Study on the capability and characteristics of heavy metals enriched on microplastics in marine environment

Microplastics altered contaminant behavior and toxicity in natural waters

Microplastics (MPs) have received an increasing attention because of their ubiquitous presence and aquatic toxicity associated with MPs and MP-bound contaminants in the natural water. This review is to critically examine the chemical additives leached from MPs, the altered contaminant behaviors and the resulting changes in their aquatic ecotoxicity. Available data suggest that heavy metals Zn, Cr, Pb, and Cd regulated and present in plastics at the sub-mg g^-1 to mg g^-1 level can leach a significant amount depending on MPs size, aging, pH, and salinity conditions. MP-bound organic contaminants are primarily additive-derived (e.g., brominated diphenyl ethers, nonylphenol, and bisphenol A) at the µg g^-1 to mg g^-1 level, and secondarily pyrogenic and legacy origins (e.g., PAHs and PCBs) in the range of ng g^-1 and mg g^-1. MPs tend to have higher but more variable sorption capacities for organic compounds than metals (1.77 ± 2.34 vs. 0.82 ± 0.94 mg g^-1). MPs alter the behavior of heavy metals through the electrostatic interactions and surface complexation, while the transport of additive derived organic compounds are altered primarily through hydrophobic effect as supported by a positive correlation (R² = 0.71) between the logarithmic MPs-adsorbed concentrations and octanol/water partition coefficients (K_OW) of organic compounds. MPs constitute less than 0.01% of the total mass of aquatic particulates in typical waters, but play a discernible role in the local partitioning and long-distance movement of contaminants. MPs alone exert higher toxicity to invertebrates than algae; however, when MPs co-occur with pollutants, both synergistic and antagonistic toxicities are observed depending mainly on the ingestibility of MPs, the extent of sorption, MPs as a transport vector or a sink to scavenge pollutants. We finally suggest several key areas of future research directions and needed data concerning the role of MPs in mitigating pollutant leaching, transport and risk under conditions mimicking natural and polluted waters.

Adsorption behavior of Cu(II) and Cr(VI) on aged microplastics in antibiotics-heavy metals coexisting system

Recently, the microplastics, as well as the compound pollution of heavy metals and antibiotics, in the aqueous environment have attracted increasing attention, but studies on the behavior of heavy metals on aged microplastics in antibiotics-heavy metals coexisting system are limited. Herein, to explore the impact of antibiotics on the adsorption of heavy metals by aged microplastics, the adsorption behavior of Cu(II) and Cr(VI) on aged polystyrene (PS) and polyvinyl chloride (PVC) were investigated. The results presented that ciprofloxacin (CIP) had negative and positive impacts on the adsorption of Cu(II) and Cr(VI) by aged microplastics, respectively. Moreover, the existence of CIP seemed to have no evident effect on the type of adsorption isotherm model and kinetic model in most adsorption systems of Cu(II). The negative impact of CIP on adsorption of Cu(II) may result from the competition adsorption and high steric hindrance effect, while non-specific interactions between neutral antibiotic-heavy metal complexes and the hydrophobic surface of aged microplastics as well as CIP as bridges influenced positively on adsorption of Cr(VI) on aged microplastics. This work was concerned with the interaction between binary pollutants and aging microplastics to clarify the risks of microplastics in the aqueous environment.

Current status of microplastics pollution in the aquatic environment, interaction with other pollutants, and effects on aquatic organisms

Microplastics, as emerging pollutants, have received great attention in the past few decades due to its adverse effects on the environment. Microplastics are ubiquitous in the atmosphere, soil, and water bodies, and mostly reported in aqueous environment. This paper summarizes the abundance and types of microplastics in different aqueous environments and discusses the interactions of microplastics with other contaminants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), antibiotics, and heavy metals. The toxicity of microplastics to aquatic organisms and microorganisms is addressed. Particularly, the combined toxic effects of microplastics and other pollutants are discussed, demonstrating either synergetic or antagonistic effects. Future prospectives should be focused on the characterization of different types and shapes of microplastics, the standardization of microplastic units, exploring the interaction and toxicity of microplastics with other pollutants, and the degradation of microplastics, for a better understanding of the ecological risks of microplastics.

Speciation and release risk of heavy metals bonded on simulated naturally-aged microplastics prepared from artificially broken macroplastics

The negative impact of microplastics (MPs) act as metals vectors to environment and ecosystem have been paid more and more attention, and the accumulation risk of them to human body through the food chains and food webs needs to attract attention. In addition, the MPs bonded with heavy metals transport from river into the sea with high salinity may also have metals release risk. Herein, natural aged microplastics prepared from artificially broken macroplastics adsorbed with heavy metals accumulated from the natural environment were tested for their states and release risk in several simulated solution (NaCl and gastrointestinal solutions) to understand their effects on environment and human health. The adsorption capacity of different heavy metals on MPs was different during natural aging process proved by four-acid digestion method. Metals with high accumulation (including Pb, As, Cr, Mn, Ni, Zn, Co, Cu and Cd) on NAMPs were selected for further study. Results obtained via three-step extraction method showed that these heavy metals were mainly present as acid-extractable and reducible ions, which were characterized by high bioavailability. Release experiments suggested the notable Mn, Zn, As, Cr, Cu and Ni release in NaCl solution, and significant release of Mn, Zn, As, Cr, Cu, Pb and Ni in gastrointestinal solutions. The high metal release ratio in the simulated gastric solution was attributed to the weak binding of metal ions to NAMPs in acidic environment. This study will play a vital rule in assessing the ecological risks associated with MPs in natural environment.

Particles rather than released Zn2+ from ZnO nanoparticles aggravate microplastics toxicity in early stages of exposed zebrafish and their unexposed offspring

Knowledge on the interaction between microplastics (MPs) and zinc oxide nanoparticles (ZnO NPs) is limited. Here, we investigated effects of embryo-larvae exposure to 500 μg/L polystyrene MPs (5 µm), 1200 μg/L ZnO NPs (< 100 nm), 500 μg/L dissolved Zn²⁺ from ZnSO4^, and the mixtures of MPs and ZnO NPs or ZnSO4 on exposed F0 larvae and unexposed F1 larvae. Consequently, ZnO particles adhered to MPs surfaces rather than Zn²⁺, and increased Zn transport into larvae. Growth inhibition, oxidative stress, apoptosis, and disturbance of growth hormone and insulin-like growth factor (GH/IGF) axis were induced by MPs and ZnO NPs alone, which were further aggravated by their co-exposure in F0 larvae. MPs + ZnO increased apoptotic cells in the gill and esophagus compared with MPs and ZnO NPs alone. Reduced growth and antioxidant capacity and down-regulated GH/IGF axis were merely observed in F1 larvae from F0 parents exposed to MPs + ZnO. Contrary to ZnO NPs, dissolved Zn²⁺ reversed MPs toxicity, suggesting the protective role of Zn²⁺ may be not enough to ameliorate thfie negative effects of ZnO particles. To summarize, we found that particles rather than released Zn²⁺ from ZnO nanoparticles amplified MPs toxicity in early stages of exposed zebrafish and their unexposed offspring.

