Microplastics In Aquatic Environments Research Articles

Microplastic pollution in aquatic environments in Africa: status and research opportunities

The global demand for plastics has increased majorly because of their versatility, light weight, strength and cost–effectiveness. Africa is ranked top in mismanagement of plastic waste, resulting in the plastic problem in the environment. Nevertheless, plastics produce microplastics through degradation and fragmentation of plastic debris largely from anthropogenic sources. Microplastics have become ubiquitous in the natural environment, and the terrestrial environment is the major source. The propensity of microplastics to adsorb and concentrate persistent organic pollutants (POPs) provides potential health effects in the different trophic levels of organisms in both aquatic and territorial environments. Thus, the fate of microplastics is increasingly becoming a global concern. Despite the numerous global studies on the impact of microplastics in the environment, there are insufficient data available on the occurrence and distribution of microplastics and associated health effects in aquatic ecosystems in Africa. The reviewed research articles from 2000 to 2021 provide a summary of the current knowledge on the occurrence and distribution of microplastics, analytical approaches used to detect and quantify microplastics, associated health effects and mitigation measures through government policy to ban plastic use in Africa. The findings presented provide a platform for future research to focus on the associated effects of adsorbed and concentrated POPs on microplastics in aquatic environments in Africa. With the evidence presented, policymakers will make more informed decisions on the future of plastics in Africa. The authors recommend improving information and expanding knowledge through research on the fate and potential ecological impact of microplastics in aquatic environments in Africa.

Microplastic- An Imposing Commination to the Aquatic Ecosystem and its Removal Strategies in Wastewater Treatment Plants: A Systematic Review

Plastic is broadly used for various human interests (technological devices, food packaging, medical products, etc.) and there is an increasing concern about the risks for our surrounding environment and health. In particular, microplastics (MPs), both primary and secondary, occur in all environmental pockets and constitute a potential warning, since they easily enter into the food chain. Moreover, microplastics have the ability to absorb diverse pollutants, which thereby get accumulated inside human body via processes of bioaccumulation and biomagnification. A systematic review was conducted to determine the effectiveness of wastewater treatment facilities (WWTPs) in removing microplastics. Published research on the effectiveness of wastewater treatment plants (WWTPs) for microplastic removal were searched using international databases (PubMed, Science Direct, and Scopus). Contamination of MPs in aquatic environment has presently been recorded as a transpiring environmental threat because of their fatalistic impact on the ecosystem. Their sources are numerous, but, undoubtedly, all are from synthetic matters. The sources of MPs are cosmetics and products of personal care, textile and tyre, abrasion processes of some other plastic products, bitumen and paints for road marking. Due to their low density and tiny particle size, MPs get easily extravasated into the wastewater drainage systems. Therefore, the municipal wastewater treatment plants (WWTPs) are designated to be the foremost recipients of MPs prior to getting excreted into the natural water reservoirs. The focus of this article is to put forward an all-inclusive review in order to preferably understand the channels of MPs into the environment, their characteristics in wastewater, and most importantly, the removal efficiency of MPs of the subsisting wastewater treatment technologies, as arrogated by the WWTPs. This review also encompasses the expansion of budding microplastics treatment technologies that have been investigated till date. Then, in the not-too-distant future, effective and standardised techniques for measuring MPs should be developed, as well as a greater understanding of sources and strategies for reducing microplastics contamination of treated effluent.

Assessing the effects of polyethylene microplastic aging on the sorption of pyrene via simulated sunlight irradiation

The sorption and transport of environmental pollutants with microplastics (MPs) is a growing environmental concern due to the increased use and emissions of MPs and their high affinity toward many organic contaminants. This study examines the impacts of environmental aging of high-density polyethylene (HDPE) via sunlight irradiation on its molecular interactions with pyrene, a model hydrophobic organic pollutant. HDPE MPs were artificially aged under simulated sunlight irradiation for different exposure times. During aging treatments with simulated sunlight irradiation, morphological changes, such as cracks and rough surfaces, were induced on the HDPE particles; however, destructive oxidation was not observed. Batch sorption experiments were conducted on the aged and pristine MPs. Results reveal that pyrene sorption on MPs was enhanced for the aged HDPE particles and the sorption increases with increased irradiation time, indicating that aged HDPE has a higher sorption capacity than the pristine one. These results are attributed to the physical alteration in HDPE, which increases the surface area and promotes aqueous pyrene sorption on MPs. These results provide possible mechanistic explanations for the accumulation of hydrophobic organic pollutants with MPs in aquatic environments.

