Microplastic abundance, distribution and composition in the mid-west Pacific Ocean

Aging dependent plastic bag derived-microplastics as a vector of metals in lake water

The adsorption of microplastics (MPs) for metals in aquatic environment remains poorly understood due to the use of either commercial MPs, which have different property from the MPs in environments, or artificial solutions, which have not only the significantly higher concentration of metals than natural aqueous environment but also the different natures. In this study, we elaborated the adsorption throughout the aging process of plastic bag derived-MPs (initially 1-2 mm) by potassium persulfate (K₂S₂O₈) solution to metals in lake water. Comparatively, plastic bag derived-MPs had the highest adsorption capacity for Zn²⁺ followed by Fe³⁺, Pb²⁺, Mn²⁺, Cr⁶⁺, Ni²⁺, Cu²⁺ and Cd²⁺, which is not completely consistent with the literature. Both the adsorption capacity and distribution coefficients of Cu²⁺, Ni²⁺, Zn²⁺, Mn²⁺ and Pb²⁺ had significant linear correlation with carbonyl index (p < 0.05). Although the aging overall enhanced the adsorption, the adsorption capacities of MPs might fluctuate depending on metal.

Micro- and nanoplastics: A new cardiovascular risk factor?

Exposure to micro- and nanoplastics (MNPs) is inevitable due to their omnipresence in the environment. A growing body of studies has advanced our understanding of the potential toxicity of MNPs but knowledge gaps still exist regarding the adverse effects of MNPs on the cardiovascular system and underlying mechanisms, particularly in humans. Here, we reviewed up-to-date data published in the past 10 years on MNP-driven cardiovascular toxicity and mechanisms. Forty-six articles concerning ADME (absorption, distribution, and aggregation behaviors) and toxicity of MNPs in the circulatory system of animals and human cells were analyzed and summarized. The results showed that MNPs affected cardiac functions and caused toxicity on (micro)vascular sites. Direct cardiac toxicity of MNPs included abnormal heart rate, cardiac function impairment, pericardial edema, and myocardial fibrosis. On (micro)vascular sites, MNPs induced hemolysis, thrombosis, blood coagulation, and vascular endothelial damage. The main mechanisms included oxidative stress, inflammation, apoptosis, pyroptosis, and interaction between MNPs and multiple cellular components. Cardiovascular toxicity was determined by the properties (type, size, surface, and structure) of MNPs, exposure dose and duration, protein presence, the life stage, sex, and species of the tested organisms, as well as the interaction with other environmental contamination. The limited quantitative information on MNPs' ADME and the lack of guidelines for MNP cardiotoxicity testing makes risk assessment on cardiac health impossible. Furthermore, the future directions of cardiovascular research on MNPs are recommended to enable more realistic health risk assessment.

Size-dependent toxicological effects of polystyrene microplastics in the shrimp Litopenaeus vannamei using a histomorphology, microbiome, and metabolic approach

Due to the wide application of plastic products in human life, microplastic pollution in water has recently attracted more attention. Many studies have revealed the size-dependent toxicity of microplastics. Here, we investigated the toxicological effects of polystyrene microplastics (PS-MPs) on the white leg shrimp, Litopenaeus vannamei, a profitable aquaculture species, using a comprehensive histomorphological, microbiome, and metabolomic approach to verify whether smaller particles are more toxic than larger particles. L. vannamei were experimentally exposed to water containing PS-MPs of four sizes (0.1, 1.0, 5.0, and 20.0 μm) for 24 h at 10 mg/L (acute experiment) and 12 d at 1 mg/L (subchronic experiment). After 24 h of acute exposure, PS-MP accumulation in shrimp indicated that the ingestion and egestion of PS-MPs had a size-dependent effect, and smaller particles were more bioavailable. The tissue morphological results of subchronic experiments showed that, for the guts and gills, the smaller sizes of the PS-MPs exhibited greater damage. In addition, 16 S rRNA gene amplicon sequencing showed that the alpha diversity was higher under larger PS-MP exposure. Correlated with changes in intestinal bacteria, we found a greater enrichment of metabolic pathways in hemolymph proteins and metabolites in larger PS-MP groups, such as "arginine and proline metabolism", "protein digestion and absorption", "lysine degradation". Interestingly, the activity or content of biomarkers of oxidative stress showed a peak at 1 μm and 5 μm. Under specific sizes of PS-MPs, the abundance of the pathogen Vibrio and probiotic bacteria Rhodobacter (5-μm) and Bacillus and Halomonas (1-μm) were simultaneously enriched. Our results indicated that PS-MP exposure can cause size-dependent damage to shrimp, yet specific particle size can be influential differently in regard to some research indicators. Therefore, it can enhance our comprehensive understanding of the impacts of microplastics on shrimp health and suggests that specific particle size should be considered when assessing the size-dependent toxicity of microplastics.

Current status of microplastics and nanoplastics removal methods: Summary, comparison and prospect

In modern society, plastics also play an indispensable role in people's lives due to their various excellent properties. However, when these plastic products are discarded after being used, after being subjected to external influences, they will continue to be worn, damaged and degraded into micro- and nano-scale plastics, which are microplastics and nanoplastics (M/NPs). Although people's attention has been paid to M/NPs at present, the focus is still mainly on the detection and hazard of M/NPs, and how to remove M/NPs is relatively less popular. This review was written in order to draw the attention of more researchers to remove M/NPs. This review first briefly introduces the research background of M/NPs, and also shows the main analytical methods currently used for qualitative and quantitative M/NPs. Then, most of the current literature on the removal of M/NPs was collected, and they were classified, summarized, and introduced according to the classification of physical, physicochemical, and biological methods. The advantages and disadvantages of various methods are summarized, and they are also compared, which can help more researchers choose the appropriate method for research. In addition, the application scenarios of these methods are briefly introduced. Finally, some future research directions are proposed for the current research status of M/NPs removal. It is hoped that this will further promote the development on the method of removing M/NPs.

