Surface adsorption of metallic species onto microplastics with long-term exposure to the natural marine environment

Trophic and environmental influences on trace element concentrations in Australian fur seals

Trace elements (TE) in living organisms can have detrimental health impacts depending on their concentration. As many TEs are obtained through diet, trophic niche changes associated with the impacts of anthropogenic activities and climate-change may influence exposure to top predators. The Australian fur seal (Arctocephalus pusillus doriferus; AUFS) represents the greatest resident, marine predator biomass in south-eastern Australia. With adult female foraging ranges limited to the continental shelf, their source of TEs is geographically restricted. Plasma, red blood cell and milk samples collected between 1998 and 2022 at Kanowna Island, were analysed for TEs (As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, Sn, V and Zn) using inductively-coupled plasma mass-spectrometry (ICP-MS). Plasma fatty-acid profiles and ocean climate variables were used to investigate trophic and environmental influences, respectively, on TE concentrations. Estimated whole blood concentrations in lactating females were comparable to levels reported in other marine mammals, except for Se and Mn. Correlations between adult tissues were negative for Mn and positive for As, Hg and Sn. Molar Se:Hg were high but within reported levels for pinnipeds. Element concentrations in pup plasma were greater than lactating females for Fe, Mn and Sn indicative of high transplacental transfer while doses of Se and As from milk exceeded tolerable effect levels for humans. Relationships with fatty-acid profiles suggest diet influenced concentrations of Cu, Hg, Mn, Sn, V and Zn in adult plasma. In addition, inter-annual variation in TE concentrations were influenced by broad-scale climate indices, including the Southern Annular Mode and the Southern Oscillation Index, and local conditions associated with the seasonally-active Bonney Upwelling. These findings indicate that TE concentrations in blood and milk of AUFS are and will continue to be affected by anticipated oceanographic changes, mediated by alterations in prey type availability, with potential impacts on the population's health.

Combined toxicity of polyvinyl chloride microplastics and copper to marine jacopever (Sebastes schlegelii)

Marine organisms commonly encounter co-stress resulting from the coexistence of microplastics (MPs) and heavy metals pollution in marine environments. Nevertheless, the combined effects and toxicity mechanisms of MPs and heavy metals on marine organisms remain unclear. This study integrated growth, physiological, morphological, and biochemical markers to assess the individual and combined toxicity of polyvinyl chloride MPs (PVC MPs, 1 × 104 particles/L) and copper (Cu, 200 μg/L) on marine jacopever (Sebastes schlegelii). The results revealed that co-exposure to MPs and Cu had a more detrimental impact on jacopever compared to the single-exposure groups, as evidenced by the enhanced growth inhibition, respiratory stress, and hepatotoxicity. This phenomenon may be attributed to PVC MPs accelerating the accumulation of Cu in jacopever liver. Therefore, peroxidation damage occurred in the co-exposed liver and may result in liver dysfunction. These findings contribute valuable insights into the risks associated with the coexistence of MPs and heavy metal pollution in marine ecosystems.

Microplastics as vectors of other contaminants: Analytical determination techniques and remediation methods

The ubiquitous and persistent presence of microplastics (MPs) in aquatic and terrestrial ecosystems has raised global concerns due to their detrimental effects on human health and the natural environment. These minuscule plastic fragments not only threaten biodiversity but also serve as vectors for contaminants, absorbing organic and inorganic pollutants, thereby causing a range of health and environmental issues. This review provides an overview of microplastics and their effects. This work highlights available analytical techniques for detecting and characterizing microplastics in different environmental matrices, assessing their advantages and limitations. Additionally, this review explores innovative remediation approaches, such as microbial degradation and other advanced methods, offering promising prospects for combatting microplastic accumulation in contaminated environments. The focus on environmentally-friendly technologies, such as the use of microorganisms and enzymes for microplastic degradation, underscores the importance of sustainable solutions in plastic pollution management. In conclusion, this article not only deepens our understanding of the microplastic issue and its impact but also advocates for the urgent need to develop and implement effective strategies to mitigate this critical environmental challenge. In this context, the crucial role of advanced technologies, like quantitative Nuclear Magnetic Resonance spectroscopy (qNMR), as promising tools for rapid and efficient microplastic detection, is emphasized. Furthermore, the potential of the enzyme PETase (polyethylene terephthalate esterase) in microplastic degradation is examined, aiming to address the growing plastic pollution, particularly in saline environments like oceanic ecosystems. These innovations offer hope for effectively addressing microplastic accumulation in contaminated environments and minimizing its adverse impacts.

