Systematical insights into distribution and characteristics of microplastics in near-surface waters from the East Asian Seas to the Arctic Central Basin

Occurrence, detection and ecotoxicity of microplastics in selected environments-a systematic appraisal

Microplastics (MPs) are being released into the environment in large quantities, especially in less developed parts of the world. This group of pollutants is mostly leached into the environment through heavy plastic dumpsites, pharmaceutical and personal care product containers, hospital wastes, plastic package accessories, and litter from food packaging. Consequently, these compounds are found in different compartments of the ecosystem, such as soils, sediments, biota, and, surprisingly, drinking water. The present study systematically appraised recent studies on MP pollution in the Asian and African environments. It also summarized the trends in the methods for the environmental monitoring of MPs and the removal strategies that have been employed. From the data gathered, the two key instrumentations involved are the microscopes for visualization and the Fourier transform-infra-red (FT-IR) spectrometer to classify or characterize the MPs. Based on the surveyed works of literature, China and South Africa have relatively more information on MP contamination of diverse matrices within their countries. Meanwhile, studies on the status of MP contamination should be conducted across all countries. Hence, this study becomes an eye-opener regarding the commencement of research works on the MP contamination of the environment, especially in other Asian and African countries with little or no information. Furthermore, the literature on ecotoxicity studies of MPs was investigated to ascertain the toxic nature of these compounds. This aspect of research is vital because it serves as a prerequisite for the remediation of these compounds. Microplastics have been declared lethal to biotic components, so all hands must be on deck to continuously remove them from the environment.

Occurrence of microplastics in the Haima cold seep area of the South China Sea

The pollution of deep-sea microplastics has received increasing attention. As a special ecosystem in the deep sea, the cold seep area is of great significance for studying the distribution of microplastics in the deep sea. In this work, the distribution and characteristics of microplastics in seawater, sediments, and shellfish in the Haima cold seep area and the correlation between the characteristics of microplastics in different media and the type of media were studied. Microplastics were found in all three media. The abundance of microplastics in different samples from the Haima cold seep area ranged 1.8-3.8 items/L for the seawater, 11.47-96.8 items/kg (d.w.) for the surface sediments, and 0-5 items/individual (0-0.714 items/g) for the shellfish. The amount of microplastics ingested by shellfish varied among different species. The microplastics in these three media were mainly fibrous, dark-colored, small-sized rayon, polyethylene terephthalate (PET), and polyethylene (PE). In the correlation analysis of microplastic characteristics among the three media, it was found that the characteristics of microplastics in different media in the same area were closely related, and each pair of variables showed a significant positive correlation (P ≤ 0.05). The distinctive geographical conditions would accelerate the interchange of microplastics among various media. Principal component analysis showed that habitat contribute to microplastic feature differences in shellfish. Differences in correlation were observed between the characteristics of shellfish microplastics in different regions and the characteristics of microplastics in surrounding seawater and sediments.

Effect of ultraviolet aged polytetrafluoroethylene microplastics on copper bioavailability and Microcystis aeruginosa growth

Microplastics (MPs) are ubiquitous in aquatic environments, which can act as carriers to affect the bioavailability of heavy metals. The aging process in the environment changes the physicochemical properties of MPs, thereby affecting their environmental behavior and co-toxicity with other pollutants. However, relevant research is limited. In this study, we compared the properties and Cu2+ adsorption capacity of pristine and aged polytetrafluoroethylene (PTFE) MPs and further explored the influence on copper bioavailability and bio-effects on Microcystis aeruginosa. Aging process induced surface oxidation and cracks of PTFE MPs, and decreased the stability of MPs in water by increasing zeta potential. PTFE MPs had a strong adsorption capacity for Cu2+ and increased the bioavailability of copper to microalgae, which was not affected by the aging process. Pristine and aged PTFE MPs adhered to cyanobacterium surfaces and caused shrinkage and deformation of cells. Inhibition of cyanobacterium growth, photosynthesis and reduction of total antioxidant capacity were observed in the treatment of PTFE MPs. Combined exposure of pristine MPs and Cu2+ had stronger toxic effects to cyanobacterium, and increased Microcystin-LR release, which could cause harm to aquatic environment. Aging reduced the toxic effects of PTFE MPs on microalgae. Furthermore, soluble exopolysaccharide (EPS) content was significantly higher in co-exposure of aged MPs and Cu2+, which could reduce the toxicity to cyanobacterium cells. These results indicate that aging process alleviates the toxicity to microalgae and environmental risks caused by PTFE MPs. This study improves understanding of the combined toxicity of aged MPs and metals in freshwater ecosystems.

