to significant surface changes in sulfur-rich anaerobic environments, such as sewage and wastewater treatment plants. Aged MPs can have a profound impact on environmental behaviors of various toxic pollutants, especially heavy metals. Although previous studies have investigated the adsorption characteristics of metal ions on MPs that are aged in aerobic environments, the sorptive interactions of sulfur-aged MPs in anaerobic environments with mercury, i.e., Hg(II), are largely unknown. In this study, laboratory investigations were conducted to study the sorptive behaviors of Hg(II) by six common MPs treated anaerobically in the presence of sulfide. Adsorption isotherms show that the sulfur aging process greatly enhances the MP sorption capacity of Hg(II). The mechanisms including changes in the specific surface area, electrostatic interactions, surface precipitation, and surface functional groups are responsible for the enhanced adsorption capacities of sulfur-aged MPs. The thiol group that forms on the MP surface plays a dominant role in enhancing the MP adsorption capacity of Hg(II), which is determined by the formation of unsaturated bonds in the molecular chains of MPs. Furthermore, the pathways of surface chemical transformation of MPs during sulfur aging have been proposed. This study promotes our understanding of the potential hazard of MPs as well as the fate and transport of heavy metals in the presence of aged MPs.

Plastisphere on microplastics: In situ assays in an estuarine environment

In this study, the influence of the plastisphere on metals accumulation and weathering processes of polystyrene (PSMPs) and nylon microplastics (NyMPs) in polluted waters during a 129 day-assay were studied. MPs were characterized through scanning electron microscopy (SEM) with Energy dispersive X-ray (EDX), X-ray diffraction (XRD), attenuated total reflectance Fourier transformed infrared (ATR-FTIR) spectroscopy, contact angle, and thermogravimetric analysis (TGA). Also Cr, Mn, Zn, Cd, Pb, and Cu in the plastisphere on MPs were analyzed during the assay. Potentially pathogenic Vibrio, Escherichia coli, and Pseudomonas spp. were abundant in both MPs. Ascomycota fungi (Phona s.l., Alternaria sp., Penicillium sp., and Cladosporium sp.), and yeast, were also identified. NyMPs and PSMPs exhibited a decrease in the contact angle and increased their weights. SEM/EDX showed weathering signs, like surface cracks and pits, and leaching TiO₂ pigments from NyMPs after 42 days. XRD displayed a notorious decrease in NyMPs crystallinity, which could alter its interaction with external contaminants. Heavy metal accumulation on the plastisphere formed on each type of MPs increased over the exposure time. After 129 days of immersion, metals concentrations in the plastisphere on MPs were in the following order Cr ˃ Mn ˃ Zn ˃ Cu ˃ Pb ˃ Cd, demonstrating how the biofilm facilitates metal mobilization. The results of this study lead to a better understanding of the impact of marine plastic debris as vectors of pathogens and heavy metals in coastal environments.

Risk associated with microplastics in urban aquatic environments: A critical review

The presence of microplastics (MPs) has been recognized as a significant environmental threat due to adverse effects spanning from molecular level, organism health, ecosystem services to human health and well-being. MPs are complex environmental contaminants as they bind to a wide range of other contaminants. MPs associated contaminants include toxic chemical substances that are used as additives during the plastic manufacturing process and adsorbed contaminants that co-exist with MPs in aquatic environments. With the transfer between the water column and sediments, and the migration within aquatic systems, such contaminants associated MPs potentially pose high risk to aquatic systems. However, only limited research has been undertaken currently to link the environmental risk associated with MPs occurrence and movement behaviour in aquatic systems. Given the significant environmental risk and current knowledge gaps, this review focuses on the role played by the abundance of different MP species in water and sediment compartments as well as provides the context for assessing and quantifying the multiple risks associated with the occurrence and movement behaviour of different MP types. Based on the review of past literature, it is found that the physicochemical properties of MPs influence the release/sorption of other contaminants and current MPs transport modelling studies have primarily focused on virgin plastics rather than aged plastics. Additionally, risk assessment of contaminants-associated MPs needs significantly more research. This paper consolidates the current state-of-the art knowledge on the source to sink movement behaviour of MPs and methodologies for assessing the risk of different MP species. Moreover, knowledge gaps and emerging trends in the field are also identified for future research endeavours.