SERS detection of surface-adsorbent toxic substances of microplastics based on gold nanoparticles and surface acoustic waves

Microplastics adsorb toxic substances and act as a transport medium. When microplastics adsorbed with toxic substances accumulate in the body, the microplastics and the adsorbed toxic substances can cause serious diseases, such as cancer. This work aimed to develop a surface-enhanced Raman spectroscopy (SERS) detection method for surface-adsorbent toxic substances by forming gold nanogaps on microplastics using surface acoustic waves (SAWs). Polystyrene microparticles (PSMPs; 1 μm) and polycyclic aromatic hydrocarbons (PAHs), including pyrene, anthracene, and fluorene, were selected as microplastics and toxic substances, respectively. Gold nanoparticles (AuNPs; 50 nm) were used as a SERS agent. The Raman characteristic peaks of the PAHs adsorbed on the surface of PSMPs were detected, and the SERS intensity and logarithm of the concentrations of pyrene, anthracene, and fluorene showed a linear relationship (R2 = 0.98), and the limits of detection were 95, 168, and 195 nM, respectively. Each PAH was detected on the surface of PSMPs, which were adsorbed with toxic substances in a mixture of three PAHs, indicating that the technique can be used to elucidate mixtures of toxic substances. The proposed SERS detection method based on SAWs could sense toxic substances that were surface-adsorbed on microplastics and can be utilized to monitor or track pollutants in aquatic environments.

Extractability and phytotoxicity of heavy metals and essential elements from plastics in soil solutions and root exudates

Plastic waste is increasing and is a serious environmental problem. Among the threats associated with plastics is the release of contaminants into the environment. This study aimed to evaluate the efficiency of metals release from plastics (low-density polyethylene (LDPE), polyethylene terephthalate (PET), and polypropylene (PP)) as affected by different soil solution types, artificial root exudates, and distilled water. The extent of metal release varied depending on the type of solution and plastic used. Metals were leached most effectively from plastics in soil solutions, followed by root exudates, and least effectively by distilled water. LDPE released the highest concentrations of Cu and Na into solution, PP released the greatest amount of Fe, and PET released the most Cr. The efficiencies of Mg and Zn release from the plastics (PP and PET) varied by solution type. Among the plastics studied, LDPE exhibited the strongest ability to adsorb metals, such as Fe, Cr, Mg, and Zn from soil solutions. The amount of metal released from the plastics was also dependent on pH, dissolved organic carbon (DOC) concentrations, and the electrical conductivity (EC) of the solutions. Moreover, plastic extracts were found to have negative effects on germination and growth in Lepidium sativum.

Effects and applications of surfactants on the release, removal, fate, and transport of microplastics in aquatic ecosystem: a review

