Visible light photocatalytic degradation of polypropylene microplastics in a continuous water flow system

Microplastics: Occurrences, treatment methods, regulations and foreseen environmental impacts

Microplastics are a silent threat that represent a high degree of danger to the environment in its different ecosystems and of course will also have an important impact on the health of living organisms. It is evident the need to have effective treatments for their treatment, however this is not a simple task, this as a result of the behavior of microplastics in wastewater treatment plants due to their different types and nature, their long molecular chain, reactivity against water, size, shape and the functional groups they carry. Wastewater treatment plants are at the circumference of the release of these wastes into the environment. They often act as a source of many contaminations, which makes this problem more complex. Challenges such as detection in the current scenario using the latest analytical techniques impede the correct understanding of the problem. Due to microplastics, treatment plants have operational and process stability problems. This review paper will present the in-depth situation of occurrence of microplastics, their detection, conventional and advanced treatment methods as well as implementation of legislations worldwide in a comprehensive manner. It has been observed that no innovative or new technologies have emerged to treat microplastics. Therefore, in this article, technologies targeting wastewater treatment plants are critically analyzed. This will help to understand their fate, but also to develop state-of-the-art technologies or combinations of them for the selective treatment of microplastics. The pros and cons of the treatment methods adopted and the knowledge gaps in legislation regarding their implementation are also comprehensively analyzed. This critical work will offer the development of new strategies to restrict microplastics.

Developments in advanced oxidation processes for removal of microplastics from aqueous matrices

Continuous incorporation of microplastics (MPs) and their fragmented residues into the ecosystem has sparked significant scientific apprehensions about persistence, a multitude of sources, and toxicity impacts on human health and aquatic entities. Overcoming this multifaceted hazard necessitates the development of novel techniques with robust efficiencies to eliminate microplastics from the environmental compartments. Coagulation, flocculation, and membrane filtration are non-destructive techniques but necessitate extra steps for microplastic degradation, whereas biological means have been confirmed less efficient (less than 15% degradation). Recent reports have emphasized advanced oxidation processes (AOPs) as practical treatment alternatives, representing superior catalytic efficacy for microplastic degradation (≈30-95%). Nevertheless, additional investigations should be carried out to evaluate the performance of AOPs in degrading microplastics under real environmental matrices. Moreover, the detection of transformed metabolites, degradation mechanistic insights, and toxicity bioassays are required to substantiate AOP assumption as feasible remediation substitutes. This review focuses on the source, occurrence, discharge, transportation, and associated paramount health risks of microplastics. Advanced oxidation processes-assisted removal of microplastics from the aqueous matrices is thoroughly vetted with up-to-date findings. Factors affecting the degradation of MPs have been discussed in detail. In addition to the generalized mechanistic insights into photocatalytic degradation, the risk assessment of aging intermediates is also comprehended. Finally, the review was concluded by emphasizing current research gaps and incoming research tendencies to provide guidelines for efficiently addressing microplastic pollution.

Prospects of TiO2-based photocatalytic degradation of microplastic leachates related disposable facemask, a major COVID-19 waste

COVID-19 is one of the serious catastrophes that have a substantial influence on human health and the environment. Diverse preventive actions were implemented globally to limit its spread and transmission. Personnel protective equipment (PPE) was an important part of these control approaches. But unfortunately, these types of PPE mainly comprise plastics, which sparked challenges in the management of plastic waste. Disposable face masks (DFM) are one of the efficient strategies used across the world to ward off disease transmission. DFMs can contribute to micro and nano plastic pollution as the plastic present in the mask may degrade when exposed to certain environmental conditions. Microplastics (MPs) can enter the food chain and devastate human health. Recognizing the possible environmental risks associated with the inappropriate disposal of masks, it is crucial to avert it from becoming the next plastic crisis. To address this environmental threat, titanium dioxide (TiO2)-based photocatalytic degradation (PCD) of MPs is one of the promising approaches. TiO2-based photocatalysts exhibit excellent plastic degradation potential due to their outstanding photocatalytic ability, cost efficiency, chemical, and thermal stability. In this review, we have discussed the reports on COVID-19 waste generation, the limitation of current waste management techniques, and the environmental impact of MPs leachates from DFMs. Mainly, the prominence of TiO2 in the PCD and the applications of TiO2-based photocatalysts in MPs degradation are the prime highlights of this review. Additionally, various synthesis methods to enhance the photocatalytic performance of TiO2 and the mechanism of PCD are also discussed. Furthermore, current challenges and the future research perspective on the improvement of this approach have been proposed.

Surfactant-sodium dodecyl sulfate enhanced degradation of polystyrene microplastics with an energy-saving electrochemical advanced oxidation process (EAOP) strategy

Microplastics have been identified as a kind of emerging pollutant with potential ecological risks, and it is an urgent endeavor to find proper technologies for their remediation. Electrochemical advanced oxidation process (EAOP) technology has exhibited robust performance in the removal of various refractory organic pollutants. In this study, we explored a new remediation strategy for polystyrene microplastics (PS MPs), introducing sodium dodecyl sulfate (SDS) to enhance its degradation performance in boron-doped diamond (BDD) anode adopted EAOP. At first, we investigated the degradation behaviors of SDS in the BDD electrolysis. According to the SDS half-life under various current densities, the SDS addition strategy into EAOP is proposed; that is, supplement SDS to 500 mg/L at every half-life during electrolysis except the last cycle. Results indicated that SDS addition greatly enhanced MPs degradation rate in 72 h of EAOP, about 1.35-2.29 times higher than that in BDD electrolysis alone. The SDS assisted EAOP also led to more obvious changes in the particle size, morphology, and functional groups of the MPs. After treatment, a variety of alkyl-cleavage and oxidation products were identified, which attributed to the strong attack of oxidants (i.e., persulfate) on the MPs. The enhanced persulfate generation and oxidants adsorption on MPs can explain the enhancement effect in the EAOP strategy. Cost analysis results showed the surfactant only accounts for < 0.05% of the total operating costs in the SDS assisted EAOP. In general, the current study provided new insight into the effective way to improve the EAOP efficiency of microplastics.

