Microplastic pollution in the surface waters of Italian Subalpine Lakes

Impact of sub-chronic polystyrene nanoplastics exposure on hematology, histology, and endoplasmic reticulum stress-related protein expression in Nile tilapia (Oreochromis niloticus)

Nanoplastics (NPs) are one of the most hazardous marine litters, having the potential to cause far-reaching impacts on the environment and humankind. The effect of NPs on fish health has been studied, but their impact on the subcellular organelles remains unexplored. The present investigation studied the possible implications of polystyrene-nanoplastics (PS-NPs) on the hematology, tissue organization, and endoplasmic reticulum (ER) stress-related proteins in Nile tilapia (Oreochromis niloticus). Fish were exposed to ∼100 nm PS-NPs at environmentally relevant (0.1 mg/L), and sublethal (1, 10 mg/L) concentrations for 14 days through water exposure. The growth performance and hematological parameters such as erythrocytes, hemoglobin, hematocrit, and leucocytes decreased, while thrombocytes increased with PS-NPs dose-dependently. The gills, liver, kidney, and heart tissues displayed increasing degrees of pathology with increased concentrations of PS-NPs. The gills showed severe epithelial hyperplasia and lamellar fusion. The liver had an abstruse cellular framework, membrane breakage, and vacuolation. While glomerular and tubular atrophy was the most prominent pathology in the kidney tissue, the heart displayed extensive myofibrillar loss and disorderly arranged cardiac cells. The ER-stress-related genes such as bip, atf6, ire1, xbp1, pkr, and apoptotic genes such as casp3a, and bax were over-expressed, while, the anti-apoptotic bcl2 was under-expressed with increasing concentrations of PS-NPs. Immunohistochemistry and blotting results of GRP78, CHOP, EIF2S, and ATF6 in gills, liver, kidney, and heart tissues affirmed the translation to ER stress proteins. The results revealed the sub-lethal adverse effects and the activation of the ER-stress pathway in fish with sub-chronic exposure to PS-NPs.

Photochemically induced aging of polystyrene nanoplastics and its impact on norfloxacin adsorption behavior

The co-occurrence of nanoplastics (NPs) and antibiotics in the environment is a growing concern for ecological safety. As NPs age in natural environments, their surface properties and morphology may change, potentially affecting their interactions with co-contaminants such as antibiotics. It is crucial to understand the effect of aging on NPs adsorption of antibiotics, but detailed studies on this topic are still scarce. The study utilized the photo-Fenton-like reaction to hasten the aging of polystyrene nanoplastics (PS-NPs). The impact of aging on the adsorption behavior of norfloxacin (NOR) was then systematically examined. The results showed a time-dependent rise in surface oxygen content and functional groups in aged PS-NPs. These modifications led to noticeable physical changes, including increased surface roughness, decreased particle size, and improved specific surface area. The physicochemical changes significantly increased the adsorption capacity of aged PS-NPs for norfloxacin. Aged PS-NPs showed 5.03 times higher adsorption compared to virgin PS-NPs. The adsorption mechanism analysis revealed that in addition to the electrostatic interactions, van der Waals force, hydrogen bonding, π-π* interactions and hydrophobic interactions observed with virgin PS-NPs, aged PS-NPs played a significant role in polar interactions and pore-filling mechanisms. The study highlights the potential for aging to worsen antibiotic risk in contaminated environments. This study not only enhances the comprehension of the environmental behavior of aged NPs but also provides a valuable basis for developing risk management strategies for contaminated areas.

Microplastics pollution in the Asian water tower: source, environmental distribution and proposed mitigation strategy

Microplastics generated from fragmentation of leftover plastics and industrial waste has reached in the remotely located Asian water tower (AWT) region, the 3rd pole of earth and origin site of several freshwater rivers. The accumulation of microplastics in AWT ecosystem has potential to alter the climatic condition contributing in global warming and disturbing the biodiversity structural dynamics. The present paper provides a comprehensive critical discussion over quantitative assessment of microplastics in different ecosystems (i.e. river, lakes, sediment and snow or glacier) of AWT. The hydrodynamic fate and transport of microplastics and their ecological impact on hydromorphology and biodiversity of AWT has been exemplified. Furthermore, key challenges, perspectives and research directions are identified to mitigate microplastics associated problems. During survey, the coloured polyethylene and polyurethane fibers are the predominant microplastics found in most areas of AWT. These bio-accumulated MPs alter the rhizospheric community structure and deteriorate nitrogen fixation process in plants. Significance in climate change, MPs pollution is enhancing the emissions of greenhouse gases (NH3 by ∼34% and CH4 by ∼9%), contributing in global warming. Considering the seriousness of MPs pollution, this review study can enlighten the pathways to investigate the effect of MPs and to develop monitoring tools and sustainable remediation technologies with feasible regulatory strategies maintaining the natural significance of AWT region.

Synthesis of recyclable and light-weight graphene oxide/chitosan/genipin sponges for the adsorption of diclofenac, triclosan, and microplastics

Emerging micropollutants, such as pharmaceuticals and microplastics (MPs), have become a pressing water environmental concern. The aim of this study is to synthesize chitosan sponges using graphene oxide (GO) and genipin (GP) for the removal of pharmaceuticals (diclofenac (DCF) and triclosan (TCS)) and MPs, verify their adsorption mechanisms, evaluate the effects of temperature, pH, and salinity on their adsorption capacities, and determine their reusability. The GO5/CS/GP sponge exhibited a macroporous nature (porosity = 95%, density = 32.6 mg/cm3). GO and cross-linker GP enhanced the adsorption of DCF, TCS, and polystyrene (PS) MPs onto the CS sponges. The adsorption of DCF, TCS, and PS MPs involved multiple steps: surface diffusion and pore diffusion of the sponge. The adsorption isotherms demonstrated that Langmuir model was the most fitted well model to explain adsorption of TCS (qm = 7.08 mg/g) and PS MPs (qm = 7.42 mg/g) on GO5/CS/GP sponge, while Freundlich model suited for DCF adsorption (qm = 48.58 mg/g). DCF adsorption was thermodynamically spontaneous and endothermic; however, the adsorption of TCS and PS MPs was exothermic (283-313 K). The optimal pH was 5.5-7 due to the surface charge of the GO5/CS/GP sponge (pHzpc = 5.76) and ionization of DCF, TCS, and PS MPs. As the salinity increased, DCF removal efficiency drastically decreased due to the weakening of electrostatic interactions; however, TCS removal efficiency remained stable because TCS adsorption was mainly caused by hydrophobic and π-π interactions rather than electrostatic interaction. The removal of PS MPs was enhanced by the electrostatic screening effects of high Na+ ions. PS nanoplastics (average size = 26 nm) were removed by the GO5/CS/GP sponge at a rate of 73.0%, which was better than that of PS MPs (41.5%). In addition, the GO5/CS/GP sponge could be recycled over five adsorption-desorption cycles.

Evaluation of potentially toxic elements and microplastics in the water treatment facility

The potentially harmful effects of consuming potentially toxic elements (PTEs) and microplastics (MPs) regularly via drinking water are a significant cause for worry. This study investigated PTEs (Cd, Cu, Cr, Ni, Pd, Zn, Co), MPs, turbidity, pH, conductivity, and health risk assessment in the water treatment plant in Kielce, Poland. Zn had the highest concentrations throughout the water treatment facility, whereas Cd, Pb, and Co had lower concentrations (< 0.1 µg/L). The order of the concentrations among the specified PTEs was like Zn˃Cu˃Ni˃Cr˃Cd˃Pb and Co. The minimum turbidity was 0.34, and the maximum was 1.9 NTU. The range of pH in water samples was 6.51-7.47. The conductivity was 1,203-1,445 ms in water samples. These identified MPs were categorized into fiber and fragments. The color of these identified MPs was blue, red, black, green, and transparent. The minimum and maximum size of the MPs was 196 and 4,018 µm, while the average size was 2,751 ± 1,905 µm. The average concentration of MPs per liter of the water treatment plant was 108.88 ± 55.61. The elements listed are C, O, Na, Mg, Al, Si, K, Ca, and Ti. Fe and Zn were the predominant elements seen using EDX. HQ values of the PTEs were less than one for adults and children. The human health risk associated with all detected PTEs revealed that the HQ values exhibit a satisfactory degree of non-carcinogenic adverse health risk. HI values for adults and children age groups were less than one. In most water treatment samples, the carcinogenic value exceeds the threshold value of 10-6. The PTEs and MP concentrations in drinking water should be periodically monitored to minimize consumers' environmental pollution and health risks.