Microplastics (MPs) and surfactants (STs) are emerging pollutants in the environment. While many studies have focused on the interactions of STs with MPs, there has not been a comprehensive review focusing on the effect of STs on MPs in aquatic ecosystems. This review summarizes methods for removal of MPs from wastewater (e.g., filtration, flotation, coagulation/flocculation, adsorption, and oxidation-reduction) and the interactions and effects of STs with MPs (adsorption, co-adsorption, desorption, and toxicity). STs can modify MPs surface properties and influence their removal using different wastewater treatments, as well as the adsorption-desorption of both organic and inorganic chemicals. The concentration of STs is a crucial factor that impacts the removal or adsorption of pollutants onto MPs. At low concentrations, STs tend to facilitate MPs removal by flotation and enhance the adsorption of pollutants onto MPs. High ST concentrations, mainly above the critical micelle concentrations, cause MPs to become dispersed and difficult to remove from water while also reducing the adsorption of pollutants by MPs. Excess STs form emulsions with the pollutants, leading to electrostatic repulsion between MPs/STs and the pollutant/STs. As for the toxicity of MPs, the addition of STs to MPs shows complicated results, with some cases showing an increase in toxicity, some showing a decrease, and some showing no effect.

Seasonal pollution and surface characteristics of microplastics in surface water in the Wanzhou section of the Three Gorges Reservoir, China

The pollution of freshwater environments with microplastics (MPs) has attracted increasing attention owing to their threats to aquatic ecosystems and human health. Here, we sampled and analyzed MPs from mainstream, tributary, and backwater areas in the Wanzhou section of the Three Gorges Reservoir (TGR) in impoundment and flood periods. Microplastic pollution was the most severe in the backwater areas. The average abundance of MPs reached the highest value in the flood period (5.27±3.47×107 items km-2), which was 3-5 times that in the impoundment period. In the 0.3-5 mm size class, the 1-5 mm fraction was the most abundant, accounting for more than 81% in the flood period and 68% of the total MP particle abundance in the impoundment period in the mainstream and backwater areas. However, 0.3-1 mm MPs contributed more than 50% in the tributaries during the impoundment period. Polystyrene, polypropylene, and polyethylene MPs were detected in foam, fragment, sheet, and line-shaped MP particles. White, opaque, foamed polystyrene MPs contributed 32-81% to total MP particle abundance in the watershed. Microplastic particle surfaces showed signs of damage and oxidation, and ten different elements were found. Oxygen was clustered on the surface of foam and fragment MPs. Microplastic pollution was severe in the Wanzhou watershed. Especially in the backwater areas, oxidized MPs of variable shapes derived mainly from surface runoff in the flood period and sewage discharge in the impoundment period were abundant. The results of this study contribute to understanding seasonal pollution patterns and surface characteristics of MPs in the TGR and similar watersheds.

New insights into the migration, distribution and accumulation of micro-plastic in marine environment: A critical mechanism review

Microplastics (MPs) are widely distributed in the marine environment, posing a significant threat to marine biota. The contribution of anthropogenic and terrestrial sources to the aquatic ecosystem has led to an increase in MPs findings, and their abundance in aquatic biota has been reported to be of concern. MPs are formed mainly via photo degradation of macroplastics (large plastic debris), and their release into the environment is a result of the degradation of additives. Eco-toxicological risks are increasing for marine organisms, due to the ingestion of MPs, which cause damage to gastrointestinal (GI) tracts and stomach. Plastics with a size <5 mm are considered MPs, and they are commonly identified by Raman spectroscopy, Fourier transfer infrared (FTIR) spectroscopy, and Laser direct infrared (LDIR). The size, density and additives are the main factors influencing the abundance and bioavailability of MPs. The most abundant type of MPs found in fishes are fiber, polystyrenes, and fragments. These microscale pellets cause physiological stress and growth deformities by targeting the GI tracts of fishes and other biota. Approximately 80% MPs come from terrestrial sources, either primary, generated during different products such as skin care products, tires production and the use of MPs as carrier for pharmaceutical products, or secondary plastics, disposed of near coastal areas and water bodies. The issue of MPs and their potential effects on the marine ecosystem require proper attention. Therefore, this study conducted an extensive literature review on assessing MPs levels in fishes, sediments, seawater, their sources, and effects on marine biota (especially on fishes), chemo-physical behavior and the techniques used for their identification.