Mitigation of microfibers release from disposable masks - An analysis of structural properties

The use of disposable face masks increased rapidly among the general public to control the COVID-19 spread. Eventually, it increased the disposal of masks and their associated impacts on environmental pollution. Hence, this study aims to analyze the impact of nonwoven fabric structural parameters and weathering on the microfiber release characteristics. Spunbond polypropylene nonwoven with four different weights and meltblown nonwoven with two different weights were used in this study to analyze microfiber release at dry, and wet conditions to simulate improper disposal in the environment. Exposure to sunlight significantly increases the microfiber release from 35 to 50% for spunbond fabric and 56-89% for meltblown fabric. Weathering in sunlight structurally affected the tensile properties of the polypropylene fibers due to photodegradation. The study showed that each mask can produce 1.5 × 10² and 3.45 × 10¹ mg of microfiber/mask respectively in dry and wet states. In the case of structural parameters, a higher GSM (grams per square meter), abrasion resistance, bursting strength, and thickness showed a positive correlation with microfiber release in both fabrics. Significantly a higher microfiber release was reported with meltblown fabric than the spunbond for a given GSM. The presence of finer fibers and more fibers per unit area in meltblown fabric was noted as the main cause. Nonwoven fabric GSM and the number of fibers in a specific area showed a higher influence on microfiber release. Based on the mask consumption reported in the literature, India alone can produce around 4.27 × 10² tons of microfibers/week as an average of dry and wet conditions. The study suggests that the proper selection of physical parameters can significantly reduce the microfiber fiber release at all stages.

Removal of nanoplastics in water treatment processes: A review

Nanoplastics are drawing a significant attention as a result of their propensity to spread across the environment and pose a threat to all organisms. The presence of nanoplastics in water is given attention nowadays as the transit of nanoplastics occurs through the aquatic ecosphere besides terrestrial mobility. The principal removal procedures for macro-and micro-plastic particles are effective, but nanoparticles escape from the treatment, increasing in the water and significantly influencing the society. This critical review is aimed to bestow the removal technologies of nanoplastics from aquatic ecosystems, with a focus on the treatment of freshwater, drinking water, and wastewater, as well as the importance of transit and its impact on health concerns. Still, there exists a gap in providing a collective knowledge on the methods available for nanoplastics removal. Hence, this review offered various nanoplastic removal technologies (microorganism-based degradation, membrane separation with a reactor, and photocatalysis) that could be the practical/effective measures along with the traditional procedures (filtration, coagulation, centrifugation, flocculation, and gravity settling). From the analyses of different treatment systems, the effectiveness of nanoplastics removal depends on various factors, source, size, and type of nanoplastics apart from the treatment method adopted. Combined removal methods, filtration with coagulation offer great scope for the removal of nanoplastics from drinking water with >99 % efficiency. The collected data could serve as base-line information for future research and development in water nanoplastics cleanup.

Advanced oxidation processes for the elimination of microplastics from aqueous systems: Assessment of efficiency, perspectives and limitations

Microplastics act as a vector of heavy metals, organic pollutants, pathogens and resistance genes in the environment further aggravate the pollution of plastics. The conventional wastewater/water treatment processes can physically capture and remove most of microplastics, but the success rates varies. How to quickly remove a large amount of microplastics from aqueous system is a key research topic at present. Recently, advanced oxidation processes (AOPs) as a green elimination strategy has attracted attention because of its effective elimination, strong destruction and safety. The molecular chain of microplastics can be gradually degraded into small molecular organics until H₂O and CO₂ by strong oxidizing free radical produced by AOPs. Unfortunately, problematically, the elimination of microplastics in aqueous system by AOPs is recently carried out on a laboratory scale. The application and implementation of this strategy are restricted by long reaction time, low liquid phase degradation efficiency and the formation of nanoplastics. Generally, the technology is still in its infancy, and most studies are carried out under laboratory conditions. The degradation of microplastics in aqueous system also needs appropriate conditions, but it is not always feasible under field conditions in AOPs. Although AOPs can be used as a green degradation technology to eliminate microplastics in aqueous systems in theory, it still needs to be furtherly explored in practical application. Consequently, before AOPs as a green elimination strategy is successfully applied to the effective remove microplastics, more in-depth research is still required, such as the setting from single condition to complex environment, the transfer from laboratory scale to field scale, and systematic toxicity evaluation of corresponding products.

Tracking microplastics biodegradation through CO2 emission: Role of photoaging and mineral addition

Once microplastics (MPs) enter the terrestrial ecosystem, they may affect the assessment of soil carbon storage and the fluxes of greenhouse gases. This study showed microbial incubation diminished the size and dissolved organic carbon (DOC) content of MPs and introduced more oxygen-containing functional groups to MPs potentially through microbial colonization. The aged MPs generally showed higher carbon mineralization ratio (0.010-0.876 %) than the pristine MPs (0.007-0.189 %), which was supported by their higher enzyme activities and DOC content. Interestingly, four model minerals increased the DOC release and CO₂ emission from MPs by altering MPs physicochemical properties and shaping the habitat for microbial growth. The higher enzyme activities in mineral artificial soils, except for montmorillonite, served as a potential valid explanation for their higher mineralization. The high CO₂ emission but low enzyme activity in montmorillonite artificial soil was due to most DOC being already mineralized. Aging and minerals altered the microflora and enhanced the expression of some C metabolism- and N-related functional genes, which supplemented the cause of higher CO₂ and N₂O emissions from the corresponding artificial soils. Overall, the increased biomineralization of MPs carbon by minerals was divergent from the protective role of minerals on soil organic carbon.

Microplastics in aquatic systems, a comprehensive review: origination, accumulation, impact, and removal technologies

Although the discovery of plastic in the last century has brought enormous benefits to daily activities, it must be said that its use produces countless environmental problems that are difficult to solve. The indiscriminate use and the increase in industrial production of cleaning, cosmetic, packaging, fertilizer, automotive, construction and pharmaceutical products have introduced tons of plastics and microplastics into the environment. The latter are of greatest concern due to their size and their omnipresence in the various environmental sectors. Today, they represent a contaminant of increasing ecotoxicological interest especially in aquatic environments due to their high stability and diffusion. In this regard, this critical review aims to describe the different sources of microplastics, emphasizing their effects in aquatic ecosystems and the danger to the health of living beings, while examining, at the same time, those few modelling studies conducted to estimate the future impact of plastic towards the marine ecosystem. Furthermore, this review summarizes the latest scientific advances related to removal techniques, evaluating their advantages and disadvantages. The final purpose is to highlight the great environmental problem that we are going to face in the coming decades, and the need to develop appropriate strategies to invert the current scenario as well as better performing removal techniques to minimize the environmental impacts of microplastics.