Combined toxicity of polystyrene microplastics and ammonium perfluorooctanoate to Daphnia magna: Mediation of intestinal blockage

Microplastics (MPs) have worldwide accumulated in aquatic environments and coexisted with various water contaminants including perfluorinated compounds (PFCs) that are frequently detected. The adverse effects of individual MPs or PFCs on aquatic organisms have been extensively reported; however, the combined toxicity of MPs and PFCs remains unknown. This study evaluated the combined toxicity of MPs [pristine and aged polystyrene (PS)] and a PFC [ammonium perfluorooctanoate (APFO)] to Daphnia magna under different concentration ratios by three classic methods: toxicity unit, additive index, and mixed toxicity index. The adsorption kinetics of APFO on MPs, aggregation of MPs in exposure medium, MP gut fullness of daphnids, intestinal histology, and lipid peroxidation were analyzed to reveal the mechanism underlying the combined toxicity. Our results showed that the combined toxic modes varied with the concentration ratios of MPs to APFO (antagonism at 4:1 and 1:4, synergism at 3:1, 1:2, and 1:3, and partial addition/antagonism at 2:1 and 1:1 for pristine PS + APFO; antagonism at all ratios except partial addition/antagonism at 3:1 and 1:3 for aged PS + APFO), which could be attributed to the alteration of MP aggregation and thus MP gut fullness in the daphnids. The combined toxicity was further confirmed to occur in the daphnid's gut, which was reflected in physiological and biochemical responses mediated by intestinal blockage. Observable intestinal damages under co-exposures at μg•L−1 levels indicated the risks from future long-term exposure to MPs and PFCs in aquatic environments. This work demonstrates the necessity of assessing combined toxicity with different concentration ratios and provides new insights into the potential risks of MPs in aquatic environments.

Biofilm formation and its implications on the properties and fate of microplastics in aquatic environments: A review

Particulate plastic fragments (micro and nano-plastics) in aquatic environments provide abundant solid substrates, which serve as an important habitat for a variety of microorganisms. Surfaces of microplastics (MPs) exhibit hydrophobicity that facilitate the adsorption of dissolved organic carbon (DOC) in the aquatic environment. Furthermore, MPs act as substrata, as well as a carbon source including the readily bioavailable DOC, which promote the formation of microbial biofilms. These biofilms have varied metabolic actions that govern the subsequent succession of micro- and meso-organisms habitation of MPs. The assemblage of ecosystems colonising the plastic environment is often referred to as the “plastisphere”. Polymer type, environmental conditions, including nutrient status, salinity, and season, affect the microbial composition of the biofilm. Microbial habitation accelerated by biofilm formation on particulate plastics enables the movement of microorganisms, especially in the aquatic environment, and impacts the transport and toxicity of contaminants associated with these particulate plastic fragments. This review paper describes the processes of microbial habitation and subsequent biofilm formation, the factors affecting biofilm formation, and the implications of biofilm formation on the mobility of microorganisms, degradation of MPs, and the bioavailability of contaminants associated with MPs.

Towards realistic predictions of microplastic fiber transport in aquatic environments: Secondary motions

Microplastics fibers are abundant in aquatic environments and are an emerging environmental threat. Understanding how fibers are transported in aquatic environments is essential for identifying pollution hotspots and developing remediation strategies. Over recent years, an increasing number of drag models have been proposed to describe the transport of microplastics in aquatic environments. However, none of the proposed models consider secondary motions, which are responsible for non-vertical settling motions. To investigate the role of secondary motions, an experimental setup with an image processing technique was developed to capture the spatial-temporal kinematics of microplastic fibers settling in quiescent water. A new drag model, which adopts the crosswise sphericity to consider the effects of secondary motions of a microplastic fiber and the Aschenbrenner shape factor to account for the unique morphology of the microplastic fiber, was proposed and evaluated. Secondary motions of microplastic fibers have profound effects on their settling trajectories and deposited positions. The settling motion and drag coefficient of a microplastic fiber is an orientation-dependent process. Moreover, the secondary motion is strongly dependent on the fiber dimension and density. The here-proposed drag model is proven to more accurately characterize the settling motion of microplastic fibers compared to existing models that neglect secondary motions. The methodology and model from this study can be used to progress towards improved and realistic predictions of the transport of microplastic fibers in aquatic environments.

