Identification and quantification of microplastics using Nile Red staining

Selective visual staining of polyurethane microplastics by novel colorimetric and near-infrared (NIR) fluorescent dye: Application to environmental water and natural soil samples

Microplastics can cause environmental pollution and ecosystem destruction as well as human health problems. Among the types of microplastics, polyurethane (PU) is particularly resistant to heat and difficult to decompose, causing disposal problems, and is evaluated as one of the most hazardous polymers. We present a novel colorimetric and near-infrared (NIR) fluorescence dye, (E)-N-(2-((4-(diphenylamino)benzylidene)amino)phenyl)- 7-nitrobenzo[c][1,2,5]oxadiazol-4-amine (DPNA), designed for selective visual PU microplastic staining. The intramolecular charge transfer (ICT) properties of DPNA are demonstrated through density functional theory (DFT) calculations along with solvatochromic shift. DPNA exhibits red color and red fluorescence emission, showing promising potential as a staining dye. To achieve selective PU microplastic staining, we establish an optimized experimental procedure with the staining dye DPNA by evaluating the staining efficiency under different staining solvent compositions and staining times. DPNA can distinguish PU by both red fluorescence signal and red coloration among different types of microplastics. In addition, DPNA well stain fresh PUs with diverse sizes and at various pH range of 5-9, and the aged PUs can also be dyed as effectively as the fresh PU. Most importantly, DPNA selectively stains PU among 11 types of microplastics and 5 types of natural particles in environmental water and soil with and without any pre-treatments. The adsorption mechanism of DPNA on PU microplastic is demonstrated through field emission scanning electron microscopes (FE-SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and non-covalent interaction (NCI)-reduced density gradient (RDG) analyses, and proposed that intermolecular hydrogen bonding has a significant effect.

Fluorescent labelling combined with confocal differential Raman spectroscopy to detect microplastics in seawater

As an emerging marine pollutant, microplastics represent a focal point in global monitoring and management efforts. With seawater accounts for 97 % of the total global water resources, scientific assessments of microplastics in seawater are crucial for pollution control and management of marine environments. This study focuses on investigating microplastics in near-shore seawater and proposes a rapid and accurate detection method using a constructed confocal Raman spectroscopy detection system. By optimizing the pretreatment process of seawater microplastic samples, the efficient removal of organic matter interference in microplastic detection is achieved. Employing fluorescent labeling addresses the issues of prolonged detection time and high false positive rates associated with traditional methods, enabling rapid differentiation between microplastics and other substances and significantly enhancing detection efficiency and accuracy. Additionally, the use of differential Raman spectroscopy effectively mitigates fluorescence signal interference, thus improving the signal-to-noise ratio of the spectra. By employing dual-wavelength laser excitation at 784 nm/785 nm, microplastics such as polyethylene (PE), polypropylene (PP), polystyrene (PS) ranging in size from 60 to 500 μm are successfully detected in seawater. The results demonstrate that the proposed pretreatment method for seawater microplastics and novel detection techniques enable rapid screening and comprehensive non-destructive detection of microplastics in seawater, thereby facilitating the characterization of marine microplastics and providing scientific support for enhancing the management of microplastic pollution and ecological risk control.

Passive biomonitoring of airborne microplastics using lichens: A comparison between urban, natural and protected environments

Currently, natural and urban ecosystems are affected by different types of atmospheric deposition, which can compromise the balance of the environment. Plastic pollution represents one of the major threats for biota, including lichens. Epiphytic lichens have value as bioindicators of environmental pollution, climate change, and anthropic impacts. In this study, we aim to investigate the lichen bioaccumulation of airborne microplastics along an anthropogenic pollution gradient. We sampled lichens from the Genera Cladonia and Xanthoria to highlight the effectiveness of lichens as tools for passive biomonitoring of microplastics. We chose three sites, a "natural site" in Altipiani di Arcinazzo, a "protected site" in Castelporziano Presidential estate and an "urban site" in the centre of Rome. Overall, we sampled 90 lichens, observed for external plastic entrapment, melt in oxygen peroxide and analysed for plastic entrapment. To validate the method, we calculated recovery rates of microplastics in lichen. Particularly, 253 MPs particles were detected across the 90 lichen samples: 97 % were fibers, and 3 % were fragments. A gradient in the number of microplastic fibers across the sites emerged, with increasing accumulation of microplastics from the natural site (n = 58) to the urban site (n = 116), with a direct relationship between the length and abundance of airborne microplastic fibers. Moreover, we detected the first evidences of airborne mesoplastics entrapped by lichens. On average, the natural site experienced the shortest fibre length and the centre of Rome the longest. No differences in microplastics accumulation emerged from the two genera. Our results indicated that lichens can effectively be used for passive biomonitoring of microplastic deposition. In this scenario, the role of lichens in entrapping microplastics and protecting pristine areas must be investigated. Furthermore, considering the impact that airborne microplastics can have on human health and the effectiveness of lichens as airborne microplastic bioindicators, their use is encouraged.