Recent advances in the breakdown of microplastics: strategies and future prospectives

Microplastics pollution is becoming a major environmental issue, and exposure to microplastics has been associated with numerous adverse results to both the ecological system and humans. This work summarized the state-of-the-art developments in the breakdown of microplastics, including natural weathering, catalysts-assisted breakdown and biodegradation. Characterization techniques for microplastic breakdown involve scanning electron microscopy, Fourier infrared spectroscopy, X-ray photoelectron spectroscopy, etc. Bioavailability and adsorption capacity of microplastics may change after they are broken down, therefore leading to variety in microplastics toxicity. Further prospectives for should be focused on the determination and toxicity evaluation of microplastics breakdown products, as well as unraveling uncultivable microplastics degraders via cultivation-independent approaches. This work benefits researchers interested in environmental studies, particularly the removal of microplastics from environmental matrix.

Rapid surface degradation of co-axially arranged polypropylene globules by nanoporous carbonized TiO2 assisted with UV-C

The degradation of plastics, especially polypropylene (PP), is difficult since it is the most hydrophobic polymer. Photocatalytic degradation of PP films has been reported to be one of the most efficient degradation techniques. However, it is still insignificant to employ it in field applications. In this study, TiO₂ nanoparticles supported on amorphous carbon with nanoporosity (TiO₂@NC) are used as a photocatalyst to degrade macro-sized co-axially oriented PP globules under the influence of UV-C irradiation. Surface characterization such as SEM, ATR-FTIR, and XPS of the PP globules was performed. The SEM images distinctly showed the surface degradation phenomenon. Interestingly, the ATR-FTIR spectra demonstrated a significant rise in the band intensity in the -OH radical region and fairly in the CO region as well, with the increase in the photocatalytic time. Surprisingly, in the XPS spectra, the intensity of C-1s spectra kept on falling, and the intensity of O-1s spectra kept on rising with the increase in the photocatalytic time. The higher surface area due to nanoporosity of TiO₂@NC enhanced the photocatalytic degradation of PP globules than previously reported studies. TiO₂@NC seems to be a potential catalyst for the degradation of different types of polymers.

Removal of microplastics and nanoplastics from urban waters: Separation and degradation

The omnipresent micro/nanoplastics (MPs/NPs) in urban waters arouse great public concern. To build a MP/NP-free urban water system, enormous efforts have been made to meet this goal via separating and degrading MPs/NPs in urban waters. Herein, we comprehensively review the recent developments in the separation and degradation of MPs/NPs in urban waters. Efficient MP/NP separation techniques, such as adsorption, coagulation/flocculation, flotation, filtration, and magnetic separation are first summarized. The influence of functional materials/reagents, properties of MPs/NPs, and aquatic chemistry on the separation efficiency is analyzed. Then, MP/NP degradation methods, including electrochemical degradation, advanced oxidation processes (AOPs), photodegradation, photocatalytic degradation, and biological degradation are detailed. Also, the effects of critical functional materials/organisms and operational parameters on degradation performance are discussed. At last, the current challenges and prospects in the separation, degradation, and further upcycling of MPs/NPs in urban waters are outlined. This review will potentially guide the development of next-generation technologies for MP/NP pollution control in urban waters.

Immobilized enzyme/microorganism complexes for degradation of microplastics: A review of recent advances, feasibility and future prospects

Environmental prevalence of microplastics has prompted the development of novel methods for their removal, one of which involves immobilization of microplastics-degrading enzymes. Various materials including nanomaterials have been studied for this purpose but there is currently a lack of review to present these studies in an organized manner to highlight the advances and feasibility. This article reviewed more than 100 peer-reviewed scholarly papers to elucidate the latest advances in the novel application of immobilized enzyme/microorganism complexes for microplastics degradation, its feasibility and future prospects. This review shows that metal nanoparticle-enzyme complexes improve biodegradation of microplastics in most studies through creating photogenerated radicals to facilitate polymer oxidation, accelerating growth of bacterial consortia for biodegradation, anchoring enzymes and improving their stability, and absorbing water for hydrolysis. In a study, the antimicrobial property of nanoparticles retarded the growth of microorganisms, hence biodegradation. Carbon particle-enzyme complexes enable enzymes to be immobilized on carbon-based support or matrix through covalent bonding, adsorption, entrapment, encapsulation, and a combination of the mechanisms, facilitated by formation of cross-links between enzymes. These complexes were shown to improve microplastics-degrading efficiency and recyclability of enzymes. Other emerging nanoparticles and/or enzymatic technologies are fusion of enzymes with hydrophobins, polymer binding module, peptide and novel nanoparticles. Nonetheless, the enzymes in the complexes present a limiting factor due to limited understanding of the degradation mechanisms. Besides, there is a lack of studies on the degradation of polypropylene and polyvinyl chloride. Genetic bioengineering and metagenomics could provide breakthrough in this area. This review highlights the optimism of using immobilized enzymes/microorganisms to increase the efficiency of microplastics degradation but optimization of enzymatic or microbial activities and synthesis of immobilized enzymes/microorganisms are crucial to overcome the barriers to their wide application.

Effect of land use on microplastic pollution in a major boundary waterway: The Arvand River

The occurrence of microplastics (MPs) was investigated in the Arvand River (Iran). The Arvand River (200 Km) is a major water body that flows through land with diverse use and it meets the Persian Gulf. This study constitutes the first assessment of MP pollution (prevalence and physico-chemical characteristics) in the Arvand river, both in the sediment and in the water. MP monitoring has been carried out in 24 stations located along the river. The MP pollution found ranged between 1 and 291 items·L^-1 and 70 to 15,620 items·kg^-1 (dw), in water and sediment, respectively. The majority of MPs were fibres, black/grey and yellow/orange in colour, and mainly 250-500 μm and >1000 μm in size. Polyethylene terephthalate (PET), polypropylene (PP), nylon (NYL), high-density polyethylene (HDPE), and polystyrene (PS) were found in sediment samples. All these polymers, except HDPE, were also identified in the water samples. PET and PP were dominant in the water samples; whereas PET and PS were the most abundant in the sediments. The vicinity of urban wastewater effluents could be behind MP pollution in both water and sediments. Significant differences (p < 0.05) of MP concentrations were affected by different land uses when comparing MP levels in undisturbed natural area with urban areas. A strong correlation between MP fibres and fragments found with PCA biplots revealed their similar distribution in water. In the sediment samples, fibre and fragment MP particles were significantly correlated with colloidal particles (e.g., clay and organic matter) suggesting a relevant role of colloidal particles in the aquatic ecosystem of the Arvand River in transporting MPs. This study contributes to the better understanding of the presence of MP in major rivers, which are systems that have been scarcely investigated for this type of pollution, and it can inform interventions to reduce MP inputs to the river and sea.