Manta Net: The Golden Method for Sampling Surface Water Microplastics in Aquatic Environments

Microplastics (MPs) (plastic particles < 5 mm in size) have become the most ubiquitous type of anthropogenic litter contaminating aquatic environments worldwide, and are capable of harming aquatic organisms and entering the food web. Microplastic research has rapidly evolved over several decades, with many studies sampling microplastic in surface waters. For sea surface sampling of MPs, different net devices have been used. But although there is an increasing number of studies using these devices to quantifying MPs in different aquatic environments, data comparison is difficult due to the lack of standardised, harmonised sampling methods and data reporting units. The Manta net device is actually the most commonly used method for sea surface sampling of MPs. The three main parts of this net are: the floating/stabilizing part, the opening mouth and the net bag, and each of them can have its own specifications. These specifications, along with the sampling methods, can be critical for the efficiency of the sampling accurate quantification of MPs in the aquatic environments. The use of different mesh sizes, inconsistency in trawling duration, speed and distance, and in the net opening dimensions, make it impossible to compare the studies between each other. This review analyzes the methodologies and characteristics of Manta nets used for MPs sampling, discussing factors that can impact the efficiency of the sampling and the quantification of MPs, and proposes recommendations in order to improve and standardize the sampling protocol.

Development of simplified characterization factors for the assessment of expanded polystyrene and tire wear microplastic emissions applied in a food container life cycle assessment

AbstractTo date, life cycle assessment (LCA) does not include a methodology for assessing the impacts of plastic litter leaked to the environment. This limits the applicability of LCA as a tool to compare the potential impacts of single‐use plastics and their alternatives on ecosystem quality and human health. As a contribution to tackle this issue, this work proposes simplified fate and characterization factors (CFs) for modeling the impacts of two types of microplastics—expanded polystyrene and tire and road wear particles—in the marine environment. In terms of fate mechanisms, this work explores different sedimentation, degradation, and fragmentation rate scenarios, based on literature values and expert estimates. Whereas the fate of expanded polystyrene is sensitive to the different fragmentation, degradation, and sedimentation scenarios, for tire and road wear particles the fate is primarily sensitive to sedimentation. The fate factors are integrated into CFs using an existing exposure and effect factor for microplastics in aquatic environments. Since the CFs of the two studied microplastics show important differences, these results reveal the need for developing polymer‐specific CFs. Finally, the CFs are tested in a case study of on‐the‐go food containers (one single‐use plastic, two compostable alternatives, and one reusable plate). Depending on the fate scenario, plastic litter impacts range from barely noticeable to more than doubling the total potential damage to ecosystem quality, compared to no plastic litter impact assessment. The high uncertainty of the results encourages further research on modeling microplastic fate and impacts in detail.

In-situ quantitative monitoring the organic contaminants uptake onto suspended microplastics in aquatic environments

Microplastics act as a source of organic contaminants in aquatic environments and thus affect their environmental fate and toxicity. Because of the weak and reversible interactions between microplastics and organic species, the organic coronas vary with their surrounding environments. Thus, in order to evaluate the possible environmental risks of microplastics, methods for evaluating the dynamic uptake of organic contaminants onto suspended microplastics in aquatic environments are greatly desired. In this work, a UV–vis spectroscopy-based approach was developed for in-situ monitoring organic contaminants uptake onto suspended microplastics after correcting the light scattering interference from microplastics suspensions and establishing the nonlinear relationship between concentration and light absorbance of organic species. The inverse adding-doubling method based on radiative transfer theory was adopted to correct the light scattering effect of suspensions. Then, the resulting mixed absorption spectra were decomposed to calculate the concentrations of the aqueous and adsorbed organic species simultaneously with a nonlinear calibration method. The uptake processes of bisphenol A and p-nitrophenol onto nylon 66 microparticles were monitored with this approach and confirmed by high-performance liquid chromatography analysis. The approach was validated by applying it to natural water samples, and the equilibrium adsorption capacity was found to be interfered mainly by the protein-like substances. This approach has high accuracy, good reproducibility, remarkable universality, and ease of handling, and also provides a potential tool for characterizing the corona formation process on suspended particles both in natural and artificial environments, such as eco-corona formation and engineering surface modification on nano/micro-particles.

