Long-term interactions between microplastics and floating macrophyte Lemna minor: The potential for phytoremediation of microplastics in the aquatic environment

Comparative toxic effect of tire wear particle-derived compounds 6PPD and 6PPD-quinone to Chlorella vulgaris

N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), a widely used antioxidant in rubber products, and its corresponding ozone photolysis product N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD-Q), have raised public concerns due to their environmental toxicity. However, there is an existing knowledge gap on the toxicity of 6PPD and 6PPD-Q to aquatic plants. A model aquatic plant, Chlorella vulgaris (C. vulgaris), was subjected to 6PPD and 6PPD-Q at concentrations of 50, 100, 200, and 400 μg/L to investigate their effects on plant growth, photosynthetic, antioxidant system, and metabolic behavior. The results showed that 6PPD-Q enhanced the photosynthetic efficiency of C. vulgaris, promoting growth of C. vulgaris at low concentrations (50, 100, and 200 μg/L) while inhibiting growth at high concentration (400 μg/L). 6PPD-Q induced more oxidative stress than 6PPD, disrupting cell permeability and mitochondrial membrane potential stability. C. vulgaris responded to contaminant-induced oxidative stress by altering antioxidant enzyme activities and active substance levels. Metabolomics further identified fatty acids as the most significantly altered metabolites following exposure to both contaminants. In conclusion, this study compares the toxicity of 6PPD and 6PPD-Q to C. vulgaris, with 6PPD-Q demonstrating higher toxicity. This study provides valuable insight into the risk assessment of tire wear particles (TWPs) derived chemicals in aquatic habitats and plants.

Integration of ecological restoration and landscape aesthetics: Mechanisms of microplastic retention by optimization of aquatic plants landscape design in urban constructed wetlands - A case study of the living water park in Chengdu

Microplastic (MP) pollution is prevalent in urban water environments, with increasing evidence of its negative environmental impacts. This study examines the role and mechanisms of aquatic plant landscapes in the ecological remediation of MP (0.05-5 mm) in urban constructed wetland parks, using the Living Water Park in Chengdu as a case study. Over a period of two years, a systematic investigation of MP characteristics, abundance and distribution in the water environment as well as aquatic plant landscapes in the park. Sampling was carried out for the three stages of the Fuhe River before, during and after its flow through the park, and for the water bodies at each step of the water purification system within the Living Water Park, and a total of 66 samples of freshwater microplastics (MPs)were collected at 8 preliminary and 25 official sampling sites selected. MPs were observed in all samples, with higher abundance found in more close-to-natural areas, such as ecological wetlands and streams. Aquatic plants play a crucial role in MP remediation through adsorption, uptake (Mp ≤ 5 μm) and accumulation. A positive correlation was found between MP abundance, aquatic plant species diversity, and public landscape evaluation. More diverse and layered wetland plant configurations exhibited better MP remediation capabilities. The study suggests specific aquatic plant species and combinations for optimal MP remediation, emphasizing the importance and feasibility of aquatic plant landscapes in urban constructed wetland parks. The findings highlight the potential of urban constructed wetland parks for MP remediation and provide important doi:ces for their long-term development and landscape design, proposing strategies from plant combination optimization to integrated landscape design and maintenance.

Traversing the potential of phytoremediation and phycoremediation as pioneering technologies in microplastic mitigation - A critical review

With the advent of numerous reports related to health and environmental hazards associated with microplastics (MPs), scientists have been engrossed in developing sustainable technologies for MP mitigation. Conventional methods for the remediation of MPs have several limitations, but with the increasing demand for biological mitigation methods, the latest technologies are prioritized. Among biological-driven methods, phytoremediation and phycoremediation are the two peaking approaches that have gained momentum because of their eco-friendliness, cost-effectiveness, and recyclability options. Investigations of the mechanisms underlying phytoremediation and phycoremediation processes can provide possible insights into practical applications in the present scenario. Modern instrumentation is a prerequisite for identifying and characterizing MPs and quantifying their removal efficiency. The current investigation highlights a unique combination of elaborate discussions on the use of plants in the mitigation of MPs, bibliometric analysis of the current status of research, their relevance to the modern context, and the development of a combinatorial strategy to amalgamate the advantages of these two unique processes via the concept of constructed wetlands for synergistically mitigating MPs. Thus, this review provides fresh insights into addressing MP pollution with sustainable ideologies to achieve improved mitigation outcomes without compromising the balance of the ecosystem.

A low-impact nature-based solution for reducing aquatic microplastics from freshwater ecosystems

Effective nature-based solutions (NBS) and strategies for freshwater microplastic (MP) pollution are beneficial for reducing ecological and human health risks. This study proposed an innovative NBS for the in-situ retention of aquatic MPs. By evaluating the tolerance and MP retention efficiency of different submerged macrophytes, Myriophyllum aquaticum was identified as a well-suited system for optimization as NBS for operational MP retainment practice. The response surface method and artificial neural network modeling were applied to determine the optimal operational strategy of this solution, which was determined to be at a flow rate of 60 L/h, aeration intensity of 5 m3/(m2·h), and plant density of 190 plants/m2. Under this strategy, an average MP retention of 93.38% was achieved for the actual tested lake. The retention of MPs was particularly effective for particle sizes larger than 100 μm (especially films and fragments) and for the 4 polymer types. At the same time, also total nitrogen and phosphorus levels in the treated waters were reduced by 80.0% and 78.4% respectively, reflecting the added environmental value for water purification. This NBS provides a feasible strategy for mitigating MP pollution, but further research is needed on its long-term applicability and potential ecological effects in a wider range of specific environments, and effective development of plant harvesting cycle strategies is also essential to achieve long-lasting MP pollution removal.