Photon-induced redox chemistry on pyrite promotes photoaging of polystyrene microplastics

The mineral particles in sediment could affect polystyrene microplastics (PS-MPs) prosperity through physical and chemical interactions. Pyrite with semiconducting properties is the most abundant metal sulfide mineral in the sediments of lake and river mouths. The widespread sunlight and the coexistence of PS-MPs and pyrite in lake or river water due to frequently water fluctuation is a typical photoaging environment for PS-MPs. The oxidation of reactive oxygen species (ROS) generated from pyrite would degrade the PS-MPs in theory. However, researches about photoaging of PS-MPs mediated by pyrite are paucity. Here, we investigated the photoaging process of PS-MPs affected by pyrite under simulated light condition. Remarkably, surface morphology of PS-MPs mediated by pyrite was broken. And the oxygen-containing functional group of PS-MPs increased, as revealed by Fourier Transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and contact angle test. 2D-COS analysis showed photoaging of PS-MPs with pyrite happened in the following order: C-H > C=C > C=O > C-O > OH. The photoaging of PS-MPs and transformation of intermediate were accelerated by ROS (O₂·^-, ·OH and ¹O₂) generated from pyrite. The free ·OH may play a major role in the promotion. Because the interfacial ROS reactions on pyrite surface were limited due to the electrostatic repulsion between pyrite and PS-MPs. The study explored photoaging behavior of PS-MPs accelerated by pyrite, which could be helpful for understanding photon-induced redox chemistry on PS-MPs via widespread sulfide metal minerals on earth's surface and providing further information to assess potential risks of PS-MPs.

Zinc oxide nanoparticles dissolution and toxicity enhancement by polystyrene microplastics under sunlight irradiation

Zinc oxide nanoparticles (ZnO NPs) dissolution is a critical process for the transformation and toxicity of ZnO NPs in aquatic environments. However, the effect of microplastics (MPs) on dissolution and toxicity of ZnO NPs under sunlight irradiation is still lacking. Herein, the dramatic increase in sunlight-induced ZnO NPs dissolution by polystyrene (PS) MPs was proven, which was attributed to the increase in h⁺-dependent and proton-dependent ZnO NPs dissolution by PS MPs, yielding ¹O₂ generation inhibition and acid release, respectively. The sizes, functional groups and aging status of PS MPs and pH were characteristic ZnO NPs dissolution through modifying ¹O₂, •OH and O₂^•- generation and acid release. Furthermore, the ZnO NPs dissolution affected by PS MPs also occurred in three realistic water samples, which were mainly governed by dissolved organic matter (DOM) and CO₃^2-, rather than Cl^- or SO₄^2-. The PS MPs (1 μg/mL) dramatically altered the Zn²⁺:ZnO ratio in ZnO NPs suspension after 96 h of sunlight irradiation and presented vehicle effects on Zn²⁺, which in turn significantly increased the ion-related toxicity of ZnO NPs to Daphnia magna. Based on the PS MPs enhanced dissolution and toxicity of ZnO NPs, the effects of PS MPs on the environmental risk assessment of ZnO NPs should be seriously considered in freshwater environments under sunlight irradiation.

Mechanically durable anti-bacteria non-fluorinated superhydrophobic sponge for highly efficient and fast microplastic and oil removal

Microplastics (MPs) pollution evolves into a global environmental problem to be solved urgently. Although many studies are exploring ways to remove MPs from water environment, most of them are lack of selectivity and low efficiency. Herein, considering the fascinating absorption selectivity of superwetting materials, a robust magnetic-responsive superhydrophobic and superoleophilic sponge was firstly used to quickly eliminate MPs from water with very high efficiency. The functional sponge was fabricated by a non-fluorinated coating technique that consisted of polydimethylsiloxane (PDMS) grafted Fe₃O₄ particle, PDMS grafted halloysite nanotubes, and PDMS binder. The coated sponge achieved excellent mechanically durable and chemically stable superhydrophobicity that resisted a series of severe treatments. It was unquestionable to show very fast oil absorption. What's more, it especially showed very high adsorption capacity (24.3-48.2 mg/g) and could quickly adsorb almost 100% MPs (polypropylene, polyvinyl chloride, and polyethylene) from aqueous suspensions. Moreover, the removal rates remained almost 100% for these MPs after 50 cycles. Besides, the coated sponge had excellent salt tolerance and antibacterial activity to Escherichia coli (E. coli) (99.91%) and Staphylococcus aureus (S. aureus) (90.46%). The adsorption mechanism of the coating was discussed from the perspectives of molecular structure, electronic effect, steric hindrance, and size-scale effect. The absorption driving force mainly derived from the intra-particle diffusion under capillary attraction, whilst slight electrostatic interaction, hydrogen bond interaction, and σ-p (or p-p) conjugation between PDMS and MPs. This functional sponge was destined to be a new strategy in the removal of MPs and other solid pollutants, especially in the high-salinity and rich-microorganism water environment.

Nanomaterials for microplastic remediation from aquatic environment: Why nano matters?

The contamination of microplastics in aquatic environment is regarded as a serious threat to ecosystem especially to aquatic environment. Microplastic pollution associated problems including their bioaccumulation and ecological risks have become a major concern of the public and scientific community. The removal of microplastics from their discharge points is an effective way to mitigate the adverse effects of microplastic pollution, hence has been the central of the research in this realm. Presently, most of the commonly used water or wastewater treatment technologies are capable of removing microplastic to certain extent, although they are not intentionally installed for this reason. Nevertheless, recognizing the adverse effects posed by microplastic pollution, more efforts are still desired to enhance the current microplastic removal technologies. With their structural multifunctionalities and flexibility, nanomaterials have been increasingly used for water and wastewater treatment to improve the treatment efficiency. Particularly, the unique features of nanomaterials have been harnessed in synthesizing high performance adsorbent and photocatalyst for microplastic removal from aqueous environment. This review looks into the potentials of nanomaterials in offering constructive solutions to resolve the bottlenecks and enhance the efficiencies of the existing materials used for microplastic removal. The current efforts and research direction of which studies can dedicate to improve microplastic removal from water environment with the augmentation of nanomaterial-enabled strategies are discussed. The progresses made to date have witnessed the benefits of harnessing the structural and dimensional advantages of nanomaterials to enhance the efficiency of existing microplastic treatment processes to achieve a more sustainable microplastic cleanup.