Synthetic microplastic abundance and composition along a longitudinal gradient traversing the subtropical gyre in the North Atlantic Ocean

Plastic pollution has been reported in the North Atlantic Ocean since the 1970s, yet limited data over subsequent decades pose challenges when assessing spatio-temporal trends in relation to global leakages and intervention strategies. This study quantified microplastics within the upper ocean along a longitudinal transect of the North Atlantic and its subtropical gyre. Microplastics were sampled from surface and subsurface (-25 m) water using a manta trawl and NIKSIN bottle respectively. The surface water polymer community varied significantly between geographic positions ('inshore', 'gyre', 'open ocean'), and was significantly influenced by fragment quantity. Compared to other positions, the North Atlantic gyre was associated with high concentrations of polyethylene, polypropylene, acrylic and polyamide fragments. Subsurface water was dominated by polyamide and polyester fibres. Backtracked 2-year Lagrangian simulations illustrated connectivity patterns. Continued monitoring of microplastics throughout the water column of the North Atlantic Ocean is required to address knowledge gaps and assess spatio-temporal trends.

Microplastic contamination in terrestrial ecosystems: A study using barn owl (Tyto alba) pellets

Microplastics (MPs) are recognised as an emerging environmental problem that needs to be carefully monitored. So far, MPs have been widely recorded in marine and freshwater ecosystems. Still, few studies have focused on MP occurrence in terrestrial ecosystems, although soils are suspected to be one of the main MP reservoirs. To test a non-invasive method for assessing MP contamination in terrestrial ecosystems, we analysed the pellets of a top terrestrial predator, the barn owl (Tyto alba). Sixty pellets were collected from three agricultural areas (20 pellets each) and analysed to assess both barn owl diet and MP content. Thirty-four MPs were confirmed by micro-Fourier Transform Infrared Spectroscopy (μ-FTIR) analysis in 33% of the pellets (min-max 1-5 MPs per pellet). Most of the detected items were microfibres (88.2%). Polyethylene terephthalate, polyacrylonitrile and polyamide were the most abundant polymers. One of the three sites was significantly less contaminated. In the two sites with the highest MP occurrences, barn owl diet was characterised by predation on synanthropic rodents, particularly brown rats (Rattus norvegicus), which may indicate habitat degradation and increased exposure to MPs. Analyses also suggest that Savi's pine vole (Microtus savii) is the prey least at risk of MP contamination, probably due to its strictly herbivorous diet. We argue that the analysis of barn owl pellets may represent a cost-effective method for monitoring MP contamination in terrestrial ecosystems.

Wide occurrence of seven phthalate plasticizers and two typical microplastics in pig feed

Plastics are widely used as packaging and engineering materials in feed processing, which leads to the potential contamination of plasticizers and microplastics (MPs) in animal feeds. In this study, the concentrations of two typical MPs, i.e., polyethylene terephthalate (PET) and polycarbonate (PC), and seven phthalates (PAEs) as well as their corresponding monoester metabolites (mPAEs) in 45 pig feed samples in China were analyzed by mass spectrometers. Among PAEs, dibutyl phthalate (DBP) and bis(2-ethylhexyl) phthalate (DEHP) were detected in all samples, and DEHP showed the highest concentrations of 8.26-2464 μg/kg, which accounted for 65.6% of the total detected PAEs. PET MPs (<MDL-302 μg/kg) were detected in 97.8% of samples. Meanwhile, mPAEs were also detected in feed samples with high detection rates but of much lower concentrations. A significantly positive correlation was observed between DEHP and PET MPs. This indicates that the sources of DEHP and MPs in feeds are homologous, mainly from processing and packaging. Besides, the significantly positive correlations between DBP/DEHP and mBP/mEHP indicated the degradation of PAEs to mPAEs during feed production and transportation. The estimated daily intake (EDI) of PAEs and PET MPs were 2.40-70.3 and 0.800-7.79 μg/kg-bw-day, respectively. The results of this study provided new insight into the first evidence of the co-occurrence and risk of MPs, PAE, and mPAEs in pig feed.

Microplastics as Contaminants in Water Bodies and Their Threat to the Aquatic Animals: A Mini-Review

Microplastics (MPs), which are particles with a diameter of less than 5 mm, have been extensively studied due to their serious global pollution. Typically, MPs in water originate from terrestrial input. A number of studies have reported the presence of MPs as a stressor in water environments worldwide, and their potential threat to the aquatic animals, affecting the growth, oxidative stress responses, body composition, histopathology, intestinal flora, and immune and reproduction systems. During the plastic degradation process, a large variety of toxic substances are released. MPs have been proposed to be the carriers of toxic chemicals and harmful microorganisms. A study of the literature on MP pollution and stress on the aquatic animals associated with MPs was carried out.

Assessment of manta trawling and two newly-developed surface water microplastic monitoring techniques in the open sea

The ubiquitous microplastic (MP) pollution across the waterways, sediments, biota, and atmosphere has amplified concerns at a global scale. Unfortunately, harmonized MP monitoring protocols are absent for accurate evaluation on MP pollution. Few large-scale MP sampling programs involving different designs have been implemented in the open sea. In this study, a manta trawling and two newly custom-built pump filtration systems, namely, a trawl-underway pump combination system coupled in conjunction with an in-situ filtration device (Y-shaped filter, New Type I) and a stationary onboard pumping coupled to Y-shaped filter (New Type II), were evaluated for MP pollution in the mid-North Pacific Ocean. The trawling-based systems (manta trawl and New Type I) collected samples covering a large area, whereas New Type II operated at a fixed site. The new systems achieved fractionated filtration of MPs on site and prevented airborne contamination. The electronic fuel meter installed in the New Type II yielded a more accurate volume. Results showed that the average MP abundance of the aforementioned sampling techniques were 0.65, 2.56, and 7.48 items m^-3, respectively. The abundances in the same particle size range (0.3-5.0 mm) from the new systems were higher. The recovered MPs from all systems were mainly white and polypropylene. Note that the MPs from the manta trawl were primarily fragments; however, they were mainly fibers from the new systems. This corroborated the capability of new systems in harvesting small items (0.1-0.3 mm) and fibers. The cost analysis showed that the new systems beat the manta trawl concerning price performance. The study results provide alternatives for future MP sampling, which will ultimately aid in the method harmonization and standardization of MP sampling.