Ecotoxic effects of microplastics and contaminated microplastics - Emerging evidence and perspective

The high prevalence and persistence of microplastics (MPs) in pristine habitats along with their accumulation across environmental compartments globally, has become a matter of grave concern. The resilience conferred to MPs using the material engineering approaches for outperforming other materials has become key to the challenge that they now represent. The characteristics that make MPs hazardous are their micro to nano scale dimensions, surface varied wettability and often hydrophobicity, leading to non-biodegradability. In addition, MPs exhibit a strong tendency to bind to other contaminants along with the ability to sustain extreme chemical conditions thus increasing their residence time in the environment. Adsorption of these co-contaminants leads to modification in toxicity varying from additive, synergistic, and sometimes antagonistic, having consequences on flora, fauna, and ultimately the end of the food chain, human health. The resulting environmental fate and associated risks of MPs, therefore greatly depend upon their complex interactions with the co-contaminants and the nature of the environment in which they reside. Net outcomes of such complex interactions vary with core characteristics of MPs, the properties of co-contaminants and the abiotic factors, and are required to be better understood to minimize the inherent risks. Toxicity assays addressing these concerns should be ecologically relevant, assessing the impacts at different levels of biological organization to develop an environmental perspective. This review analyzed and evaluated 171 studies to present research status on MP toxicity. This analysis supported the identification and development of research gaps and recommended priority areas of research, accounting for disproportionate risks faced by different countries. An ecological perspective is also developed on the environmental toxicity of contaminated MPs in the light of multi-variant stressors and directions are provided to conduct an ecologically relevant risk assessment. The presented analyses will also serve as a foundation for developing environmentally appropriate remediation methods and evaluation frameworks.

Correlation of metals and degraded marine (micro)plastic litter in geologically similar coastal areas with different anthropogenic characteristics

The association and statistical correlation of anthropogenically important trace metals (TM) Cd, Cu, Pb, Zn and degraded marine microplastic (MP) extracted from the bulk debris samples at two locations from two marine systems, estuarine and coastal, in the Croatian Adriatic coastal area were assessed. The abundance of MP particles at both sites were primarily defined by local wave climate, with the open coastal site containing 9-fold more microplastic particles (>4 mm) as compared to the semi-closed estuarine, or twice as much considering bulk plastics. Generally, the higher abundance of adsorbed metal on MP were observed in the more anthropogenically influenced estuary than in the open coastal site and followed the order: polystyrene > polypropylene > low density polyethylene. The amounts of adsorbed zinc were the highest on all types of plastics at both sites, while the affinity of polystyrene for metals followed: Zn > Pb ≈ Cu > Cd.

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.

Excretion characteristics of nylon microplastics and absorption risk of nanoplastics in rats

Ingestion of environmental microplastics (MPs) by animals is receiving a great health concern, because of its potential adverse effects on organisms. Most ingested MPs will be excreted, while the health threats depend largely on the excretory dynamics. Although the excretion characteristics of MPs in invertebrates and fishes have been studied, information on the excretion of MPs in mammals remains lacking, especially for the fibrous MPs. Here, fibrous and granular MP and nanoplastic (NP) of nylon polymer (polyamide 66, PA66) were exposed in rats by oral in the first day, then the excretion behavior of ingested PA66 in rats was quantified using mass quantification of liquid chromatography with tandem mass spectrometry (LC-MS-MS) together with the microscope observation. Although most of the ingested PA66-MP or PA66-NP was excreted within 48 h, the three forms of PA66 were not completely cleared by the rats even after seven days excretion. The excretion of PA66 in rats was well-described by a first-order kinetics model, and the calculated half-lives of elimination of PA66 polymer in rats are 19.9 h (fibrous PA66-MP), 23.7 h (granular PA66-MP), and 36.9 h (PA66-NP), indicating rats excrete smaller MPs more slowly than the bigger ones. This was further confirmed by the particle size distribution of granular PA66-MP observed in feces. Besides, approximately 30% of the ingested PA66-NP were failed to be detected in feces, while the occurrence of PA66-NP in rat serum induced by PA66-NP ingestion was found. This indicates that PA66-NP can pass through the gut barrier and entered the blood circulation. Therefore, the health risks of ingested MPs, especially for the NPs, deserve further attention.