Polystyrene microplastics alleviate the developmental toxicity of silver nanoparticles in embryo-larval zebrafish (Danio rerio) at the transcriptomic level

Since silver nanoparticles (AgNPs) and polystyrene microplastics (PS-MP) share common environmental niches, their interactions can modulate their hazard impacts. Herein, we assessed the developmental toxicity of 1 mg/L PS-MP, 0.5 mg/L AgNPs and the mixtures of AgNPs and PS-MP on embryo-larval zebrafish. We found that AgNPs co-exposure with PS-MP remarkably decreased mortality rates, malformation rates, heart rates and yolk sac area, while it increased hatching rates and eye size compared to the AgNPs group. These phenomena revealed that the cell cycle, oxidative stress, apoptosis, lipid metabolism, ferroptosis and p53 signalling pathway were obviously affected by single AgNPs exposure at 96 hpf (hours post fertilization). Interestingly, all these effects were effectively ameliorated by co-exposure with PS-MP. The combination of transcriptomic and metabolomic analyses showed that the imbalance of DEGs (differentially expressed genes) and DEMs (differentially expressed metabolites) (PI, phosphatidylinositol and TAG-FA, triacylglycerol-fatty acid) disturbed both the cell cycle and lipid metabolism following single AgNPs exposure and co-exposure with PS-MP. These findings suggest that PS-MP attenuates the developmental toxicity of AgNPs on embryo-larval zebrafish. Overall, this study provides important insight into understanding the transcriptional responses and mechanisms of AgNPs alone or in combination with PS-MPs on embryo-larval zebrafish, providing a reference for ecological risk assessment of combined exposure to PS-MP and metal nanoparticles.

A review of tire wear particles: Occurrence, adverse effects, and control strategies

Tire wear particles (TWPs), common mixed particulate emerging contaminants in the environment, have global per capita emissions accounting for 0.23-1.9 kg/year, attracting global attention recently due to their wide detection, small size, mobility, and high toxicity. This review focuses on the occurrence characteristics of TWPs in multiple environmental media, adverse effects on organisms, potential toxicity mechanisms, and environmental risk prevention and control strategies of TWPs. The environmental fate of TWPs throughout the entire process is systematically investigated by the bibliometric analysis function of CiteSpace. This review supplements the gap in the joint toxicity and related toxicity mechanisms of TWPs with other environmental pollutants. Based on the risks review of TWPs and their additives, adverse impacts have been found in organisms from aquatic environments, soil, and humans, such as the growth inhibition effect on Chironomus dilutes. A multi-faceted and rationalized prevention and control treatment of "source-process-end" for the whole process can be achieved by regulating the use of studded tires, improving the tire additive formula, growing plants roadside, encouraging micro-degradation, and other methods, which are first reviewed. By addressing the current knowledge gaps and exploring prospects, this study contributes to developing strategies for reducing risks and assessing the fate of TWPs in multiple environmental media.

Microplastics footprint in nature reserves-a case study on the microplastics in the guano from Yancheng Wetland Rare Birds National Nature Reserve, China

Bio-ingestion of microplastics poses a global threat to ecosystems, yet studies within nature reserves, crucial habitats for birds, remain scarce despite the well-documented ingestion of microplastics by avian species. Located in Jiangsu Province, China, the Yancheng Wetland Rare Birds Nature Reserve is home to diverse bird species, including many rare ones. This study aimed to assess the abundance and characteristics of microplastics in common bird species within the reserve, investigate microplastic enrichment across different species, and establish links between birds' habitat types and microplastic ingestion. Microplastics were extracted from the feces of 110 birds, with 84 particles identified from 37.27% of samples. Among 8 species studied, the average microplastic abundance ranged from 0.97 ± 0.47 to 43.43 ± 61.98 items per gram of feces, or 1.5 ± 0.87 to 3.4 ± 1.50 items per individual. The Swan goose (Anser cygnoides) exhibited the highest microplastic abundance per gram of feces, while the black-billed gull (Larus saundersi) had the highest abundance per individual. The predominant form of ingested microplastics among birds in the reserve was fibers, with polyethylene being the most common polymer type. Significant variations in plastic exposure were observed among species and between aquatic and terrestrial birds. This study represents the first quantitative assessment of microplastic concentrations in birds within the reserve, filling a crucial gap in research and providing insights for assessing microplastic pollution and guiding bird conservation efforts in aquatic and terrestrial environments.

The power of green: Harnessing phytoremediation to combat micro/nanoplastics

Plastic pollution and its potential risks have been raising public concerns as a global environmental issue. Global plastic waste may double by 2030, posing a significant challenge to the remediation of environmental plastics. In addition to finding alternative products and managing plastic emission sources, effective removal technologies are crucial to mitigate the negative impact of plastic pollution. However, current remediation strategies, including physical, chemical, and biological measures, are unable to compete with the surging amounts of plastics entering the environment. This perspective lays out recent advances to propel both research and action. In this process, phytoaccumulation, phytostabilization, and phytofiltration can be applied to reduce the concentration of nanoplastics and submicron plastics in terrestrial, aquatic, and atmospheric environments, as well as to prevent the transport of microplastics from sources to sinks. Meanwhile, advocating for a more promising future still requires significant efforts in screening hyperaccumulators, coupling multiple measures, and recycling stabilized plastics from plants. Phytoremediation can be an excellent strategy to alleviate global micro/nanoplastic pollution because of the cost-effectiveness and environmental sustainability of green technologies.

Seaweeds as a major source of dietary microplastics exposure in East Asia

Microplastics (MPs) occurrence in marine ecosystems is well known, but their accumulation in seaweeds and subsequent human exposure remain understudied. This research quantifies MPs presence in two commonly consumed seaweeds, kelp (Saccharina japonica) and nori (Pyropia yezoensis), in East Asia, revealing widespread contamination dominated by microfibers (<500 μm). Based on dietary patterns, human uptake through seaweed consumption was estimated and quantified. Notably, Chinese people consume an estimated 17,034 MPs/person/year through seaweed consumption, representing 13.1% of their total annual MPs intake. This seaweeds-derived exposure surpasses all other dietary sources, contributing up to 45.5% of overall MPs intake. The highest intake was in South Korea, followed by North Korea, China, and Japan. This research identifies seaweeds as a major, previously overlooked route of dietary MPs exposure. These findings are crucial for comprehensive risk assessments of seaweed consumption and the development of mitigation strategies, particularly for populations in East Asian countries.

