Microplastics In Environment Research Articles

Effect of nanoplastic intake on the dopamine system during the development of male mice

Exposure to environmental microplastics has been demonstrated to impact health. However, its effect on development remains unclear. This study investigated whether consumption of nanoplastics (NPx) during development affects social and cognitive functions in rodents. In this study, we utilized male Institute of Cancer Research mice; they were divided into five subgroups based on the duration of NPx administration. NPx (100 nm) was orally administered via gavage for 6 days from gestational day (GTD) 7, representing the mid-gestation period, and for 5–6 days from GTD13 to birth, representing the late-gestation period; the male offspring were used for experiments. NPx was orally administered for 15 days starting at postnatal day (PND) 21 as the juvenile, PND38 as the adolescent, and PND56 as adulthood. On PND77, offspring were assessed for locomotion, social behavior, and nest-building tests. We observed that NPx administration altered dopamine system responses in GTD13 and PND56 groups. Social behavior was similarly affected by NPx treatment, with GTD13 and PND56 groups displaying decreased familiarity. Additionally, NPx treatment enhanced local field potentials in the prefrontal cortex, nucleus accumbens, and amygdala of GTD7 group and in the striatum of GTD13 group, while amphetamine treatment induced changes of local field potentials compared to saline treatment in the prefrontal cortex and the ventral tegmental area of CTR, GTD7, PND21, and PND56 groups. Taken together, these results showed that NPx treatment induced changes in social behavior partly depending on developmental stage, and these changes are associated with neural circuits innervated by the dopamine system.

The Extraction and Characterization of Microplastics of Biocompost and Water Samples Collected from the Different Semi-Urban Agronurseries

ABSTRACT Biocomposting at national and regional levels has recently been recognized as one of the feasible, nature-based solutions to prevent the accumulation and reuse of biodegradable waste in enhanced and effective mitigation measures for urban and semi-urban waste management. Recent research has mainly focused on organic compost contamination, as the negative effects of MP on soil systems have been extensively studied. According to current research, organic compost used as fertilizer on farmland contains many microplastics. In this context, microplastics (MPs) have been regarded as a global environmental problem and an emerging soil contaminant. The physico-chemical properties of water and compost samples were analyzed by APHA and AOAC methods. The extraction of microplastics was done using the density separation. In the current study, agricultural waste-based biocompost and water samples used for the production of biocompost were collected from four different agricultural nurseries in semi-urban areas of the Coimbatore city. The physicochemical properties (including heavy metal content) of the biocompost and water samples tested were on par/equal/lower than Indian standards. Interestingly, in the biocompost samples, 85% of the microplastic fragments and 15% of the fiber types were identified only in BC-B and BC-C, respectively, with different colors such as red, brown, blue, light yellow and transparency. However, no microplastics were found in the biocompost samples of BC-A and BC-D. Microplastic polymers such as polymethyl methacrylate (PMMA), polypropylene (PP), and ethylene vinyl acetate (EVA) were identified through ATR-FTIR analysis. The results suggest that semi-urban agricultural gardening may lead to the accumulation of microplastics in terrestrial environments, which may negatively impact soil and plant health. This study contributes to growing research into microplastic contamination in organic compost and its potential impact on agriculture and terrestrial ecosystems.

The significant impact of MPs in the industrial/municipal effluents on the MPs abundance in the Nakdong River, South Korea

Owing to extensive plastic consumption, wastewater from households, business establishments, and industrial activities have been recognised as a significant contributor to microplastics (MPs) in aquatic environments. This case study represents the first investigation of MPs in the Nakdong River, Republic of Korea, that traverses through the largest industrial complex midstream and densely populated cities of Daegu and Busan downstream before flowing into the sea. Monitoring of MP abundance in effluents discharged from three municipal, two industrial, and one livestock wastewater treatment plant (WWTP) into the Nakdong River was conducted over four seasons from August 2022 to April 2023. Identification and quantification of MPs were performed using micro-Fourier transform infrared spectrometry. Seasonal variation in MPs in the Nakdong River was found to be strongly influenced by the nearest upstream WWTPs and rivers, exhibiting a linear relationship that decreased gradually with increasing distance from the WWTPs. The average concentrations of MPs in the six effluent sources ranged from 101 ± 13 to 490 ± 240 particles/L during the yearly monitoring period, while MP concentrations in the river ranged between 79 ± 25 and 120 ± 43 particles/L. Industrial effluents contained higher amounts of discharged MPs (314 ± 78 particles/L) than municipal sources (201 ± 61 particles/L). Notably, two municipal WWTPs, located in the highly densely populated city, discharged the highest total MP amounts per day and released the greatest volumes of effluents. This study provides valuable insights into the monitoring and impact of effluents on MPs in rivers, which could inform MP treatment and management strategies for in river and marine environments.