A critical review of microplastics in the soil-plant system: Distribution, uptake, phytotoxicity and prevention

Microplastics (MPs) are creating an emerging threat on the soil ecosystems and are of great global concern. However, the distribution in soil-plant system, as well as the phytotoxicity and impact mechanisms of MPs remain largely unexplored so far. This study introduced the diverse sources of MPs and showed the significant spatial variation in the global geographic distribution of MPs contamination based on data collected from 116 studies (1003 sampling sites). We systematically discussed MPs phytotoxicity, such as plant uptake and migration to stems and leaves, delaying seed germination, impeding plant growth, inhibiting photosynthesis, interfering with nutrient metabolism, causing oxidative damage, and producing genotoxicity. We further highlighted the alterations of soil structure and function by MPs, as well as their self and load toxicity, as potential mechanisms that threaten plants. Finally, this paper provided several preventive strategies to mitigate soil MPs pollution and presented research gaps in the biogeochemical behavior of MPs in soil-plant systems. Meanwhile, we recommended that methods for the quantitative detection of MPs accumulated in plant tissues should be explored and established as soon as possible. This review will improve the understanding of the environmental behavior of MPs in soil-plant systems and provide a theoretical reference to better assess the ecological risk of MPs.

Microbial adaptation to co-occurring vanadium and microplastics in marine and riverine environments

Vanadium (V) and microplastics have been respectively detected in environmental media, posing threats to ecosystem and human health. However, their co-existence situations in environment with microbial adaptation have been poorly understood. In this study, water and sediments collected from potential V polluted marine and riverine ecosystems were analyzed to reveal the distribution of V and microplastics with microbial responses. High concentrations of V (1.65-6.92 μg/L in water and 6.16-347.92 mg/kg in sediment) and microplastics (800-15600 item/m³ in water and 20-700 item/kg in sediment) co-occurred in aquatic environment. Less rich and diverse bacterial communities were colonized on microplastics compared to surrounding environment. Plastic-degrading taxa (e.g., Ralstonia, Rhodococcus) and V(V) reducers (e.g., Bacillus, Pseudomonas) were enriched in microplastic biofilms. Redundancy analysis showed that V, together with nutrients, ambient conditions and Cr, contributed significantly to the compositions of microbial community on microplastics. Besides directly acting on microbial community, V could also alter it by influencing environmental factors (e.g., pH), as indicated through structural equation model. This study advances understanding the previously ignored interactions of biogeochemical processes of V and microplastics in aquatic environment.

Microplastics as an aquatic pollutant affect gut microbiota within aquatic animals

The adverse impact of microplastics (MPs) on gut microbiota within aquatic animals depends on the overall effect of chemicals and biofilm of MPs. Thus, it is ideal to fully understand the influences that arise from each or even all of these characteristics, which should give us a whole picture of consequences that are brought by MPs. Harmful effects of MPs on gut microbiota within aquatic organisms start from the ingestion of MPs by aquatic organisms. According to this, the present review will discuss the ingestion of MPs and its following results on gut microbial communities within aquatic animals, in which chemical components, such as plastic polymers, heavy metals and POPs, and the biofilm of MPs would be involved. This review firstly analyzed the impacts of MPs on aquatic organisms in detail about its chemical components and biofilm based on previous relevant studies. At last, the significance of field studies, functional studies and complex dynamics of gut microbial ecology in the future research of MPs affecting gut microbiota is discussed.

Insights into the interaction of microplastic with silver nanoparticles in natural surface water

The combined pollution induced by microplastics (MPs) and other pollutants, such as nanomaterials, has received increasing attention. The interaction between MPs and silver nanoparticles (AgNPs) may affect both their behaviors in natural environments, however, knowledge on these effects remains limited. In this study, AgNPs and three common MPs, polypropylene (PP), polyethylene (PE), and polystyrene (PS), were co-exposed to natural freshwater and brackish water to investigate the interaction between MPs and AgNPs in natural surface water. The results showed that the environmental behaviour of AgNPs in natural freshwater and brackish water is first of all affected by water chemistry and only in second instance affected by MPs. In natural freshwater, AgNPs remained stable largely dominated by dissolved organic matter (DOM), parts of which were subsequently captured by three MPs in the form of single particles without significant difference. In contrast, both ionic strength and DOM contributed to the aggregation of AgNPs in natural brackish water. PE and PP captured a small amount of AgNPs in the form of aggregates in natural brackish water, while the majority of AgNP aggregates were trapped by PS in natural brackish water. Therefore, both water chemistry and MPs types were found to play crucial roles in the interaction between MPs and AgNPs. These observations also revealed that MPs could serve as carriers for AgNP transport and advance the current understanding of combined pollution between MPs and engineered nanomaterials in natural aquatic environments.

Microplastics as a vehicle of heavy metals in aquatic environments: A review of adsorption factors, mechanisms, and biological effects

Microplastics (MPs) have recently attracted much attention due to their widespread distribution in the aquatic environment. Microplastics can act as a vector of heavy metals in the aquatic environment, causing a potential threat to aquatic organisms and human health. This review mainly summarized the occurrence of microplastics in the aquatic environment and their interaction with heavy metals. Then, we considered the adsorption mechanisms of MPs and heavy metals, and further critically discussed the effects of microplastics properties and environmental factors (e.g., pH, DOM, and salinity) on the adsorption of heavy metals. Finally, the potential risks of combined exposure of MPs and heavy metals to aquatic biota were briefly evaluated. This work aims to provide a theoretical summary of the interaction between MPs and heavy metals, and is expected to serve as a reference for the accurate assessment of their potential risks in future studies.

Direct identification and visualisation of real-world contaminating microplastics using Raman spectral mapping with multivariate curve resolution-alternating least squares

Microplastics (MPs) contamination is ubiquitous in environmental matrices worldwide. Moreover these pollutants can be ingested by organisms and transported to organs via the circulatory system. Although efficient methods for the analysis of MPs derived from environment matrices and organisms' tissue samples have been developed after special sample pre-treatment, there remains a need for an optimised approach allowing direct identification and visualisation these MPs in real environmental matrices and organismal samples. Herein, we firstly used a multivariate curve resolution-alternating least squares (MCR-ALS) analysis of Raman hyperspectral imaging data to direct identification and visualisation of MPs in a complex serum background. Four common MPs types including polyethylene (PE), polystyrene (PS), polypropylene (PP) and polyethylene terephthalate (PET) were identified and visualised either individually or in mixtures within spiked samples at an 8-μm spatial resolution. Moreover, Raman imaging based on MCR-ALS was successfully applied in fish faeces biological samples and environmental sand samples for in situ MPs identification directly without washing or removal of organic matter. The current results demonstrate Raman imaging based on MCR-ALS as a novel imaging approach for direct identification and visualisation of MPs, through extraction of MPs' chemical spectra within a complicated biological or environmental background whilst eliminating overlapping Raman bands and fluorescence interference.

Size-dependent adsorption of waterborne Benzophenone-3 on microplastics and its desorption under simulated gastrointestinal conditions

Microplastics (MPs) are global pollutants with heightened environmental and health concerns in recent years because of their worldwide distribution across aquatic environments, ability to load chemical contaminants and the potential for ingestion by animals, including human. In this study, three commonly used and environmentally detected plastics, i.e. polystyrene, polyethylene, polypropylene with sizes of 550, 250 and 75 μm, plus two submicron-sized polystyrene microplastics (5 and 0.5 μm) were assessed as solid adsorbents for a prevalent UV filter, benzophenone-3 (BP-3). The affinity and process of adsorption exhibited differentials among different sizes and types of MPs. Apparent desorption of BP-3 from MPs under simulated gastrointestinal conditions was not significantly enhanced, which might be due to the presence of the enzyme proteins, indicating potential risk of the contaminants carried by MPs. The desorption of BP-3 from MPs was affected by the size, type of MPs and the components of the gastrointestinal fluid.