Lower concentration polyethylene microplastics can influence free-floating macrophyte interactions by combined effects of many weak interactions: A nonnegligible ecological impact

Microplastics (MPs) are ubiquitous in freshwater ecosystems and their accumulation has been considered an emerging threat. Early research on the effects of MPs on macrophytes primarily focused on the toxicological impacts on individual macrophytes, with several studies suggesting that lower concentrations of MPs have little impact on macrophytes. However, the ecological implications of lower MP concentrations on macrophyte communities remain largely unexplored. Here, we experimented to assess the effects of lower concentrations including 25 mg/L, 50 mg/L, 75 mg/L, and 100 mg/L of polyethylene (PE) microplastics on Spirodela polyrhiza and Lemna minor, and their community. Our results also indicated that PE concentrations below 100 mg/L had no significant effect on relative growth rate, specific leaf area, Chlorophyll a, Chlorophyll b, Chlorophyll a + b, carotenoid, malondialdehyde (MDA), catalase, and soluble sugar of monocultural S. polyrhiza. However, a lower concentration of PE significantly decreased the MDA of monocultural L. minor and significantly affected the comprehensive index of S. polyrhiza. These findings suggested that lower concentrations of PE can influence interactions between macrophytes maybe due to the cumulative effects of many weak interactions. Additionally, our study showed that 75 mg/L and 100 mg/L PE additions decreased the competitive balance index value of two macrophytes under mixed-culture condition. This result implied that the ecological influence of lower concentration MPs on macrophytes may manifest at the community level rather than at the population level, due to species-specific responses and varying degrees of sensitivity of macrophytes to PE concentrations. Thus, our study emphasizes the need to closely monitor the ecological consequences of emerging contaminants such as MPs accumulation on macrophyte communities, rather than focusing solely on the morphology and physiology of individual macrophytes.

Microplastics and nanoplastics: Source, behavior, remediation, and multi-level environmental impact

Plastics introduced into the natural environment persist, degrade, and fragment into smaller particles due to various environmental factors. Microplastics (MPs) (ranging from 1 μm to 5 mm) and nanoplastics (NPs) (less than 1 μm) have emerged as pollutants posing a significant threat to all life forms on Earth. Easily ingested by living organisms, they lead to ongoing bioaccumulation and biomagnification. This review summarizes existing studies on the sources of MPs and NPs in various environments, highlighting their widespread presence in air, water, and soil. It primarily focuses on the sources, fate, degradation, fragmentation, transport, and ecotoxicity of MPs and NPs. The aim is to elucidate their harmful effects on marine organisms, soil biota, plants, mammals, and humans, thereby enhancing the understanding of the complex impacts of plastic particles on the environment. Additionally, this review highlights remediation technologies and global legislative and institutional measures for managing waste associated with MPs and NPs. It also shows that effectively combating plastic pollution requires the synergization of diverse management, monitoring strategies, and regulatory measures into a comprehensive policy framework.

Unraveling the micro- and nanoplastic predicament: A human-centric insight

Micro- and nanoplastics are vast anthropogenic pollutants in our direct surroundings with a robust environmental stability and a potential for a long-lasting and increasing global circulation. This has raised concerns among the public and policy makers for human health upon exposure to these particles. The micro- and nanoplastic burden on humans is currently under debate, along with criticism on the experimental approaches used in hazard assessment. The present review presents an overview of the human-relevant aspects associated with the current micro-and nanoplastic burden. We focus on environmental circulation and the estimation of exposure quantities to humans, along with a state-of-the-art overview of particle accumulation in over 15 human organs and other specimen. Additionally, data regarding particle characteristics used in toxicity testing was extracted from 91 studies and discussed considering their environmental and human relevance.

Optimization of microplastic removal based on the complementarity of constructed wetland and microalgal-based system

As one of the emblematic emerging contaminants, microplastics (MPs) have aroused great public concern. Nevertheless, the global community still insufficiently acknowledges the ecological health risks and resolution strategies of MP pollution. As the nature-based biotechnologies, the constructed wetland (CW) and microalgal-based system (MBS) have been applied in exploring the removal of MPs recently. This review separately presents the removal research (mechanism, interactions, implications, and technical defects) of MPs by a single method of CWs or MBS. But one thing with certitude is that the exclusive usage of these techniques to combat MPs has non-negligible and formidable challenges. The negative impacts of MP accumulation on CWs involve toxicity to macrophytes, substrates blocking, and nitrogen-removing performance inhibition. While MPs restrict MBS practical application by making troubles for separation difficulties of microalgal-based aggregations from effluent. Hence the combined strategy of microalgal-assisted CWs is proposed based on the complementarity of biotechnologies, in an attempt to expand the removing size range of MPs, create more biodegradable conditions and improve the effluent quality. Our work evaluates and forecasts the potential of integrating combination for strengthening micro-polluted wastewater treatment, completing the synergistic removal of MP-based co-pollutants and achieving long-term stability and sustainability, which is expected to provide new insights into MP pollution regulation and control.

Recognition and detection technology for microplastic, its source and health effects

Microplastic (MP) is ubiquitous in the environment which appeared as an immense intimidation to human and animal health. The plastic fragments significantly polluted the ocean, fresh water, food chain, and other food items. Inadequate maintenance, less knowledge of adverse influence along with inappropriate usage in addition throwing away of plastics items revolves present planet in to plastics planet. The present study aims to focus on the recognition and advance detection technologies for MPs and the adverse effects of micro- and nanoplastics on human health. MPs have rigorous adverse effect on human health that leads to condensed growth rates, lessened reproductive capability, ulcer, scrape, and oxidative nervous anxiety, in addition, also disturb circulatory and respiratory mechanism. The detection of MP particles has also placed emphasis on identification technologies such as scanning electron microscopy, Raman spectroscopy, optical detection, Fourier transform infrared spectroscopy, thermo-analytical techniques, flow cytometry, holography, and hyperspectral imaging. It suggests that further research should be explored to understand the source, distribution, and health impacts and evaluate numerous detection methodologies for the MPs along with purification techniques.