Toxicity of environmental and polystyrene plastic particles on the bivalve Corbicula fluminea: focus on the molecular responses.

Among aquatic organisms, filter feeders are particularly exposed to the ingestion of microplastics (MPs) and nanoplastics (NPs). The present study investigates the effect of environmental microplastics (ENV MPs) and nanoplastics (ENV NPs) generated from macro-sized plastic debris collected in the Garonne River (France), and polystyrene NPs (PS NPs) on the freshwater bivalve Corbicula fluminea. Organisms were exposed to plastic particles at three concentrations: 0.008, 10, and 100 μg L-1 for 21 days. Gene expression measurements were conducted in gills and visceral mass at 7 and 21 days to assess the effects of plastic particles on different functions. Our results revealed: (i) an up-regulation of genes, mainly involved in endocytosis, oxidative stress, immunity, apoptosis, and neurotoxicity, at 7 days of exposure for almost all environmental plastic particles and at 21 days of exposure for PS NPs in the gills, (ii) PS NPs at the three concentrations tested and ENV MPs at 0.008 μg L-1 induced strong down-regulation of genes involved in detoxication, oxidative stress, immunity, apoptosis, and neurotoxicity at 7 days of exposure in the visceral mass whereas ENV MPs at 10 and 100 μg L-1 and all ENV NPs induced less pronounced effects, (iii) overall, PS NPs and ENV MPs 0.008 μg L-1 did not trigger the same effects as ENV MPs 10 and 100 μg L-1 and all ENV NPs, either in the gills or the visceral mass at 7 and 21 days of exposure. This study highlighted the need to use MPs and NPs sampled in the environment for future studies as their properties induce different effects at the molecular level to living organisms.

Microplastics and viruses in the aquatic environment: a mini review.

Microplastics (MPs) have been widely found in the environment and have exerted non-negligible impacts on the environment and human health. Extensive research has shown that MPs can act as carriers for viruses and interacts with them in various ways. Whether MPs influence the persistence, transmission and infectivity of virus has attracted global concern in the context of increasing MPs contamination. This review paper provides an overview of the current state of knowledge regarding the interactions between MPs and viruses in aquatic environments. Latest progress and research trends in this field are summarized based on literature analysis. Additionally, we discuss the potential risks posed by microplastic-associated viruses to human health and the environmental safety, highlighting that MPs can affect viral transmission and infectivity through various pathways. Finally, we underscores the need for further research to address key knowledge gaps, such as elucidating synergistic effects between MPs and viruses, understanding interactions under real environmental conditions, and exploring the role of biofilms in virus-MPs interactions. This review aims to contribute to a deeper understanding on the transmission of viruses in the context of increasing MPs pollution in water, and promote actions to reduce the potential risks.

Unfolding the interaction of radioactive Cs and Sr with polyethylene-derived microplastics in marine environment