Effect of urbanization and water quality on microplastic distribution in Conceição Lagoon watershed, Brazil

Urbanization in watersheds leads to the introduction of sources of microplastics and other pollutants in water bodies. However, the effect of urbanization on microplastic pollution and the relationship between microplastics and water quality are not well understood. We assessed the distribution of microplastics in tributaries urbanized, non-urbanized and in the receiving lagoon body of Conceição Lagoon watershed. The results show that urbanization significantly affects water quality but does not differentiate tributaries in terms of microplastic concentrations. Microplastic concentrations were lower in the receiving lagoon body compared with the tributaries, highlighting their importance in microplastic pollution in the studied lagoon. Microplastic concentration was correlated with low N:P ratios in the lagoon and associated with high levels of total phosphorus, which indicate the discharge of effluents. The correlations between microplastic concentration, water temperature, and dissolved oxygen in the lagoon were based on the temporal variations of these variables. Precipitation and wind velocity had influence on microplastic distribution in the watershed. Our findings underscore the importance of evaluating water quality parameters and meteorological variables to comprehend the microplastic distribution at small watersheds.

Microplastic pollution in high-altitude Nainital lake, Uttarakhand, India

Microplastics (MPs) contamination has been reported in all environmental compartments, but very limited information is available at higher-altitude lakes. Nainital Lake, located at a high altitude in the Indian Himalayas, has various ecosystem services and is the major source of water for Nainital town, but the MP abundance is still unknown. This study presents the first evidence of the abundance and distribution of MP in Nainital Lake. Surface water and sediment samples were analysed from 16 different sites in and around the catchment area of Nainital Lake. The MP were observed in all the samples, and their abundance in surface water was 8.6-56.0 particles L-1 in the lake and 2.4-88.0 particles L-1 in hotspot sites. In the surface sediment, MP abundance ranged from 0.4-10.6 particles g-1, while in the hotspot sediment, the mean abundance was 0.6 ± 0.5 particles g-1. Fibers were the dominant MP, while 0.02-1 mm were the predominant size of MP particles. The results of chemical characterization showed the presence of six polymers, among which high-density polyethylene was the most abundant. The Polymer Hazard Index assessment classified the identified polymers as low-to high-risk categories, with a higher abundance of low- (polypropylene) and medium- (polyethylene)-risk polymers. Tourist activities and run-off catchments can be considered the major sources of MP, which can affect the ecosystem. Minimal concentrations of MP were observed in the tube well and drinking water, which depicts the direct risks to humans and, thus, the need for remedial measures to prevent MP contamination in drinking water. This study improves the knowledge of MP contamination in the higher-altitude freshwater lake, which can be the major pathway for the transport of MP to the rivers, and also emphasizes the need for waste management in Nainital town.

Monthly variability of floating plastic contamination in Lake Maggiore (Northern Italy)

The monitoring of plastics in freshwater ecosystems has witnessed a significant increase in recent years, driven by the awareness that approximately 80 % of marine plastic litter originates from terrestrial sources transported to the seas through lakes and rivers. Consequently, it is imperative to develop monitoring plans that offer a comprehensive understanding of plastic contamination in these aquatic environments, given their seasonal variations in hydrochemical characteristics and anthropogenic sources. Historically, most global lake monitoring campaigns have been limited to one-time or, at most, seasonal sampling. In this context, the primary objective of the present study was to assess the quantitative and qualitative monthly variations of floating plastics in Lake Maggiore, a large European lake with high ecological and economic significance. Twelve transverse transects were conducted from January to December 2022 using a Manta-net with a 100 μm mesh. Characterization of each plastic particle was performed using a μ-Fourier Transform Infrared Spectroscope (μFT-IR). The results revealed relatively low levels of contamination in Lake Maggiore when compared with other lakes worldwide exclusively from a secondary origin. However, a considerable heterogeneity was observed, both quantitatively and qualitatively. Notably, we identified a 13-fold difference between the minimum (0.02 plastics/m3 in September) and maximum (0.29 plastics/m3 in December) concentrations of plastics, accompanied by significant variations in polymer composition. Our monitoring underscored the necessity of also considering the temporal variation as a potential factor influencing plastic contamination in a lake. Moreover, frequent sampling emerged as a crucial requirement to accurately gauge the extent of plastic pollution, yielding robust and valuable data essential for effective environmental management.

An investigation into the stability and degradation of plastics in aquatic environments using a large-scale field-deployment study

The fragmentation of plastic debris is a key pathway to the formation of microplastic pollution. These disintegration processes depend on the materials' physical and chemical characteristics, but insight into these interrelationships is still limited, especially under natural conditions. Five plastics of known polymer/additive compositions and processing histories were deployed in aquatic environments and recovered after six and twelve months. The polymer types used were linear low density polyethylene (LLDPE), oxo-degradable LLDPE (oxoLLDPE), poly(ethylene terephthalate) (PET), polyamide-6 (PA6), and poly(lactic acid) (PLA). Four geographically distinct locations across Aotearoa/New Zealand were chosen: three marine sites and a wastewater treatment plant (WWTP). Accelerated UV-weathering under controlled laboratory conditions was also carried out to evaluate artificial ageing as a model for plastic degradation in the natural environment. The samples' physical characteristics and surface microstructures were studied for each deployment location and exposure time. The strongest effects were found for oxoLLDPE upon artificial ageing, with increased crystallinity, intense surface cracking, and substantial deterioration of its mechanical properties. However, no changes to the same extent were found after recovery of the deployed material. In the deployment environments, the chemical nature of the plastics was the most relevant factor determining their behaviours. Few significant differences between the four aquatic locations were identified, except for PA6, where indications for biological surface degradation were found only in seawater, not the WWTP. In some cases, artificial ageing reasonably mimicked the changes which some plastic properties underwent in aquatic environments, but generally, it was no reliable model for natural degradation processes. The findings from this study have implications for the understanding of the initial phases of plastic degradation in aquatic environments, eventually leading to microplastics formation. They can also guide the interpretation of accelerated laboratory ageing for the fate of aquatic plastic pollution, and for the testing of aged plastic samples.

Microplastics affect mosquito from aquatic to terrestrial lifestyles and are transferred to mammals through mosquito bites

Microplastics (MPs) transfer from the environment to living organisms is a nonignorable global problem. As a complete metamorphosis insect, the larvae and adult Culex quinquefasciatus mosquito live in aquatic and terrestrial environments, respectively, where they easily access MPs. However, little is known about mosquitoes' potential role in MPs accumulation throughout ecosystems. Therefore, we conducted a study with different MPs particle sizes (0.1/1/10 μm) and concentrations (0.5/5/50 μg/mL) on Cx. quinquefasciatus to address this issue. Once exposed at the young larval stage, MPs could accompany the mosquitoes their entire life. The fluorescence signals of MPs in the larvae were mainly located in the intestines. Its intensity increased (from 3.72 × 106 AU to 5.45 × 107 AU) as the concentrations of MPs increases. The fluorescence signals of MPs were also detected in the blood and skin tissues of mice bitten by adult mosquitoes with MPs containing in their bodies. Mosquitos exposed to MPs showed longer larval pupation and eclosion time as well as lower adult body weight. In addition, MPs significantly reduced the lethal effect of pyrethroid insecticides (97.77 % vs. 48.88 %, p < 0.05) with 15.1 % removal of the deltamethrin concentration. After MPs exposure, the relative abundance of the Cx. quinquefasciatus gut microbiome, such as Wolbachia spp., Elizabethkingia spp., and Asaia spp., changed as the MPs size and concentration changes. Mosquitoes provide a new pathway for MPs accumulation and transfer to higher-level living organisms. Moreover, MPs significantly reduce the control effect of deltamethrin, providing new guidelines for mosquito insecticide application in MPs contamination circumstances.