Mechanistic understanding on the uptake of micro-nano plastics by plants and its phytoremediation

Contaminated soil is one of today's most difficult environmental issues, posing serious hazards to human health and the environment. Contaminants, particularly micro-nano plastics, have become more prevalent around the world, eventually ending up in the soil. Numerous studies have been conducted to investigate the interactions of micro-nano plastics in plants and agroecosystems. However, viable remediation of micro-nano plastics in soil remains limited. In this review, a powerful in situ soil remediation technology known as phytoremediation is emphasized for addressing micro-nano-plastic contamination in soil and plants. It is based on the synergistic effects of plants and the microorganisms that live in their rhizosphere. As a result, the purpose of this review is to investigate the mechanism of micro-nano plastic (MNP) uptake by plants as well as the limitations of existing MNP removal methods. Different phytoremediation options for removing micro-nano plastics from soil are also described. Phytoremediation improvements (endophytic-bacteria, hyperaccumulator species, omics investigations, and CRISPR-Cas9) have been proposed to enhance MNP degradation in agroecosystems. Finally, the limitations and future prospects of phytoremediation strategies have been highlighted in order to provide a better understanding for effective MNP decontamination from soil.

Growth, physiological parameters and DNA methylation in Spirodela polyrhiza (L.) Schleid exposed to PET micro-nanoplastic contaminated waters

The effects of polyethylene terephthalate micro-nanoplastics (PET-MNPs) were tested on the model freshwater species Spirodela polyrhiza (L.) Schleid., with focus on possible particle-induced epigenetic effects (i.e. alteration of DNA methylation status). MNPs (size ∼ 200-300 nm) were produced as water dispersions from PET bottles through repeated cycles of homogenization and used to prepare N-medium at two environmentally relevant concentrations (∼0.05 g L-1 and ∼0.1 g L-1 of MNPs). After 10 days of exposure, a reduction in fresh and dry weight was observed in treated plants, even if the average specific growth rate for both frond number and area was not altered. Impaired growth was coupled with a MNP-induced decrease of chlorophyll fluorescence parameters (i.e. ΨETo and Piabs, indicators of photochemical efficiency) and starch concentration, as well as with alterations in plant ionomic profile and oxidative status. The methylation-sensitive amplification polymorphism (MSAP) technique was used to assess possible changes in DNA methylation levels induced by plastic particles. The analysis showed unusual hypermethylation in 5'-CCGG sites that could be implicated in DNA protection from dangerous agents (i.e. reactive oxygen species) or in the formation of new epialleles. This work represents the first evidence of MNP-induced epigenetic modifications in the plant world.

Comparative Phytotoxicity of Metallic Elements on Duckweed Lemna gibba L. Using Growth- and Chlorophyll Fluorescence Induction-Based Endpoints

In this study, we exposed a commonly used duckweed species-Lemna gibba L.-to twelve environmentally relevant metals and metalloids under laboratory conditions. The phytotoxic effects were evaluated in a multi-well-plate-based experimental setup by means of the chlorophyll fluorescence imaging method. This technique allowed the simultaneous measuring of the growth and photosynthetic parameters in the same samples. The inhibition of relative growth rates (based on frond number and area) and photochemical efficiency (Fv/Fo and Y(II)) were both calculated from the obtained chlorophyll fluorescence images. In the applied test system, growth-inhibition-based phytotoxicity endpoints proved to be more sensitive than chlorophyll-fluorescence-based ones. Frond area growth inhibition was the most responsive parameter with a median EC50 of 1.75 mg L-1, while Fv/Fo, the more responsive chlorophyll-fluorescence-based endpoint, resulted in a 5.34 mg L-1 median EC50 for the tested metals. Ag (EC50 0.005-1.27 mg L-1), Hg (EC50 0.24-4.87 mg L-1) and Cu (EC50 0.37-1.86 mg L-1) were the most toxic elements among the tested ones, while As(V) (EC50 47.15-132.18 mg L-1), Cr(III) (EC50 6.22-19.92 mg L-1), Se(VI) (EC50 1.73-10.39 mg L-1) and Zn (EC50 3.88-350.56 mg L-1) were the least toxic ones. The results highlighted that multi-well-plate-based duckweed phytotoxicity assays may reduce space, time and sample volume requirements compared to the standard duckweed growth inhibition tests. These benefits, however, come with lowered test sensitivity. Our multi-well-plate-based test setup resulted in considerably higher median EC50 (3.21 mg L-1) for frond-number-based growth inhibition than the 0.683 mg L-1 median EC50 derived from corresponding data from the literature with standardized Lemna-tests. Under strong acute phytotoxicity, frond parts with impaired photochemical functionality may become undetectable by chlorophyll fluorometers. Consequently, the plant parts that are still detectable display a virtually higher average photosynthetic performance, leading to an underestimation of phytotoxicity. Nevertheless, multi-well-plate-based duckweed phytotoxicity assays, combined with chlorophyll fluorescence imaging, offer definite advantages in the rapid screening of large sample series or multiple species/clones. As chlorophyll fluorescence images provide information both on the photochemical performance of the test plants and their morphology, a joint analysis of the two endpoint groups is recommended in multi-well-plate-based duckweed phytotoxicity assays to maximize the information gained from the tests.