Microplastics and Heavy Metals Removal from Fresh Water and Wastewater Systems Using a Membrane

Water pollution, resulting from the degradation of plastics into microplastics, exposes humans and other living organisms to contaminated drinking water. Microplastics are capable of adsorbing toxic heavy metals which are carcinogenic and may affect the reproductive functions of living organisms. Hence, this study focuses on the characterization and quantification of microplastics in water to raise the awareness and propose a method of dealing with this emerging pollutant in various aqueous environments. The microplastics were separated from water using polyvinylidene difluoride (PVDF) and PVDF modified with carbon nano-onions (CNOs). The PVDF exhibited the highest concentration of microplastics in the wastewater influent (140 ± 1.85 MP/L) compared to the effluent (8.8 ± 2.10 MP/L), tap water (6.5 ± 5.77 MP/L), and lake water (10 ± 2.65 MP/L). The stereo microscope displayed red, blue, and black colored plastics. The morphological properties were determined using SEM. ATR-FTIR, equipped with Spectrum 10 Spectroscopy Software was used to establish the presence of high-density polyethylene (50%), poly(1,4-butylene terephthalate) (16.6%), nylon 12 (16.6%), and cellulose (16.6%) in the influent. The quantification of heavy metals extracted from the microplastics indicated that the concentrations of As (1.759 to 8.699 mg/L), Cu (83.176 mg/L) and Zn (0.610 mg/L) were above the acceptable limits. Our work is beneficial for the development of a microplastics monitoring protocol for various municipalities. Water treatment plants may also include the treatment of microplastics in the influent and monitor the effluent before the water is released back into the environment.

Photocatalytic Degradation of Polyethylene Microplastics and Disinfection of E. coli in Water over Fe- and Ag-Modified TiO2 Nanotubes

In this study, Fe- and Ag-modified TiO2 nanotubes were synthesized via an anodization method as photocatalysts for degradation of polyethylene microplastics and disinfection of Escherichia coli (E. coli). The anodization voltage, as well as the Fe3+ or Ag+ concentrations on TiO2 nanotubes were evaluated and correlated to their corresponding photocatalytic properties. TiO2 nanotubes were firstly synthesized by anodization of Ti plates in a glycerol-based electrolyte, followed by incorporation of either Fe or Ag via a Successive Ionic Layer Adsorption and Reaction (SILAR) method with Fe(NO3)3 and AgNO3 as Fe and Ag precursors, respectively. UV-Vis DRS shows that the addition of Fe or Ag on TiO2 nanotubes causes a redshift in the absorption spectra. The X-ray diffractograms indicate that, in the case of Fe-modified samples, Fe3+ was successfully incorporated into TiO2 lattice, while Ag scatters around the surface of the tubes as Ag and Ag2O nanoparticles. A microplastic degradation test was carried out for 90 mins inside a photoreactor with UVC illumination. TiO2 nanotubes that are anodized with a voltage of 30 V exhibit the best degradation results with 17.33% microplastic weight loss in 90 mins. Among the modified TiO2 nanotubes, 0.03 M Ag-TiO2 was the only one that surpassed the unmodified TiO2 in terms of microplastic degradation in the water, offering up to 18% microplastic weight loss in 90 min. In terms of E. coli disinfection, 0.03M Ag-TiO2 exhibit better performance than its unmodified counterpart, revealing 99.999% bactericidal activities in 10 mins. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Ageing and fragmentation of marine microplastics

The generation of small fragments from the environmental ageing of microplastics (MPs) is still a poorly known process. This work addresses the fragmentation of MPs obtained from marine debris consisting of polyethylene and polypropylene (PE and PP in environmental mixture) and polystyrene (PS) after exposure to accelerated ageing by irradiation and mechanical stirring. Number particle size distribution in the 1-100 μm range was assessed by combining laser diffractometry with particle counts from flow cytometry. The results showed the generation of a high number of small MP particles, which reached 10⁵-10⁶ items/mg of plastic with most fragments <2 μm. The results showed that environmentally aged MPs give rise to a larger number of small MPs in a pattern consistent with progressive fragmentation in the three spatial dimensions. The proportion of small MPs was much higher than that found in current sampling campaigns, suggesting a severe underestimation of the environmental presence of small MPs. We also demonstrated the generation of nanoplastics (NPs) in the fraction <1 μm from irradiated runs. The results showed that the mechanism that produced nanoplastics (NPs) from MPs was irradiation, which yielded up to 10¹¹-10¹³ NPs/g with particle size in the few hundreds of nm range. Our results are relevant for the assessment of fate and risk of plastic debris in the environment showing that the number of small plastic fragments produced during the ageing of MPs is much larger than expect from the extrapolation of larger size populations.

Photocatalytic degradation of (micro)plastics using TiO2-based and other catalysts: Properties, influencing factor, and mechanism

(Micro)plastics pollution has raised global concern because of its potential threat to the biota. The review on recent developments of photocatalytic degradation of (micro)plastics is still insufficient. In this study, we have discussed various bare and composites photocatalysts involved in the photocatalytic degradation of (micro)plastics. The photocatalytic mechanisms and factors affecting the degradation were also discussed. To improve the performance of photocatalysts, their surface is modified with metal or non-metal dopants. These doped photocatalysts are then compounded with a variety of environmentally friendly and nontoxic polymers to prepare multifunctional composites. The generation of reactive oxygen species (ROS) plays an important role in the photocatalytic degradation of (micro)plastics, and superoxide ions (O₂^-) and hydroxyl radicals (OH) participate in the photocatalytic degradation, leading to the breaking of the polymer chain and the production of some intermediates. Although satisfactory progress has been achieved in the photodegradation of (micro)plastics, most photocatalytic degradation technologies investigated to date cannot realize the complete mineralization of (micro)plastics. Furthermore, based on the current challenges of the existing photocatalytic degradation technologies, perspectives for future research directions have been proposed. This review presents a systematic summary of the progress made in the photocatalytic degradation of (micro)plastics and offers a comprehensive reference for future research on improving the (micro)plastics photocatalytic degradation efficiency.