Alkaline aging significantly affects Mn(II) adsorption capacity of polypropylene microplastics in water environments: Critical roles of natural organic matter and colloidal particles

Most microplastic particles may undergo various aging in water environments. In this work, surface physicochemical properties were firstly compared among pristine polypropylene (PP-pris) microplastics, and two aged ones obtained after pretreated with HCl (PP-acid) and NaOH (PP-alka). When compared with PP-pris and PP-acid, PP-alka had a much stronger Mn(II) adsorption capacity. The results regarding the role of natural organic matter and colloidal particle concentrations on adsorption demonstrated that for water solutions either containing kaolin or not, humic acid (HA) had significantly negative influence on Mn(II) adsorption capacity of PP-alka due to their complexation and competition effects, and its negative influence became enhanced with increasing kaolin concentrations. Besides, established conceptual models of adsorption were applied to comprehensively explore adsorption mechanisms of PP-alka for Mn(II) in the coexistence of HA and kaolin. An important suggestion was that in complicated adsorption-reactor system, great numbers of microplastics-kaolin heteroaggregates might be formed via ion bridging of Mn(II) and/or polymer bridging of HA. So these formed aggregates were possible to re-organize themselves, under pre-set vibration-speed conditions, for achieving a more stable structure. As a consequence, Mn(II) adsorption behaviors would be affected by changes in steric-hindrance effects of HA molecules and surface charge distribution of resultant heteroaggregates.

Interactions of microplastics with organic, inorganic and bio-pollutants and the ecotoxicological effects on terrestrial and aquatic organisms

As emerging contaminants, microplastics (MPs) have attracted global attention. They are a potential risk to organisms, ecosystems and human health. MPs are characterized by small particle sizes, weak photodegradability, and are good environmental carriers. They can physically adsorb or chemically react with organic, inorganic and bio-pollutants to generate complex binary pollutants or change the environmental behaviors of these pollutants. We systematically reviewed the following aspects of MPs: (i) Adsorption of heavy metals and organic pollutants by MPs and the key environmental factors affecting adsorption behaviors; (ii) Enrichment and release of antibiotic resistance genes (ARGs) on MPs and the effects of MPs on ARG migration in the environment; (iii) Formation of "plastisphere" and interactions between MPs and microorganisms; (iv) Ecotoxicological effects of MPs and their co-exposures with other pollutants. Finally, scientific knowledge gaps and future research areas on MPs are summarized, including standardization of study methodologies, ecological effects and human health risks of MPs and their combination with other pollutants.

CH4 and CO2 Emissions from the Decomposition of Microplastics in the Bottom Sediment—Preliminary Studies

In recent years, a significant new threat to the environment has emerged, namely contamination with microplastics and their degradation products. The decomposition products of microplastics include, among others, greenhouse gases that are responsible for climate change. The article analyzes the emission of carbon dioxide and methane during the decomposition of various types of plastics in the form of microplastics in the bottom sediments in the presence of water. The research covers plastic materials made of polyvinyl chloride with a high and low content of plasticizers, polypropylene, and rubber. All analyzed microplastics generated the tested greenhouse gases. However, the quantity of gases generated depended on the type of polymer used. The highest concentration of methane, at 25,253 ppm after 180 days of incubation, was characterized by high plasticizer polyvinyl chloride, i.e., di (2-ethylhexyl) phthalate. In the case of carbon dioxide emissions, the values were comparable. The maximum value was obtained at 65,662 ppm for polypropylene microplastics. The influence of particle size on the amount of the emissions of these gases was also investigated. During the decomposition of microplastics in the bottom sediments in the presence of water, it was observed that the smaller the microplastic particles are, the greater the production of methane and carbon dioxide.