Characterization and source analysis of heavy metals contamination in microplastics by Laser-Induced Breakdown Spectroscopy

The increasing presence of microplastics in marine environment is a critical issue and the plastic-metal contamination has received much attention. However, conventional methods for heavy metal determination are time-consuming, need sample pretreatments, require a strict operation environment, or have high limits of detection. In this study, heavy metals contaminated microplastics samples collected from a remote coral island were quantified and analyzed by using Laser-Induced Breakdown Spectroscopy (LIBS). The characters of the trace metals in microplastics were used to determine the sources of the contaminants, and the potential origins of the metals were demonstrated from the statistical analysis. LIBS is a facile and non-destructive trace analysis technique and the strategy led to rapid and multi-metals detection of individual samples. Heavy metals such as copper (Cu), lead (Pb), iron (Fe), cadmium (Cd), zinc (Zn), manganese (Mn), chromium (Cr) were detected and quantified in the individual microplastics samples. The findings showed that LIBS is a promising strategy for the characterization of microplastics and for the analysis of the source of heavy metals contaminants present in the microplastics particles.

Spatial distribution and potential sources of microplastics in the Songhua River flowing through urban centers in Northeast China

Microplastics (MPs) have elicited increasing concerns in freshwater systems worldwide. However, little information is available on the MP pollution in the Songhua River, the third largest river in China. And the understanding of the sources and pathways of MPs is limited. In this study, MPs were sampled from river water and wastewater treatment plants in five cities along the Songhua River to investigate the occurrence, spatial distribution, characteristics, and potential sources of MPs. Polyethylene, polypropylene and polystyrene accounted for more than 95% of the total MPs. MP pollution was determined to be spatially heterogeneous. The concentration of MPs in the urban center was always considerably higher than that in the upper reach, and irregular variation was observed from the urban center to the lower reach for each city. Urbanization was one of the primary driving forces of spatial variability. Statistically significant positive correlations (p-value < 0.05) were noted between the average concentration of MPs in river water and population density (p = 0.0023) and number of industrial enterprises above designated size (p = 0.0042) of each city. Line and fiber were the major shapes, and white was the most dominant color. Large (1-5 mm) and small (≤ 1 mm) MP particles accounted for 50% each. Multiple correspondence analysis as a new methodological approach was conducted to elucidate the sources of MPs for the first time. The potential sources of MPs included daily use, fishing, agricultural, and industrial productions. This work provides information about MP contamination for future studies on freshwater systems and new insights into the source apportionment of MPs.

Microplastics and trace metals in fish species of the Gulf of Mannar (Indian Ocean) and evaluation of human health

The importance of microplastic (MPs) contamination in marine environments is reflected by increasing number of studies in fish species. Some even dedicated to the toxicological effects from the ingestion. Microplastics (MPs) and their trace metal composition were examined in the muscle and intestine of five commercially important fish species (i.e., Sufflamen fraenatus, Heniochus acuminatus, Atropus atropos, Pseudotriacanthus and Leiognathus brevirostris) from Thoothukudi at the Gulf of Mannar coast in south India. The abundance and morphology of MPs (size, shape, and texture) in muscle and intestinal were investigated by micro-Fourier Transform Infrared Spectroscopy (μ-FT-IR) and atomic force microscope (AFM). ICP-OES was used to investigate the adsorption/leaching of trace metals in microplastics in order to assess health risk for adults and children. Particles of 100-250 μm and white color dominated, and the mean abundances (items/100 g) of total MPs were more in Pseudotriacanthus (muscle: 51.2; intestine: 50.1) compared to Heniochus acuminatus (muscle: 9.6; intestine: 15), Leiognathus brevirostris (muscle: 12; intestine: 13.2) and Atropus atropus (muscle: 15.2; intestine: 44.1). Polyethylene (35.3%), polypropylene (27.2%), polyamide (nylon) (22.2%) and fiber (15.3%) represented the MPs present in muscles, and polyamide (nylon) (30.2%), polyethylene (28.1%), polypropylene (25.9%), and fiber (15.8%) composed the intestine MPs. We estimated possible consumption of 121-456 items of MPs/week by adults and about 19-68 items of MPs/week by children by considering the sizes of safe meals. Zn, Cu, Mn and Cr in these fish species reflected influence of the sewage waste. However, the non-carcinogenic risk evaluated through EDI, THQ, HI, and CR did not suggest any immediate health problem for the consumers.

Unique metalloid uptake on microplastics: The interaction between boron and microplastics in aquatic environment

Boron pollution in the aquatic environment has a hazardous effect on human health and the ecosystem as a metalloid pollutant, and few researchers have focused on the potential interaction between boron and microplastics. We investigated the adsorption of boron on four types of microplastics (polyvinyl chloride (PVC), aged PVC, polystyrene (PS), and aged PS). The adsorption behavior was explored by kinetics, isotherm models, and several aqueous factors, including pH, humic acid, ionic strength (Na⁺), metal ion types (Mg²⁺, Ca²⁺, Cu²⁺, and Al³⁺), and the seawater environment. The adsorption capacities on microplastics were followed: aged PVC (0.91 mg/g) > aged PS (0.197 mg/g) > virgin PVC (0.1 mg/g) > virgin PS (0.005 mg/g). The adsorption kinetics and isotherm models suggested monolayer adsorption and chemisorption. Humic acid and high pH significantly inhibited the adsorption due to the complexation and hydrolysis of boric acid (B(OH)₃), respectively. The presence of metal ions may enhance or hinder adsorption, depending on the boron species, ion concentration, ion type, and microplastics categories. The unique interaction mainly depended on surface complexations of B(OH)₃ with oxygen-containing groups on microplastics surface. Because aged microplastics have more oxygen-containing groups, they can combine more B(OH)₃, and PVC can adsorb more boron due to the CCl bond and surface diffusion. In the aquatic environment, however, metal ions may occupy these binding sites, and the electrostatic force between borate ([B(OH)₄]^-) and microplastics will take precedence. In the simulated intestines of warm-blooded animals, we achieved the greatest boron desorption ratio on microplastics. This work explored the adsorption characteristics of boron by microplastics and revealed potential environmental risks of metalloid enrichment.

Microplastics pollution in the ocean: Potential carrier of resistant bacteria and resistance genes

Microplastics pollution in marine environments is concerning. Microplastics persist and accumulate in various sections of the ocean where they present opportunity for micropollutant accumulation and microbial colonisation. Even though biofilm formation on plastics was first reported in the 1970's, it is only in recent years were plastic associated biofilms have gained research attention. Plastic surfaces pose a problem as they are a niche ready for colonisation by diverse biofilm assemblages, composed of specific bacterial communities and putative pathogens prone to acquiring ARGs and resistance in the biofilm. However, the nature of antibiotic resistance on aquatic plastic debris is not yet fully understood and remains a concern. Given the inevitable increase of plastic production and waste generation, microplastics released into the environment may prove to be problematic. This review explores microplastic waste in the ocean and possible concerns that may arise from the presence of microplastics in conjunction with favourable conditions for the development and dispersal of antibiotic resistance in the ocean and food web.