Biofragmentation of Polystyrene Microplastics: A Silent Process Performed by Chironomus sancticaroli Larvae

Polystyrene (PS) is one of the main synthetic polymers produced around the world, and it is present in the composition of a wide variety of single-use objects. When released into the environment, these materials are degraded by environmental factors, resulting in microplastics. We investigated the ability of Chironomus sancticaroli (Diptera, Chironomidae) to promote the fragmentation of PS microspheres (24.5 ± 2.9 μm) and the toxic effects associated with exposure to this polymer. C. sancticaroli larvae were exposed to 3 different concentrations of PS (67.5, 135, and 270 particles g-1 of dry sediment) for 144 h. Significant lethality was observed only at the highest concentration. A significant reduction in PS particle size as well as evidence of deterioration on the surface of the spheres, such as grooves and cracks, was observed. In addition, changes in oxidative stress biomarkers (SOD, CAT, MDA, and GST) were also observed. This is the first study to report the ability of Chironomus sp. to promote the biofragmentation of microplastics. The information obtained demonstrates that the macroinvertebrate community can play a key role in the degradation of plastic particles present in the sediment of freshwater environments and can also be threatened by such particle pollution.

Current patterns and trends of microplastic pollution in the marine environment: A bibliometric analysis

Microplastics are pervasive in the natural environment and pose a growing concern for global health. Plastic waste in marine environments has emerged as a global issue, threatening not only marine biota but also human health due to its implications for the food chain. This study aims to discern the patterns and trends of research, specifically on Marine Microplastic Pollution (MMP), based on a bibliometric analysis of scientific publications from 2011 to 2022. The methodology utilized in this study comprises three stages: (a) creating a bibliographical dataset from Scopus by Elsevier and the Web of Science Core Collection by Clarivate Analytics, (b) analyzing current research (trends and patterns) using bibliometric analysis through Biblioshiny tool, and (c) examining themes and subthemes in MMP research (wastewater treatment, plastic ingestion, the Mediterranean Sea, microplastics pollution, microplastics in freshwater, microplastic ingestion, plastic pollution, and microplastic pollution in the marine environment). The findings reveal that during the studied period, the number of MMP publications amounted to 1377 articles, with an average citation per publication of 59.23 and a total citation count of 81,553. The most cited article was published in 2011, and since then, the number of publications on this topic has been increasing steadily. The author count stood at 5478, with 22 trending topics identified from the 1377 published titles. Between 2019 and 2022, the countries contributing most to the publication of MMP articles were China, the United States of America (USA), and the United Kingdom (UK). However, a noticeable shift in the origin of author countries was observed in the 2019-2022 timeframe, transitioning from a dominance by the USA and the UK to a predominance by China. In 2019, there was a substantial increase in the volume of publications addressing the topic of microplastics. The results show that the most prevalent themes and subthemes pertained to MMP in the Mediterranean Sea. The journals with the highest number of MMP articles published were the Marine Pollution Bulletin (253 articles) and Science of the Total Environment (190 articles). The analysis concludes that research on MMP remains prominent and appears to be increasing each year.

The adsorption and its mechanism of venlafaxine by original and aged polypropylene microplastic and the changes of joint toxicity

Conjugation with the increment of consumption of polypropylene (PP) masks and antidepressants during pandemic, PP microplastics (MPs) and Venlafaxine (VEN) widely co-existed in surface waters. However, their environmental fate and the combined toxicity were unclear. Hence, we investigated the adsorption behaviors, and associated mechanisms of PP MPs for VEN. The impact factors including pH, salinity, and MPs aging were estimated. The results indicated PP MPs could adsorb amount of VEN within 24 h. The pseudo second-order kinetic model (R2 = 0.97) and Dubinin-Radushkevich model (R2 = 0.89) fitted well with the adsorption capacity of PP MPs for VEN, implying that chemical adsorption accompanied by electrostatic interaction might be the predominant mode for the interactions between PP MPs and VEN. Meanwhile, the adsorption capacity of PP MPs declined from pH of 2.5-4.5 and then increased from 4.5 to 9.5. The increased salinity (5-35 ppt) significantly suppressed the adsorption capacity. Aging by sunlight and UV triggered the formation of new functional group (carbonyl) on MPs, and then enhanced the adsorption capacity for VEN. Gaussian Model analysis further evidenced the electrostatic adsorption occurring in PP MPs and VEN. The combined exposure to PP MPs and VEN showed significantly antagonistic toxicity on Daphnia magna. The adsorption of VEN by PP MPs mitigated the lethal effects and behavioral function impairment posed by VEN on animals, implying the potential protective effects on zooplankton by PP MPs. This study for the first time provides perspective for assessing the environmental fate of MPs and antidepressants in aquatic system.

Psychrobacter species enrichment as potential microplastic degrader and the putative biodegradation mechanism in Shenzhen Bay sediment, China

Microplastic (MP) pollution has emerged as a pressing environmental concern due to its ubiquity and longevity. Biodegradation of MPs has garnered significant attention in combatting global MP contamination. This study focused on MPs within sediments near the sewage outlet of Shenzhen Bay. The objective was to elucidate the microbial communities in sediments with varying MPs, particularly those with high MP loads, and to identify microorganisms associated with MP degradation. The results revealed varying MP abundance, ranging from 211 to 4140 items kg-1 dry weight (d. w.), with the highest concentration observed near the outfall. Metagenomic analysis confirmed the enrichment of Psychrobacter species in sediments with high MP content. Psychrobacter accounted for ∼16.71% of the total bacterial community and 41.71% of hydrocarbon degrading bacteria at the S3 site, exhibiting a higher abundance than at other sampling sites. Psychrobacter contributed significantly to bacterial function at S3, as evidenced by the Kyoto Encyclopedia of Genes and Genomes pathway and enzyme analysis. Notably, 28 enzymes involved in MP biodegradation were identified, predominantly comprising oxidoreductases, hydrolases, transferases, ligases, lyases, and isomerases. We propose a putative mechanism for MP biodegradation, involving the breakdown of long-chain plastic polymers and subsequent oxidation of short-chain oligomers, ultimately leading to thorough mineralization.

Adsorption of clarithromycin on polystyrene nanoplastics surface and its combined adverse effect on serum albumin

Emerging contaminants, such as antibiotics and nanoplastics, have garnered significant attention due to their potential adverse effects on diverse ecosystems. Antibiotic adsorption on the surface of nanoplastics potentially facilitates their long-range transport, leading to the synergistic effects of the complex. This research aims to examine the adsorption behavior of clarithromycin binding with polystyrene nanoplastics surface as well as their interaction between drug adsorbed polystyrene nanoplastics with serum albumin. Different spectroscopic methods were used to find out the interaction between clarithromycin and nanoplastics, under stimulated physiological conditions UV-vis spectroscopy showed a maximum of 22.8% percentage of the drug adsorbed with the polystyrene nanoplastics surface after 6 h of incubation. The fluorescence spectroscopic results demonstrated that the fluorescence intensity of serum albumin was quenched by the clarithromycin-polystyrene nanoplastics (CLA-PSNP) complex through static quenching. We calculated the number of binding stoichiometry, binding constants, and thermodynamic parameters. This study revealed that the CLA-PSNP binds to serum albumin spontaneously and its hydrophobic interactions played a significant role. The conformational changes in the structure of serum albumin were revealed from the findings of synchronous fluorescence spectra, CD spectra, and 3D fluorescence spectra, leading to the disturbance in functional activity. This study focuses valuable insights into the intermolecular interactions between clarithromycin-adsorbed polystyrene nanoplastics and serum albumin and its potential molecular-level biological toxicity.

A study on managing plastic waste to tackle the worldwide plastic contamination and environmental remediation

Over the past 50 years, the emergence of plastic waste as one of the most urgent environmental problems in the world has given rise to several proposals to address the rising levels of contaminants associated with plastic debris. Worldwide plastic production has increased significantly over the last 70 years, reaching a record high of 359 million tonnes in 2020. China is currently the world's largest plastic producer, with a share of 17.5%. Of the total marine waste, microplastics account for 75%, while land-based pollution accounts for responsible for 80-90%, and ocean-based pollution 10-20% only in overall pollution problems. Even at small dosages (10 μg/mL), microplastics have been found to cause toxic effects on human and animal health. This review examines the sources of microplastic contamination, the prevalent reaches of microplastics, their impacts, and the remediation methods for microplastic contamination. This review explains the relationship between the community composition and the presence of microplastic particulate matter in aquatic ecosystems. The interaction between microplastics and emerging pollutants, including heavy metals, has been linked to enhanced toxicity. The review article provided a comprehensive overview of microplastic, including its fate, environmental toxicity, and possible remediation strategies. The results of our study are of great value as they illustrate a current perspective and provide an in-depth analysis of the current status of microplastics in development, their test requirements, and remediation technologies suitable for various environments.