Distribution and Fate of Polyethylene Microplastics Released by a Portable Toilet Manufacturer into a Freshwater Wetland and Lake

A portable toilet manufacturer in northwest Indiana (USA) released polyethylene microplastic (MP) pollution into a protected wetland for at least three years. To assess the loads, movement, and fate of the MPs in the wetland from this point source, water and sediment samples were collected in the fall and spring of 2021-2023. Additional samples, including sediment cores and atmospheric particulates, were collected during the summer of 2023 from select areas of the wetland. The MPs were isolated from the field samples using density separation, filtration, and chemical oxidation. Infrared and Raman spectroscopy analyses identified the MPs as polyethylene, which were quantified visually using a stereomicroscope. The numbers of MPs in 100 mL of the marsh water closest to the source ranged from several hundred to over 400,000, while the open water samples contained few microplastics. Marsh surface sediments were highly contaminated with MPs, up to 18,800 per 30.0 g dry mass (dm), compared to core samples in the lower depths (>15 cm) that contained only smaller MPs (<200 µm), numbering 0-480 per 30.0 g (dm). The wide variations in loads of MP contaminants indicate the influence of numerous factors, such as proximity to the point source pollution, weather conditions, natural matter, and pollution sinks, namely sediment deposition. As proof of concept, we demonstrated a novel remediation method using these real-world samples to effectively agglomerate and remove MPs from contaminated waters.

Insights into the shape-dependent effects of polyethylene microplastics on interactions with organisms, environmental aging, and adsorption properties

The shape-dependent effects of microplastics have been studied in the context of ingestion but have not been considered in other environmental processes. Therefore, we investigated how the shape of polyethylene microplastics (spheres, fragments, and films) affects interactions with plants, aging, and their adsorption properties. The shape had no effect on the growth rate and chlorophyll content of duckweed Lemna minor, but the fragments strongly adhered to the plant biomass and reduced the root length. The adsorption process of the model organic compound (methylene blue dye) was described by the same kinetic model for all shapes-the experimental data best fit the pseudo-second order model. However, twice as much methylene blue was adsorbed on films as on fragments and spheres. During environmental aging, most biofilm developed on films. The biofilm on spheres contained significantly less photosynthetic microorganisms, but twice as much extracellular polymeric substances (EPS) as on fragments and films. This suggests that the attachment of microorganisms to spherical particles is limited and therefore more intensive production of EPS is required for stable biofilm formation. From the results of this study, it is evident that the shape of microplastics significantly affects not only ecotoxicity but also other environmentally relevant processes.

Phytoremediation: A promising approach to remove microplastics from the aquatic environment

Due to the increasing amount of microplastics (MPs) in the environment, various technologies for their removal have been investigated. One of the possible technologies are phytoremediation methods, but insufficient understanding of the interactions between MPs and aquatic macrophytes limits their further development. In this context, the aim of this study was to investigate the interactions between polyethylene MPs and the floating aquatic macrophyte Lemna minor in terms of the extent and time frame of MPs adhesion to the plant biomass, the stability of the interactions under water movement and understanding the nature of the adsorption process through the adsorption isotherm models. The results showed that the maximum number of adhered MPs was reached after 24 h. With increased amount of plant biomass the number of adhered MPs increased as well. Slow movement of water had no statistically significant effect on the adhesion of MPs. Among several adsorption models, the Freundlich adsorption isotherm model was the best fit to the experimental data, which assumes weak binding of MPs to plant biomass. Finally, 79% of MPs was removed during 15 cycles of phytoremediation (i.e., the biomass was removed and replaced with new biomass 15 times) and it was calculated that 53 cycles would be needed to remove all MPs from the water phase under test conditions.

The organism fate of inland freshwater system under micro-/nano-plastic pollution: A review of past decade

Micro- and nano-plastics (MPs/NPs) are characterized by their small size and extensive surface area, making them global environmental pollutants with adverse effects on organisms at various levels, including organs, cells, and molecules. Freshwater organisms, such as microalgae, emerging plants, zooplankton, benthic species, and fish, experience varying impacts from MPs/NPs, which are prevalent in both terrestrial and aquatic inland environments. MPs/NPs significantly impact plant physiological processes, including photosynthesis, antioxidant response, energy metabolism, and nitrogen removal. Extended exposure and ingestion to MPs/NPs might cause metabolic and behavioral deviations in zooplankton, posing an extinction risk. Upon exposure to MPs/NPs, both benthic organisms and fish display behavioral and metabolic disturbances, due to oxidative stress, neural toxicity, intestinal damage, and metabolic changes. Results from laboratory and field investigations have confirmed that MPs/NPs can be transported across multiple trophic levels. Moreover, MPs/NPs-induced alterations in zooplankton populations can impede energy transfer, leading to food scarcity for filter-feeding fish, larvae of benthic organism and fish, thus jeopardizing aquatic ecosystems. Furthermore, MPs/NPs can harm the nervous systems of aquatic organisms, influencing their feeding patterns, circadian rhythms, and mobility. Such behavioral alterations might also introduce unforeseen ecological risks. This comprehensive review aims to explore the consequences of MPs/NPs on freshwater organisms and their interconnected food webs. The investigation encompasses various aspects, including behavioral changes, alterations in physiology, impacts on metabolism, transgenerational effects, and the disruption of energy transfer within the ecosystem. This review elucidated the physiological and biochemical toxicity of MPs/NPs on freshwater organisms, and the ensuing risks to inland aquatic ecosystems.

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

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

Emergence of microplastics in the aquatic ecosystem and their potential effects on health risks: The insights into Vietnam

The increase of microplastic contamination in Vietnam is a growing concern due to various domestic, agricultural, and industrial activities. The use of plastic mulch and sludge application in agricultural farmland, textile production, daily consumer items, cleaning agents, and health/personal care products contribute significantly to the increasing microplastic pollution in the aquatic ecosystem. The concentration of microplastics reported in surface water ranged from 0.35 to 519,000 items m-3, with fibers and fragments being the most prevalent shapes. Notably, the high concentration of microplastics was observed in lakes, canals, and megacities such as Ha Noi and Ho Chi Minh City, which poses potential health risks to the local community via drinking-water supply and food chains. As an emerging pollutant, MPs are the transport vectors for contaminants in environmental matrices that act as a carrier of hazardous pollutants, release toxic compounds, and evenly aggregate/accumulate in biota. Recent studies have reported the presence of microplastics in various marine organisms, including fish and shellfish, highlighting the risk of ingestion of these particles by humans and wildlife. Thus, it is imperative to monitor microplastic contamination in the ecosystem to provide helpful information for the government and local communities. Efforts should be taken to reduce microplastic pollution at the source to minimize potential effects on ecological and health safety. This review paper emphasizes the urgent need for further research on microplastic pollution in Vietnam and highlights potential solutions to mitigate this emerging environmental threat. KEYWORKS: single-use plastics; microplastics; ecosystems; plastic waste; health risk; ecological and health safety; pollution mitigation.