Recent advances on ecological effects of microplastics on soil environment

The mass production and wide application of plastics and their derivatives have led to the release of a large number of discarded plastic products into the natural environment, where they continue to accumulate due to their low recycling rate and long durability. These large pieces of plastic will gradually break into microplastics (<5 mm), which are highly persistent organic pollutants and attract worldwide attention due to their small particle size and potential threats to the ecosystem. Compared with the aquatic system, terrestrial systems such as soils, as sinks for microplastics, are more susceptible to plastic pollution. In this article, we comprehensively summarized the occurrence and sources of microplastics in terrestrial soil, and reviewed the eco-toxicological effects of microplastics in soil ecosystems, in terms of physical and chemical properties of soil, soil nutrient cycling, soil flora and fauna. The influence of microplastics on soil microbial community, and particularly the microbial community on the surface of microplastics, were examined in detail. The compound effects of microplastics and other pollutants, e.g., heavy metals and antibiotics, were addressed. Future challenges of research on microplastics include development of new techniques and standardization for the extraction and qualitative and quantitative analysis of microplastics in soils, toxic effects of microplastics at microbial or even molecular levels, the contribution of microplastics to antibiotic resistance genes migration, and unraveling microorganisms for the degradation of microplastics. This work provides as a better understanding of the occurrence, distribution and potential ecological risks of microplastics in terrestrial soil ecosystems.

Horizontal variation of microplastics with tidal fluctuation in the Chao Phraya River Estuary, Thailand

Microplastic (MP) pollution in estuarine environments is poorly characterized globally, although they are extensive buffer regions between terrestrial, freshwater and seawater environments. This research aims to investigate MP pollution levels and variations of MPs abundance with tidal fluctuation. Fourteen samples were collected from the surface water of the Chao Phraya River Estuary, Thailand using the Manta net at flood and ebb tides. The average abundance of microplastics at flood tide was 5.16 × 10⁵ particles/km² and at ebb tide was 3.11 × 10⁵ particles/km². The abundance of microplastics in the estuary was directly related to the tidal fluctuation, creating an accumulation of microplastics in the study area. Polypropylene, polyethylene, and polystyrene were the most common polymers. The findings provide important information on the pollution status of microplastics in the Chao Phraya River Estuary and the variation of suspended microplastics with tidal fluctuation should be considered in future estuarine microplastic studies.

Interactions and effects of microplastics with heavy metals in aquatic and terrestrial environments

Contamination of waters and soils with microplastics (MPs) is an emerging environmental issue worldwide. MPs constitute a cocktail of various additives and polymers besides adsorbing toxic heavy metals from the environment. This co-occurrence of MPs with heavy metals poses a threat to the health of organisms and is poorly understood. Ingestion of MPs contaminated with heavy metals may also result in subsequent transfer of heavy metals up in the food chain. MPs surfaces play a crucial role in the adsorption of heavy metals. Aged/biofouled MPs facilitate greater adsorption of metals and certain microplastic (MP) polymers adsorb some metals more specifically. External factors involved in the process of adsorption/accumulation of heavy metals are the solution pH, salinity, and the concentration of relevant heavy metals in the media. Desorption greatly depends upon pH of the external solution. This is more concerning as the guts/digestive systems of organisms have low pH which could enhance the desorption of toxic metals and making them accumulate in their bodies. The aim of this article is to discuss the abundance, distribution, adsorption, and desorption behavior of MPs for heavy metals, and their combined toxic effects on flora and fauna based on the limited research on this topic in the literature. There is an overarching need to understand the interactions of MPs with heavy metals in different ecosystems so that the extent of ecotoxic effects they pose could be assessed which would help in the environmental regulation of these pollutants.

Microplastics pollution in the intertidal limpet, Nacella magellanica, from Beagle Channel (Argentina)

Microplastics (MPs) have been identified in diverse marine invertebrates; however, there are few studies on limpets. This study aimed to evaluate and compare the presence of MPs in Nacella magellanica among sites of the Beagle Channel with different degree of anthropogenic influence. Intertidal limpets were sampled in three sites: Ushuaia Bay (UB) (inside Ushuaia city), a site with high anthropogenic influence owing to population growth, and fisheries, industrial and port activities; Ensenada Zaratiegui (EZ) and Playa Larga (PL) (west and east of Ushuaia city, respectively), both sites with a certain degree of environmental protection and low anthropogenic influence. MPs were isolated from the whole soft tissue of individuals by oxidative digestions with H₂O₂ (30%; 1:10 w/v). MPs occurrence was 100% in organisms from UB and EZ, whereas 90% in PL. Limpets from UB showed 10 ± 6.69 MPs/ind and 2.22 ± 0.78 MPs/g ww, while in PL and EZ there were 2.90 ± 2.02 MPs/ind and 0.96 ± 0.94 MPs/g ww; and 5.60 ± 2.59 MPs/ind and 2.41 ± 1.47 MPs/g ww, respectively. Fibres were the most abundant MPs type, followed by fragments and films. Fibres and films were identified as semi-synthetic cellulose and, although the polymer matrix of fragments was masked by copper phthalocyanine, one of them could be identified as polystyrene. As expected, the highest abundance of MPs was found in UB. However, a lower abundance of particles was detected in PL (downstream of UB) than in EZ (upstream of UB). This could be due to the influence of both the main current of the Beagle Channel and fluvial discharges, reducing the buoyancy of MPs. More studies are needed to understand the contribution of regional and local features to the accumulation of MPs in these environments and their interaction with the biota.

Coexistence and Adsorption Properties of Heavy Metals by Polypropylene Microplastics

Plastic particles with a diameter of 5 mm or less are called microplastics. Microplastics are one of the primary sources of pollution in the environment. It has been proven that microplastics are also carriers of heavy metals, but there are few studies on their adsorption mechanism. In this study, the adsorption of Pb, Cu, Cd, and Zn by polypropylene (PP) microplastics was analyzed and discussed. The morphology of PP was observed by scanning electron microscopy (SEM), the surface elemental composition of PP was determined by X-ray photoelectron spectroscopy (XPS), and the functional groups of PP were analyzed by Fourier transform infrared spectroscopy (FTIR). The results showed that the adsorption behavior of microplastics to different heavy metals could be balanced in 32 hours. Kinetics experiments showed that the adsorption process could be fitted well by a two-stage dynamic model, and the adsorption of Pb and Cu by PP is greater than that of Cd and Zn. The Freundlich model has the best fitting effect on Pb for the adsorption isothermal results. The Langmuir model showed that the process is favorable for adsorption. The adsorption of mixed heavy metals by microplastics showed that when the concentration of the mixed adsorption mass was low, the presence of a coexistence system promoted the adsorption of Zn and Cu by microplastics. With an increasing concentration, the adsorption of 4 heavy metals by microplastics is inhibited.