Priorities to inform research on marine plastic pollution in Southeast Asia

Southeast Asia is considered to have some of the highest levels of marine plastic pollution in the world. It is therefore vitally important to increase our understanding of the impacts and risks of plastic pollution to marine ecosystems and the essential services they provide to support the development of mitigation measures in the region. An interdisciplinary, international network of experts (Australia, Indonesia, Ireland, Malaysia, the Philippines, Singapore, Thailand, the United Kingdom, and Vietnam) set a research agenda for marine plastic pollution in the region, synthesizing current knowledge and highlighting areas for further research in Southeast Asia. Using an inductive method, 21 research questions emerged under five non-predefined key themes, grouping them according to which: (1) characterise marine plastic pollution in Southeast Asia; (2) explore its movement and fate across the region; (3) describe the biological and chemical modifications marine plastic pollution undergoes; (4) detail its environmental, social, and economic impacts; and, finally, (5) target regional policies and possible solutions. Questions relating to these research priority areas highlight the importance of better understanding the fate of marine plastic pollution, its degradation, and the impacts and risks it can generate across communities and different ecosystem services. Knowledge of these aspects will help support actions which currently suffer from transboundary problems, lack of responsibility, and inaction to tackle the issue from its point source in the region. Being profoundly affected by marine plastic pollution, Southeast Asian countries provide an opportunity to test the effectiveness of innovative and socially inclusive changes in marine plastic governance, as well as both high and low-tech solutions, which can offer insights and actionable models to the rest of the world.

Distribution characteristics of microplastics in surface and subsurface Antarctic seawater

Microplastics have attracted worldwide attention due to their potential threat to the marine ecosystem, with such pollutants even detected in the polar seas. Although in-depth research on microplastics has increased in recent years, studies in Antarctic waters remain relatively scarce compared with coastal waters and open oceans. In this study, microplastics in surface and subsurface Antarctic waters were investigated. The average microplastic abundance in the surface water was 0.10 ± 0.14 items/m³, with highest abundance in the Ross Sea, and the average microplastic abundance in the subsurface water was 1.66 ± 1.20 items/m³, with highest abundance in the Dumont d'Urville Sea. Polyester was the main microplastic in the surface waters (87.3%), while polypropylene (33.1%), polyester (28.7%), and polyethylene (22.8%) were the dominant microplastics in the subsurface waters. Results indicate that microplastic pollution in Antarctic waters may come from the Antarctic continent as well as southward transport from the ocean at mid- and low latitudes.

Floating microplastics pollution in the Central Atlantic Ocean of Morocco: Insights into the occurrence, characterization, and fate

This work presents preliminary results about abundance, distribution, characteristics, sources, and fate of microplastics (MPs) in the Central Atlantic Ocean (CAO) of Morocco. The investigation was conducted into three subsections, each characterized by different types of human activities and covering rural, village, and urban areas. MPs were detected in 100 % of the sampling sites. The abundances varied from 0.048 to 3.305 items/m³, with a mean abundance of 0.987 ± 1.081 items/m³. MPs abundance was higher in surface seawater linked to urban areas compared to village and rural areas. The dominant polymer type was polyester (PET-53.8 %) followed by polypropylene (PP-24.36 %), polyamide (PA-7.56 %), polystyrene (PS-6.88 %), polyvinyl chloride (PVC-2.64 %), ethylene vinyl acetate (EVA-2.60 %), polyetherurethane (PUR-1.36 %), and acrylic (AC-0.8 %). Fibers were the most dominant shapes accounting for over 50 %. MPs were mainly smaller than 2 mm in size (71 %) and characterized by colorful aspects. These findings suggested that wastewater treatment plant (WWTP) effluents and anthropogenic activities (industry, tourism, sanitation, and fishing) are the major pollution sources of MPs in the study area. SEM/EDX micrographs showed different weathering degrees and chemical elements adhered to the MPs surface.

Microplastics in the environment: Recent developments in characteristic, occurrence, identification and ecological risk

Microplastics (MPs) are developing as persistent pollutants that are causing significant concern in terms of environmental health. A microplastic is a particle of plastic that is less than 5 mm in diameter, which has penetrated and harmed the environment. MPs have been the subject of numerous analyses, including several adverse assessments; however, most of these studies have focused on their presence in coastal environments. The current state of knowledge regarding the characteristics, occurrences, and potential impact of MPs in the terrestrial ecosystem is incomplete. The goal of this study is to undertake a thorough review of existing knowledge and scientific publications on MP occurrences in the environment, their fate and mobility, and their consequences, as well as to explore such discoveries. MPs have been elaborately discussed in this review in terms of their occurrences, features, and origins in the oceans, freshwater, sediments, soils, and the atmosphere, along with the data obtained from experiments and models on the fate and mobility of MPs in the environment. This paper also includes research data on the environmental toxicity, bioavailability, and bioaccumulation of MPs.