To unveil the interaction of radioactive Cs and Sr with polyethylene-derived microplastics in the marine environment, a mesocosm study was conducted in a stepwise manner by investigating the uptake capability of microplastics at three different stages: pristine, radiation-exposed, and marine-exposed microplastics. The study demonstrates that the physio-chemical properties of microplastics undergo significant alterations upon exposure to the environment, leading to the emergence of biofilm formation upon marine exposure, while radiation exposure induces surface roughness and cracks. Biofilm growth enhances the uptake of radionuclides by microplastics. However, the growth of biofilms increases the density of microplastics through aggregation, leading to a buoyancy transition from positive to negative buoyancy. Various interaction mechanisms, such as electrostatic, ion–dipole, and physical diffusion interactions, were identified as important mechanisms playing key roles in radionuclide binding to polyethylene-derived microplastics. Despite the significantly lower apparent distribution coefficients observed for radio Cs (in the range of 7.3–23.6 L/kg) and Sr (in the range of 4.3–8.06 L/kg) in the marine system, typically 2–3 orders of magnitude lower than those on marine suspended sediment, this study offers compelling evidence that microplastics in marine environments are capable of sequestering radio Cs and Sr. Consequently, microplastics can potentially accumulate these radionuclides, highlighting their role as potential reservoirs as well as vectors of radionuclides in marine environments.

Occurrence of Microplastics in the Tissues of Nile Tilapia (Orechromis niloticus) from Zobe Dam, Katsina State, Nigeria

A study of the detection of microplastics on Oreochromis niloticus in Zobe Reservoir, Katsina State, Nigeria was carried out. Three fish sampling sites were used; the upstream (Tsawatsawa), midstream (Makera), and downstream (Garhi) were selected based on variation of anthropogenic activities. A total number of one hundred and forty-four (144) fish samples with a total weight (MTW) and total length (MTL) varied between 134.1 ±1.50 to 154.2± 3.41g and 17.5 ± 0.10– 22.1± 0.54 cm respectively, were collected and analysed for the presence of microplastics using standard protocols. Fourier Transform Infrared Spectrophotometer (FTIR) was used for the chemical characterization of microplastic composition examined in the fish species. The examination of microplastic occurrence in different sampled fish gills, liver, and kidney revealed the presence of Polystyrene, Polypropylene, Polyethylene terephthalate, Nylon, Polyester, and Polyvinyl chloride. Fish from all sampling sites revealed varying histopathological alterations ranging from lifting of epithelium thickening, distortion of the primary lamellae, and degeneration of secondary lamellae, blood congestion, and massive lamellae degeneration in the gill tissues. Liver tissues had hepatocyte hypertrophy, sinusoidal dilatation and cytoplasmic vacuolation, presence of lipid granules, cellular infiltration, cytoplasmic vacuolation, and haemorrhage. The kidney tissues were presented with Bowman’s capsules hyperplasia, tubular elongation, renal tubular epithelium shrinkage, hyperplasia, and cytoplasmic vacuolization of renal cells. The severity of the damage varies from site to site indicating that the water body is experiencing pollution at varying locations. Our findings provide important insights into the prevalence and distribution of microplastics in this particular environment.

Effect of Biofouling on the Sorption of Organic Contaminants by Microplastics.

Microplastics in the aquatic environment are susceptible to colonization by surrounding microorganisms, which form biofilms over the microplastic's surface. These biofilm-laden microplastics can then interact with a diverse array of contaminants. In the present study, biofilms were grown on microplastics in a laboratory setting using Pseudomonas aeruginosa as a model biofilm-forming bacterium for periods of 5 to 15 days. The sorption of three organic compounds representing different levels of hydrophobicity, namely methylene blue (MB), phenanthrol, and phenanthrene, was used to evaluate the effect of biofilm biomass on the adsorption of organic contaminants to microplastics. The sorption of MB and phenanthrol was found to increase with biofouling time, indicating affinity between these contaminants and the biofilm biomass on the particle. However, the presence of a biofilm did not influence the sorption of phenanthrene on the microplastics. These results suggest that the hydrophobicity of organic contaminants plays a major role in how biofouling of microplastics will influence contaminant sorption by microplastics. For some contaminants, biofilm can enhance the role of microplastics as contaminant vectors. These findings emphasize the need to understand the biomass load on environmental microplastics and the contaminants that associate with it for an accurate representation of the risk associated with microplastics in the environment. Environ Toxicol Chem 2024;43:1973-1981. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Assessment of Microplastic Pollution Across the Malabar Coast, India