Spatiotemporal profile and ecological impacts of major and trace elements in surface sediments of marginal seas of the Arctic and Northern Pacific Oceans

The status and ecological impacts of sedimentary elements of the marginal seas of Arctic and Northern Pacific Oceans was investigated during 2016 to 2018 by using inductively coupled plasma mass spectrometry. Industrial (0.006 mg kg-1-64.6 g kg-1), precious (0.003-43.8 mg kg-1), rare earth (0.006-112.9 mg kg-1), and heavy metal (0.009-398.9 mg kg-1) elements showed spatial variation, and temporal uniformity. The results indicated ΣREEs and light REEs enrichment compared to chondrite and heavy REEs, respectively, while nonsignificant positive and negative δCe and δEu anomalies existed, respectively. High contamination and extreme enrichment of priority control, industrial (As, Mo, Re, Sb), precious (Au, Ir, Pd, Pt, and Ru) and RE elements indicated potential moderate to high ecological and biological risks. The study highlighted the ecological importance and fragile nature of these ecosystems and calls for an urgent action to ensure sustainability of these ecosystems.

Impact of flooding on microplastic abundance and distribution in freshwater environment: a review

Due to smaller particle size (0.1 µm-5 mm), non-biodegradable or slowly degradable nature, and high accumulation capacity in the environment, microplastics are becoming a cause of concern throughout the globe. The abundance and distribution of microplastics in aquatic compartments are strongly influenced by various natural and anthropogenic variables. Hydrodynamic conditions like flood events, caused due to extreme precipitation, accelerate the transport and settlement of microplastics in freshwater bodies. This review highlights the current literature which focuses on the effect of flooding on microplastic abundance, characterization, and distribution in freshwater environments worldwide. However, only limited research papers are identified through focused literature search, as this area of research is relatively new. Most of the studies reported increased and decreased abundance of microplastics in water and sediment samples, respectively, during post-flooding period with the exception of few studies. We also evaluate the post-flooding abundances of different morphological shape and polymer type of microplastics. Fragments, fibers, beads, and film were the most frequently reported microplastic shape and polystyrene, and polyethylene was the dominant polymer type found in freshwater environments. Future research should focus on more advanced techniques to understand microplastic fluxes under flood condition and the dominance of various natural and human-induced factors over one another in determining microplastic abundance. This will further enhance to mitigate microplastic pollution in freshwater environments.

Phthalate acid ester release from microplastics in water environment and their comparison between single and competitive adsorption