Microplastics: A major source of phthalate esters in aquatic environments

Phthalate esters (PAEs) are predominant additives in plastics, their widespread contamination in aquatic environments has raised global concern. Here, twelve plastic products were prepared as microplastics to investigate their release behaviors of PAEs. Six out of 15 PAEs were quantified after 14 days of incubation in water. The leaching potentials were plastic type-specific, where the pencil case (polyvinyl chloride, PVC) represented the highest migrations with total ∑₁₅ PAEs concentration of 6660 ± 513 ng/g, followed by the cleaning brush-1 (polyamide, PA, ~1830 ng/g) and rubber glove (1390 ± 57.5 ng/g). Conversely, the straw (polypropylene, PP), cleaning brush-2 (polyethylene terephthalate, PET) and shampoo bottle (PET) released the lowest amounts of PAEs, with 50.3 ± 8.21, 93.9 ± 91.8 and 104.35 ng/g, respectively. The release patterns of PAE congeners were polymer type-related, where di-n-butyl phthalate (DBP) dominated the leaching from PA, PP and PET microplastics (47-84%), diethyl phthalate leached the most from PVC and rubber microplastics (45-92%), while diisobutyl phthalate and DBP dominated the leaching from PE microplastics (68-94%). Water chemical properties could affect PAEs migration and the kinetic leaching process was well fitted with the pseudo-first-order model. Approximately 57.8-16,100 kg/year of PAEs were estimated to be released into oceans from microplastics.

Optimization of polypropylene microplastics removal using conventional coagulants in drinking water treatment plants via response surface methodology

Background and purpose

The ubiquitous presence of microplastics (MPs) in aquatic environments has been studied widely. Due to toxicological impacts of MPs and associated contaminants, it is crucial to understand the performance of MPs removal in drinking water treatment plants (DWTPs). Few studies have investigated removal characteristics of MPs via coagulation/flocculation processes, yet removal characterization of polypropylene microplastics (PPMPs) in this process is poorly understood. This study aims to optimize coagulation of virgin PPMPs in conventional DWTPs.

Methods

In this study, samples were synthesized through response surface methodology (RSM), polyaluminium chloride (PACl) was applied as a conventional coagulant to remove PPMPs in the coagulation/flocculation process, which has the least density among common polymers and is one of the most abundant manufactured polymers worldwide. A particle size analyzer (PSA) was used to measure floc size at different pH levels. Additionally, a zeta potential analyzer was used to measure stability of the flocs at different pH.

Results

Base on the experimental range in Design-Expert, results revealed that the optimum removal rate was predicted to be at pH 9, PACl concentration of 200 ppm, polyacrylamide (PAM) concentration of 21 ppm, and PPMPs size of d < 0.25 mm. According to the predicted optimum condition, actual and predicted removal rates were 18.00 ± 1.43% and 19.69%, respectively.

Conclusion

According to this study, PACl is not capable of efficiently removing virgin PPMPs in DWTPs, thereby exposing humans to eco-toxicological impacts of PPMPs through tap water.

Microplastic pollution in the surface seawater in Zhongsha Atoll, South China Sea

The prevalence of microplastics in the marine environment has attracted extensive attention. So far, no information is known regarding the temporal and spatial variations of microplastics in Zhongsha Atoll. This study, for the first time, comprehensively investigated the occurrence and distribution of microplastics in the surface seawater in Zhongsha Atoll based on two ocean cruises. The abundances of microplastics measured in the surface seawater of Zhongsha Atoll were in the ranges of not detected (ND) to 67 items/m³, and ND to 160 items/m³ in 2019 and 2020, respectively. All microplastics detected in Zhongsha Atoll were fibers, most of which were transparent and less than 2 mm. Polyethylene terephthalate was the dominating composition of microplastics. These results suggested that sewage, surface runoff, atmospheric deposition by neighboring land, and fishing activities may be the primary pollution sources. This study provides critical information on microplastic pollution in Zhongsha Atoll for the first time, calling for more research in the management of marine plastic debris in the future.

Progress in the Degradability of Biodegradable Film Materials for Packaging

In today’s world, the problem of “white pollution” is becoming more and more serious, and many countries have paid special attention to this problem, and it has become one of the most important tasks to reduce polymer waste and to protect the environment. Due to the degradability, safety, economy and practicality of biodegradable packaging film materials, biodegradable packaging film materials have become a major trend in the packaging industry to replace traditional packaging film materials, provided that the packaging performance requirements are met. This paper reviews the degradation mechanisms and performance characteristics of biodegradable packaging film materials, such as photodegradation, hydrodegradation, thermo-oxidative degradation and biodegradation, focuses on the research progress of the modification of biodegradable packaging film materials, and summarizes some challenges and bottlenecks of current biodegradable packaging film materials.

Zonal Distribution Characteristics of Microplastics in the Southern Indian Ocean and the Influence of Ocean Current

As a new type of pollutant, microplastics widely exist in the marine environment and have attracted a lot of attention from the international community. In order to study the distribution of microplastics and the influence of ocean current, microplastic samples in seawater of the southern Indian Ocean were collected using a peristaltic pump equipped on-board and concentrated on site. Qualitative and quantitative analyses of microplastics were performed using a stereo-microscope and a micro-Fourier transform infrared spectroscope attenuated total reflection. The results showed that the average abundance of microplastics in seawater of the southern Indian Ocean was 2.3 ± 2.1 items/m3, which was consistent with that in other oceans. Polyethylene terephthalate (PET), polyethylene (PE), Rayon, polyamide (PA), and polyvinylidene chloride (PVDC) were the main polymers of microplastics in the southern Indian Ocean. The size range of all detected microplastics was 108.2–4703.0 µm. All microplastics had different colors, such as black, red, yellow, gray, blue, green, purple, and transparent. Fiber was the dominant shape of microplastics. The abundance distribution of microplastics fluctuated in the latitudinal direction. The abundance of microplastics from the present study area was higher in the coastal region of the South Africa continent and the Indian Ocean garbage patch, with an average abundance of 4.0 items/m3. The average abundance of microplastics was relatively high in the convergence area of the circulation, which revealed that the ocean current facilitated the agglomeration and transportation of microplastics.