Generation of micro(nano)plastics and migration of plastic additives from Poly(vinyl chloride) in water under radiation-free ambient conditions

A batch experiment was conducted to observe the liberation of micro- and nano-sized plastic particles and plastic additive-originated organic compounds from poly(vinyl chloride) under radiation-free ambient conditions. The weathering of PVC films in deionized water resulted in isolated pockets of surface erosion. Additional ^●OH from Fenton reaction enhanced PVC degradation and caused cavity erosion. The detachment of plastic fragments from the PVC film surfaces was driven by autocatalyzed oxidative degradation. Over 90% of micro-sized plastic particles were <60 μm in length. The detached plastic fragments underwent intensified weathering, which involved strong dehydrochlorination and oxidative degradation. Further fragmentation of micro-sized particles into nano-sized particles was driven by oxidative degradation with complete dehydrochlorination being achieved following formation of nanoplastics. 20 organic compounds released from the PVC films into the solutions were identified. And some of them can be clearly linked to common plastic additives. In the presence of additional ^●OH, the coarser nanoplastic particles (>500 nm) tended to be rapidly disintegrated into finer plastic particles (<500 nm), while the finest fraction of nanoplastics (<100 nm) could be completely decomposed and disappeared from the filtrates. The micro(nano)plastics generated from the PVC weathering were highly irregular in shape.

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.

Adsorption of Different Pollutants by Using Microplastic with Different Influencing Factors and Mechanisms in Wastewater: A Review

The studies on microplastics are significant in the world. According to the literature, microplastics have greatly specific surface areas, indicating high adsorption capacities for highly toxic pollutants in aquatic and soil environments, and these could be used as adsorbents. The influencing factors of microplastic adsorption, classification of microplastics, and adsorption mechanisms using microplastics for adsorbing organic, inorganic, and mixed pollutants are summarized in the paper. Furthermore, the influence of pH, temperature, functional groups, aging, and other factors related to the adsorption performances of plastics are discussed in detail. We found that microplastics have greater advantages in efficient adsorption performance and cost-effectiveness. In this paper, the adsorptions of pollutants by microplastics and their performance is proposed, which provides significant guidance for future research in this field.

Microplastics in the Gulf of Mexico: A Bird’s Eye View

Microplastic debris is a persistent, ubiquitous global pollutant in oceans, estuaries, and freshwater systems. Some of the highest reported concentrations of microplastics, globally, are in the Gulf of Mexico (GoM), which is home to the majority of plastic manufacturers in the United States. A comprehensive understanding of the risk microplastics pose to wildlife is critical to the development of scientifically sound mitigation and policy initiatives. In this review, we synthesize existing knowledge of microplastic debris in the Gulf of Mexico and its effects on birds and make recommendations for further research. The current state of knowledge suggests that microplastics are widespread in the marine environment, come from known sources, and have the potential to be a major ecotoxicological concern for wild birds, especially in areas of high concentration such as the GoM. However, data for GoM birds are currently lacking regarding typical microplastic ingestion rates uptake of chemicals associated with plastics by avian tissues; and physiological, behavioral, and fitness consequences of microplastic ingestion. Filling these knowledge gaps is essential to understand the hazard microplastics pose to wild birds, and to the creation of effective policy actions and widespread mitigation measures to curb this emerging threat to wildlife.