Review of Microplastic Distribution, Toxicity, Analysis Methods, and Removal Technologies

Microplastic contamination has become a problem, as plastic production has increased worldwide. Microplastics are plastics with particles of less than 5 mm and are absorbed through soil, water, atmosphere, and living organisms and finally affect human health. However, information on the distribution, toxicity, analytical methods, and removal techniques for microplastics is insufficient. For clear microplastic analytical methods and removal technologies, this article includes the following: (1) The distribution and contamination pathways of microplastics worldwide are reviewed. (2) The health effects and toxicity of microplastics were researched. (3) The sampling, pretreatment, and analytical methods of microplastics were all reviewed through various related articles. (4) The various removal techniques of microplastics were categorized by wastewater treatment process, physical treatment, chemical treatment, and biological treatment. This paper will be of great help to microplastic analysis and removal techniques.

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

Plastic and microplastic pollution is an environmental and societal concern. The interaction of plastic with organic chemicals in the environment has attracted scientific interest. New evidences have highlighted an unexpectedly high affinity of environmental plastics also for metal ions. The degree and typology of plastic ageing (including from mechanical, UV and biological degradations) appear as a pivotal factor determining such an interaction. These earlier evidences recently opened a new research avenue in the plastic pollution area. This review is the first to organize and critically discuss knowledge developed so far. Results from field and laboratory studies of metal accumulation on plastic are presented and the environmental factors most likely to control such an interaction are discussed. On the light of this knowledge, a generalist conceptual model useful for building hypotheses on the mechanisms at stake and directing future studies was elaborated and presented here. Furthermore, all available data on the thermodynamics of the plastic-metal interaction obtained from laboratory experiments are inventoried and discussed here, highlighting methodological and technical challenges that can potentially affect cross-comparability of data and their relevance for environmental settings. Finally, insights and recommendations on experimental approaches and analytical techniques that can help overtaking current limitations and knowledge gaps are proposed.

Microplastics (MPs) Act as Sources and Vector of Pollutants-Impact Hazards and Preventive Measures

Currently, people are paying more and more attention to the interaction between microplastics (MPs) and chemical substances (including metals and organic substances), so it is necessary to understand the relationship between MPs and chemical substances. In this review, we explored (1) MPs may become a source of chemical substances. (2) MPs can also be used as a carrier for attaching pollutants. (3) No matter what role MPs play, MPs and the attached chemical substances will have harmful effects on biological systems. However, because the current research is not deep enough, more experimental areas are needed to explore the interaction mechanism and the principle of toxicity. In addition, laws and policies need to be developed that actively promote and strive to develop biodegradable alternative microplastics to reduce the harm of microplastics and their additives to the environment.

Characteristics of expanded polystyrene microplastics on island beaches in the Pearl River Estuary: abundance, size, surface texture and their metals-carrying capacity

While expanded polystyrene (EPS) microplastics have been widely recognized as one of the most important components of plastic litter in the intertidal zones of the global ocean, our understanding of their environmental fate on island beaches is insufficient. In this study, we intended to reveal that the latest EPS microplastic pollution status on 5 island beaches in the Pearl River Estuary, China, by comprehensively assessing the abundance, distribution, size, surface texture and carrying capacity of heavy metals (Cd, As, Cr, Ni, Cu, Pb, Mn, Fe, Al). High level of EPS microplastic abundance ranged from 328 to 82,276 particles m^-2 was found, with the highest abundance at Guishan Island and the lowest at Dong'ao Island. Spatial distribution of EPS microplastic abundance was significantly different among different islands. EPS microplastics in the size range of 1-2 mm were the most abundant. The content of heavy metals in EPS microplastics collected on the beaches was greater than that in the new EPS products. The average concentrations of heavy metals in EPS microplastics from 5 islands are Cd (0.27 ± 0.19 μg g^-1), As (5.50 ± 3.84 μg g^-1), Cr (14.9 ± 8.25 μg g^-1), Cu (15.0 ± 7.66 μg g^-1), Ni (17.2 ± 17.6 μg g^-1), Pb (24.8 ± 7.39 μg g^-1), Mn (730 ± 797 μg g^-1), Fe (8340 ± 4760 μg g^-1), and Al (9624 ± 6187 μg g^-1), respectively. The correlation between heavy metals in EPS microplastics and sediments was better than that between heavy metals in EPS microplastics and seawater. The study results indicated that EPS microplastics could act as a carrier for the transport of heavy metals, which might pose a threat to biological and human health.

Influence of Microplastics on the Mobility, Bioavailability, and Toxicity of Heavy Metals: A Review

Microplastics (MPs) can pose ecological risk to the environment and have the potential to negatively affect human health, raising serious public concerns. It is recognized that MPs could act as a vector for various environmental pollutants including heavy metals and potentially influencing their mobility, fate, and bioavailabilty in the environment. However, knowledge on the mechanisms underpinning the interaction processes between MPs and heavy metals is far from clear. This review discusses the effects of MPs on the adsorption/desorption, speciation and bioavailability, and toxicity of various heavy metals. The present review also systematically identifies the environmental factors (e.g., pH, ionic strength, and organic matters) that could affect their interaction processes. This work aims to establish a meaningful perspective for a comprehensive understanding of the indirect ecological risks of MPs as vectors for contaminants. The work also provides a reference for the development of better regulatory strategies in mitigating the negative effects caused by the co-existence of MPs and heavy metals.

Enhanced sorption of the UV filter 4-methylbenzylidene camphor on aged PET microplastics from both experimental and theoretical perspectives

In this study, the morphology and sorption behavior of polyethylene terephthalate (PET) microplastics during the aging process are investigated. To clarify the sorption mechanism of aged PET microplastics, the common sunblock 4-methylbenzylidene camphor (4-MBC) was chosen as the target contaminant, and UV irradiation was used for the laboratory aging simulation. The results show that oxygen-containing functional groups (carboxylic, carbonyl, ketone and hydroxyl groups) increase on the surface of aged PET microplastics. Based on density functional theory (DFT) simulations, the camphor part of 4-MBC acts as a hydrogen bond acceptor, whereas the carboxylic group on aged PET microplastics acts as a hydrogen bond donor. The formation of hydrogen bonding causes increased sorption of 4-MBC on aged PET microplastics. The sorption capacity increased from 5 to 11 μg g^-1 for 50 ppb 4-MBC with 100 mg PET microplastics after a five-day aging process. Other environmental factors that affect sorption were also identified; a higher pH value and the presence of salinity reduced the amount of sorption. The sorption of virgin PET ranged from 8.0 to 3.4 μg g^-1 and the sorption of aged PET ranged from 22 to 5 μg g^-1 at pH 4 to 10. In the presence of salinity (10% seawater), the virgin PET sorption dropped to 2.1 μg g^-1 while the aged PET sorption dropped to 4 μg g^-1. A similar phenomenon was also observed in the sorption behavior under natural sunlight (the sorption of PET increased from 0.4 to 0.8 μg g^-1 after 6 months of aging). The potential risk to ecosystems of aged PET microplastics under prolonged sunlight exposure in the natural environment could be greater than that predicted for virgin microplastics.