Effects of microplastics and cadmium on growth rate, photosynthetic pigment content and antioxidant enzymes of duckweed (Lemma minor)

Cadmium (Cd) and polyethylene (PE) seriously contaminate the aquatic environment and threaten human health. Many studies have reported the toxic effects of Cd and PE on plants, whereas few have reported the combined contamination of these two pollutants. In this study, duckweed (Lemma minor) was used as an indicator to explore the effect of PE microplastics (PE-MPs) at concentrations of 10, 50, 100, 200, and 500 mg/L on tolerance to 1 mg/L Cd. The results showed that different concentrations of PE-MPs inhibited the growth rate and chlorophyll content of duckweed to different degrees, both of which were minimal at 50 mg/L PE-MPs, 0.11 g/d, and 0.32 mg/g, respectively. The highest Cd enrichment (7.77 mg/kg) and bioaccumulation factors (94.22) of duckweed were detected when Cd was co-exposed with 50 mg/L of PE-MPs. Catalase and peroxidase activity first decreased and then increased with increasing PE-MPs concentrations, showing "hormesis effects", with minimum values of 11.47 U/g and 196.00 U/g, respectively. With increasing concentrations of PE-MPs, the effect on superoxide dismutase activity increased and then declined, peaking at 162.05 U/g, and displaying an "inverted V" trend. The amount of malondialdehyde rose with different PE-MPs concentrations. This research lay a foundation for using duckweed to purify water contaminated with MPs and heavy metals.

Effects of microplastics on the phytoremediation of Cd, Pb, and Zn contaminated soils by Solanum photeinocarpum and Lantana camara

Microplastics are emerging pollutants and have become a global environmental issue. The impacts of microplastics on the phytoremediation of heavy metal-contaminated soils are unclear. A pot experiment was conducted to investigate the effects of four additions (0, 0.1%, 0.5%, and 1% w·w-1) of polyethylene (PE) and cadmium (Cd), lead (Pb), and zinc (Zn) contaminated soil on the growth and heavy metal accumulation of two hyperaccumulators (Solanum photeinocarpum and Lantana camara). PE significantly decreased the pH and activities of dehydrogenase and phosphatase in soil, while it increased the bioavailability of Cd and Pb in soil. Peroxidase (POD), catalase (CAT), and malondialdehyde (MDA) activity in the plant leaves were all considerably increased by PE. PE had no discernible impact on plant height, but it did significantly impede root growth. PE affected the morphological contents of heavy metals in soils and plants, while it did not alter their proportions. PE increased the content of heavy metals in the shoots and roots of the two plants by 8.01-38.32% and 12.24-46.28%, respectively. However, PE significantly reduced the Cd extraction amount in plant shoots, while it significantly increased the Zn extraction amount in the plant roots of S. photeinocarpum. For L. camara, a lower addition (0.1%) of PE inhibited the extraction amount of Pb and Zn in the plant shoots, but a higher addition (0.5% and 1%) of PE stimulated the Pb extraction amount in the plant roots and the Zn extraction amount in the plant shoots. Our results indicated that PE microplastics have negative effects on the soil environment, plant growth, and the phytoremediation efficiency of Cd and Pb. These findings contribute to a better knowledge of the interaction effects of microplastics and heavy metal-contaminated soils.

Multiple endpoints of polyethylene microplastics toxicity in vascular plants of freshwater ecosystems: A study involving Salvinia auriculata (Salviniaceae)

More recently, the number of studies on the impacts of microplastics (MPs) on plants has drawn attention considerably. However, many of these studies focused on terrestrial plants, with vascular plants from freshwater ecosystems being little studied. Thus, we aimed to evaluate the possible effects of exposure of Salvinia auriculata, for 28 days, to different concentrations of polyethylene MPs (PE MPs - diameter: 35.46 ± 18.17 µm) (2.7 ×10⁸ and 8.1 ×10⁸ particles/m³), using different biomarkers. Our data indicated that exposure to PE MPs caused alterations in plant growth/development (inferred by the lower floating frond number, "root" length, and the number of "roots"), as well as lower dispersion of individuals in the experimental units. Plants exposed to PE MPs also showed lower epidermal thickness (abaxial leaf face) and a longer length of the central leaf vein and vascular bundle area. Ultrastructural analyses of S. auriculata exposed to MPs revealed rupture of some epidermal cells and trichomes on the adaxial and abaxial, leaf necrosis, and chlorosis. In the "roots", we observed dehydrated filamentous structures with evident deformations in plants exposed to the pollutants. Both on the abaxial leaf face and on the "roots", the adherence of PE MPs was observed. Furthermore, exposure to PE MPs induced lower chlorophyll content, cell membrane damage, and redox imbalance, marked by reduced catalase and superoxide dismutase activity and increased production of reactive oxygen and nitrogen species as well as malondialdehyde. However, in general, we did not observe the dose-response effect for the evaluated biomarkers. The values of the integrated biomarker response index, the principal component analysis (PCA) results and the hierarchical clustering analysis confirmed the similarity between the responses of plants exposed to different PE MPs concentrations. Therefore, our study sheds light on how PE MPs can affect S. auriculata and reinforces that putting these pollutants in freshwater environments might be hazardous from an ecotoxicological point of view.