ROS-Responsive and Self-Tumor Curing Methionine Polymer Library Based Nanoparticles with Self-Accelerated Drug Release and Hydrophobicity/Hydrophilicity Switching Capability for Enhanced Cancer Therapy

The applications of amino acid-based polymers are impeded by their limited structure and functions. Herein, a small library of methionine-based polymers (Met-P) with programmed structure and reactive oxygen species (ROS)-responsive properties is developed for tumor therapy. The Met-P can self-assemble into sub-100 nm nanoparticles (NPs) and effectively load anticancer drugs (such as paclitaxel (PTX) (P@Met-P NPs)) via the nanoprecipitation method. The screened NPs with superior stability and high drug loading are further evaluated in vitro and in vivo. When encountering with ROS, the Met-P polymers will be oxidized and then switch from a hydrophobic to a hydrophilic state, triggering the rapid and self-accelerated release of PTX. The in vivo results indicated that the screened P@2Met10 NPs possessed significant anticancer performance and effectively alleviated the side effects of PTX. More interestingly, the blank 2Met10 NPs displayed an obvious self-tumor inhibiting efficacy. Furthermore, the other Met-P NPs (such as 2Met8, 4Met8, and 4Met10) are also found to exhibit varied self-anti-cancer capabilities. Overall, this ROS-responsive Met-P library is a rare anticancer platform with hydrophobic/hydrophilic switching, controlled drug release, and self-anticancer therapy capability.

Assessment of microplastic contamination in commercially available fishes

Plastics have widespread applications for human use, but their disposal poses a significant threat to living organisms and these plastics end up in the marine environment. They will be fragmented into small pieces as a result of ultraviolet exposure, climatic changes, and temperature changes; Microplastics (MPs) are plastics that are less than 5 mm in size. The level of MP (Microplastic) pollution in commercially harvested fish from different habitant in Vellore, India is currently unknown. Therefore, this study aimed to determine the presence and characteristics of ingested or inhaled MPs in marine and freshwater fishes highly consumed by the local population. Fish gills and gastrointestinal tracts were aseptically dissected and digested (30% hydrogen peroxide), then filtered and examined under a microscope for the presence of MPs. Further analysis was performed on the samples using Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) and Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray (EDAX). Of the samples analysed, a total of 875 MPs were recovered from 32 fishes, with 478 from marine fishes and 397 from freshwater fishes. The most common colours of the MPs were blue and black, while stereo microscopy analysis revealed that the majority of MPs were fibers (91%), followed by fragments (8%) and a small number of films. The ATR-FTIR analysis identified polyvinyl alcohol (39.76%), polyethylene (16.51%), methylcellulose (12.84%) and styrene (9.07%), as the predominant types of MPs in the fish samples. This study highlights the significant impact of MP pollution on marine ecosystems. The research provides insight into the nature and extent of MPs in fish from both marine and freshwater habitats, with an aim for policies and interventions aimed to reduce plastic pollution in the locality.

Biodegradable microplastics: Uptake by and effects on the rockpool shrimp Palaemon elegans (Crustacea: Decapoda)

Ingestion of microplastics can lead to deleterious consequences for organisms, as documented by numerous laboratory studies. The current knowledge is based on a multitude of effect studies, conducted with conventional fossil-based and non-degradable plastics. However, there is a lack of information about the acceptance and the effects of novel bio-based and biodegradable plastics. Biodegradable plastics are considered an alternative to conventional plastics and are showing rapidly growing production rates. Biodegradable plastics can disperse into the environment in the same way as conventional plastics do, becoming available to marine organisms. This study aims to provide new insights into the uptake and effects of biodegradable microplastics on marine invertebrates. Rockpool shrimp, Palaemon elegans, were fed with algal flakes coated with polylactic acid (PLA), polyhydroxybutyrate-co-valerate (PHBV) and conventional low-density polyethylene (LDPE) microparticles. Live observations showed that all of the different types of microplastics were ingested. After dissection of the shrimp, less LDPE particles were found in the stomachs than PLA and PHBV particles. This indicates a longer retention time of biodegradable microplastics compared to conventional microplastics. Presumably, less LDPE particles were ingested or evacuated from the stomach, probably by regurgitation. The ingestion of microparticles of all types of plastics induced enzymatic activity of short-chain carboxylesterases in the midgut glands of the shrimp. However, only PLA induced enzymatic activity of medium-chain carboxylesterases. Palaemon elegans showed no oxidative stress response after ingestion of microparticles, irrespective of polymer type. From our results we conclude that biodegradable plastics might have different effects than conventional plastics. The longer retention times of biodegradable plastics might enhance exposure to leaching additives and other harmful substances. Our study provides new insights into how biodegradable plastics might affect aquatic fauna and indicate that the use of biodegradable plastics needs to be reconsidered to some extent.