Microplastics in Aquatic Environments: Recent Advances in Separation Techniques

Separation and removal of microplastic pollution from aquatic environments as a global environmental issue is classified as one of the major concerns in both water and wastewater treatment plants. Microplastics as polymeric particles less than 5 mm in at least one dimension are found with different shapes, chemical compositions, and sizes in soil, water, and sediments. Conventional treatment methods for organic separation have shown high removal efficiency for microplastics, while the separation of small microplastic particles, mainly less than 100 µm, in wastewater treatment plants is particularly challenging. This review aims to review the principle and application of different physical and chemical methods for the separation and removal of microplastic particles from aquatic environments, especially in water treatments process, with emphasis on some alternative and emerging separation methods. Advantages and disadvantages of conventional separation techniques such as clarification, sedimentation, floatation, activated sludge, sieving, filtration, and density separation are discussed. The advanced separation methods can be integrated with conventional techniques or utilize as a separate step for separating small microplastic particles. These advanced microplastic separation methods include membrane bioreactor, magnetic separation, micromachines, and degradation-based methods such as electrocatalysis, photocatalysis, biodegradation, and thermal degradation.

Migration characteristics of microplastics based on source-sink investigation in a typical urban wetland

Although urban wetlands are key transition sub-ecosystems connecting urban microplastic pollution sources to freshwater environments, few studies have reported microplastic migration characteristics in urban wetlands. Recent studies have only focused on the occurrence of microplastics in wetlands. Thus, this study investigated the occurrence of microplastics in sources and sinks (surface water, sediment, effluent, and agricultural waste) and analyzed the migration characteristics of microplastics in a typical urban wetland, namely the Huixian Wetland, Guilin. The abundance of microplastics was in the ranges of 16.5–89.0 items/L, 16.8 × 103–52.8 × 103 items/kg, and 172.0–605.0 items/L in the surface water, sediment, and effluent, respectively. Most of the microplastic settlement at 1–2 km downstream of the source of pollution in this wetland presented with a total decrease of 53.7–61.4% for microplastics in the surface water, whereas microplastics of smaller sizes (100–500 µm) were retained more in surface water than the smallest (50–100 µm) and large (500–5000 µm) microplastics. Clustering analysis and principal component analysis showed that effluent was the major source of microplastics in the urban section of this wetland, and agricultural wastes also played a role in the suburbs. This first quantification of small-sized (50–500 µm) microplastic removal throughout an urban wetland provides key reference information for controlling the environmental risk of microplastics in aquatic environments.

A Mini-Review of Strategies for Quantifying Anthropogenic Activities in Microplastic Studies in Aquatic Environments.

Microplastic pollution is no longer neglected worldwide, as recent studies have unveiled its potential harm to ecosystems and, even worse, to human health. Numerous studies have documented the ubiquity of microplastics, reflecting the necessity of formulating corresponding policies to mitigate the accumulation of microplastics in natural environments. Although anthropogenic activities are generally acknowledged as the primary source of microplastics, a robust approach to identify sources of microplastics is needed to provide scientific suggestions for practical policymaking. This review elucidates recent microplastic studies on various approaches for quantifying or reflecting the degree to which anthropogenic activities contribute to microplastic pollution. Population density (i.e., often used to quantify anthropogenic activities) was not always significantly correlated with microplastic abundance. Furthermore, this review argues that considering potential sources near sample sites as characteristics that may serve to predict the spatial distribution of microplastics in aquatic environments is equivocal. In this vein, a watershed-scale measure that uses land-cover datasets to calculate different percentages of land use in the watershed margins delineated by using Geographic Information System (GIS) software is discussed and suggested. Progress in strategies for quantifying anthropogenic activities is important for guiding future microplastic research and developing effective management policies to prevent microplastic contamination in aquatic ecosystems.