Aging behavior of microplastics affected DOM in riparian sediments: From the characteristics to bioavailability

Riparian zone is a hub for microplastics (MPs), and MPs accumulation also changes the function of the riparian zone (e.g., carbon pool) to pose a great threat to river ecosystems. Although it is known that MPs can be aged for changing their characteristic after accumulating in riparian sediment, the effect of MP aging behavior on sediment dissolved organic matter (DOM) bioavailability and carbon emission has not been elucidated. In this study, effects of pristine and aged MPs on the DOM characteristics and components were investigated in sediment. The results showed that pristine MPs increased DOM humification and promoted the formation of larger molecular weight components, thereby reducing DOM bioavailability by approximately 16~23% and inducing negative priming effect. However, inhibition of MPs on DOM bioavailability and the priming effect decreased with aging behavior. Mathematical models revealed that the fulvic acid-like substance of sediment DOM was the driven factor in the influence of sediment carbon stability. Further microbial analysis found that higher carbohydrate metabolism promoted DOM humification, thereby reducing CO₂ emissions approximately by 19~26% after MPs accumulation. Thus, this study provided an integrated picture to understand the risk of MPs accumulation in sediment for a long term on terrestrial and aquatic ecosystems.

Recent advances in toxicological research and potential health impact of microplastics and nanoplastics in vivo

As emerging pollutants, direct and indirect adverse impacts of micro(nano)plastics (MPs/NPs) are raising an increasing environmental concern in recent years due to their poor biodegradability and difficulty in recycling. MPs/NPs can act as carriers of bacteria, viruses, or pollutants (such as heavy metals and toxic organic compounds), and may potentially change the toxicity and bioavailability of pollutants. Ingested or attached MPs/NPs can also be transferred from low-trophic level organisms to high-nutrient organisms or even the human body through the food chain transfer process. This article reviews the emerging field of micro- and nanoplastics on organisms, including the separate toxicity and toxicity of compound after the adsorption of organic pollutants or heavy metals, as well as possible mechanism of toxicological effects and evaluate the nano- and microplastics potential adverse effects on human health. The inherent toxic effects MPs/NPs mainly include the following: physical injury, growth performance decrease and behavioral alteration, lipid metabolic disorder, induced gut microbiota dysbiosis and disruption of the gut's epithelial permeability, neurotoxicity, damage of reproductive system and offspring, oxidative stress, immunotoxicity, etc. Additionally, MPs/NPs may release harmful plastic additives and toxic monomers such as bisphenol A, phthalates, and toluene diisocyanate. The vectors' effect also points out the potential interaction of MPs/NPs with pollutants such as heavy metals, polycyclic aromatic hydrocarbons, organochlorine pesticides, polychlorinated biphenyls, perfluorinated compounds, pharmaceuticals, and polybrominated diphenyl ethers. Nevertheless, these potential consequences of MPs/NPs being vectors for contaminants are controversial.

The Burden of Microplastics Pollution and Contending Policies and Regulations

The relationship between humans and plastics has become intricate due to their versatile nature and low production cost. Plastics generation has surpassed that of other manufactured products, which, coupled with the prevailing poor waste management systems, makes it a serious problem for the terrestrial and aquatic environments as its final destination. Their extensive presence has continued to pose a significant threat, not only to the aquatic ecosystem but also to the approximately 3 billion people relying on it for their livelihood. Even more disturbing were the recent findings of these plastics in food and drinking water and the evidence of human exposure, the long-term health effects of which are largely unknown. This ubiquitous phenomenon has over time put plastics under critical observation, leading to the development of many local and international policies, resolutions, and directives aimed at addressing and reversing the menace. This review provided the first snapshot of the global and local governance strategies currently aimed at mitigating plastic pollution, their limitations, and future directions. The findings of the review revealed several aspects of microplastics (MPs) pollution to be overlooked in policy formulation, a laxity in policy implementation, and an apparent lack of indices to ascertain the impact of the regulations. Furthermore, there is currently no regulation on MPs contamination of food and drinking water and an apparent lack of funding for research into the health effects of plastics and their alternatives. This, therefore, necessitates the need for a well-coordinated approach at international and national levels to scale up these policies in all countries and translate them from paper to measurable, holistic, and realizable actions that will address all forms of plastic pollution.