ABSTRACTRecent scientific investigations have highlighted concerning levels of microplastic contamination in marine ecosystems, posing significant risks to marine organisms and human populations. This study aimed to assess the prevalence of microplastics in water, sediment, and tissues of commercially important fish species along the Malabar coast in Northwest Kerala, India. Using Fourier transform infrared spectroscopy (FTIR), six predominant polymer types were identified, including HDPE, PET, and nylon. The investigation revealed notable abundances of transparent microplastic particles, measuring <1 mm in diameter, particularly in gastrointestinal and gill tissues, with gastrointestinal tissues exhibiting the highest concentration of microplastics. A diverse array of morphotypes, including fragments (48.08%), fibers (28.84%), filaments (19.23%), and granules (3.85%), were observed within the coastal zone. The study implicates various sources of contamination, such as direct discharges, runoff, and inadequate wastewater management practices, contributing to the substantial presence of microplastics in coastal environments. In light of these findings, the study emphasizes the urgent need for the implementation of effective regulatory measures to mitigate plastic pollution in marine ecosystems. These results underscore the critical importance of proactive intervention to safeguard the health of marine ecosystems and human populations in coastal regions.

Differentiation of petro-sourced plastic microfilaments from organic microfilaments by SEM-EDX in environmental samples

Quantifying microplastics (MPs) in marine environments is challenging due to the complexities of differentiation from other materials. This study aims to distinguish petro-sourced plastic microfilaments from organic ones in environmental samples using scanning electron microscope coupled with energy dispersive X-ray (SEM-EDX) analysis. Therefore, 38 particles resembling MPs (PRMPs) from sediments and organisms in Madagascar were analyzed. MPs identification thresholds were determined from SEM-EDX analysis of macroplastics and seaweed, the primary sources of microfilaments. SEM-EDX results of the 38 PRMPs were compared with identification/misidentification made by five MPs observation experts. Results indicated that a carbon/oxygen (C/O) ratio >1 distinguished macroplastics and MPs from other sources (seaweed and organic microfilaments). SEM-EDX analysis identified 81.58% of PRMPs as MPs. The average error made by one observer was 36.32%. These findings highlight the need for a method to assess identification error in MPs quantification and recommend SEM-EDX analysis of microfilaments to gauge observer error.

Transport of polystyrene microplastics in bare and iron oxide-coated quartz sand: Effects of ionic strength, humic acid, and co-existing graphene oxide

This research explored the effects of widely utilized nanomaterial graphene oxide (GO) and organic matter humic acid (HA) on the transport of microplastics under different ionic solution strengths in bare sand and iron oxide-coated sand. The results found transport of polystyrene microplastics (PS) did not respond to the presence of HA in sand that contains large amounts of iron oxide. Compared to bare quartz sand, ionic strength had little effect: <20 % of PS passed through Fe sand columns. There was a significant promotion of PS transport in the presence of GO, however, which can be attributed to the increased surface electronegativity of PS and steric hindrance. Moreover, GO combined with HA significantly promoted the transport of PS in the Fe sand, and transport further increased when the concentration of HA increased from 5 to 10 mg/L. Interestingly, the degree of this increase exactly corresponded to the change in the surface charge of the microplastics, demonstrating that electrostatic interaction dominated the PS transport. Further results indicated that co-existing pollutants had significant impacts on the transport of microplastics under various conditions by altering the surface characteristics of the plastic particles and the spatial steric hindrance within porous media. This research will offer insights into predicting the transport and fate of microplastics in complex environments.

Physio-chemical degradation of single-use plastics in natural weather and marine environments