A critical review on the interactions of microplastics with heavy metals: Mechanism and their combined effect on organisms and humans

Although individual toxicity of microplastics (MPs) to organism has been widely studied, limited knowledge is available on the interactions between heavy metals and MPs, as well as potential biological impacts from their combinations. The interaction between MPs and heavy metals may alter their environmental behaviors, bioavailability and potential toxicity, leading to ecological risks. In this paper, an overview of different sources of heavy metals on MPs is provided. Then the recent achievements in adsorption isotherms, adsorption kinetics and interaction mechanism between MPs and heavy metals are discussed. Besides, the factors that influence the adsorption of heavy metals on MPs such as polymer properties, chemical properties of heavy metals, and other environmental factors are also considered. Furthermore, potential combined toxic effects from MPs and heavy metals on organisms and human health are further summarized.

Questioning the suitability of available microplastics models for risk assessment - A critical review

The rise of microplastic (MP) pollution in the environment has been bolstering concerns regarding MPs' unknown environmental fate, transport, and potential toxicity toward living forms. However, the use of real environmental plastics for risk assessment is often hindered due to technical and practical challenges such as plastics' heterogeneity and their wide size distribution in the environment. To overcome this issue, most available data in the field is generated using plastic models as surrogates for environmental samples. In this critical review, we describe the gaps in risk assessments drawn from these plastic models. Specifically, we compare physicochemical properties of real environmental plastic particles to synthesized polymeric micro-beads, one of the most commonly used plastic models in current literature. Several surface and bulk characteristics including size, surface chemistry, polymer type, and morphology are shown to not only be inherently different between environmental MP's and synthesized micro-beads, but also drive behavior in fate, transport, and toxicity assays. We highlight the importance of expressing real-world physicochemical characteristics in representative MP models and outline how current state-of-the-art models are limited in this regard. To address this issue, we suggest future areas of research such as combinations of mechanical, photochemical, and thermal degradation processes to simulate real-world weathering, all in an effort to increase realism of plastic modeling and allow more robust and reliable environmental MP risk assessment in the future.

Ecotoxicological effects of microplastics on aquatic organisms: a review

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

Occurrence, effect, and fate of residual microplastics in anaerobic digestion of waste activated sludge: A state-of-the-art review

The plastic products have large consumption over last decades, resulting in a serious microplastics (MPs) pollution. Specially, the main removal way of MPs from wastewater is to transfer MPs from liquid to solid phase, leading to its enrichment in waste activated sludge (WAS). Anaerobic digestion has been served as the most potential technique to achieve both resource recovery and sludge reduction, herein this review provides current information on occurrence, effect, and fate of MPs in anaerobic digestion of WAS. The effects of MPs on WAS anaerobic digestion are greatly related to forms, particles sizes, contents, compositions and leachates of MPs. Also, the presence of MPs not only can change the effects of other pollutants on anaerobic digestion of WAS, but also can affect the fates of them. Besides, the future perspectives focused on the fate, effect and final removal of MPs during WAS anaerobic digestion process are outlined.

Effects of polystyrene microplastic on uptake and toxicity of copper and cadmium in hydroponic wheat seedlings (Triticum aestivum L.)

Microplastics are widespread in freshwater environments, their biological effects and combined effects of other pollutants have attracted extensive attention. In this study, we investigated the adsorption properties of heavy metals onto polystyrene (PS) microplastics as well as the bioavailability and toxicity of microplastics and heavy metals by hydroponic wheat seedlings experiment. Results showed that PS microplastics (0.5 µm, 100 mg/L) had no significant effect on wheat seedlings growth, photosynthesis, and reactive oxygen species (ROS) content. However, PS microplastics could adsorb copper and cadmium, with a predominantly chemisorption. The accumulation of copper and cadmium in wheat seedlings reduced in the presence of PS microplastics, which meant the toxic effect by heavy metals might be mitigated. Compared with single heavy metals treatments, the combination of PS microplastics and heavy metals increased chlorophyll content, enhanced photosynthesis and reduced the accumulation of ROS. These findings suggest that PS microplastics (0.5 µm, 100 mg/L) have a mitigating effect on the bioavailability and toxicity of copper and cadmium.

Polystyrene Nanoplastics as Carriers of Metals. Interactions of Polystyrene Nanoparticles with Silver Nanoparticles and Silver Nitrate, and Their Effects on Human Intestinal Caco-2 Cells

Environmental plastic wastes are continuously degraded to their micro and nanoforms. Since in the environment they coexist with other pollutants, it has been suggested that they could act as vectors transporting different toxic trace elements, such as metals. To confirm this, we have assessed the potential interactions between nanopolystyrene, as a model of nanoplastic debris, and silver compounds (silver nanoparticles and silver nitrate), as models of metal contaminant. Using TEM-EDX methodological approaches, we have been able to demonstrate metal sorption by nanopolystyrene. Furthermore, using Caco-2 cells and confocal microscopy, we have observed the co-localization of nanopolystyrene/nanosilver in different cellular compartments, including the cell nucleus. Although the internalization of these complexes showed no exacerbated cytotoxic effects, compared to the effects of each compound alone, the silver/nanopolystyrene complexes modulate the cell’s uptake of silver and slightly modify some harmful cellular effects of silver, such as the ability to induce genotoxic and oxidative DNA damage.

Concentrations of trace elements in tissues of loggerhead turtles (Caretta caretta) from the Tyrrhenian and the Ionian coastlines (Calabria, Italy)

Toxic trace elements from both, natural and anthropogenic origin, pose a threat to aquatic environments and marine wildlife due to their long-range transport, bioaccumulative nature, and biomagnification through the food chain. Being long-lived and migratory animals, sea turtles can be exposed to elevated levels of toxic elements, and are therefore considered sentinel species for chemical pollution. In this study, concentrations of trace elements (arsenic, cadmium, lead, mercury) were determined in tissues of 46 loggerhead sea turtles (Caretta caretta) stranded along Tyrrhenian and Ionian coasts of Calabria, in Southern Italy, between 2014 and 2020. Curved carapace length (CCL), curved carapace width (CCW), body mass (BM), and sex were determined and the correlations of these parameters with toxic elements concentrations were investigated. During necropsy, kidney, liver, and muscle tissues were collected and the concentration and distribution of metals determined. Muscle tissues showed the lowest toxic element burdens, except for As that showed the highest mean concentrations in this tissue. The kidney was the main accumulation organ for Cd, while similar levels of Hg and Pb were measured in kidney, liver, and muscle tissues. The risk assessment performed for Cd, Hg, and Pb in sea turtles' liver highlighted possible negative effects on sea turtles' health and the need for marine turtle toxicology researches. This is the first study reporting levels and distribution of toxic elements in tissues of Caretta caretta turtles from the Tyrrhenian and Ionian coasts of Calabria.

The potential of microplastics as adsorbents of sodium dodecyl benzene sulfonate and chromium in an aqueous environment

Considering the omnipresence of microplastics (MPs) in aquatic environments, they are expected to exert significatn impacts as carriers for diverse waterborne pollutants. In this work, the adsorptive behavior of two ionic components (i.e., sodium dodecyl benzene sulfonate (SDBS) and Cr(VI)) has been explored against the two types of MPs as model adsorbents, namely poly (ethylene terephthalate) (PET) and polystyrene (PS). The influence of key variables (e.g., pH, particle size, and dose of the MPs) on their adsorption behavior is evaluated from various respects. The maximum adsorption capacity values of SDBS on PET and PS are estimated to be 4.80 and 4.65 mg⋅g^-1, respectively, while those of Cr(VI) ions are significantly lower at 0.080 and 0.072 mg⋅g^-1, respectively, The adsorptive equilibrium of SDBS is best described in relation to pH and MP size by a Freundlich isotherm. In contrast, the adsorption behavior of Cr(VI) is best accounted for by a Langmuir isotherm to indicate its adsorption across at least two active surface sites.