What Are Lake Beaches Made of? An Assessment of Plastic Beach Litter on the Shores of Como Bay (Italy)

Plastic waste dispersion is a well-recognized environmental threat, despite continuous efforts towards improving waste disposal management over the last few decades. Plastic litter is known to strongly impact upon water bodies and shorelines, affecting the health of ecosystems and impacting upon the aesthetic value of sites. Moreover, plastic waste that is abandoned on beaches contributes towards different degradation processes that potentially lead to the formation of secondary microplastics (MPs), with likely cascade effects upon the whole ecosystem. In this view, this study aims to characterize the plastic beach litter found on the shores of the western basin of Como Lake (Italy) to better understand the origin of MPs in littoral sediments, including the recognition of object typologies and the chemical characterization of polymers using Fourier-transformed infrared analysis (FTIR). The results highlighted that the most abundant polymers on beaches are polypropylene (PP) and polyethylene (PE), representing 73% of the collected polymers. This confirms that floating, low-density polymers are more likely to accumulate on beaches. Moreover, almost 66% of litter is represented by commonly used manufactured items (disposable objects, packaging, and everyday items). This evidence, combined with the analysis of the main environmental features of the sampling sites (the main winds, distance to urban areas, and the presence of tributaries) indicate that abundance of beached litter is mainly linked to beach accessibility and the local winds. These results highlight that multiple factors affect the environmental fate of plastic litter and give insights into the assessment of secondary microplastics in beach sediments.

Transport and retention patterns of fragmental microplastics in saturated and unsaturated porous media: A real-time pore-scale visualization

The environmental behaviors of microplastics (MPs) have garnered ever-increasing attention globally. To overcome the limitations of commonly used "black box", a real-time pore-scale visualization system including microscope, charge coupled device (CCD) microscope camera, and flow cell (connected with pump and sample collector) was used to unravel the transport and retention mechanisms of fragmental microplastics (FMPs) in saturated and unsaturated porous media. The breakthrough curves (BTCs) of effluent concentrations from the flow cells were used to quantitatively analyze FMPs transport. The videos gathered from different transport scenarios indicated that FMPs can move along with the bulk flow in porous media, but also move around the sand surfaces via sliding, rolling, and saltating patterns. The FMPs were retained in porous media mainly via deposition and straining in saturated porous media. Interestingly, little FMPs were captured by the air-water interface in unsaturated conditions. The mobility of FMPs varied with environmental factors, which became lower at higher solution ionic strength (IS), smaller grain size, and lower water content in porous media. Flow rate barely affected the transport of FMPs under 0.1 mM IS with the mass recovery rate ranging between 65.8 and 67.5%, but significantly enhanced FMPs mobility under 10 mM IS through reducing the moving rate. The IS and grain size showed a more significant effect on the transport of FMPs in unsaturated porous media. Our findings, for the first time, visually deciphered the transport and retention patterns of MPs with fragmental shapes on pore-scale, expanding our current knowledge of the fate and transport of more realistic MPs in the environment.

Exploring the Adsorption of Pb on Microalgae-Derived Biochar: A Versatile Material for Environmental Remediation and Electroanalytical Applications

Biochar, a carbon material obtained by pyrolysis of biomasses, is increasingly applied in environmental remediation and sensing thanks to its functional properties, cost-effectiveness and eco-friendliness. The adsorption capacity of biochar, strictly dependent on its specific surface area, heteroatom doping and surface functional groups, is crucial for these applications. Here, biochar produced at low temperature (350 °C) from a marine microalga (Nannochloropsis sp.) is proposed as an efficient adsorbent of lead (II) ions in aqueous solution; this production strategy promotes the natural self-doping of biochar without requiring harsh conditions. The kinetics and thermodynamics of the adsorption process, as well as the effect of pH, ionic strength and dissolved organic matter on the adsorption efficiency were systematically assessed. The microalgae-derived biochar shows superior adsorption performances compared to a nutshell-derived one (used as a reference of lignocellulosic feedstocks) under all the tested conditions. The microalgae-derived biochar was finally used to decorate screen-printed carbon electrodes to improve the electroanalytical performances towards the voltammetric detection of lead (II) ions. A two-fold increase in sensitivity was obtained compared to the unmodified electrode thanks to the enhanced electron transfer and adsorption properties provided by biochar. These results highlight the potentialities of microalgae-derived biochar for environmental and sensing applications.