The ability of microplastics (MPs) to adsorb environmental pollutants has been extensively studied. However, little is known about the ability of MPs to release inherent additives and the interaction between them. This paper explored the effects of environmental factors on the release of phthalic acid esters (PAEs) from three different types of microplastics (polyethylene microplastics (PE-MPs), polypropylene microplastics (PP-MPs), and polystyrene microplastics (PS-MPs)) by simulating water environments, as well as the differences in the adsorption of one or more PAEs by MPs. The results showed that the types of MPs, single environmental factors, and combined environmental factors had a great influence on the release of di(2-ethylhexyl) phthalate (DEHP). In the influence of a single environmental factor, the releasing amount of DEHP increased significantly. When the pH value increased from 5 to 9, the release of three PAEs from all MPs decreased. Moreover, under the combined influence of three environmental factors, the DEHP release from PP-MPs was most affected by environmental factors, and the order of influence of the three environmental factors was ionic strength > organic matter > pH. The DEHP release of PS-MPs was the highest (0.058 ± 0.023 μg/L), followed by PP-MPs (0.038 ± 0.010 μg/L) and PE-MPs (0.035 ± 0.008 μg/L). Adsorption kinetics and isotherm fitting showed that the adsorption process of the three MPs was suitable for the pseudo-second-order kinetic model, and the Freundlich adsorption isotherm had a higher fitting degree. Compared with single adsorption, the competitive adsorption of three PAEs increased the adsorption capacity of DEHP and decreased the adsorption capacity of dibutyl phthalate (DBP) and diisobutyl phthalate (DIBP). These findings help predict the potential of MPs to release toxic additives under different environmental conditions.

Detection of microplastic traces in four different types of municipal wastewater treatment plants through FT-IR and TED-GC-MS

Large amounts of microplastics are discharged into wastewater treatment plants (WWTPs), from where some of them are released into natural waterbodies on account of their not being fully eliminated by WWTPs. To investigate the behavior and emission of microplastics from WWTPs, we selected four WWTPs with different treatment technologies, including anaerobic-anoxic-aerobic (A2O), sequence batch reactor (SBR), media, and membrane bioreactor (MBR). The number of microplastics detected using Fourier transform infrared (FT-IR) spectroscopy ranged from 520 to 1820 particles/L in influent and from 0.56 to 2.34 particles/L in effluent. The microplastic removal efficiencies of four WWTPs were over 99%, indicating that the type of treatment technologies did not significantly affect the removal rate of microplastics. In the unit process for each WWTP, the major stages relating to microplastic removal were the secondary clarifier and tertiary treatment processes. Most microplastics detected were categorized as fragments and fibers, while other types were hardly detected. The size of more than 80% of microplastic particles detected in WWTPs ranged between 20 and 300 μm, indicating that they were significantly smaller than the size threshold defined for microplastics. Therefore, we used thermal extraction-desorption coupled with gas chromatography-mass spectroscopy (TED-GC-MS) to evaluate the microplastic mass content in all four WWTPs, and the results were compared with those of the FT-IR analysis. In this method, only four components, namely polyethylene, polypropylene, polystyrene, and polyethylene terephthalate, were analyzed because of the analysis limitation, and the total microplastic concentration represented the sum of four components concentrations. The influent and effluent microplastic concentrations estimated by TED-GC-MS ranged from not detectable to 160 μg/L and 0.04-1.07 μg/L, respectively, indicating a correlation coefficient of 0.861 (p < 0.05) between the TED-GC-MS and FT-IR results, when compared to the combined abundance of the four microplastic components by FT-IR analysis.

Macroecotoxicological approaches to emerging patterns of microplastic bioaccumulation in crabs from estuarine and marine environments

Despite the increasing plastic discharge into the environment, few articles have dealt with the macroecological implications of microplastics (MPs) bioaccumulation on organisms. We performed a meta-analysis of MPs accumulation in true crabs and pseudocrabs worldwide and made use of macroecotoxicological approaches to know if: I) functional traits influence the bioaccumulation of MPs in the tissues of crabs; II) there is a latitudinal pattern of MPs bioaccumulation; III) there are tissues that can accumulate more MPs; IV) crabs can sort particles according to size, color, shape and type. Our results showed that functional traits influence the accumulation of MPs. Smaller crabs in size and weight and with shorter lifespans tended to exhibit more plastic particles. According to the environment, estuarine crabs from the intertidal and muddy substrates held more MPs. Also, burrowers exhibited significantly more particles in the tissues than omnivorous crabs. Besides, we recorded that crabs from low latitudes tended to exhibit more plastic particles, probably because of the mangroves' location that acts as traps for MPs. Non-human-consumed crabs accumulated significantly more MPs than human-consumed ones. Considering the tissues, gills were prone to accumulate more debris than the digestive tract, but without significant differences. Finally, colorless fibers of 1-5 mm of PA, PP and PET were the predominant characteristics of MPs, suggesting that crabs accumulated denser types but did not sort plastic according to color. These results indicate that functional traits might influence the accumulation of MPs and that there are coastal regions and geographical areas where crabs tend to accumulate more MPs. Analyzing MPs accumulation patterns with macroecological tools can generate information to identify the most affected species and define priorities for monitoring and implementing actions toward reducing plastic use globally.