Beyond ingestion: Adhesion of microplastics to aquatic organisms

The interactions of microplastics with aquatic organisms have been studied primarily using animal species, with dietary ingestion being the most important uptake route. However, recent research indicated that microplastics also interact with biota via bioadhesion. This process has been studied in aquatic macrophytes under laboratory conditions where microplastics adhered to their biomass, but monitoring studies also confirmed that microplastic bioadhesion occurs in other species and in the natural environment. Similarly, microplastics adhere to microorganisms, and in the aquatic environment they can be retained by ubiquitous biofilms. This can occur on a natural substrate such as sediment or rocks, but biofilms are also responsible for enhanced bioadhesion of microplastics to other biotic surfaces such as plant surfaces. Adhesion to these large biotic surfaces could influence the abundance and bioavailability of microplastics in the environment. Only few studies have been conducted on the bioadhesion of microplastics to animals, but their results confirmed that bioadhesion may be even greater than particle ingestion by some animals, such as corals or bivalves. However, the ecotoxicological effects are not yet fully understood and the possible transport of microplastics, e.g. adhered to fish or aquatic insects, also needs to be considered. In summary, bioadhesion seems to be an important process for the interactions of microplastics and biota. Neglecting bioadhesion in an environmental context may limit our understanding of the behavior, fate, and effects of microplastics in the aquatic environment.

Phytoremediation of toxic chemicals in aquatic environment with special emphasis on duckweed mediated approaches

The discharge of toxic chemicals into water bodies and their linked detrimental effects on health is a global concern. Phytoremediation, an environment-friendly plant-based technology, has gained intensive interest over the last decades. For the aquatic phytoremediation process, the commonly available duckweeds have recently attracted significant attention due to their capacity to grow in diverse ecological niches, fast growth characteristics, suitable morphology for easy handling of biomass, and capacity to remove and detoxify various potential toxic elements and compounds. This review presents the progress of duckweed-assisted aquatic phytoremediation of toxic chemicals. A brief background of general phytoremediation processes, including the different phytoremediation methods and advances in understanding their underlying mechanisms, has been described. A summary of different approaches commonly practiced to assess the growth of the plants and their metal removal capacity in the phytoremediation process has also been included. A vast majority of studies have established that duckweed is an efficient plant catalyst to accumulate toxic heavy metals and organic contaminants, such as pesticides, fluorides, toxins, and aromatic compounds, reducing their toxicity from water bodies. The potential of this plant-based phytoremediation process for its downstream applications in generating value-added products for the rural economy and industrial interest has been identified.

Polystyrene microplastics reduce Cr(VI) and decrease its aquatic toxicity under simulated sunlight

Microplastics (MPs) serve as vectors for chromium (Cr), influencing its fate and toxicity in aquatic environments, and have attracted much attention recently. However, it is still unknown whether MPs mediate Cr species transformation under sunlight irradiation. This study confirmed that polystyrene (PS) MPs could reduce Cr(VI) to Cr(III) under sunlight irradiation, with a photoreduction rate constant of 0.0023 h^-1. PS MPs-mediated Cr(VI) reduction was predominantly dependent on O₂^•- and simultaneously suppressed by ¹O₂, •OH and ³PS* . Aged PS MPs were exposed to simulated sunlight irradiation for 0, 200, 500, and 800 h, and Cr(VI) reduction was hindered by increased ¹O₂ and •OH formation and light-screening effects (decreased photon absorption). The size, functional groups and concentration of PS MPs and environmental factors (e.g., humic acid, pH, Mg²⁺, Fe³⁺ and O₂) strongly affected Cr(VI) reduction. Furthermore, Cr(VI) reduction induced by PS MPs could occur in reservoir water, and the reduction rate was faster than that in double distilled (DD) water. Correspondingly, PS MPs (1 mg/L) decreased the oxidative stress induced by Cr(VI) to Lemna minor in reservoir water after 96 h of sunlight irradiation. This study provided deep insight into how PS MPs affect Cr species transformations and hazardous effects in realistic aquatic environments under sunlight conditions.

Morpho-biochemical Responses and Disturbed Redox Homeostasis in Barley Under Benzyl-butyl Phthalate Stress

The present study is aimed to address the morphometric consequences, yield attributes, and biochemical responses of barley plants under the stress of an endocrine disruptor i.e., benzyl-butyl phthalate (BBP). The morphometric analyses (plant length, dry weight, and net primary productivity) revealed that the inhibition induced by BBP was concentration- and time-dependent. The seed weight and the number of seeds per spike have also significantly declined with an increase in BBP doses. Similarly, BBP exhibited significant alterations over the control in the biochemical indices viz., pigments, sugars, proteins, proline, malonaldehyde, and hydrogen peroxide contents of barley plants. Furthermore, BBP stress negatively influenced the activities of antioxidative enzymes viz., SOD, POD, CAT, APX, and GR of barley with an increase in doses and exposure durations due to the over-produced reactive oxygen species. The uptake and transport of BBP were determined and observed as a responsible cue for these toxicological implications in barley plants under BBP exposure. The correlation of barley plants' morpho-biochemical responses with BBP uptake and transport was also established using Pearson's correlation. Thus, this study indicated the toxicological behavior of meagerly explored phthalate (i.e., BBP) in the crop plant and these observations can be utilized for the generation of tolerant cultivars.

Micro- and nano-plastics pollution and its potential remediation pathway by phytoremediation

This review proposed that phytoremediation could be applied for the decontamination of MPs/NPs. Micro- and nano-plastics (MPs < 5 mm; NPs < 100 nm) are emerging contaminants. Much of the recent concerns have focused on the investigation of their pollution and their potential eco-toxicity. Yet little review was available on the decontamination of MPs/NPs. Recently, the uptake of MPs/NPs by plants has been confirmed. Here, in view of the current knowledge, this review introduces MPs/NPs pollution and highlights the updated information about the interaction between MPs/NPs and plants. This review proposed that phytoremediation could be a potential possible way for the in situ remediation of MPs/NPs-contaminated environment. The possible mechanisms, influencing factors, and existing problems are summarized, and further research needs are proposed. This review herein provides new insights into the development of plant-based process for emerging pollutants decontamination, as well as the alleviation of MPs/NPs-induced toxicity to the ecosystem.