Plastic pollution has reached concerning levels globally, with single-use plastic products (SUPs) comprising at least 50% of plastic waste. This study investigates the physical and chemical degradation of frequently used SUPs, including petroleum-based and bio-based plastics, in natural Northern European coastal weather and marine environments over a three-year period from 2019 to 2022. Addressing a critical knowledge gap, this research was based on a hypothesis that real-world ageing studies on SUPs would produce more accurate time- and process-lines for their transformation from macro-to microplastics than are available today based on the modeling studies more frequently used. The study employs optical examination, mechanical testing, Fourier Transform Infrared (FTIR) spectroscopy, and Gas Chromatography-Mass Spectrometry (GC-MS) to determine and relate physical and chemical changes with time. The results indicate that SUPs undergo significantly faster degradation in natural weather than predicted to date. Photooxidation emerges as the primary degradation pathway for all SUPs, emphasizing the role of light in plastic breakdown. Importantly, physical degradation to microplastics in natural environments is not always associated with significant chemical changes such as breaking chemical bonds. Black SUPs exhibit greater resistance to visible light and ultraviolet radiation than equivalent white and transparent examples. In marine environments, SUPs degrade measurably slower than in air, their degradation slowing with increasing distance from the water surface. Our findings indicate the urgent need for strategies that mitigate the impacts of photo-oxidation of SUPs. Such strategies may include a focus on the removal of post-use SUPs from pavements, roads, beaches, and water surfaces where photo-oxidation is faster than underwater and underground. Preferential use of black SUPs over white or transparent should also be considered.

Mechanistic analysis of membrane fouling by microplastics in a gravity-driven ceramic membrane reactor for roofing rainwater reuse

The presence of microplastics (MPs) in aquatic environments is a direct consequence of human activities and social development. Consequently, the removal of MPs is essential in water treatment processes, including the membrane filtration of roofing rainwater. Additionally, MPs carried by roofing rainwater pose potential risks to both the ecosystem and human health. However, the fouling behavior of MPs and their impact on the performance of gravity-driven ceramic membranes (GDCMs) remains largely unexplored. In this study, we investigated the effects of the coexisted MPs in rainwater, specifically granulate and fiber MPs, on the formation of fouling layers. We examined their physical and biological characteristics, such as components and microbial community structure. The results demonstrated a positive correlation between the formation of the biological functional layer and the diverse morphology of MPs, which led to a significant decrease in membrane permeability and exacerbated membrane fouling, while having no remarkable influence on permeate quality. Furthermore, different shapes of MPs exhibited varying characteristics: the cake layer of the granulate-MPs group exhibited superior compressibility, while the fiber-MPs group formed and matured more rapidly. MPs not only directly combined with organic matter but also induced metabolic products of microorganisms. Therefore, understanding the primary mechanisms of membrane fouling by MPs in GDCMs for roofing rainwater reuse is of utmost importance. Our study presents novel insights into the mechanisms of membrane fouling in the presence of coexisting MPs in roofing rainwater reuse and provides guidance for improving the performance of GDCMs in the presence of MPs.

Microplastic identification in marine environments: A low-cost and effective approach based on transmitted light measurements

Microplastics have become a significant concern for the well-being of marine ecosystems. Small fragments of plastic debris are released into the environment from both the direct disposal of plastic products and the deterioration of larger items. Ingestion of microplastics by marine life can result in detrimental effects, including physical harm and the accumulation of toxic chemicals in their tissues. The aim of this research is to design a compact and cost-effective measurement system for effectively detecting and quantifying microplastics in marine environments. The proposed system uses a 2.4-inch liquid-crystal display (LCD) panel and a digital USB microscope, both of which are connected to a single-board computer, with a dedicated python-based graphical user interface (GUI). Specifically, the light transmitted through plastic and organic samples was measured in order to identify and classify them. Various types of materials, such as polypropylene, polyvinyl chloride, polycarbonate, polyethylene, and organic algae samples, were tested and the metrological performance of the system has been estimated. The transmittance of the samples analyzed was primarily influenced by their opacity and thickness. In general, thicker materials exhibited significantly lower transmittance values. This trend was particularly evident in organic components and opaque plastic samples, where transmittance was significantly low. In addition, the experimental results suggest that the colour of the material also affects transmittance, although as a secondary factor. The employed technique could be used to identify and distinguish samples based on material properties, thereby allowing the proposed system to be a valuable tool for further research on microplastics in marine environments.