Internalization and cytotoxicity of polystyrene microplastics in human umbilical vein endothelial cells

Ubiquitous micro(nano)plastics (MNPs) are emerging environmental pollutants, which pose a potential threat to human health. When MNPs enter the blood circulatory system, vascular endothelium is one of the most important target organs that directly interact with the MNPs. However, little is known about the cytotoxicity of MNPs to vascular endothelial cells. In this study, we investigated the uptake and cytotoxic effects of polystyrene MNPs with a particle size of 1 μm (1-μm PS-MNPs) on human umbilical vein endothelial cells (HUVECs) in vitro. Our study found that interaction between HUVECs and 1-μm PS-MNPs was at a very low level. Even at the high exposure concentration of 25 μg/mL, the percentage of HUVECs combined with fluorescent 1-μm PS-MNPs was only 3.80% using flow cytometry analysis. Moreover, there were no significant differences in inflammation, autophagy, reactive oxygen species (ROS) level, lactate dehydrogenase (LDH) release, and adhesion molecule expression following exposure to 1-μm PS-MNPs (5, 10, and 25 μg/mL) for 48 h, except for a remarkable decrease in cell viability at the extremely high concentration of 100 μg/mL. Herein, 1-μm PS-MNPs showed a low level of acute toxicity to HUVECs in vitro, and we expect these results contribute to the further risk assessment of MNPs on human health.

Microplastic Interactions and Possible Combined Biological Effects in Antarctic Marine Ecosystems

Antarctica and the Southern Ocean are the most remote regions on Earth, and their quite pristine environmental conditions are increasingly threatened by local scientific, tourism and fishing activities and long-range transport of persistent anthropogenic contaminants from lower latitudes. Plastic debris has become one of the most pervasive and ubiquitous synthetic wastes in the global environment, and even at some coastal Antarctic sites it is the most common and enduring evidence of past and recent human activities. Despite the growing scientific interest in the occurrence of microplastics (MPs) in the Antarctic environment, the lack of standardized methodologies for the collection, analysis and assessment of sample contamination in the field and in the lab does not allow us to establish their bioavailability and potential impact. Overall, most of the Southern Ocean appears to be little-affected by plastic contamination, with the exception of some coastal marine ecosystems impacted by wastewater from scientific stations and tourist vessels or by local fishing activities. Microplastics have been detected in sediments, benthic organisms, Antarctic krill and fish, but there is no clear evidence of their transfer to seabirds and marine mammals. Therefore, we suggest directing future research towards standardization of methodologies, focusing attention on nanoplastics (which probably represent the greatest biological risks) and considering the interactions of MPs with macro- and microalgae (especially sea-ice algae) and the formation of epiplastic communities. In coastal ecosystems directly impacted by human activities, the combined exposure to paint chips, metals, persistent organic pollutants (POPs), contaminants of emerging interest (CEI) and pathogenic microorganisms represents a potential danger for marine organisms. Moreover, the Southern Ocean is very sensitive to water acidification and has shown a remarkable decrease in sea-ice formation in recent years. These climate-related stresses could reduce the resilience of Antarctic marine organisms, increasing the impact of anthropogenic contaminants and pathogenic microorganisms.

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.