Adsorption and desorption behaviors of antibiotics by tire wear particles and polyethylene microplastics with or without aging processes

Tire wear particles (TWP), as the significant proportion of microplastics (MPs), has adsorbed much attention due to its widespread presence in aquatic ecosystem. However, compared with traditional MPs, few studies have investigated the interaction between TWP and coexisting contaminants. The adsorption-desorption behavior of chlortetracycline (CTC) and amoxicillin (AMX) by original and aged TWP was studied, and polyethylene (PE) was studied for comparison. After aging, small holes and cracks were produced on the surfaces of the TWP and PE. Meanwhile, the specific surface areas (S_BET) of TWP and PE increased, but the aged TWP had a larger S_BET than the aged PE, which indicated that TWP was more likely to degrade than PE. The adsorption kinetics results showed that the adsorption of CTC and AMX by TWP and PE conformed to the pseudo-second-order model. The adsorption isotherm results showed that the Freundlich model could describe the adsorption isotherm data of TWP and PE. The adsorption capacity of antibiotics by TWP increased by 1.13-23.40 times, and by 1.08-14.24 times on PE, after aging. Desorption experiments showed that the desorption amount of antibiotics on TWP and PE in simulated gastric fluid was greater than that in ultrapure water. The desorption amount and rate of CTC and AMX from TWP were higher than those of PE, indicating that TWP might be more harmful to the aquatic environment and organisms. These findings indicated that, compared with PE, TWP might have stronger carrier effects on antibiotics, which might pose more serious potential risks to the aquatic environment and organisms, especially considering the effects of the aging process. This study would expand the research on environmental risk of MPs and contribute to providing new insights into the evaluation of tire material particles.

Occurrence of microplastic in livestock and poultry manure in South China

Microplastic (MP) contamination in soil has attracted much attention, and increasing evidence suggests that MPs can accumulate in agricultural soils through fertilization by compost. In addition, the most common raw materials for composting are livestock and poultry manure wastes. Because the presence of MPs may threaten the safe utilization of fertilizers composted by livestock and poultry wastes during crop planting, it is necessary to understand the contamination risk of MPs present in livestock and poultry manure. In this study, the distribution of MPs in 19 livestock and poultry farms with 3 different species was investigated by using FTIR microscopy. A total of 115 items manure MPs and 18 items feed MPs were identified as PP and PE types dominated by colorful fragments and fibers. Furthermore, after comparing the compositions of plastic products used in the feeding process, we proposed two transport pathways for MP pollution in manure and one potential transport pathway in feeds. Our result proved that the application of swine and poultry manure directly could be a new route of MPs in agricultural soil, furthermore, the presence of MPs could threaten the safety of resource utilization in agricultural soil by using swine and poultry manure for manure potentially. Not, only that, our study also provided a reference for the remediation of MP-contaminated soil.

Occurrence of microplastics and heavy metals accumulation in native oysters Crassostrea Gasar in the Paranaguá estuarine system, Brazil

The ubiquitous presence of contaminants in the marine environment is considered a global threat to marine organisms. Heavy metals and microplastics are two distinct classes of pollutants but there are interactions between these two stressors that are still poorly understood. We examined the potential relationship between heavy metals (Al, Cr, Mn, Fe, Ni, Cu, Zn, As, Cd, Ba, Hg, Pb) and microplastic particles in oysters sampled along the Paranaguá Estuarine System. The results suggested high levels of As and Zn in the bivalves, which are destined for human consumption. Microplastic particles were found in oysters from all sampled locations, demonstrating the spread of this pollutant in the marine environment and its ability to bioaccumulate in oysters. However, our data did not demonstrate a direct relationship between microplastics and heavy metals, suggesting that these particles are not the main route for heavy metal contamination of oysters in the Paranaguá Estuarine System.

Mechanism analysis of heavy metal lead captured by natural-aged microplastics

In this paper, the mechanism of lead (Pb(II)) captured by natural-aged microplastics in aqueous medium was explored. Compared with pristine microplastics, the natural-aged microplastics were more efficient for adsorbing Pb(II). After treated by hydrochloric acid (HCl) or sodium hydroxide (NaOH), the organic film was damaged and the adsorption efficiency decreased obviously, which proved that the organic film played an important role in Pb(II) capture. The fitting results of the isothermal adsorption model showed that this adsorption process was more in line with Langmuir model than with Freundlich model, and the maximum adsorption amount (13.60 mg/g) could also be obtained from the Langmuir model. Based on the comprehensive analysis of XRD, XPS and FTIR results, it was found that Pb(II) capture by natural-aged microplastics was mainly determined by the oxygen containing functional groups (carboxyl and hydroxyl groups) on the organic film. Besides, the measurement results of Zeta potential and pH effect showed that electrostatic interaction was mainly responsible for the Pb(II) capture process.

Microplastics in the environment: Occurrence, perils, and eradication

Microplastics (MPs) with sizes < 5 mm are found in various compositions, shapes, morphologies, and textures that are the major sources of environmental pollution. The fraction of MPs in total weight of plastic accumulation around the world is predicted to be 13.2% by 2060. These micron-sized MPs are hazardous to marine species, birds, animals, soil creatures and humans due to their occurrence in air, water, soil, indoor dust and food items. The present review covers discussions on the damaging effects of MPs on the environment and their removal techniques including biodegradation, adsorption, catalytic, photocatalytic degradation, coagulation, filtration and electro-coagulation. The main techniques used to analyze the structural and surface changes such as cracks, holes and erosion post the degradation processes are FTIR and SEM analysis. In addition, reduction in plastic molecular weight by the microbes implies disintegration of MPs. Adsorptive removal by the magnetic adsorbent promises complete elimination while the biodegradable catalysts could remove 70-100% of MPs. Catalytic degradation via advanced oxidation assisted by S O 4 • - or O H • radicals generated by peroxymonosulfate or sodium sulfate are also adequately covered in addition to photocatalysis. The chemical methods such as sol-gel, agglomeration, and coagulation in conjunction with other physical methods are discussed concerning the drinking water/wastewater/sludge treatments. The efficacy, merits and demerits of the currently used removal approaches are reviewed that will be helpful in developing more sophisticated technologies for the complete mitigation of MPs from the environment.

Effect of microplastics and arsenic on nutrients and microorganisms in rice rhizosphere soil

The presence of microplastics and arsenic in soil can endanger crop growth; therefore, their effects on the properties of rhizosphere soil should be evaluated. Large (10-100 µm) and small (0.1-1 µm) polystyrene (PSMP) and polytetrafluorethylene (PTFE) particles were added to soil with different arsenic concentrations (1.4, 24.7, and 86.3 mg kg^-1) to investigate the combined effect of microplastics and arsenic pollution on rice rhizosphere soil. After the addition of PSMP and PTFE, pH, arsenic (V) and arsenic (III) in the soil were observed to decrease. The interaction of arsenic with PSMP and PTFE resulted in this phenomenon, leading to a decrease of arsenic bioavailability in the soil. PSMP, PTFE, and arsenic reduced the abundance of Proteobacteria, increased the abundance of Chloroflexi and Acidobacteria, and inhibited soil urease, acid phosphatase, protease, dehydrogenase, and peroxidase activity via affecting the tertiary structure of the enzyme. PSMP, PTFE, and arsenic also reduced the available nitrogen and phosphorus content in the soil. Arsenic increased the soil organic matter content, whereas PSMP and PTFE reduced the organic matter content. Furthermore, microplastics inhibited the effects of arsenic on the microbial and chemical properties of the rhizosphere soil. This study revealed the effects of microplastic and arsenic pollution on rice rhizosphere microorganisms and nutrients, and elucidated the mechanism by which these pollutants retard crop growth in the designed growth medium.