How to Build a Microplastics-Free Environment: Strategies for Microplastics Degradation and Plastics Recycling

Microplastics are an emergent yet critical issue for the environment because of high degradation resistance and bioaccumulation. Unfortunately, the current technologies to remove, recycle, or degrade microplastics are insufficient for complete elimination. In addition, the fragmentation and degradation of mismanaged plastic wastes in environment have recently been identified as a significant source of microplastics. Thus, the developments of effective microplastics removal methods, as well as, plastics recycling strategies are crucial to build a microplastics-free environment. Herein, this review comprehensively summarizes the current technologies for eliminating microplastics from the environment and highlights two key aspects to achieve this goal: 1) Catalytic degradation of microplastics into environmentally friendly organics (carbon dioxide and water); 2) catalytic recycling and upcycling plastic wastes into monomers, fuels, and valorized chemicals. The mechanisms, catalysts, feasibility, and challenges of these methods are also discussed. Novel catalytic methods such as, photocatalysis, advanced oxidation process, and biotechnology are promising and eco-friendly candidates to transform microplastics and plastic wastes into environmentally benign and valuable products. In the future, more effort is encouraged to develop eco-friendly methods for the catalytic conversion of plastics into valuable products with high efficiency, high product selectivity, and low cost under mild conditions.

Investigating impact of physicochemical properties of microplastics on human health: A short bibliometric analysis and review

Microplastics (MPs) are contaminants of emerging concern that attracted the attention of researchers over the last decade. They can occur in saliva and stool, and on scalp hair together with skin. Further, MPs can end up in the human diet through seafood, honey, salt, and mineral water. They can be taken up into the plants' roots and lead to the occurrence of MPs in fruits and vegetables. Concentration of the airborne MPs was also reported in the environment. These pieces of evidence clarify that introduction of MPs to the human body through ingestion and inhalation routes should not be overlooked. Following oral exposure to MPs, hazardous chemicals can be released in the gastrointestinal tract leading to toxicity. Inhalation route deserves more attention due to the oxidative potential of the inhaled plastic particles. Although the major characteristics of MPs are being investigated, there are currently few regulations to control concentration of MPs in the environment and their human health impacts remained unclear indicating the need for further investigation. For instance, it is not clear if the present air quality limits for PM_2.5 and PM₁₀ can be used for the areas with high suspended plastic particles. Without comprehensive knowledge about the retention and egestion rates of field populations, it is difficult to deduce the ecological and human health consequences. In general, more information about MP contamination in various species and the consequences of MP uptake and retention is required to gain a better idea of MPs in the food web and their environmental fate. The finer details on the MP translocation between tissues and the fate of the small plastic particles might be obtained when considering the existing information about the application of MPs in the pharmaceutical industry. In this review article, we presented a short bibliometric analysis and investigated the link between physicochemical properties of MPs and human health.

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

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

Distribution and characterization of microplastics in marine sediments from the Montenegrin coast

PURPOSE

Plastic pollution in the world has led to an abundance of microplastics (MPs) and has been identified as a potential factor that can lead to serious environmental problems, especially in oceans and seas. Information on the current status of MPs pollution along the Montenegrin coast is insufficiently investigated. This study monitors the abundance, distribution, and sources of MPs, and identifies present polymers in the surface sediment of the Montenegrin coast, as well as comparison with previous research.

MATERIALS AND METHODS

Ten sampling sites along the Montenegrin coast were selected to collect surface sediment samples. The upper layer of sediment (0-5 cm) was collected by a Petite ponar grab. The samples were dried, and density separation was performed using a NaCl solution. The abundance and morphological characteristics of MPs were determined using an optical microscope (DP-Soft software), while FT-IR analysis was done to identify the polymer type.

RESULTS AND DISCUSSION

Microplastics were identified in all sediment samples with an average abundance of 307 ± 133 (SD) MPs/kg in dry sediment. The highest abundance of MPs was found in locations in the vicinity of highly populated areas, near wastewater discharges, and areas with high fishing and tourist activities. The most dominant shape types of MPs in all samples were filaments and fragments. The most common colors of MPs were blue and red, while the dominant MPs sizes were 0.1-0.5 mm and 0.5-1.0 mm. Of the eight identified polymers, PP, PE, and PET were the most common.

CONCLUSION

This study reveals MPs characteristics (abundance, distribution, shape type, colors, size, polymers type) in surface sediment along the Montenegrin coast, as well as the most significant sources of MPs pollution, and provides important data for further research on MPs to identify the effects of MPs pollution on the quality, health, and functionality of the marine environment.

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

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

Impact of Microplastics on Oil Dispersion Efficiency in the Marine Environment

Oil spill and microplastics (MPs) pollution has raised global concerns, due to the negative impacts on ocean sustainability. Chemical dispersants were widely adopted as oil-spill-treating agents. When MPs exist during oil dispersion, MP/oil-dispersant agglomerates (MODAs) are observed. This study explored how MPs affect oil-dispersion efficiency in oceans. Results showed that, under dispersant-to-oil volumetric ratio (DOR) 1:10 and mixing energy of 200 rpm, the addition of MPs increased the oil droplet size, total oil volume concentration, and oil-dispersion efficiency. Under DOR 1:25 and mixing energy of 120 rpm, the addition of MPs increased the oil droplet size but resulted in a decrease of total oil volume concentration and dispersion efficiency. Compared with the oil volume concentration, the oil droplet size may no longer be an efficient parameter for evaluating oil-dispersion efficiency with the existence of MODAs. A machine learning (ML)-based XGBRegressor model was further constructed to predict how MPs affected oil volume concentration and oil-dispersion efficiency in oceans. The research outputs would facilitate decision-making during oil-spill responses and build a foundation for the risk assessment of oil and MP co-contaminants that is essential for maintaining ocean sustainability.

Dropping the microbead: Source and sink related microplastic distribution in the Black Sea and Caspian Sea basins

Microplastic pollution is a growing, yet poorly understood problem. Here, we assessed the relationship between microplastic concentration and distance to rivers, shorelines, cities, sediment grain size or water depth in sediments of the world's largest (semi-)enclosed aquatic basins. Microplastic was extracted from sediment using density separation, elutriation and hydrophobic adhesion. Fibers and transparent or white microplastic particles were the most abundant shape and color. The microplastic concentration in sediments of the Black Sea was about twice as high compared to that in the Caspian Sea. Fragment concentrations decreased with depth, while fiber concentrations were independent of depth. Overall, no relationship with distance to shores, rivers and cities or with grain size was observed. However, within some depth classes concentrations were related to the distance from rivers, shores and cities.