Extraction, identification, and environmental risk assessment of microplastics in commercial toothpaste

Microplastics in personal care and food products are given much importance globally due to the adverse impact of microplastics on living beings. In the present study, microplastics from ten different commercially sold toothpaste in India were extracted by vacuum filtration and characterized with microscopic and Fourier-transform infrared spectroscopic analyses. Results revealed that colorless fragments and fibers were the microparticle types of common occurrence which ranged from 0.2 to 0.9% weight in the toothpaste with an abundance range of 32.7-83.2%. Fifty percent of the toothpaste samples showed more than 50% microplastic particle abundance indicating that the microplastic plastic particles were added by the manufacturers. The minimum size of microplastics recorded in the present study was 3.5 μm with a maximum size exceeding 400 μm. The maximum number of microplastics in the toothpaste was 167, 508 and 193 respectively, distributed in the size range of <100 μm, 100-400 μm, and >400 μm. The present study recorded four major polymer types, viz., cellophane, polypropylene, polyvinyl chloride, and polyamide in the toothpaste samples. Surprisingly, polyethylene-a common polymer reported in toothpaste was not traced in the present samples. Regarding the Indian context, the current study is a new addition to the knowledge of the occurrence of microplastics in toothpaste. The average annual addition of microplastics into the environment through toothpaste was calculated as 1.4 billion g/year for India, posing a significant threat to the environment.

Characteristics and source-pathway of microplastics in freshwater system of China: A review

China plays a key role in global plastic production, consumption and disposal, which arouses growing concern about microplastics (MPs) contamination in Chinese freshwater systems. However, few reviews have discussed the characteristics of MP pollution in whole freshwater systems at a national scale. In this review, we summarized the characteristics, sources and transport pathways of MPs in Chinese freshwater systems including surface water and sediment. Results showed that current research mainly focused on the middle and lower reaches of the Yangtze River and its tributaries, as well as lakes and reservoirs along the Yangtze River. Large-scale reservoirs, rivers and lakes located in densely populated areas usually showed higher abundances of MPs. The majority of MPs in Chinese surface water and sediment mainly consisted of polyethylene and polypropylene, and the most common morphologies were fibers and fragments. To identify the sources and pathways, we introduced the source-sink-pathway model, and found that sewage system, farmland and aquaculture area were the three most prevalent sinks in freshwater systems in China. The source-sink-pathway model will help to further identify the migration of MPs from sources to freshwater systems.

Occurrence, impact, toxicity, and degradation methods of microplastics in environment-a review

Microplastic defines as a tiny plastic particle that has a size of less than 5 mm and is ubiquitous in the environment. Due to the tiny size, this microplastic adversely affected the environment, notably aquatic life via ingestion, choking, and entanglement. This microplastic is arduous to degrade as it takes a thousand years due to the properties of plastic itself and consequently remains in nature. In dealing with microplastic issues, this paper reflects the occurrence, impact, toxicity, and degradation methods of microplastics in the environment including physical, chemical, and biological treatments. Here, the physical treatment methods include incineration treatment, ultraviolet (UV), and photocatalytic. The incineration process contributes to environmental pollution due to the release of toxic gases into the atmosphere. In addition, chemical treatments for plastic waste are the degradation process involving chemical additives such as ethylene glycol (EG), nano-magnesium oxide (MgO), diethylene glycol (DEG), and calcium or zinc (Ca/Zn) stearate as a catalyst. These treatments depend on the chemicals that can affect human health and the ecosystem. The biodegradation treatment using bacterial and fungal species can consume the microplastic without disrupting the surrounding environment and biota. It includes recent findings on the biodegradation of microplastic under aerobic and anaerobic conditions. Thus, biodegradation can be considered the best option to degrade microplastic as green and sustainable technology.

Identification and Quantification of Microplastics in Effluents of Wastewater Treatment Plant by Differential Scanning Calorimetry (DSC)

In this research, the presence of microplastics was detected through a differential scanning calorimetry (DSC) analysis of three wastewater treatment plants. One of these plants applied only a preliminary treatment stage while the others applied up to a secondary treatment stage to evaluate their effectiveness. The results showed the presence of polyethylene (PE), polystyrene (PS), polypropylene (PP) and polyethylene terephthalate (PET), which were classified as fragments, fibers or granules. During the evaluation of the plants, it was determined that the preliminary treatment did not remove more than 58% of the microplastics, while the plants applying up to a secondary treatment with activated sludge achieved microplastic removal effectiveness between 90% and 96.9%.

Kinetics of microplastic generation from different types of mulch films in agricultural soil

Upon environmental weathering, plastic materials form smaller sized microplastics, of which the contamination in agricultural fields is of significant importance and increasing social concern. Plastic mulch films are considered a major source of agricultural soil microplastic pollution. However, the mechanism and kinetics of microplastic formation from plastic mulch films were rarely understood. In this study, the rate of microplastic generation from typical mulch films, such as oxodegradable, biodegradable, and conventional non-degradable (polyethylene, PE) mulch films, were quantified in soil under simulated UV irradiation. Results showed that microplastic formation was more rapid from biodegradable mulch film, followed sequentially by oxodegradable mulch film, white PE mulch film, and black PE mulch film. The kinetics of microplastic generation strictly followed the Schwarzchild's law, with exponential growth at indexes between 1.6309 and 2.0502 in the microplastic generation model. At a cumulative UV irradiation of 2.1 MJ/m², the average quantity of microplastics released from biodegradable, oxodegradable, and white and black non-degradable mulch films were 475, 266, 163, 147 particles/cm², respectively; with particle sizes largely distributed within 0.02-0.10 mm range. Concurrent increase in crystallinity and surface erosion of the mulch films were observed upon UV irradiation, which further determined the accessibility and activity of the materials to photo-oxidation (reflected as HI indexes), therefore played a critical role on the quantity and size ranges of microplastic debris.

Release of microplastics from typical rainwater facilities during aging process

As the demand for urban flood prevention and drainage increases, a large number of plastic rainwater facilities are in use. Microplastics will be released inevitably into stormwater systems during aging and hydraulic scouring processes, which could cause potential pollution risk. This study simulated the release behavior of microplastics from three typical plastic rainwater facilities including a rainwater inspection well, rainwater storage module, and rainwater pipe (mainly composed of high-density polyethylene, polypropylene, and polyvinyl chloride, respectively) under the effects of aging and hydraulic scouring. After 15-45 days of UV aging and 72 h of hydraulic scouring, the surfaces of the three facilities were found to exhibit increases in roughness, cracks, folds, and cavities, with the most pronounced changes occurring in the rainwater storage module. As the aging time increased, oxygen-containing functional groups formed and led to carbon chain scission. Fourier transform infrared spectroscopy (FTIR), two-dimensional correlation spectroscopy (2D-COS) and X-ray photoelectron spectroscopy (XPS) of facility surfaces showed that the formation of oxygen-containing functional groups was an important factor affecting the release of microplastics. The amount of microplastics released from the three facilities ranged from 160 to 1905 items/g (microplastics/facilities), following in the order of rainwater inspection well > rainwater storage module > rainwater pipe. The particle size of the released microplastics ranged from 3 to 1363 μm, with 10-30 μm accounting for the greatest proportion of particles, 50.10%. The size of microplastics released from the rainwater inspection well and rainwater storage module increased with the aging degree, while the release from the rainwater pipe decreased. The release behavior depends mainly on the composition of the materials and the aging time. Thus, microplastics can be released from plastic rainwater facilities under suitable conditions. The results can be used to further evaluate microplastic pollution caused by urban rainwater facilities.