Microplastics in lentic environments: implications for Indian ecosystems

The paper focused on occurrence, characterization, and analytical methods of microplastic (MP) pollution in the lentic environment mainly for the Indian scenario. To understand the flow of MP from plastic waste, a material flow diagram was developed using STAN, assigning the transfer coefficients based on existing scientific literature and primary survey from local recycling facilities and industries. The quantity, morphology, and polymers of MP in the water and sediments of the lentic environment were compared for various states from 2011 to 2022. The reasons for the geographical heterogeneity in microplastics may be the migratory routes of MPs in the ecosystems like commercial uses and wastewater characteristics which possibly discharged in lentic system. Factors like particle density, water surface area, water surface depth, wind speed and direction, and water flow size mainly affect MP concentrations in the lentic water body, and mainly PHI and PLI are keys to MP risk analysis. The surface characteristics of MPs reveal that it absorbs many toxic contaminants including heavy metals. The impacts of MP on ecosystem and human health were also discussed. The impacts of socioeconomic conditions on MP concentrations for different states in India were also added. Proposed methods for plastic waste generation control also included which will help for developing policy in future to prevent MP pollution in lentic environments and also motivate future researchers to establish new standardized methods of MP analysis.

Comparison of spatiotemporal burial and contamination of heavy metals in core sediments of two plateau lakes with contrasting environments: implication for anthropogenic-driven processes

Investigating the impacts of climatic factors and human activities on sedimentary records of heavy metal (HM) contamination in lakes is essential for decision-making in global environmental monitoring and assessment. Spatiotemporal distributions of grain size (GS) and HM (Al, Cr, Mn, Ni, Cu, Zn, As, and Pb) concentrations have been conducted in core sediments that are collected from two adjacent plateau fault-bound lakes in southwest China with contrasting environments, i.e., deep oligotrophic Lake Fuxian (FX) and shallow hypertrophic Lake Xingyun (XY). Results showed that the average value of d50 in FX (4.61 μm) was lower than that in XY (8.35 μm), but the average concentrations of HMs (except Cr and Mn) in XY were higher than those in FX. Heavy metal burial rates (HMBR) were mainly controlled by sediment accumulation rates (SARs) rather than HM concentrations. The correlation coefficients between GS and HM concentrations became strong as the increasing water depths were associated with a stable sedimentary environment. Time-integrated enrichment factors (EF) and source identification of HMs between FX and XY represented that Cr, Ni, and Cu originated from natural sources but Mn, Zn, As, and Pb from anthropogenic sources, respectively. Regardless of FX and XY, the transition times of HMs from natural to anthropogenic sources occurred in the mid-1960s. Comparison of qualification impacts of climatic factors and human-induced factors on increased anthropogenic HMBR by the partial least squares path modeling (PLS-PM) implied that socio-economic activities, such as population density (PD) and gross domestic product (GDP), provided higher contributors to increased anthropogenic HMBR in XY (0.23/0.71) than FX (0.11/0.18). The comparative results of this study provided new insights into environmental monitoring and management of HM contamination for adjacent lakes with contrasting environments.

Geographical heterogeneity and dominant polymer types in microplastic contamination of lentic ecosystems: implications for methodological standardization and future research

This study examines the prevalence and distribution of microplastic polymer types in lentic ecosystems, revealing significant heterogeneity across different geographical regions and ecosystems. The most dominant type of microplastic observed was polyethylene (PE), followed by polypropylene (PP) and polystyrene (PS), which aligns with global production rates. North America, Asia, and Europe were identified as the regions with the highest microplastic contamination, with the United States, China, Italy, and Spain being the most affected countries. The physical characteristics of each ecosystem, such as wind speed, depth, and eutrophication, alongside seasonal variations, and anthropogenic activities, contributed to the observed heterogeneity in microplastics concentrations. The study highlights the need for further research on microplastics in lentic ecosystems, considering their unique physical characteristics and anthropogenic influences. A significant lack of methodological standardization in microplastics research was identified, leading to underestimation of microplastics prevalence and high heterogeneity in meta-analyses.

Distribution and abundance of microplastics in the water column of Vembanad Lake-A Ramsar site in Kerala, India

The study focuses on the occurrence, abundance and characteristics of microplastics (MPs) in the subsurface and bottom waters of Vembanad Lake, a Ramsar site in the state of Kerala. Even though several studies elucidate the prevalence of microplastic pollution in the surface waters of aquatic ecosystems, a little is known about the vertical distribution of MPs in the water column. Vembanad Lake water is greatly affected by microplastic pollution compared to other Indian lakes as it receive discharges from six rivers; a number of sewage canals and run-off. Ubiquitous distribution of MPs was found in the lake with a mean abundance of 26.79 ± 3.74 items L-1 and 52.70 ± 5.43 items L-1 in subsurface and bottom waters respectively. Fibers, constitute more than half of the total MPs in both subsurface and bottom waters. The dominance of polyamide and polypropylene with most of the MPs being fibers indicate that they originate probably from fishing activities and laundry wastewater. The particles with in the size range 100-500 μm were in excess in the water samples. Further fragmentation, increasing the number of MPs in the lake water was envisaged from the SEM images of MPs showing cracks and crevices. These MPs along with adsorbed contaminants upon ingestion by the aquatic organisms become a threat to the food web of the lake. The local population which depends mainly on the fishes and mussels of the lake for their dietary needs would be greatly affected by the contamination of the lake with MPs. Further research on MPs contamination in edible biota would give more insights on the extent and risks of MPs pollution in the lake.

Mini review of microplastic pollutions and its impact on the environment and human health

In recent years, the environmental pollution of microplastics (MPs) has increasingly drawn our attention. MPs are small fragments of plastics that are commonly dispersed in the environment. The accumulation of environmental MPs is due to population growth and urbanization, while natural disasters such as hurricanes, flooding and human activity may influence their distribution. The leaching of chemicals from MPs raises a significant safety problem and environmental approaches aimed at reducing the use and recycling of plastics, with the replacement by bioplastics and wastewater treatment developments are called for. This summary also helps in demonstrating the connection between terrestrial and freshwater MPs and wastewater treatment plants as the major contributors to environmental MPs by discharges of sludge and effluent. More research on the classification, detection, characterization and toxicity of MPs are essential to enable greater options and solutions. Control initiatives need to intensify the comprehensive study of MP waste control and management information programmes in the fields of institutional engagement, technological research and development, legislation and regulation. A comprehensive quantitative analysis approach for MPs should be created in the future, and more reliable traceability analysis methods should be built to examine further its environmental activity and existence, where this should be done to improve scientific research on MP pollution in terrestrial, freshwater and marine environments and hence, develop more scientific and rational control policies.

Microplastics in Tai lake food web: Trophic transfer and human health risk assessment

Although microplastics (MPs) in marine organisms have been widely studied, the toxicity of MPs in freshwaters and human health is still a global challenge. To fill this gap, we implemented an Ecopath and food web accumulation model to simulate the Tai Lake ecosystem, a region dependent on the tourism and seafood industries. Our results suggested the accumulation of MPs throughout the food web and ultimately reach organisms at high trophic levels, including human-being, who consume MPs through seafood. The adults were prone to consume more MPs than adolescents and children. Unlike clams, fish biota magnification factors indicated that MPs accumulation between specific predator-prey interactions is not expected. The abundance of MPs within clams reveals a potential risk of MPs entering the food web. To better understand the MPs transfer, we recommend paying greater attention to species-specific mechanisms and the resources they rely on.

Characterization of microplastics and its Pollution load index in freshwater Kumaraswamy Lake of Coimbatore, India

Microplastics are less than 5mm in diameter that enters the ecosystem through the breakdown of large plastic particles or climate and human activity. This study examined the geographical and seasonal distribution of microplastics in the surface water of Kumaraswamy Lake, Coimbatore. During seasons, including summer, pre-monsoon, monsoon, and post-monsoon, samples were collected from the lake's inlet, centre, and outlet. All sampling points contained linear low-density polyethylene, high-density polyethylene, polyethylene terephthalate, and polypropylene microplastics. Water samples contained fibre, thin, fragment, and film microplastics in black, pink, blue, white, transparent, and yellow colours. Lake's microplastic pollution load index was under 10, indicating risk I. Over four seasons, microplastic content was 8.77±0.27 particles per litre. The monsoon season had the highest microplastic concentration, followed by pre-monsoon, post-monsoon, and summer. These findings imply that the spatial and seasonal distribution of microplastics may be harmful to the fauna and flora of the lake.