Identification of microplastics in conventional drinking water treatment plants in Tehran, Iran

The presence of microplastics (MPs), as an emerging pollutant is a growing concern in drinking water, yet most of the studies have been carried out in surface waters and wastewater treatment plants and there are few studies on MPs in drinking water treatment plants (DWTPs). This study investigates these particles in three different conventional DWTPs in the city of Tehran, Iran, and aims to analyze these particles down to the size of 1 µm. A scanning electron microscope was utilized in this study to quantitatively analyze MPs. Accordingly, the average abundance of MPs in raw and treated water samples varied from 1996 ± 268 to 2808 ± 80 MPs L-1 and 971 ± 103 to 1401 ± 86 MPs L-1, respectively. While particles smaller than 10 µm comprised 65-87% of MPs. Moreover, µ-Raman spectroscopy was used to characterize MPs. As the results, polypropylene, polyethylene terephthalate, and polyethylene were the most abundant identified polymers among MPs, comprising more than 53% of particles. Additionally, MPs were categorized as fibers, fragments, and spheres. This study fills the knowledge gap of MPs presence in Tehran conventional DWTPs which is of high importance since they supply drinking water for more than 8 million people and investigates the performance of conventional DWTPs in removing MPs.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40201-021-00737-3.

Methods of Analyzing Microsized Plastics in the Environment

Microplastics are found in various environments with the increasing use of plastics worldwide. Several methods have been developed for the sampling, extraction, purification, identification, and quantification of microplastics in complex environmental matrices. This study intends to summarize recent research trends on the subject. Large microplastic particles can be sorted manually and identified through chemical analysis; however, sample preparation for small microplastic analysis is usually more difficult. Microplastics are identified by evaluating the physical and chemical properties of plastic particles separated through extraction and washing steps from a mixture of inorganic and organic particles. This identification has a high risk of producing false-positive and false-negative results in the analysis of small microplastics. Currently, a combination of physical (e.g., microscopy), chemical (e.g., spectroscopy), and thermal analyses is widely used. We aim to summarize the best strategies for microplastic analysis by comparing the strengths and limitations of each identification method.

Strength Characteristics of Alkali-Activated Slag Mortars with the Addition of PET Flakes

The production of ordinary Portland cement is associated with significant CO₂ emissions. To limit these emissions, new binders are needed that can be efficiently substituted for cement. Alkali-activated slag composites are one such possible binder solution. The research programme presented herein focused on the creation of alkali-activated slag composites with the addition of PET flakes as a partial substitute (5%) for natural aggregate. Such composites have a significantly lower impact in terms of CO₂ emissions in comparison to ordinary concrete. The created composites were differentiated by the amount of activator (10 and 20 wt.%) and curing temperature (from 20 to 80 °C). Their mechanical properties were tested, and a scanning electron microscope analysis was conducted. Compressive and flexural strengths ranging from 29.3 to 68.4 MPa and from 3.5 to 6.1 MPa, respectively, were achieved. The mechanical test results confirmed that a higher amount of activator improved the mechanical properties. However, the influence of the PET particles on the mechanical properties and microstructure varied with the curing temperature and amount of activator. Areas that require further research were identified.

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

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

Seasonal biofilm formation on floating microplastics in coastal waters of intensified marinculture area

The environmental pollution caused by microplastics has received increasing attention recently. In this paper, we present the results of research into the bacterium attached to microplastics in four coastal mariculture zones in southeast China during winter and summer. Polyethene and polypropylene are the main microplastics in the surface water of mariculture area. The differences between the bacteria species composition found on the surface of microplastics in winter and summer were less than that found in the planktonic bacteria, indicating that biofilms protect the bacterium that live inside. Potentially pathogenic Vibrio and Pseudomonas spp. were more abundant in samples from ShanTou and QuanZhou during the summer. Bacteria related to the degradation of microplastics were found extensively on the surface of microplastics at all of the sampling sites. More attention should be paid to the risks resulting from the accumulation of harmful bacteria on microplastic surfaces during the summer.

Spatial characteristics of microplastics in the high-altitude area on the Tibetan Plateau

Microplastics (MPs) have been widely detected in the environments, yet the sources of MPs in freshwater of remote areas at high altitude were not well understood. This study investigated the abundance and distribution of MPs in water bodies and sediments at the Qinghai-Tibet Plateau (QTP). MPs were detected in all samples (47 water and 33 sediment samples) with the mean abundance of 624.70 ± 411.39 items/m³ in water and 41.52 ± 22.31 items/kg in sediment. In descending order, the highest MP oncentrations were found in turbid rivers＞agricultural channel water＞lakes＞ordinary rivers. The results showed that MP abundance was associated with the water quality (especially COD) on the QTP, and it was negatively correlated with altitude due to less human activities (especially agricultural activities) at high altitude areas. In addition, more abundant MPs with small sized was found in the higher altitudes than low ones. Determining the effects of different environments on the distribution and degradation of MPs in the high altitude area of the QTP, this study emphasized the attention to be given to this emerging pollutant in the high altitude remote areas.

Efficient transport of atmospheric microplastics onto the continent via the East Asian summer monsoon

The presence of microplastics (MPs) in the atmosphere is a global concern because of its environmental and health impacts; however, the monsoonal transport of atmospheric MPs has not yet been investigated. To fully understand the effect of the monsoon on atmospheric MP transport, we conducted a study along the southeast coast of China during the East Asian summer monsoon (EASM). We found that the EASM transports atmospheric MPs back onto the continent at a flux of up to 212.977-213.433 kg/EASM/year. The backward trajectory and wind field results indicate that the EASM provides an effective MP transport pathway from Vietnam, the Philippines, and Malaysia to southeastern China. This suggests that only some of the airborne MPs over the ocean enter the marine ecosystem. The average abundance of atmospheric MPs over the sampling area was 0.39 items/100 m³ (0.39 ± 0.43 items/100 m³) during the EASM season, with high variability among the sampling sites. This study improves our understanding of the impact of the EASM on atmospheric MP transport, which can help quantify the contributions of atmospheric MPs to marine or terrestrial ecosystems.