The Peril of Plastics: Atmospheric Microplastics in Outdoor, Indoor, and Remote Environments

The increasing commercial, industrial, and medical applications of plastics cannot be halted during the coming years. Microplastics are a new class of plastic pollutants which have emerged as escalating environmental threats. The persistence, effects, and removal of MPs present in soil, water, and numerous organisms have become an important research field. However, atmospheric microplastics (AMPs), which are subcategorized into deposited and suspended, remain largely unexplored. This review presents the recent developments and challenges involved in fully understanding suspended and deposited AMPs. The evaluation of indoor suspended MP fibers needs to be critically investigated to understand their implications for human health. Furthermore, the transportation of AMPs to isolated locations, such as cryospheric regions, requires immediate attention. The major challenges associated with AMPs, which have hindered advancement in this field, are inconsistency in the available data, limited knowledge, and the lack of standardized methodologies for the sampling and characterization techniques of AMPs.

Simulation of the dynamic processes of microplastic suspension and deposition in a lake sediment-water system.

The occurrence of microplastics in aquatic environments has attracted increasing interest from both the public and scientists, especially their migration behaviors. Although several environmental behaviors of microplastics have been studied, the issue of microplastic suspension and deposition in lake sediment-water systems remains to be elucidated. In this study, we built an indoor sediment-water system with input and output rivers that simulated the actual situations in lakes, and aimed to explore the suspension and deposition behavior of microplastics using eight group experiments. The abundance of microplastics in overlying water and sediments in different periods was analyzed, and the characteristics of hydrodynamic disturbance on microplastic suspension and deposition were identified. Importantly, the exchange of microplastics in sediments and water under dynamic flow conditions was assessed. The results showed that the middle-scale experiment designed in this study effectively simulated the dynamic transport process of microplastics in lakes, and the hydrodynamic force had a significant impact on the suspension and deposition behaviors of microplastics. The average abundance of polystyrene, polyethylene terephthalate and polyamide microplastics was 1.07, 0.60 and 0.83 particles/L in overlying water during the suspension experiments, respectively. This showed a pattern of first rising and then falling with the extension of suspension time. Even in the environment with the maximum input water volume (8000 ml/min) in this study, only microplastics at a depth of 0 to 2 cm from the sediment were suspended. The average abundance of microplastics was 313.02 particles/kg during the deposition experiments, which gradually increased with the extension of deposition time in sediments. Finally, microplastic sizes in water of the suspension experiments and in sediments of the deposition experiments were concentrated in the range of 500 to 1500 μm and 300 to 1000 μm, respectively.

Microplastics and Antibiotics in Aquatic Environments: A Review of Their Interactions and Ecotoxicological Implications

Microplastics and antibiotics are two significant emerging pollutants found together in water bodies, raising concerns about their mutual effects. This review delves into how microplastics and antibiotics interact in aqueous environments and the ecotoxicological implications of such interactions, particularly the bioavailability of antibiotics and the prevalence of antibiotic-resistance genes. It outlines that antibiotics attach to microplastics primarily through hydrophobic, hydrogen-bonding, and electrostatic interactions. Other bonds, comprising halogen bonding, cation−π interaction, and negative charge-assisted hydrogen bonds, may also be involved to better explain antibiotic adsorption patterns. The adsorption of antibiotics to microplastics often follows the pseudo-second-order kinetic model and in some instances, the pseudo-first-order kinetic model. The common adsorption isotherms governing this interaction are the linear and Freundlich models. Microplastics may increase the biodegradation of adsorbed antibiotics due to the presence of antibiotic-degrading bacteria in the biofilms. They could also hamper direct photodegradation but facilitate indirect photodegradation of adsorbed antibiotics. However, their photodegradative effect remains inconclusive. Microplastics and antibiotics exhibit significant toxicity to algae, while their effects on fish and daphnia are less noticeable, suggesting that their combination does not pose an immediate threat to the well-being and proliferation of larger aquatic organisms. In some instances, microplastics reduce the deleterious effects of antibiotics on aquatic life. Microplastics serve as catalysts for gene transfer, enhancing the propagation of antibiotic-resistance genes in these ecosystems. This review underscores the importance of understanding the regulatory mechanisms of microplastics on antibiotic-resistance gene diversity, particularly at the gene expression level.