Effects of Microplastic Contamination on the Aquatic Plant Lemna minuta (Least Duckweed)

Microplastics are widely spread in aquatic environments. Although they are considered among the most alarming contaminants, toxic effects on organisms are unclear, particularly on freshwater plants. In this study, the duckweed Lemna minuta was grown on different concentrations (50, 100 mg/L) of poly(styrene-co-methyl methacrylate) microplastics (MP) and exposure times (T0, T7, T14, T28 days). The phytotoxic effects of MP were investigated by analyzing several plant morphological and biochemical parameters (frond and root size, plant growth, chlorophyll, and malondialdehyde content). Observations by scanning electron microscope revealed MP adsorption on plant surfaces. Exposition to MP adversely affected plant growth and chlorophyll content with respect to both MP concentrations and exposure times. Conversely, malondialdehyde measurements did not indicate an alteration of oxidative lipid damage in plant tissue. The presence of MP induced root elongation when compared to the control plants. The effects of MP on L. minuta plants were more evident at T28. These results contribute to a better understanding of MP's impact on aquatic plants and highlight that MP contamination manifests with chronic-type effects, which are thus detectable at longer exposure times of 7 days than those traditionally used in phytotoxicology tests on duckweeds.

The Response of Duckweed Lemna minor to Microplastics and Its Potential Use as a Bioindicator of Microplastic Pollution

Biomonitoring has become an indispensable tool for detecting various environmental pollutants, but microplastics have been greatly neglected in this context. They are currently monitored using multistep physico-chemical methods that are time-consuming and expensive, making the search for new monitoring options of great interest. In this context, the aim of this study was to investigate the possibility of using an aquatic macrophyte as a bioindicator of microplastic pollution in freshwaters. Therefore, the effects and adhesion of three types of microplastics (polyethylene microbeads, tire wear particles, and polyethylene terephthalate fibers) and two types of natural particles (wood dust and cellulose particles) to duckweed Lemna minor were investigated. The results showed that fibers and natural particles had no effect on the specific growth rate, chlorophyll a content, and root length of duckweed, while a significant reduction in the latter was observed when duckweed was exposed to microbeads and tire wear particles. The percentage of adhered particles was ten times higher for polyethylene microbeads than for other microplastics and natural particles, suggesting that the adhesion of polyethylene microbeads to duckweed is specific. Because the majority of microplastics in freshwaters are made of polyethylene, the use of duckweed for their biomonitoring could provide important information on microplastic pollution in freshwaters.

The impacts of nanoplastic toxicity on the accumulation, hormonal regulation and tolerance mechanisms in a potential hyperaccumulator - Lemna minor L

Plastic pollution, which is currently one of the most striking problems of our time, raises concerns about the dispersal of micro and nano-sized plastic particles in ecosystems and their toxic effects on living organisms. This study was designed to reveal the toxic effects of polystyrene nanoplastic (PS NP) exposure on the freshwater macrophyte Lemna minor. In addition, elucidating the interaction of this aquatic plant, which is used extensively in the phytoremediation of water contaminants and wastewater treatment facilities, with nanoplastics will guide the development of remediation techniques. For this purpose, we examined nanoplastic accumulation, oxidative stress markers, photosynthetic efficiency, antioxidant system activity and phytohormonal changes in L. minor leaves subjected to PS NP stress (P-1, 100 mg L^-1; P-2, 200 mg L^-1 PS NP). Our results showed no evidence of PS NP-induced oxidative damage in P-1 group plants, although PS NP accumulation reached 56 µg g^-1 in the leaves. Also, no significant changes in chlorophyll a fluorescence parameters were observed in this group, indicating unaffected photosynthetic efficiency. PS NP exposure triggered the antioxidant system in L. minor plants and resulted in a 3- and 4.6-fold increase in superoxide dismutase (SOD) activity in the P-1 and P-2 groups. On the other hand, high-dose PS NP treatment resulted in insufficient antioxidant activity in the P-2 group and increased hydrogen peroxide (H₂O₂) and lipid peroxidation (TBARS contents) by 25 % and 17 % compared to the control plants. Furthermore, PS NP exposure triggered abscisic acid biosynthesis (two-fold in the P-1 and three-fold in the P-2 group), which is also involved in regulating the stress response. In conclusion, L. minor plants tolerated NP accumulation without growth suppression, oxidative stress damage and limitations in photosynthetic capacity and have the potential to be used in remediation studies of NP-contaminated waters.

The first plastic produced, but the latest studied in microplastics research: The assessment of leaching, ecotoxicity and bioadhesion of Bakelite microplastics

Bakelite, the first synthetic plastic, is a rather unexplored material in the field of ecotoxicology, despite its long production and use. The aim of this study was to investigate the ecotoxicity of Bakelite microplastics (before and after leaching) and its leachates on four aquatic organisms: the crustacean Daphnia magna, the plant Lemna minor, the bacterium Allivibrio fischeri and the alga Pseudokirchneriella subcapitata. Bakelite microplastics before and after leaching and leachates affected all organisms, but to varying degrees. Leachates showed increased ecotoxicity to Daphnia magna, while Pseudokirchneriella subcapitata was more affected by particles. For Lemna minor and Allivibrio fischeri, the effects of particles before leaching and leachate were comparable, while the negative effect of particles after leaching was minimal or not present. All leachates were analysed, and phenol and phenol-like compounds were the predominant organics found. In addition, bioadhesion of Bakelite microplastics to the surface of Daphnia magna and Lemna minor was confirmed, but the particles were mainly weakly adhered. Results of this study suggest that, in addition to the recently studied microplastics from consumer products (e.g. from polyethylene and polystyrene), microplastics from industrial plastics such as Bakelite may be of increasing concern, primarily due to leaching of toxic chemicals.