Effects of microplastics on marine copepods

Microplastic contamination has been considered as a global environmental problem in marine ecosystem. Due to small size (< 5 mm) in overlapping with that of microalgae, microplastics can easily be ingested by a wide range of marine copepods both in the laboratory and in situ. Although many studies have reported adverse effects of microplastics on marine copepods, it still lacks a systematic overview about the bioavailability of microplastics and their potential ecological consequences. As copepods dominate zooplankton biomass and provide an essential trophic link in marine ecosystem, this review indicates the bioavailability and toxicity of microplastics in such taxon depend on the shape, size, abundance, and properties of plastics. Also, ours is purposed to tease out the possible molecular mechanisms behind. Microplastic ingestion is prevalent; they impede food intake, block the digestive tract, and cause physiological stress in copepods (e.g., immune responses, metabolism disorders, energy depletion, behavioral alterations, growth retardation, and reproduction disturbance). Notably, in response to microplastic exposure, the copepods show both species- and stage-specificity. Furthermore, microplastics can serve as vectors of organic contaminants (e.g., triclosan, chlorpyrifos, and dibutyl phthalate) and thus increase their toxicity in marine copepods, consequently aggravating the adverse impacts of microplastics in marine ecosystem. Given that most previous studies have partially used pristine microplastics and their short-term exposure might have undervalued their negative effects, more multigenerational mechanistic researches (for example, via an integration of omics-based technology and phenotypic trait analysis) are urgently required for numerous marine copepods exposed to environmental-characteristics plastics as demonstrated by aged microplastics at environmentally realistic concentrations and added with other environmental pollutants; thus it will not only provide mechanistic insights into the biological impacts of microplastics, but also help make the seawater-benchmark setting and ecological assessment for microplastic pollution in marine environment.

An extensive characterization of various environmentally relevant microplastics - Material properties, leaching and ecotoxicity testing

Microplastics in the environment occur in different sizes and shapes and are made of various polymers. Therefore, they also considerably differ in their properties and ecotoxicity. However, the majority of microplastics research uses pre-made spherical microplastics, which practically do not exist in the environment. Our work focused on a comprehensive study of six different types of microplastic that were prepared to simulate common microplastics found in the environment. All types of microplastics where chemically and physically characterized using Fourier-transform infrared spectroscopy, thermal analysis, field-emission scanning electron microscopy, optical microscopy and laser diffraction analysis. The specific surface area was determined using the BET method. Furthermore, effects of microplastics and microplastic leachates on a common duckweed (Lemna minor) were evaluated. All tested microplastics did not affect specific growth rate and chlorophyll a content in duckweed, while microplastics with a rough surface and sharp edges caused a significant reduction of duckweed root length. Microplastics made of Bakelite also showed an intensive leaching, which increased their ecotoxicity potential. Natural particles used as a control did not have any negative effect on duckweed. Overall, microplastic particles have significantly different ecotoxicity profiles depending on their physico-chemical properties. Therefore, the testing of environmentally relevant particles and their proper characterization, as well as the testing of microplastic leaching properties, is crucial for understanding of microplastics ecotoxicological potential.

Comparative study of three sampling methods for microplastics analysis in seawater

Microplastics, as an emerging pollutant, are widely spread in the oceans. The sampling method is the most basic and important factor affecting the reported microplastic abundance data. Three sampling methods, most commonly used for microplastic collection, including direct filtration with 0.45 μm pore size membrane, 20 μm sieve pre-concentration followed by 0.45 μm filtration and Manta trawling with a 150 μm mesh size net were studied. The results showed that there were orders of magnitude difference in abundance of microplastic across the three methods with 0.45 μm direct filtration yielding 1600.0-4000.0 items/m³, 20 μm sieve pre-concentration yielding 10.0-50.0 items/m³, and 150 μm trawl net yielding 0.13-0.24 items/m³. The polymer types of microplastic collected by the three methods were similar, but polymer proportions were different. PES and rayon dominated in the samples collected by direct filtration and sieve pre-concentration. PES and PP accounted for a higher proportion in the trawling samples. The abundance and polymer types of microplastics had a clear correlation between direct filtration and sieve pre-concentration (p < 0.05). More microplastic shapes were found in trawling samples. The average and median sizes of microplastics increased with increasing pore or mesh size. According to the size fraction and standard deviation of microplastic size in different samples of each method, the stability of method decreased with increasing pore or mesh size. The trawling method had a higher sampling efficiency, but its stability was weaker than the other two methods. Our results suggested that an appropriate method should be selected upon actual sampling condition and available tools during the research process to improve the credibility of the results.

Microplastics in the Aquatic Environment: Occurrence, Persistence, Analysis, and Human Exposure

Microplastics (MP) have recently been considered as emerging contaminants in the water environment. In the last number of years, the number of studies on MP has grown quickly due to the increasing consciousness of the potential risks for human health related to MP exposure. The present review article discusses scientific literature regarding MP occurrence and accumulation on the aquatic compartment (river, lake, wastewater, seafood), the analytical methods used to assess their concentration, their fate and transport to humans, and delineates the urgent areas for future research. To better analogize literature data regarding MP occurrence in the aquatic compartment we subdivided papers based on sampling, analytical methods, and concentration units with the aim to help the reader identify the similarities and differences of the considered research papers, thus making the comparison of literature data easier and the individuation of the most relevant articles for the reader’s interests faster. Furthermore, we argued about several ways for MP transport to humans, highlighting some gaps in analytical methods based on the reviewed publications. We suggest improving studies on developing standardized protocols to collect, process, and analyze samples.