Microplastics and nanoplastics: Recent literature studies and patents on their removal from aqueous environment

The presence of microplastics (MP) and nanoplastics (NP) in the environment poses significant hazards towards microorganisms, humans, animals and plants. This paper is focused on recent literature studies and patents discussing the removal process of these plastic pollutants. Microplastics and nanoplastics can be quantified by counting, weighing, absorbance and turbidity and can be further analyzed using scanning electron microscopy (SEM), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, surface-enhanced Raman spectroscopy and Raman tweezers. Mitigation methods reported are categorized depending on the removal characteristics: (i) Filtration and separation method: Filtration and separation, electrospun nanofiber membrane, constructed wetlands; (ii) Capture and surface attachment method: coagulation, flocculation and sedimentation (CFS), electrocoagulation, adsorption, magnetization, micromachines, superhydrophobic materials and microorganism aggregation; and (iii) Degradation method: photocatalytic degradation, microorganism degradation and thermal degradation; where removal efficiency between 58 and 100% were reported. As these methods are significantly distinctive, the parameters which affect the MP/NP removal performance e.g., pH, type of plastics, presence of interfering chemicals or ions, surface charges etc. are also discussed. 42 granted international patents related to microplastics and nanoplastics removal are also reviewed where the majority of these patents are focused on separation or filtration devices. These devices are efficient for microplastics up to 20 μm but may be ineffective for nanoplastics or fibrous plastics. Several patents were found to focus on methods similar to literature studies e.g., magnetization, CFS, biofilm and microorganism aggregation; with the addition of another method: thermal degradation.

Impact of aquatic microplastics and nanoplastics pollution on ecological systems and sustainable remediation strategies of biodegradation and photodegradation

The extreme degree of microplastics contamination and its negative impact on ecosystems has become a serious and emerging global concern. Microplastics are mainly generated from products that are used primarily in our everyday lives and are also generated from the fragmentation of larger plastic wastes. It easily penetrates the food chain and, when ingested by aquatic animals or humans, can pose serious health problems. Recently, several technologies have been developed to control the unrestricted spread of microplastics and possibly eradicate them; however, still under investigation. In this review, we have illustrated the types of microplastics, their harmful effect on living things, and the progress to degrade them to protect the environment and life on earth. Several promising and eco-friendly technologies including microbial and enzymatic approaches are enticing to eliminate the microplastics. Also, the photodegradation of microplastics contaminations appeals as a more fascinating approach. The metal oxide-assisted photodegradation of microplastics has also been taken into account. This work presented an impact on the comprehensive research for the effective degradation of different microplastic compositions as well as emerging green approaches for a sustainable environment and a healthier life.

Photocatalytic and biological technologies for elimination of microplastics in water: Current status

Water pollution by microplastics (MPs) has emerged as a significant environmental and public health concern. Several conventional technologies in drinking water and wastewater treatment facilities are capable of capturing a substantial portion of microplastics from surface water; however, only limited methods are available for actual destruction of microplastics. Rate of success is highly variable, and actual mechanisms which result in MP destruction are only partly known. Photocatalysis and microbial degradation technologies show promise at laboratory scale for the transformation of microplastics to water-soluble hydrocarbons, carbon dioxide and, in limited cases, useful fuels. Both photocatalytic and microbial technologies offer the potential for long-term water security and ecological stability and deserve further attention by scientists. Additional research is necessary, however, in identifying more effective semiconductors for photocatalysis, and optimal effective microbial consortia and environmental conditions to optimize microplastic biodegradation. Many more polymer types beyond polyethylene must be studied for degradation, and laboratory-scale research must be expanded to field-scale. This paper provides a comprehensive overview of processes and mechanisms for removing MPs by photocatalysis and microbial technologies. It provides useful data for research dedicated to improved removal of MPs from surface waters.

Eelgrass (Zostera marina) and its epiphytic bacteria facilitate the sinking of microplastics in the seawater

Marine microplastics have received considerable attention as a global environmental issue. However, despite the constant accumulation of microplastics in the ocean, their transport processes and mechanisms remain poorly understood. This study investigated microplastics in the sediments of seagrass meadows and nearby regions without seagrass along the Shandong coast and found that the sediment in the seagrass meadows was a sink for microplastics. Subsequently, we evaluated the influence of eelgrass (Zostera marina), a common coastal seagrass, on the sedimentation of suspended polystyrene microplastics. The results showed that 0.5, 1.0, and 2.0 g/L eelgrass leaves decreased the abundance of microplastics in seawater in a dose-dependent manner over a period of 3-48 h under shaking conditions at 120 rpm at 22 °C. After 48 h of shaking, microplastic abundances in the 0.5, 1.0, and 2.0 g/L eelgrass groups significantly decreased by 46.9%, 53.1%, and 88.4%, respectively. Microplastics can adhere to eelgrass leaves and form biofilms, which promoted the formation of white floc that traps the suspended microplastics, causing them to sink. Furthermore, two epiphytic bacteria (Vibrio and Exiguobacterium) isolated from the eelgrass leaves decreased the abundances of suspended microplastics by 95.7% and 94.5%, respectively, in 48 h by accelerating the formation of biofilms on the microplastics. Therefore, eelgrass and its epiphytic bacteria facilitated the sinking of microplastics and increased the accumulation of microplastics in the sediments of seagrass meadows in coastal regions.