Aging and Small-sized Particles Release Characteristics of Tire Microplastics in Various Environmental Media

In recent years, research on microplastics has mostly focused on thermoplastic materials, and there is a lack of research on the pollution status and environmental behavior of tire microplastics, a type of rubber elastomers. In order to investigate the aging and small-sized particles release characteristics of tire microplastics in various environmental media, the aging process of two different tire microplastics, one for cars and the other for electric bicycles, was simulated in dry and aquatic environments under laboratory conditions. The results showed that the tire microplastics would be aged after 30 d of UV illumination, which was manifested by the roughness of the surface and the appearance of cracks and flaking. The Fourier infrared spectra showed that the carbonyl index of the surface also increased. In addition, tire microplastics released a large number of small sub-micron particles under the influence of UV illumination and hydrodynamic action, and the number of particles released from car tire microplastics in aquatic environments reached 694.8 million particles per milliliter of solution at 30 d of the UV light condition, among which 694.6 million particles with a particle size of less than 1 μm were released, which was approximately 100 times of that in the dark condition. The study showed that tire microplastics in aquatic environments were more susceptible to aging and released more small particles under light conditions and that car tire microplastics released more small particles than electric bicycle tire microplastics, posing ecological and environmental risks.

Environmental microplastic interact with heavy metal in polluted soil from mine site in the North of Tunisia: Effects on heavy metal accumulation, growth, photosynthetic activities, and biochemical responses of alfalfa plants (Medicago saliva L.)

As emerging persistent pollutants, microplastic (MPs) pollution attracted increasing attention worldwide since it is posing several environmental concerns. MPs interact with heavy metals in soil and may provoke damages on soil properties and ultimately impaired plants and human health. The present study aims to evaluate alfalfa plants (Medicago sativa) response after exposure to heavy metal polluted soils from mine site in the North of Tunisia in presence of environmental microplastic. For that, soils were sampled from two sites of Jebel Ressass mine in addition to a control soil. Plants were exposed to the three soils in presence of two increasing rates of microplastics D1 (1 mg/kg of soil) and D2 (100 mg/kg of soil) for 60 days. After harvest, agronomic parameters, chlorophyll content as well as heavy metal accumulation in plants were analyzed. Furthermore, oxidative status was evaluated in terms of malondialdehyde accumulation (MDA), catalase (CAT) activities and glutathion-S-transferase (GST). Overall, our finding highlights that MPs disrupted agronomic parameters and the photosynthetic activities of alfalfa plants. Additionally, our results revealed that the presence of MPs in polluted soils cause an increase on heavy metal accumulation in alfalfa shoots. Biochemical analyses demonstrated that the combined exposure to MPs and heavy metal induced oxidative stress in alfalfa plants by increasing CAT activity and MDA accumulation. The present investigation highlights the ecological risks of microplastics in terrestrial environment.

Rapid Mass Conversion for Environmental Microplastics of Diverse Shapes.

Rivers have been recognized as the primary conveyors of microplastics to the oceans, and seaward transport flux of riverine microplastics is an issue of global attention. However, there is a significant discrepancy in how microplastic concentration is expressed in field occurrence investigations (number concentration) and in mass flux (mass concentration). Of urgent need is to establish efficient conversion models to correlate these two important paradigms. Here, we first established an abundant environmental microplastic dataset and then employed a deep neural residual network (ResNet50) to successfully separate microplastics into fiber, fragment, and pellet shapes with 92.67% accuracy. We also used the circularity (C) parameter to represent the surface shape alteration of pellet-shaped microplastics, which always have a more uneven surface than other shapes. Furthermore, we added thickness information to two-dimensional images, which has been ignored by most prior research because labor-intensive processes were required. Eventually, a set of accurate models for microplastic mass conversion was developed, with absolute estimation errors of 7.1, 3.1, 0.2, and 0.9% for pellet (0.50 ≤ C < 0.75), pellet (0.75 ≤ C ≤ 1.00), fiber, and fragment microplastics, respectively; environmental samples have validated that this set is significantly faster (saves ∼2 h/100 MPs) and less biased (7-fold lower estimation errors) compared to previous empirical models.