Nanoplastics in Aquatic Environments: Impacts on Aquatic Species and Interactions with Environmental Factors and Pollutants

Plastic production began in the early 1900s and it has transformed our way of life. Despite the many advantages of plastics, a massive amount of plastic waste is generated each year, threatening the environment and human health. Because of their pervasiveness and potential for health consequences, small plastic residues produced by the breakdown of larger particles have recently received considerable attention. Plastic particles at the nanometer scale (nanoplastics) are more easily absorbed, ingested, or inhaled and translocated to other tissues and organs than larger particles. Nanoplastics can also be transferred through the food web and between generations, have an influence on cellular function and physiology, and increase infections and disease susceptibility. This review will focus on current research on the toxicity of nanoplastics to aquatic species, taking into account their interactive effects with complex environmental mixtures and multiple stressors. It intends to summarize the cellular and molecular effects of nanoplastics on aquatic species; discuss the carrier effect of nanoplastics in the presence of single or complex environmental pollutants, pathogens, and weathering/aging processes; and include environmental stressors, such as temperature, salinity, pH, organic matter, and food availability, as factors influencing nanoplastic toxicity. Microplastics studies were also included in the discussion when the data with NPs were limited. Finally, this review will address knowledge gaps and critical questions in plastics’ ecotoxicity to contribute to future research in the field.

The development and application of advanced analytical methods in microplastics contamination detection: A critical review

Microplastics have gradually become emerging environmental contaminants for their extensive distribution, small particle size, and harmful effects on organisms. Therefore, finding accurate, efficient, and rapid analytical methods for detecting microplastics pollution has become an urgent problem. We reviewed the derivation, transport, and classification of microplastics and then highlighted the harmfulness of microplastics which would bring microplastics pollution to the environment and potential damage to organisms. Further, various analytical methods were classified into the thermal analytical method, spectral analytical approach, and other analytical methods based on detection principles. In addition, the application of each analytical method in sea and soil was concluded in detail, and the promising development prospect of each analytical method was discussed. In the end, the chemical analytical method was proposed to explore further in the direction of no sample preparation, nondestructive analysis, low detection limit and it is crucial to establish a unified detection and identification method for microplastics in different environments.

Field to laboratory comparison of metal accumulation on aged microplastics in coastal waters

The ubiquity of microplastics in the environment has attracted much attention on their risks. Though newly produced plastics were considered inert to aqueous metals, a few studies suggest aged microplastics can accumulate metals. Still, knowledge gap exists on the comparability of metal accumulation in field condition and that acquired in controlled laboratory settings. Accordingly, we comparatively assessed the field accumulation and laboratory adsorption of metals on aged microplastics in coastal waters. Microplastics of different polymeric types were aged for 8 weeks at three coastal sites with different contamination levels. Microplastics accumulated metals to substantial concentrations during ageing (median concentrations, μg g^-1: Fe = 950, Mn = 94, Zn = 19, Cu = 2.8, Ni = 1.7, Pb = 1.6, and Cd = 0.005). Adsorption capacity of (aged) microplastics was evaluated in laboratory using a stable isotope tracer method. At environmentally realistic concentrations (μg L^-1, ¹¹⁴Cd = 1.7, ⁶⁵Cu = 4.4, ⁶²Ni = 5.4, ²⁰⁶Pb = 0.5, and ⁶⁸Zn = 13), the median concentrations of newly adsorbed isotopes on the aged microplastics were 0.01, 1.4, 0.07, 0.56, and 1.1 μg g^-1, respectively, one to two orders of magnitude higher than those adsorbed on pristine microplastics. However, the composition pattern of metals accumulated on aged microplastics differed from the composition of metals newly adsorbed in laboratory: the prior one reflected the contamination status of ageing sites and varied by polymeric types; whereas the laboratory newly adsorbed metals on aged microplastics were uniformly correlated to particulate Fe and Mn concentrations, suggesting Fe and Mn mineral coatings mediated the ensuing metal adsorption. Such discrepancy unveiled the complexity of metal accumulation behavior in the real environment and highlighted that cares should be taken when translating laboratory findings to risk assessment of metal contaminated microplastics in the real environment.