Effects of microplastics in freshwater fishes health and the implications for human health

The presence of microplastics in aquatic environments has raised concerns about their abundance and potential hazards to aquatic organisms. This review provides insight into the problem that may be of alarm for freshwater fish. Plastic pollution is not confined to marine ecosystems; freshwater also comprises plastic bits, as the most of plastic fragments enter oceans via rivers. Microplastics (MPs) can be consumed by fish and accumulated due to their size and poor biodegradability. Furthermore, it has the potential to enter the food chain and cause health problems. Evidence of MPs s ingestion has been reported in >150 fish species from both freshwater and marine systems. However, microplastic quantification and toxicity in freshwater ecosystems have been underestimated, ignored, and not reported as much as compared to the marine ecosystem. However, their abundance, influence, and toxicity in freshwater biota are not less than in marine ecosystems. The interaction of MPs with freshwater fish, as well as the risk of human consumption, remains a mystery. Nevertheless, our knowledge of the impacts of MPs on freshwater fish is still very limited. This study detailed the status of the toxicity of MPs in freshwater fish. This review will add to our understanding of the ecotoxicology of microplastics on freshwater fish and give subsequent research directions.

Seasonal and spatial variations in the distribution pattern, sources and impacts of microplastics along different coastal zones of Tamil Nadu, India

We investigated spatiotemporal variations of microplastics (MPs) in Coromandel Coast, Palk Bay, Gulf of Mannar, and West Coast of Tamil Nadu, India. MPs abundance varies from 37 ± 1.52 to 189 ± 9.02 items/kg in sediment and 23 ± 15.25 to 155.25 ± 4.16 items/L in water. Highest abundance in monsoon by riverine inflow transports plastic waste to the ocean. MPs sizes 0.5-1 mm are dominant in summer with 16 polymers, while 3-4 mm dominates the monsoon with 23 polymers. Carbonyl Index shows high MP oxidation (>0.31), unrelated to spatiotemporal changes. SEM-EDAX shows weathered MPs carrying hazardous metals. High MP diversity (MPDII = 0.77) of Coromandel Coast points to many sources of pollution and the need for immediate control measures. Pollution load values indicate low degree of MP pollution (<10), polymer hazard index shows level III (10-100) and IV (100-1000), and ecological risk assessment shows minor risks (<150) at present.

Toxicity and Biodistribution of Fragmented Polypropylene Microplastics in ICR Mice

Currently, polypropylene (PP) is used in various products, thus leading to high daily exposure in humans. Thus, it is necessary to evaluate the toxicological effects, biodistribution, and accumulation of PP microplastics in the human body. In this study, administration of two particle sizes of PP microplastics (approximately 5 and 10-50 µm) did not lead to any significant changes in several toxicological evaluation parameters, including body weight and pathological examination, compared with the control group in ICR mice. Therefore, the approximate lethal dose and no-observed-adverse-effect level of PP microplastics in ICR mice were established as ≥2000 mg/kg. Furthermore, we manufactured cyanine 5.5 carboxylic acid (Cy5.5-COOH)-labeled fragmented PP microplastics to monitor real-time in vivo biodistribution. After oral administration of the Cy5.5-COOH-labeled microplastics to the mice, most of the PP microplastics were detected in the gastrointestinal tract and observed to be out of the body after 24 h in IVIS Spectrum CT. Therefore, this study provides a new insight into the short-term toxicity, distribution, and accumulation of PP microplastics in mammals.

First comparative assessment of contamination by plastics and non-synthetic particles in three bivalve species from an Italian sub-alpine lake

This study aimed to compare the contamination from plastics and non-synthetic particles in the three freshwater bivalve mollusks Unio elongatulus, (native) and Corbicula fluminea and Dreissena polymorpha (invasive), collected in Lake Maggiore, the second greatest Italian lake. Organisms were collected from eight sites located throughout the lake, during three years (2019-2021). The quali-quantitative characterization of particles has been carried out using a Fourier Transform Infrared Microscope System (μFT-IR). Results showed that both plastics and non-synthetic particles released in the water are taken up by bivalves, even though low intake-up to 6 particles/individuals-were measured for all the three species. Microfibers of both synthetic (polyester, polyamide) and natural (cellulose) origin represented the particles mostly ingested by bivalves. A significant decrease of particle loads was observed in 2020 with respect to 2019 and 2021, significantly different for D. polymorpha and U. elongatulus, suggesting a transient reduction of the particle release in the lake in this year. Our findings highlight the need to improve the understanding of the mechanisms of uptake and clearance of these contaminants by filter feeding organisms, and their adverse consequences in realistic environmental conditions.

Behavior and mechanisms of ciprofloxacin adsorption on aged polylactic acid and polyethlene microplastics

Microplastics (MPs) and antibiotics are emerging pollutants in aquatic environments. MPs can absorb antibiotics, resulting in compound pollution. Batch adsorption experiments were used to investigate the adsorption behavior of CIP on polylactic (PLA) and polyethlene (PE) under various environmental conditions. After a lengthy aging process, both MPs underwent significant physicochemical changes. The equilibrium adsorption capacities of aged PLA and PE were 0.382 mg/g and 0.28 mg/g, respectively, which increased by 18.06% and 75% compared to pristine PLA and PE. The sorption capacity of MPs increased when the pH of the solution approached the dissociation constant (6.09, 8.74) of CIP. When the salinity of the solution was 3.5%, the adsorption capacity of MPs was reduced by more than 65%. The adsorption capacity of MPs rapidly decreased when 20 mg/L fulvic acid was added. Because norfloxacin (NOR) competes for adsorption sites on the microplastic, CIP adsorption is inhibited. Based on the adsorption models, FTIR, and XPS spectra, we demonstrated that the process was monolayer adsorption, with chemical and physical mechanisms including hydrogen bonding, π-π conjugation, ion exchange, and electrostatic interactions controlling it. Thus, PLA and PE microplastics may be a potential vector for CIP in water, and their interaction is mainly influenced by the physicochemical properties of the MPs and environmental factors.

Experimental uncertainty assessment of meso- and microplastic concentrations in rivers based on net sampling

Meso- and microplastics have been collected via net sampling in marine and freshwater environments, but the effect of net clogging on evaluations of their concentrations (mPC) remains uncertain. We experimentally investigated the mPC uncertainties resulting from net clogging in the Ohori and Tone-unga Rivers, typical urban rivers in Japan, throughout 16 samplings with five filtration durations in one day. The weighted mean concentration in the Ohori River was significantly lower than that in the Tone-unga River, allowing us to examine the effect of clogging in rivers with different contamination levels. The variances in both rivers consistently tended to increase with increasing filtration duration, which can be expressed by applying the integral form of the Weibull reliability function (WRF). Furthermore, application of the WRF successfully revealed the optimal filtration durations in the Ohori and Tone-unga Rivers, which depended on the plastic abundance and sample volume. Since it could be difficult to obtain the plastic contamination level in advance, our suggestion is to predict the time sustained above 85 % filtration efficiency by applying a WRF-based model. In actuality, the sustained time in the Ohori (Tone-unga) River varied between 2.6 and 6.2 min (3.2 and 7.1 min) throughout the experiment, which permitted low mPC uncertainties of 12 % and 9.5 %, respectively. If notable uncertainty exists due to a low contamination level, a net with a high open area ratio should be used to increase the filtration duration. Hence, our results emphasize the importance of considering the open area ratio of nets used for sampling in studies. Our study provides insights into the occurrence of uncertainty due to net clogging to establish a standardized methodology for meso- and microplastic monitoring in aquatic environments via net sampling and consequently contributes to improving the sampling accuracy.