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

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

Why analysing microplastics in floodplains matters: application in a sedimentary context

Microplastics in the environment are a relatively new form of anthropogenic contamination. Right now, the research focus is on the detection of microplastic accumulation in different environmental compartments and understanding the processes that have led to its transport. Detailed information on microplastics in floodplain areas and their distribution in depth are still missing to better understand accumulation points. Therefore, this study presents on the one hand microplastic detection in fluvial sediments from nine sampling sites along a river course. Polymers were determined with infrared spectroscopy and additional sedimentary analysis of the grain size and heavy metal concentration was performed. In total, there was less microplastic in the upper than in the lower river course and slip-off slopes were identified as accumulation hotspots also in deeper sediment layers. Mostly, microplastic particles were detected in fine sediment and heavy metal concentrations along the river were similar to those of microplastics. On the other hand, besides the spatial distribution of microplastics and accumulation in floodplain areas, microplastic analysis offered information in a sedimentary context. Sedimentation rates (0.29-4.00 cm a-1) and patterns between temporal deposition and microplastic polymers were identified. The basis for the development of a dating method by detection of MPs in sediments was thus established. Microplastics as a contaminant provide, in addition to the identification of deposition areas, further data in a temporal and sedimentary perspective.

New insights into the toxic interactions of polyvinyl chloride microplastics with bovine serum albumin

The binding interaction between emerging pollutant polyvinyl chloride microplastics (PVC MPs) and bovine serum albumin (BSA) was studied by fluorescence spectroscopy, resonance scattering spectroscopy (RLS), UV-visible (UV-vis) absorption spectroscopy, circular dichroism (CD), and Fourier transform infrared (FT-IR) spectroscopy under simulative physiological conditions. Fluorescence results revealed that the fluorescence quenching of BSA induced by PVC MPs was originated from the formation of BSA-PVC complex in static quenching mode. According to Stern-Volmer equation, the binding constants (K_a) between PVC MPs and BSA at different temperatures were obtained, and the number of binding sites was 1.62. The thermodynamic parameters, enthalpy change (ΔH), entropy change (ΔS), and free energy change (ΔG) were calculated to be - 41.77 kJ mol^-1, 43.17 J mol^-1 K^-1, and - 54.63 kJ mol^-1 via Van't Hoff equation, indicating electrostatic interaction played a key role in the formation of BSA-PVC complex spontaneously. In addition, the alterations of microenvironment and secondary structure in BSA induced by PVC MPs were further confirmed by synchronous fluorescence spectra, UV-vis, FT-IR, and CD. This work not only provides further information for better understanding the binding interaction of PVC MPs with BSA, but also elucidates the potential biological toxicity of MPs at a molecular level.

Linking effects of microplastics to ecological impacts in marine environments

Recently, efforts to determine the ecological impacts of microplastic pollutants have increased because of plastic's accelerated contamination of the environment. The tiny size, variable surface topography, thermal properties, bioavailability and biological toxicity of microplastics all offer opportunities for these pollutants to negatively impact the environment. Additionally, various inorganic and organic chemicals sorbed on these particles may pose a greater threat to organisms than the microplastics themselves. However, there is still a big knowledge gap in the assessment of various toxicological effects of microplastics in the environment. Ecological risk assessment of microplastics has become more challenging with the current data gaps. Thus, a current literature review and identification of the areas where research on ecology of microplastics can be extended is necessary. We have provided an overview of various aspects of microplastics by which they interact negatively or positively with marine organisms. We hypothesize that biogeochemical interactions are critical to fully understand the ecological impacts, movement, and fate of microplastics in oceans. As microplastics are now ubiquitous in marine environments and impossible to remove, we recommend that it's not too late to converge research on plastic alternatives. In addition, strict actions should be taken promptly to prevent plastics from entering the environment.

Projecting the sorption capacity of heavy metal ions onto microplastics in global aquatic environments using artificial neural networks

Microplastics pollution and their interaction with heavy metal ions have gained global concern. It is essential to develop models to predict the sorption capacity of heavy metal ions onto microplastics in global aquatic environments, and to connect the laboratory study results with the field measurement results. In this paper, the artificial neural networks (ANN) models were established based on literature data. for The results showed that the ANN model could predict the sorption capacity of heavy metal ions (including Cd, Pb, Cr, Cu, and Zn) onto microplastics in the global environments with high correlation coefficient (R) values (0.926∼0.994). The predicted sorption capacity was influenced by the initial concentration of heavy metal ions and the salinity in surrounding water. The predicted sorption capacity in rivers and lakes was higher than that in the ocean. Aged microplastics had higher affinity to heavy metal ions than virgin microplastics. The predicted sorption capacity of Cd, Pb, and Zn ions onto large microplastics (5 mm) was less than 0.12 μg/g. The predicted amount was in agreement with the field measurement results, suggesting that the laboratory studies can provide useful information for projecting the sorption capacity of heavy metal ions onto microplastics in global aquatic environments.

Hazardous microplastic characteristics and its role as a vector of heavy metal in groundwater and surface water of coastal south India

Study of hazardous microplastics in the natural water resources is minimal compared to the sea salt, seafood and even packaged water. We presented results of the first baseline research of microplastics in groundwater and surface water from the coastal south India (Tamil Nadu state) and evaluated the heavy metal adsorption capacities of different polymers. The microplastics (up to 19.9 particles/L) were of relatively larger size in surface water (0.34-4.30 mm) compared to the groundwater (0.12-2.50 mm). Polyamide (nylon), polyester, polypropylene, polyethylene, polyvinyl chloride and cellulose were the common polymers and all of them showed different capacities of heavy metal adsorption. In two different experimental sites, the polypropylene showed higher capacity of adsorption compared to other polymers in the following orders: (i) cadmium > manganese > lead > arsenic and (ii) manganese > zinc > arsenic > lead > copper. The polyamide, however, exhibited better adsorption only for manganese. Similar to other recent findings, our results associate microplastics as a major vector to transport heavy metals in the water system. Formulation of strategies to reduce the environmental risks of particulate plastics as a potent vector for transportation of the toxic trace elements and subsequent, impact on human health through the OSPRC framework (Origins, Sources, Pathways, Receptors and Consequence) in the study area would require future research.

Microplastic's story

The problem of microplastic pollution is now the order of the day in front of everyone's eyes affecting the environment and the health of leaving creature. This work aims to retrace the history of microplastics in a critical way through a substantial bibliographic collection, defining the points still unresolved and those that can be resolved. Presence of marine litter in different environments is reviewed on a global scale, focusing in particular on micro and macro plastics definition, classification and characterization techniques.