Acute and subacute repeated oral toxicity study of fragmented microplastics in Sprague-Dawley rats

Polypropylene (PP) is the second most highly produced plastic worldwide, and its microplastic forms are found in water and food matrices. However, the effects of PP microplastics on human health remain largely unknown. Here, we prepared 85.2 µm-sized weathered PP (w-PP) microplastics by sieving the microplastic particles after fragmentation and accelerated weathering processes. The prepared particles are irregular in shape and no chemical additives including phthalates and bisphenol A were not released in simulated body fluids. Then, the w-PP samples were gavaged to rats for acute and subacute toxicity testing in accordance to the Organization for Economic Co-operation and Development (OECD) test guidelines under good laboratory practice regulations. The highest dose for gavaging to rats was 25 mg/kg bw/day, which was the maximum feasible dose based on the dispersibility of microplastics. Both toxicity testings for w-PP microplastics showed no adverse effects and mutagenicity. Thus, the no observed adverse effect level (NOAEL) of w-PP microplastics is higher than 25 mg/kg bw/day. Furthermore, the w-PP microplastics did not show any skin or eye irritation potentials in the 3-dimensional reconstructed human skin or corneal culture model. The dose of 25 mg/kg of w-PP microplastics is roughly equal to 2.82 × 105 particles/kg, which suggests that human exposure to w-PP microplastics in a real-life situation may not have any adverse effects.

Microplastics in mangroves and coral reef ecosystems: a review

Microplastic pollution has recently been identified as a major issue for the health of ecosystems. Microplastics have typically sizes of less than 5 mm and occur in various forms, such as pellets, fibres, fragments, films, and granules. Mangroves and coral reefs are sensitive and restricted ecosystems that provide free ecological services such as coastal protection, maintaining natural cycles, hotspots of biodiversity and economically valuable goods. However, urbanization and industrial activities have started contaminating even these preserved ecosystems. Here we review sources, occurrence, and toxicity of microplastics in the trophic levels of mangrove and coral reef ecosystems. We present detection methods, such as microscopic identification and spectroscopy. We discuss mitigating measures that prevent the entry of microplastics into the marine environment.

Are microplastics destabilizing the global network of terrestrial and aquatic ecosystem services?

Plastic has created a new man-made ecosystem called plastisphere. The plastic pieces including microplastics (MPs) and nanoplastics (NPs) have emerged as a global concern due to their omnipresence in ecosystems and their ability to interact with the biological systems. Nevertheless, the long-term impacts of MPs on biotic and abiotic resources are not completely understood, and existing evidence suggests that MPs are hazardous to various keystones species of the global biomes. MP-contaminated ecosystems show reduced floral and faunal biomass, productivity, nitrogen cycling, oxygen-generation and carbon sequestration, suggesting that MPs have already started affecting ecological biomes. However, not much is known about the influence of MPs towards the ecosystem services (ESs) cascade and its correlation with the biodiversity loss. MPs are perceived as a menace to the global ecosystems, but their possible impacts on the provisional, regulatory, and socio-economic ESs have not been extensively studied. This review investigates not only the potentiality of MPs to perturb the functioning of terrestrial and aquatic biomes, but also the associated social, ecological and economic repercussions. The possible long-term fluxes in the ES network of terrestrial and aquatic niches are also discussed.