Identification, Quantification and Biodegradation of Microplastics in Aquatic Environment by Metabolism of Microorganisms

Identification, Quantification and Biodegradation of Microplastics in Aquatic Environment by Metabolism of Microorganisms

Molecular Weight-Dependent Adsorption Heterogeneities of Dissolved Organic Matter on Microplastics in Aquatic Environments: Further Insights from Fluorescence Spectra Combined with Two-Dimensional Correlation Spectroscopy and Site Energy Distribution Analysis

Molecular Weight-Dependent Adsorption Heterogeneities of Dissolved Organic Matter on Microplastics in Aquatic Environments: Further Insights from Fluorescence Spectra Combined with Two-Dimensional Correlation Spectroscopy and Site Energy Distribution Analysis

Improved Settling Velocity for Microplastic Fibers: A New Shape-Dependent Drag Model

Microplastics are abundant in aquatic environments and are an emerging environmental concern. The prediction of their settling velocities is central to predictions of the residence time and concentration depth profiles of microplastics in aquatic environments. The main scientific challenge in improving the current understanding of the settling motions of microplastics is that existing drag models are deficient at reasonably predicting the settling velocities of various microplastics, especially microplastic fibers. This is because the shape factors used in the existing drag models cannot morphologically distinguish fibers from fragments and films. In this study, a new shape factor, specifically the Aschenbrenner shape factor, is proposed as a vehicle to explicitly distinguish among the morphologies of fibers, films, and fragments. With this new shape factor, a new drag model is developed and then systematically evaluated against the unique set of data provided by new experiments conducted in this study along with four other published data sets in the literature. The proposed model allows the prediction of the terminal settling velocity of microplastic fibers more accurately than existing drag models. Moreover, the new model has also shown its applicability to microplastic films and fragments. Notwithstanding, the new model appears deficient at reasonably predicting the terminal settling velocity of weathered microplastics in the field, which requires further investigations.

Microplastic in Water and Sediments at the Confluence of the Elbe and Mulde Rivers in Germany

Accumulation of microplastics in aquatic environments is an issue of emerging concern. Initially, research focused on marine systems. However, recent studies also investigate the abundance of microplastics in freshwater environments. Rivers connect terrestrial with marine ecosystems and contribute a considerable share of macro- and microplastics to the oceans. A previous study found a large amount of micro-spheres in Dessau downstream the river mouth of the Mulde. Therefore, the objective of this research was to examine whether the Mulde river with its highly industrialized catchment contributes to the microplastic pollution of the Elbe. Sediment (Van Veen grab sampler) and water samples (filter cascade with the smallest mesh size 50 μm and nets with the smallest mesh size 150 μm) were taken from the Elbe river up- and downstream the confluence with the Mulde. After extensive sample preparation, we examined the samples under a digital microscope and determined polymer types by pyrolysis Gas Chromatography/Mass Spectrometry (pyr-GC-MS). The amount of primary microplastics increased in sediment and water samples just downstream the confluence. Those microplastics originate probably from the Mulde. We measured larger amounts and different shapes of microplastics in filter cascades that have a smaller mesh size compared to the nets.

Microbial Life on the Surface of Microplastics in Natural Waters

Major water-polluting microplastics (for example, polyethylene, polypropylene and others) have lower density than water. Therefore, they are concentrated in the neustonic layer near the water-air interface altogether with dissolved or colloidal natural organic matter, hydrophobic cells and spores of bacteria. This can cause environmental and public health problems because the floating micro- and nanoparticles of plastics could be coated with biofilm of hydrophobic and often putative pathogenic bacteria. Biofilm-coated microplastics are more attractive for consumption by aquatic animals than pure microplastics, and that increases the negative impacts of microplastics. So, impacts of even small quantities of microplastics in aquatic environments must be accounted for considering their accumulation in the micro-layer of water-air interphase and its interaction with bacterioneuston. Microorganisms attached to the surface of microplastic particles could interact with them, use them as substrates for growth, to change properties and biodegrade. The study of microbial life on the surface of microplastic particles is one of the key topics to understanding their role in the environment.