First report on microplastics contamination in a meteorite impact Crater Lake from India

Microplastic pollution is a worldwide concern affecting all environmental matrices, including pristine lakes. Lentic lakes operate as a sink for microplastics (MPs), which interfere with a biogeochemical cycle and, therefore, deserve immediate attention. We present a comprehensive assessment of MPs contamination in the sediment and surface water of a geo-heritage site, Lonar lake (India). It is the third largest natural saltwater lake and only basaltic crater in the world formed by meteoric impact around 52,000 years ago. Mean MPs abundance in lakeshore sediment and surface water was 14.44 particles/kg and 2.66 particles/L, respectively. Small-sized MPs dominate the hypersaline region of the lake. Transparent and green fragments and filaments morphotypes were abundant. Most of the MPs in Lonar lake were secondary in origin. FTIR-ATR analysis revealed 16 types of polymers in the lake, of which polypropylene, polyvinyl chloride, polyethylene, high-density polyethylene, low-density polyethylene, polystyrene, and polyester were the most common. The overall pollution load index (PLI) for Lonar lake sediment and water was 1.39 and 2.58, respectively. Although all sampling stations had significant MPs pollution (PLI > 1), there was noticeable station-specific variability, which could be linked to anthropogenic activities. Irresponsible tourist behavior and religious activities, coupled with poor waste management are the leading causes of MPs contamination in the lake. The current work fills a gap in the investigation of MP pollution in a crater lake formed by a meteorite impact by being the first to provide a precise estimate of the MPs contamination in the Lonar lake.

Feasibility Study for the Development of a Low-Cost, Compact, and Fast Sensor for the Detection and Classification of Microplastics in the Marine Environment

The detection and classification of microplastics in the marine environment is a complex task that implies the use of delicate and expensive instrumentation. In this paper, we present a preliminary feasibility study for the development of a low-cost, compact microplastics sensor that could be mounted, in principle, on a float of drifters, for the monitoring of large marine surfaces. The preliminary results of the study indicate that a simple sensor equipped with three infrared-sensitive photodiodes can reach classification accuracies around 90% for the most-diffused floating microplastics in the marine environment (polyethylene and polypropylene).

Distribution of microplastics in different tissues of major commercial catches in different functional areas of the South Yellow Sea

The microplastic (MP) pollution in different tissues of six commercial catches, including (Miichthys miiuy, Eleutheronema tetradactylum, Collichthys lucidus, Mugil cephalus, Portunus trituberculatus and Exopalaemon carinicauda) in Haizhou Bay (nori farming area), Yancheng offshore (wind power construction area) and the Nantong marine ranch area of the South Yellow Sea was investigated. MPs are ubiquitous in commercial catches; the average abundance of MPs is 5.19 ± 3.64 items/individual. There are significant differences in the level of MP pollution in commercial catches among functional sea areas. The level of MP pollution in commercial catches in Haizhou Bay and Yancheng offshore is higher than that in the Nantong marine ranch areas. This difference may be related to intense anthropogenic activities such as engineering construction and mariculture. In addition to the presence in digestive tract, MPs in the skin and gills of fish and in the gills of shrimp and crabs cannot be ignored. The main shape, color and material of MPs are fiber, black-gray and celluloid (CP), respectively. Since commercial catches are consumed by humans, the potential risks of MPs in these catches to human health and marine ecology are of concern.

A critical review on recent research progress on microplastic pollutants in drinking water

Plastic pollution is an emerging issue in recent days. Persistent plastic particles reach the atmosphere, land and water by multiple pathways. Research has confirmed that the existence of plastic particles is found surprisingly everywhere, from the Artic to the Antarctic region. The probability of ingestion of plastic by all living forms is quite natural, as the whole planet's environment is polluted with microplastic particles. The bioaccumulation of microplastics is a threat and the consequences for living beings are yet to be explored. Microplastics present in different drinking water sources like rivers, lakes, treatment units etc. are studied by several researchers, covering various aspects. Research carried out by various scientists on the microplastics in different drinking water sources is highlighted in this review. In view of the previous research carried out on various aspects of microplastic particles, the necessity of a uniform protocol for qualitative and quantitative analysis of microplastic is ascertained. Microplastic pollution is an ongoing environmental concern, it must be addressed and research should be expanded.

Methods for controlled preparation and dosing of microplastic fragments in bioassays

Microplastic fragments (microfragments) are among the most abundant microplastic shapes found in marine ecosystems throughout the world. Due to their limited commercial availability, microfragments are rarely used in laboratory experiments. Here a novel method of microfragment production has been developed and validated. Polyethylene and polypropylene plastic stock (2 and 3 mm thick respectively) was ground using a cryomill, washed, and rinsed through a stack of sieves. Microfragments were prepared at three distinct size classes (53-150, 150-300, 300-1000 μm) and were confirmed to be accurate and consistent in size. Employing a novel ice cap dosing technique, microfragments were accurately dosed into experimental vials while excluding headspace, facilitating particle suspension without the aid of chemical surfactants. A proof of principle ingestion experiment confirmed the bioavailability of 53-150 μm polyethylene microfragments to brine shrimp Artemia sp. Together, these methods provide a controlled way to produce and dose microplastic fragments for experimental and analytical research.

Research status and prospects of microplastic pollution in lakes

As an emerging pollutant, microplastics have attracted widespread concern around the world. Research on microplastics was first conducted in oceans, and in recent years, inland water, especially lakes, has gradually become a hot spot. This paper systematically reviews the sampling, separation, purification, and identification technologies used to assess microplastics in lakes and summarizes the occurrence of lake microplastics worldwide. The results show that microplastics are widespread in lake water and sediment. There are obvious geographical differences in the occurrence of microplastics. The abundance of microplastics in different lakes varies greatly. The forms are mostly fibrous and fragments, and the main polymers are polypropylene (PP) and polyethylene (PE). Previous papers have failed to comment in as much detail on the microplastic sampling techniques employed within lake systems. The sampling and analysis methods are critical to accurately evaluating contamination results. Due to the widespread presence of microplastics and the lack of uniform standards, there are various sampling methods. Trawls and grabs are most widely used in the sampling of lake water bodies and sediment, and sodium chloride and hydrogen peroxide are the most widely used media for flotation and digestion, respectively. In the future, it will be critical to establish unified standards for lake microplastic sampling and analysis technology, further explore the migration mechanism of microplastics in lake systems, and pay attention to the impact of microplastics on lake ecosystems.

Spectroscopic investigations on the interaction between nano plastic and catalase on molecular level

As an emerging pollutant that is easily bonded with some functional proteins and the effects of their physiological expressions, nano plastics (NPs) have been widely detected in various environmental mediums, even in human blood. Compared to microplastics, less information on the interactions between NPs and proteins has been reported. Here, the interaction mechanism between common polystyrene nano plastics (PSNPs) and catalase (CAT) under two typical physiological conditions, pH 7.4 and 4.0, was investigated by UV-visible spectroscopy, circular dichroism (CD), and dynamic light scattering (DLS). Compared with the enhanced catalytic effects when increasing PSNPs at pH 7.4, a trend of initial inhibition and enhanced activity was observed at pH 4.0. Spectroscopic analysis and calculation results indicated that their binding was static, with only one binding site and stronger interactions under acidic conditions. UV-visible and CD spectra analysis demonstrated that the difference in enzymatic activity could be mainly attributed to the conformational alternation of CAT in the presence of PSNPs, which is obviously affected by solution chemistry. The change was also revealed by the hydrodynamic diameter and zeta potentials of the complexes supplied by DLS analysis. This study will help understand the health risks of nano plastic pollution and provide a theoretical basis for studying their toxicological effects.

Dissolved organic matter derived from biodegradable microplastic promotes photo-aging of coexisting microplastics and alters microbial metabolism

Dissolved organic matter (DOM) leaching from biodegradable microplastics (BMPs) and its characteristics and corresponding environmental implication are rarely investigated. In this study, the main component of DOM leachate from the two BMPs (polyadipate/butylene terephthalate (PBAT)/polycaprolactone (PCL)) was verified by using excitation-emission matrix-parallel factor analysis (EEM-PARAFAC). The PBAT-DOM (PBOM) was aromatized and terrestrial. Comparatively, PCL-DOM (PLOM) had low molecular weight. PBOM contained protein-like components while PLOM contained tryptophan and tyrosine components. Interestingly, both PBOM and PLOM could accelerate the decomposition and oxidation of coexisting polystyrene (PS) under light irradiation. Further, the difference in composition and the properties of BMPs-DOM significantly affected its photochemical activity. The high territoriality and protein-like component of PBOM significantly promoted the generation of ¹O₂ and O₂^•-, which caused faster disruptions to the backbone of PS. Simultaneously, the microbial community's richness, diversity, and metabolism were obviously improved under the combined pressure of aged PS and BMPs-DOM. This study threw light on the overlooked contribution of DOM derived from BMPs in the aging process of NMPs and their impact on the microbial community and provided a promising strategy for better understanding of combined MPs' fate and environmental risk.