A Rapid Method for Detecting Microplastics Based on Fluorescence Lifetime Imaging Technology (FLIM)

With the increasing use and release of plastic products, microplastics have rapidly accumulated in ecological environments. When microplastics enter the food chain, they cause serious harm to organisms and humans. Microplastics pollution has become a growing concern worldwide; however, there is still no standardized method for rapidly and accurately detecting microplastics. In this work, we used fluorescence lifetime imaging technology to detect four kinds of Nile red-stained and unstained microplastics, and the unique phasor fingerprints of different microplastics were obtained by phasor analysis. Tracing the corresponding pixels of the “fingerprint” in the fluorescence lifetime image allowed for the quick and intuitive identification of different microplastics and their location distributions in a mixed sample. In our work, compared with staining the four microplastics with a fluorescent dye, using the phasor “fingerprint library” formed by the autofluorescence lifetimes of the microplastics was more easily distinguished than microplastics in the mixed samples. The feasibility of this method was further tested by adding three single substances—SiO₂, chitin and decabromodiphenyl ethane (DBDPE), and surface sediments to simulate interferent in the environment, and the results providing potential applications for the identification and analysis of microplastics in complex environments.

Release of Microplastics from Reusable Kitchen Plasticware and Generation of Thermal Potential Toxic Degradation Products in the Oven

Plastics are one of the most important technical materials at present, yet they are associated with a whole series of environmental problems such as micro-and nanoplastics or their plasticizers, which have become increasingly relevant in recent years. While there are many studies that focus on microplastics (MPs) introduced into the human body through commercially produced food, there are nearly none that consider the MPs we ingest through homemade food made with plastic kitchen utensils such as mixing bowls. To investigate this, samples were obtained by exposing different plastic bowls made of acrylonitrile–butadiene–styrene (ABS), polypropylene (PP), melamine, polyethylene (PE), polystyrene (PS), and styrene–acrylonitrile (SAN), to mechanical stress and then analyzed via infrared spectroscopy. This not only raises the question of whether microplastics are incorporated into foods but also the extent to which the degradation products produced by thermal stress in an oven could play a toxicological role. Degradation products were generated by pyrolysis and analyzed afterwards using gas chromatography mass spectrometry. There were differences in the number of microplastic particles abraded by the different types of plastic, with the most consisting of melamine (898 particles) and the least consisting of low-density polyethylene (331 particles). There were also differences in the number and relevance of the thermal degradation products for the different plastics, so that a human toxicological assessment would have to be evaluated in further work.

"Non-traditional" stable isotopes applied to the study of trace metal contaminants in anthropized marine environments

The advent of Multicollector ICP-MS inaugurated the analysis of new metal isotope systems, the so-called "non-traditional" isotopes. They are now available tools to study geochemical and ecotoxicological aspects of marine metal contamination and hence, to push the frontiers of our knowledge. However, such applications are still in their infancy, and an accessible state-of-the-art describing main applications, obstacles, gaps, and directions for further development was missing from the literature. This paper fills this gap and aims to encourage the marine scientific community to explore the contributions of this newly available information for the fields of chemical risk assessment, biomonitoring, and trophic transfer of metal contaminants. In the current "Anthropocene" epoch, metal contamination will continue to threaten marine aquatic ecosystems, and "non-traditional" isotopes can be a valuable tool to detect human-induced changes across time-space involving metal contaminants, and their interaction with marine biota.