Role of biofilms in the degradation of microplastics in aquatic environments

AbstractMicroplastics are pollutants of emerging concern that have already gained significance in recent years because of their recalcitrant nature and their detrimental effects on living beings and the ecosystem. Due to their small size, microplastics are easily integrated into biogeochemical cycles and food webs, drastically affecting the environment. Our current knowledge on the interactions of microplastics with various components of ecosystems is limited; however, considering their potential long‐term impact, massive research efforts are underway to understand the environmental fate of microplastics and any possible strategies for remediation. In marine ecosystems, plastic surfaces are mostly colonized by microorganisms that form biofilms. Plastic‐biofilm interactions potentially influence the physical and chemical properties of the polymer, thereby leading to its degradation. Hence, to mitigate the foreseen nuisance of microplastics contamination, biofilms are being considered as potential candidates for the remediation of marine environments. Though the interactions between plastic and microbes are still inadequately understood, much of the research in the field is being focused on this aspect. In this review, we discuss several types and sources of microplastics, along with their trophic transfer and negative impacts on ecosystem. In addition, we focus on the current knowledge and explain the research gaps in understanding plastic‐microbe interactions in marine environments, while highlighting the role of biofilms in the degradation of microplastic debris. Finally, we comment on the future aspects and research priorities in this field to further elaborate the role of microorganisms in determining the fate of microplastics in aquatic ecosystems. © 2021 Society of Chemical Industry (SCI).

Microbial adaptation to co-occurring vanadium and microplastics in marine and riverine environments

Vanadium (V) and microplastics have been respectively detected in environmental media, posing threats to ecosystem and human health. However, their co-existence situations in environment with microbial adaptation have been poorly understood. In this study, water and sediments collected from potential V polluted marine and riverine ecosystems were analyzed to reveal the distribution of V and microplastics with microbial responses. High concentrations of V (1.65–6.92 μg/L in water and 6.16–347.92 mg/kg in sediment) and microplastics (800–15600 item/m3 in water and 20–700 item/kg in sediment) co-occurred in aquatic environment. Less rich and diverse bacterial communities were colonized on microplastics compared to surrounding environment. Plastic-degrading taxa (e.g., Ralstonia, Rhodococcus) and V(V) reducers (e.g., Bacillus, Pseudomonas) were enriched in microplastic biofilms. Redundancy analysis showed that V, together with nutrients, ambient conditions and Cr, contributed significantly to the compositions of microbial community on microplastics. Besides directly acting on microbial community, V could also alter it by influencing environmental factors (e.g., pH), as indicated through structural equation model. This study advances understanding the previously ignored interactions of biogeochemical processes of V and microplastics in aquatic environment.

Insights into the molecular interaction between poly(vinylpyrrolidone)-iodine disinfection system and polypropylene microplastics in aquatic environment

Microplastics (MPs) as emerging contaminants may not only act as an extra compartment for partitioning of disinfectant but also greatly affect the bactericidal power of disinfection agents. This is the first study to investigate the interaction of MPs with poly(vinylpyrrolidone)-iodine (PVP-I) disinfection system, particularly associated with the identification and characterization of the iodine species at molecular level. The results showed that the presence of MPs increased the loss of triiodide ion (I3−) in PVP-I system, which was even accelerated upon oxygen exposure. An obvious blue shift from 1714 to 1665 cm−1 at the vibrational band was observed for iodine-soaked MPs, which was resulted from the hydrogen bonding interaction as one of potential adsorption mechanisms. The interaction resulted in the affinity of polyiodide ions (I3− and I5−) in PVP-I system to MPs as foreign objects, thereby impairing the bactericidal power of PVP-I system. More evident loss of I3− in aged MP suspension was observed compared to pristine MP suspension, suggesting the enhanced interaction of PVP-I system with aged MPs. The interaction was weakened in aquaculture water, due to the photosensitive substances and alkaline condition. These findings confirmed that the interaction between polyiodide ions (I3− and I5−) and MPs in form of hydrogen bond reduced the bactericidal power of PVP-I disinfection system. This study provides a comprehensive insight in to the mechanisms involved in the interaction between MPs and PVP-I disinfection system, and would be helpful for evaluating the environmental behavior of MPs and the bactericidal power of the PVP-I system upon MP exposure in aquaculture environment.