Arsenic adsorption by carboxylate and amino modified polystyrene micro- and nanoplastics: kinetics and mechanisms

We investigated adsorption characteristics of As(III) and As(V) onto two different functionalized polystyrene (PS) microplastics (MPs). Our results show that there is the potential for PS MPs to adsorb both As(III) and As(V). Using a particle size of 80-82 nm, maximum As(III) and As(V) adsorption capacities of 0.57 mg/g and 0.37 mg/g were obtained by PS-COOH MPs. These capacities were markedly higher than those for PS-NH₂ MPs, which were 0.41 mg/g and 0.27 mg/g, respectively. The pseudo-second-order adsorption kinetic model was found to effectively describe the sorption kinetics of As(III)/As(V) on two different functionalized PS MPs. Langmuir isotherms better represented the equilibrium adsorption results. The kinetic models, XPS, and FTIR results indicate that hydrogen bonding, hydroxyl complexation, and outer-sphere surface complexation may have partly contributed to adsorption of As onto PS MPs. Adsorption capacity markedly decreases with increasing salinity or presence of humic acids (HA), suggesting an inhibiting effect of salinity and HA through outer-sphere complexation. These findings confirm that microplastics have great potential to adsorb As and hence are ultimately highly likely to affect the environmental behavior of As in an ecosystem.

Environmental Risks of Microplastics on the Spatial and Temporal Gradient in a River Originating from the Western Himalayas

The presence of microplastics in different environmental matrices has raised many concerns about potential effects of microplastics on humans and freshwater ecosystems. In Pakistan, rivers potentially receive microplastics from anthropogenic activities in their catchments. However, research studies regarding microplastics' presence, distribution, and risks are scarce in Pakistan. To bridge the gap, the present study was conducted to evaluate microplastic pollution in the Chenab River. Surface water samples were collected from selected sites on the Chenab River using a manta trawl in the low-flow season during postmonsoon (October) 2019 and 2020 and in the high-flow season during monsoon (July) 2020 and 2021. Samples were digested, followed by density separation and filtration. Identification and polymer characterization of microplastics were completed using stereomicroscopy and attenuated total reflection Fourier transform infrared spectroscopy, respectively. Microplastics were found in all samples with significant spatiotemporal variation in microplastic concentration, with an average of 45.98 ± 10.45 microplastics/m³ in the low-flow season and 34.66 ± 16.15 microplastics/m³ in the high-flow season. Among microplastic shapes, fibers were the most dominant shape, whereas polyethylene terephthalate (38.2%) and polypropylene (19%) were the most abundant polymers. Polymer risk index analysis and pollution load index demonstrated that most of the sites ranked as safe. The potential ecological risks from single polymers and combined polymers showed minor risks posed by microplastics. The present study is the first step to focus on microplastic pollution in the Chenab River; it will help river managers to mitigate the microplastic pollution without compromising the ecological integrity of the river. Environ Toxicol Chem 2023;42:727-739. © 2023 SETAC.

Recent developments in microplastic contaminated water treatment: Progress and prospects of carbon-based two-dimensional materials for membranes separation

Micro (nano)plastics pollution is a noxious menace not only for mankind but also for marine life, as removing microplastics (MPs) is challenging due to their physiochemical properties, composition, and response toward salinity and pH. This review provides a detailed assessment of the MPs pollution in different water types, environmental implications, and corresponding treatment strategies. With the advancement in nanotechnology, mitigation strategies for aqueous pollution are seen, especially due to the fabrication of nanosheets/membranes mostly utilized as a filtration process. Two-dimensional (2D) materials are increasingly used for membranes due to their diverse structure, affinity, cost-effectiveness, and, most importantly, removal efficiency. The popular 2D materials used for membrane-based organic and inorganic pollutants from water mainly include graphene and MXenes however their effectiveness for MPs removal is still in its infancy. Albeit, the available literature asserts a 70- 99% success rate in micro/nano plastics removal achieved through membranes fabricated via graphene oxide (GO), reduced graphene oxide (rGO) and MXene membranes. This review examined existing membrane separation strategies for MPs removal, focusing on the structural properties of 2D materials, composite, and how they adsorb pollutants and underlying physicochemical mechanisms. Since MPs and other contaminants commonly coexist in the natural environment, a brief examination of the response of 2D membranes to MPs removal was also conducted. In addition, the influencing factors regulate MPs removal performance of membranes by impacting their two main operating routes (filtration and adsorption). Finally, significant limitations, research gaps, and future prospects of 2D material-based membranes for effectively removing MPs are also proposed. The conclusion is that the success of 2D material is strongly linked to the types, size of MPs, and characteristics of aqueous media. Future perspectives talk about the problems that need to be solved to get 2D material-based membranes out of the lab and onto the market.

Characterization of ingested MPs and their relation with growth parameters of endemic and invasive fish from a coastal wetland

Microplastic (MP) contamination is a persistent and ubiquitous threat to aquatic ecosystems. This study quantifies MP ingestion by fish inhabiting the Anzali Wetland (Iran), a hotspot of biodiversity. Growth parameters have been monitored in endemic demersal fish (Caspian spined loach, Sabanejewia caspia), and invasive benthopelagic species (Prussian carp, Carassius gibelio) in the wetland and compared with their internal content of MPs. MPs were extracted from the gastrointestinal (GI) tracts following digestion of the samples in alkaline medium and observation of the extracts with microscopy (Scanning Electron Microscopy equipped with an Energy-Dispersive X-ray microanalyzer (SEM-EDS) and confocal Raman microscopy). A total of 84.6 % of the study fish (n = 26) were contaminated with MPs. Fibres were the only type of MPs found in the GI tracts, and these were mainly dark blue and made of polycarbonate and nylon in both investigated species. The mean numbers of MPs in the GI tracts of the carp and the loach were 3.6 and 3.7 respectively. MPs had smooth surfaces in most cases although some presented brittle, fragmented, and uneven surfaces and signs of degradation. The growth rates of Carassius gibelio and Sabanejewia caspia, measured with the b value (growth factor), were 2.91 and 2.15 respectively. Carassius gibelio can play a significant role in the transport of MPs to other aquatic organisms inhabiting the Anzali wetland, and hence can cause potential harm to them. Carassius gibelio MP contamination was more pronounced with increasing gut mass in older specimens. Due to the presence of MPs and in fish that can be consumed, there could be a trophic transfer to humans. Regarding Sabanejewia caspia, although not statistically significant, their uptake of MPs tends to increase in older specimens with smaller size and body weight. This can imply that MP pollution causes inappropriate conditions and results in negative growth. The findings of this work provide new insights into MP contamination in the Anzali wetland, specifically in endemic fish. These results will be important in conservation and management programs.

Release of millions of micro(nano)plastic fragments from photooxidation of disposable plastic boxes

The widespread use of disposable plastic boxes is exacerbating the dangers of microplastics (MPs); however, little is known about the fragmentation behavior of MPs during aging. In this study, the dynamic evolution on the release of micro(nano)plastics and photoaging properties of two disposable plastic boxes (polypropylene (PP) and polystyrene (PS)) were investigated under light irradiation and mechanical abrasion. Results showed that the weight of PP and PS was decreased by 53 % and 100 %, respectively after 60 d of ultraviolet irradiation (UV60). Moreover, a large number of fragmented particles were produced from the combined light irradiation and abrasion, with 0.142 ± 0.006 and 0.141 ± 0.013 million micro(nano)plastics/mL particles from PP and PS boxes, respectively, and the nanometer range (<100 nm) accounted for 70.8 % and 46.8 %. The correlation model of the average size or alteration time versus carbonyl index (CI) was developed, which indicated that the fragmentation behavior was mainly related to the photooxidation, though mechanical abrasion also played a certain enhancing role. Additionally, PS was susceptible to the fragmentation and photooxidation compared to PP possibly since the phenyl ring of PS was more vulnerable to UV attack than the methyl of PP. The findings of this study clarify the dynamic fragmentation process of micro(nano)plastics of disposable plastic boxes and provide useful information to access environmental fate of MPs more holistically.