Challenges and opportunities in bioremediation of micro-nano plastics: A review

Rising level of micro-nano plastics (MNPs) in the natural ecosystem adversely impact the health of the environment and living organisms globally. MNPs enter in to the agro-ecosystem, flora and fauna, and human body via trophic transfer, ingestion and inhalation, resulting impediment in blood vessel, infertility, and abnormal behaviors. Therefore, it becomes indispensable to apply a novel approach to remediate MNPs from natural environment. Amongst the several prevailing technologies of MNPs remediation, microbial remediation is considered as greener technology. Microbial degradation of plastics is typically influenced by several biotic as well as abiotic factors, such as enzymatic mechanisms, substrates and co-substrates concentration, temperature, pH, oxidative stress, etc. Therefore, it is pivotal to recognize the key pathways adopted by microbes to utilize plastic fragments as a sole carbon source for the growth and development. In this context, this review critically discussed the role of various microbes and their enzymatic mechanisms involved in biodegradation of MNPs in wastewater (WW) stream, municipal sludge, municipal solid waste (MSW), and composting starting with biological and toxicological impacts of MNPs. Moreover, this review comprehensively discussed the deployment of various MNPs remediation technologies, such as enzymatic, advanced molecular, and bio-membrane technologies in fostering the bioremediation of MNPs from various environmental compartments along with their pros and cons and prospects for future research.

Identification of micro- and nanoplastics released from medical masks using hyperspectral imaging and deep learning

In this study, dark-field microscopy-based hyperspectral imaging augmented with deep learning data analysis was applied for effective visualisation, detection and identification of microplastics released from polypropylene medical masks.

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.

A clean and efficient flotation towards recovery of hazardous polyvinyl chloride and polycarbonate microplastics through selective aluminum coating: Process, mechanism, and optimization

Polyvinyl chloride (PVC) and polycarbonate (PC) microplastics are major sources of hazardous chlorine and bisphenol A, threatening the ecosystem and environment. Plastic recycling can control the source of microplastics pollution, but the recycling of PVC and PC will be prevented by invalid separation. We established a novel and clean flotation method to separate PVC and PC microplastics by using aluminum coating. Trace amounts of Al(OH)₃ can selectively coat the PVC microplastics surface due to its strong affinity for PVC. The contact angle of PVC decreases by 24° due to abundant hydroxyl groups of Al(OH)₃ coating, whereas PC remained hydrophobic. Response surface methodology (RSM) combining Box-Behnken design (BBD) is used to optimize modification. A quadratic model is established to predict PC purity, explore the interaction between pH, aluminum chloride concentration, and ultrasonic duration. The recovery and purity of microplastics can exceed 99.65% with parameter optimization. The effects of multi-component, brand, shape, size, and mass ratio of plastics are utilized to evaluate the application potential. The suitable situations and limits of this method are disclosed. The aluminum coating offers significant benefits over other modifications in terms of reaction temperature, treatment time, and pollution prevention. Flotation based on aluminum coating provides a new insight for separating and recycling microplastics.

Incidence of plastic ingestion by the shortfin mako, Isurus oxyrinchus, off the northeast coast of Taiwan

This present study documents the incidence of plastic digestion by shortfin mako shark (Isurus oxyrinchus), caught by the Taiwanese small-scale tuna longline fishery in the Northwest Pacific Ocean (between the northeast coast of Taiwan and Japan). In 20 stomachs of shortfin mako, nearly 10% of samples contained at least one piece of plastic debris. The ingested plastic debris was found in the forms of films (5.0 cm) and fragments (3.0 mm) and was identified as polypropylene (PP) based on its polymer characteristics. The results from the analysis provide evidence for the anthropogenic origin and potential intake pathway of direct engulfment of ingested plastics. Our results also confirmed the low incidence of plastic ingestion in shortfin mako, suggesting that pelagic marine species may be relatively less affected by plastic pollution. Future research efforts are thus needed to assess the long-term impact of plastic pollution on marine species.

Microplastics as an emerging source of particulate air pollution: A critical review

Accumulation of plastic litter exerts pressure on the environment. Microplastics (MPs) pollution has become a universal challenge due to the overexploitation of plastic products and unsystematic dumping of plastic waste. Initial studies on MPs and their implications had been confined to aquatic and terrestrial ecosystems, but recent research has also focused on MPs in the air. Their impacts on urban air quality and atmospheric transport to pristine habitats have emerged to be a serious concern. However, the extent and the significance of impacts of airborne particulate matter (PM) MPs on human health are not clearly understood. Further, the influence of airborne MPs on indoor and outdoor air quality remains unknown. We highlight the human health impacts of airborne PM-MPs with a special focus on the occupational safety of the industry workers, their possible influence on Air Quality Index (AQI), their potential exposure, and accumulation in the canopy/arboreal, above-canopy and atmospheric (aerial) habitats. The present review emphasizes the data limitations and knowledge gaps on the atmospheric transport and contribution of particulate plastics to the worsening of overall urban air quality and throws critical perspectives on whether atmospheric MPs pollution is trivial or an actual matter of concern.

Post COVID-19 pandemic: Biofragmentation and soil ecotoxicological effects of microplastics derived from face masks

Because of the COVID-19 pandemic, used face masks have increasingly littered the environment and are causes for concern since they are commonly made of plastics such as polypropylene. Understanding production of microplastics from face masks is essential for predicting the post COVID-19 pandemic impact on the soil ecosystem. We investigated the generation of nanofibers from meltblown face mask filters (MB filters) and their adverse effects on soil species, particularly the earthworm and springtail. Results of MB filter soil bioassays at a high concentration (1000 mg/kg dry soil) suggest inhibited reproduction and stunted growth in springtails, decreased intracellular esterase activity in earthworm coelomocytes, and inhibited spermatogenesis in male earthworm reproductive tissues. Moreover, it was estimated that generation of nanofibers from microfibers and fragments of MB filters might occur in the soil ecosystem post COVID-19. This study does not oppose the use of face masks but aims to encourage appropriate disposal of the masks. Preservation of human health and the ecosystem should be prioritized even amidst the COVID-19 pandemic.

Bibliometric Analysis on the Papers Dedicated to Microplastics in Wastewater Treatments

The presence of microplastics (MPs) in the environment is becoming a problem for soils and seas, as well as for the food chain of animals and humans. The scientific community has been called upon to contribute to solving the problem and several papers have been published, especially in the last decade. The aim of this work is to carry out a bibliometric analysis of the scientific literature dedicated to the problem of MPs, highlighting its course over the years, and to identify the sectors to which the research could be profitably addressed. The VOSviewer software has been used to perform the analysis of the data in which specific maps were used to represent the network of the relationships among countries, journals, organizations, authors, and keywords related to the investigated topic and subtopics. The results of the survey demonstrated that during the investigated range of time, most attention has been paid to the individuation of the MPs, and to marine pollution, while a gap seems to exist in the possible advanced oxidation processes specifically addressing the degradation of MPs and their derivates.