Quantitative Analysis of Polystyrene and Poly(methyl methacrylate) Nanoplastics in Tissues of Aquatic Animals

Micro- and nanoplastics unavoidably enter into organisms and humans as a result of widespread exposures through drinking waters, foods, and even inhalation. However, owing to the limited availability of quantitative analytical methods, the effect of nanoplastics inside animal bodies is poorly understood. Herein, we report a sensitive and robust method to determine the chemical composition, mass concentration, and size distribution of nanoplastics in biological matrices. This breakthrough is based on a novel procedure including alkaline digestion and protein precipitation to extract nanoplastics from tissues of aquatic animals, followed by quantitative analysis with pyrolysis gas chromatography-mass spectrometry. The optimized procedure exhibited good reproducibility and high sensitivity with the respective detection limits of 0.03 μg/g for polystyrene (PS) nanoplastics and 0.09 μg/g poly(methyl methacrylate) (PMMA) nanoplastics. This method also preserved the original morphology and size of nanoplastics. Furthermore, to demonstrate the feasibility of the proposed method, 14 species of aquatic animals were collected, and PS nanoplastics in a concentration range of 0.093-0.785 μg/g were detected in three of these animals. Recovery rates of 73.0-89.1% were further obtained for PS and PMMA nanospheres when they were spiked into the tissues of Zebra snail and Corbicula fluminea at levels of 1.84-2.12 μg/g. Consequently, this method provides a powerful tool for tracking nanoplastics in animals.

A review of the removal of microplastics in global wastewater treatment plants: Characteristics and mechanisms

Wastewater treatment plants (WWTPs) are considered to be the main sources of microplastic contaminants in the aquatic environment, and an in-depth understanding of the behavior of microplastics among the critical treatment technologies in WWTPs is urgently needed. In this paper, the characteristics and removal of microplastics in 38 WWTPs in 11 countries worldwide were reviewed. The abundance of microplastics in the influent, effluent, and sludge was compared. Then, based on existing data, the removal efficiency of microplastics in critical treatment technologies were compared by quantitative analysis. Particularly, detailed mechanisms of critical treatment technologies including primary settling treatment with flocculation, bioreactor system, advanced oxidation and membrane filtration were discussed. Thereafter, the abundance load and ecological hazard of the microplastics discharged from WWTPs into the aquatic and soil environments were summarized. The abundance of microplastics in the influent ranged from 0.28 particles L^-1 to 3.14 × 10⁴ particles L^-1, while that in the effluent ranged from 0.01 particles L^-1 to 2.97 × 10² particles L^-1. The microplastic abundance in the sludge within the range of 4.40 × 10³-2.40 × 10⁵ particles kg^-1. In addition, there are still 5.00 × 10⁵-1.39 × 10¹⁰ microplastic particles discharged into the aquatic environment each day Moreover, among the critical treatment technologies, the quantitative analysis revealed that filter-based treatment technologies exhibited the best microplastics removal efficiency. Fibers and microplastics with large particle sizes (0.5-5 mm) were easily separated by primary settling. Polyethene and small-particle size microplastics (<0.5 mm) were easily trapped by bacteria in the activated sludge of bioreactor system. The negative impact of microplastics from wastewater treatment plant was worthy of attention. Moreover, unknown transformation products of microplastics and their corresponding toxicity need in-depth research.

Environmental fate and impacts of microplastics in aquatic ecosystems: a review

Wide usage of plastic products leads to the global occurrence of microplastics (MPs) in the aquatic environment. Due to the small size, they can be bio-ingested, which may cause certain health effects. The present review starts with summarizing the main sources of various types of MPs and their occurrences in the aquatic environment, as well as their transportation and degradation pathways. The analysis of migration of MPs in water environments shows that the ultimate fate of most MPs in water environments is cracked into small fragments and sinking into the bottom of the ocean. The advantages and disadvantages of existing methods for detection and analysis of MPs are summarized. In addition, based on recent researches, the present review discusses MPs as carriers of organic pollutants and microorganisms, and explores the specific effects of MPs on aquatic organisms in the case of single and combined pollutants. Finally, by analysing the causes and influencing factors of their trophic transfer, the impact of MPs on high-level trophic organisms is explored.

The sources, fate and impacts of microplastics in aquatic ecosystems.

Adsorption behavior of the antibiotic levofloxacin on microplastics in the presence of different heavy metals in an aqueous solution

In recent years, the composite pollution of microplastics with organic pollutants and heavy metal ions in the water environment, including their combined toxicity, has received increasing attention. However, the mechanism underlying the joint effect of antibiotics and heavy metals on the surface behavior of microplastics has not been reported. The primary purpose of this article was to analyze the adsorption of levofloxacin (OFL) onto polyvinyl chloride (PVC) in an aqueous solution. The adsorption behavior was studied using kinetics, thermodynamics, and isotherm models, and the effects of several environmental factors, such as ionic strength, fulvic acid, and heavy metals, were determined. The adsorption kinetics and isotherms models indicated that the whole adsorption process was controlled by both intraparticle and outer diffusion, as well as chemical adsorption, which was the dominant mechanism. Based on the results of the thermodynamic experiment, the adsorption process was a nonspontaneous and exothermic reaction process. Furthermore, the presence of Cu²⁺, Zn²⁺, and Cr³⁺ ions significantly promoted the adsorption of OFL, but the presence of Cd²⁺ and Pb²⁺ ions inhibited its adsorption. At the same time, the presence of the ionic strength and fulvic acid remarkably restricted the adsorption process. These findings confirmed that electrostatic interactions, ion exchange, intermolecular hydrogen bonds, and halogen bond cooperation were the main adsorption mechanisms. This paper mainly discusses the interaction between combinations of pollutants with microplastics, which provides theoretical guidance for the interface behavior, migration and transformation of marine microplastics in the actual environment.