Polystyrene microplastics enhanced copper-induced acute immunotoxicity in red swamp crayfish (Procambarus clarkii)

Microplastic pollution has attracted a lot of attention in recent years. Not only can it be ingested by animals, but it can easily become a carrier of other pollutants, forming a composite pollutant with potentially toxic effects on organisms. We investigated the effect of Cu on the accumulation of polystyrene microplastics (PS) in the gills of Procambarus clarkii and whether PS exacerbated the immune toxicity of Cu to P. clarkii were exposed to Cu, PS and PS+Cu for 48 h, the accumulation of PS in gill and hepatopancreas immune and antioxidant indices were analyzed. The objective was to investigate the toxic effects of Ps and Cu compound pollutants on P. clarkii and whether the accumulated pollutants would cause food safety problems. The results showed that microplastic particles adhered to each other and aggregated in the PS+Cu group, and the number of microplastic particles in gill in the PS+Cu group was significantly lower than that in the PS group. Compared with the other two treatment groups, SOD, CAT, GPx activities and MDA content increased significantly in the PS+Cu group and were relatively delayed. At 12 h, 24 h, 36 h and 48 h, the SOD mRNA expression levels in the PS+Cu group were all significantly lower than those in the Cu group (P < 0.05). At 24 h and 48 h, CAT mRNA expression in the PS+Cu group was significantly higher than that in the Cu group (P < 0.05). Crustin 4 mRNA expressions in the PS+Cu group was significantly higher than that in the Cu group at 12 h and 36 h (P < 0.05). The results demonstrate that the PS and Cu compound reduced the accumulation of microplastic particles in the gill. PS particles delayed Cu entry into P. clarkii for a short time (12 h) and reduced the toxic effect, but with the increase of exposure time (24 h and 48 h), the toxic effect of PS and Cu complexes on P. clarkii increases, and the large accumulation of PS and Cu complexes may cause food safety problems.

Effect of Fe and Al based coagulants and disinfectants on polyethylene microplastics removal in coagulation process through response surface methodology

Microplastic (MP) pollution has been rising as a threatening risk and recently has appealed to the attention of more researchers. In this study, influential parameters affecting the removal rate of polyethylene microplastics (PEMPs) were optimized through response surface methodology (RSM). In Box Behnken Design (BBD), independent parameters were pH, PEMP size, coagulant dosage and polyacrylamide dosage. Two experimental sets were conducted, one with ferric chloride and the second with poly aluminum chloride as two commonly applied coagulants in drinking water treatment plants (DWTPs). Comparing the results of optimized parameters, PAC was a better coagulant with the predicted removal rate of 58.19%, while the removal rate with ferric chloride as a coagulant was predicted to be 56.37%. Moreover, some experiments were conducted to analyze the effect of ozone gas and sodium hypochlorite as disinfectants on removal rate. The highest removal rate was observed when 2 ppm of O₃ was added to the solution coagulated with optimal dosage of PAC, reaching the removal rate of 76.8%.

Recent Advances in Micro-/Nanoplastic (MNPs) Removal by Microalgae and Possible Integrated Routes of Energy Recovery

Reliance on plastic has resulted in the widespread occurrence of micro-/nanoplastics (MNPs) in aquatic ecosystems, threatening the food web and whole ecosystem functions. There is a tight interaction between MNPs and microalgae, as dominant living organisms and fundamental constituents at the base of the aquatic food web. Therefore, it is crucial to better understand the mechanisms underlying the interactions between plastic particles and microalgae, as well as the role of microalgae in removing MNPs from aquatic ecosystems. In addition, finding a suitable route for further utilization of MNP-contaminated algal biomass is of great importance. The present review article provides an interdisciplinary approach to elucidate microalgae-MNP interactions and subsequent impacts on microalgal physiology. The degradation of plastic in the environment and differences between micro- and nanoplastics are discussed. The possible toxic effects of MNPs on microalgal growth, photosynthetic activity, and morphology, due to physical or chemical interactions, are evaluated. In addition, the potential role of MNPs in microalgae cultivation and/or harvesting, together with further safe routes for biomass utilization in biofuel production, are suggested. Overall, the current article represents a state-of-the-art overview of MNP generation and the consequences of their accumulation in the environment, providing new insights into microalgae integrated routes of plastic removal and bioenergy production.

Review on the ecotoxicological impacts of plastic pollution on the freshwater invertebrate Daphnia

The environmental impacts of plastic pollution have recently attracted universal attention, especially in the aquatic environment. However, research has mostly been focused on marine ecosystems, even though freshwater ecosystems are equally if not more polluted by plastics. In addition, the mechanism and extent to which plastic pollution affects aquatic biota and the rates of transfer to organisms through food webs eventually reaching humans are poorly understood, especially considering leaching hazardous chemicals. Several studies have demonstrated extreme toxicity in freshwater organisms such Daphnia. When such keystone species are affected by ambient pollution, entire food webs are destabilized and biodiversity is threatened. The unremitting increase in plastic contaminants in freshwater environments would cause impairments in ecosystem functions and structure, leading to various kinds of negative ecological consequences. As various studies have reported the effects on daphnids, a consolidation of this literature is critical to discuss the limitations and knowledge gaps and to evaluate the risk posed to the aquatic environment. This review was undertaken due to the evident need to evaluate this threat. The aims were to provide a meaningful overview of the literature relevant to the potential impact of plastic pollution and associated contaminants on freshwater daphnids as primary consumers. A critical evaluation of research gaps and perspectives is conducted to provide a comprehensive risk assessment of microplastic as a hazard to aquatic environments. We outlined the challenges and limitations to microplastic research in hampering better-focused investigations that could support the development of new plastic materials and/or establishment of new regulations.

Microplastics in ASEAN region countries: A review on current status and perspectives

A literature assessment was conducted to determine the current state of microplastics research in ASEAN countries focusing on 1) microplastics in water, sediment, and water organisms; 2) microplastics' sources and dispersion; and 3) microplastics' environmental consequences, including human toxicity. ASEAN countries contributed only about 5 % of the global scholarly papers on microplastics, with Indonesia contributing the most followed by Malaysia and Thailand. The lack of standard harmonized sampling and processing methodologies made comparisons between research difficult. ASEAN contributes the most to plastic trash ending up in the ocean, indicating a need for more work in this region to prevent plastic pollution. Microplastics are found in every environmental compartment; however, their distribution and environmental consequences have not been sufficiently investigated. There are very few studies on microplastics in the human blood system as well as respiratory organs like the lungs, indicating that more research is needed.

Effect of Polystyrene Synthesis Method on Water Sorption and Glass Transition

Commodity PS is synthesized via free radical polymerization, whereas PS in block copolymers (BCPs) is typically synthesized via living anionic polymerization. The purpose of this work is to investigate how the synthesis method impacts important properties such as water sorption and glass transition temperature (T_g). Water sorption is important because the performance of nanostructured polymer membranes in various applications is known to be affected by environmental conditions such as humidity. T_g is important because it dictates processing conditions, both for commodity PS as well as BCPs such as thermoplastic elastomers. Water sorption in commercial PS was found to be 0.5 mg_water/g_polymer at the highest humidities investigated (about 80%), in agreement with literature. On the other hand, syndiotactic PS synthesized anionically at low temperature absorbed more water, up to 1.5 mg_water/g_polymer, due to higher free volume. The greatest impact on water sorption was due to addition of hydrophilic hydroxyl chain ends to atactic PS, which resulted in water sorption of up to 2.3 mg_water/g_polymer. In addition to measuring water sorption and dry T_g separately, the impact of relative humidity on PS T_g was examined. Combined differential scanning calorimetry and dynamic mechanical analysis show that on going from the dry state to high humidity, the T_g of PS decreases by 5 °C. Moreover, the tensile storage modulus of PS decreases from 1.58 GPa at 0% RH to 0.53 GPa at 40% RH. In addition to the practical relevance of this study, this report fills a gap in experimental literature by using a poor solvent system, PS/water, to examine plasticization in the pure polymer limit.