Airborne microplastics in urban, rural and wildland environments on the Tibetan Plateau

The concentration of airborne microplastics is largely unknown in the remote high mountain area of the Tibetan Plateau. Here we report airborne microplastic concentrations of 2.5-58.8 n/m3 in urban, rural and wildland areas across the Tibetan Plateau, with smaller (∼89% <100 µm) fragments (>80%) dominating. Polyethylene terephthalate, polyethylene, polyamide and polystyrene were the dominant polymers of airborne microplastics on the Tibetan Plateau. Distribution of airborne microplastics was positively correlated with anthropogenic activity indices, such as population density and nighttime light intensity. Although the contribution of long-range atmospheric transport is valid, dispersed villages also appear to be a source of airborne microplastics for wildland areas across the Tibetan Plateau.

Micro- and nano-plastics in the atmosphere: A review of occurrence, properties and human health risks

The ubiquitous occurrence of micro/nano plastics (MNPs) poses potential threats to ecosystem and human health that have attracted broad concerns in recent decades. Detection of MNPs in several remote regions has implicated atmospheric transport as an important pathway for global dissemination of MNPs and hence as a global health risk. In this review, the latest research progress on (1) sampling and detection; (2) origin and characteristics; and (3) transport and fate of atmospheric MNPs was summarized. Further, the current status of exposure risks and toxicological effects from inhaled atmospheric MNPs on human health is examined. Due to limitations in sampling and identification methodologies, the study of atmospheric nanoplastics is very limited today. The large spatial variation of atmospheric MNP concentrations reported worldwide makes it difficult to compare the overall indoor and outdoor exposure risks. Several in vitro, in vivo, and epidemiological studies demonstrate adverse effects of immune response, apoptosis and oxidative stress caused by MNP inhalation that may induce cardiovascular diseases and reproductive and developmental abnormalities. Given the emerging importance of atmospheric MNPs, the establishment of standardized sampling-pretreatment-detection protocols and comprehensive toxicological studies are critical to advance environmental and health risk assessments of atmospheric MNPs.

A low-cost TICT-based staining agent for identification of microplastics: Theoretical studies and simple, cost-effective smartphone-based fluorescence microscope application

A novel staining agent, (5-(4-(diethylamino)benzylidene)- 1,3-dimethylpyrimidine-2,4,6(1 H,3 H,5 H)-trione) (DDB) was developed for the effective detection of environmentally harmful microplastics. DDB has competitive cost advantages, namely its facile synthesis and high yield, over Nile Red (NR), which is commonly used for microplastic staining. The unique photophysical properties of DDB, including emissive twisted intramolecular charge transfer (TICT) and aggregation-induced emission (AIE), were corroborated via spectroscopic investigations and density functional theory (DFT) calculations. Notably, DDB demonstrated superior selectivity for staining microplastics (polyethylene (PE), polyurethane (PU), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), and polyethylene terephthalate (PET)) over non-plastic materials in water. Furthermore, modulation of the solvent environment during the staining process yielded distinct fluorescence in both the green and red channels for specific types of plastic with the interplay between locally excited (LE) and TICT states. Treatment with 5% ethanol results in the selective staining of PE and PET with the emission of red fluorescence, whereas treatment with 30% ethanol facilitates the selective staining of PU, PVC, and PET with the emission of green fluorescence. Additionally, DDB could selectively stain microplastics in spiked soil and river water samples. Furthermore, a smartphone-based fluorescence microscope was developed at a cost below $100, validating the effective detection of microplastics stained with the newly synthesized DDB. The outcomes of this research demonstrate the potential of DDB as an economical and efficient agent for selective microplastic detection.

Benthic foraminifera in Gulf of Mexico show temporal and spatial dynamics of microplastics

Microplastics have accumulated in the environment since plastic production began, with present-day observations that range from marine trenches to mountains. However, research on microplastics has only recently begun so it is unclear how they have changed over time in many oceanic regions. Our study addressed this gap by quantifying the temporal and spatial dynamics of microplastics in two deep-water regions of the Gulf of Mexico (GOM). We isolated agglutinated foraminifera from sediment cores and assessed microplastics that were incorporated into their tests. Our results indicated that microplastics were incorporated by agglutinated foraminifera after plastic production began. Microplastics were higher at deep-water sites and closer to the Mississippi River. This study confirms the presence of microplastic incorporation into agglutinated foraminifera tests and investigates microplastics in deep-water sediments in the GOM. Additional work is needed to fully identify the distribution of microplastics across the GOM and other oceanic basins.

Identification and physico-chemical characterization of microplastics in marine aerosols over the northeast Arabian Sea

Microplastics (MPs) in the atmosphere can undergo long-range transport from emission regions to pristine terrestrial and oceanic ecosystems. Due to their inherent toxic and hazardous characteristics, MPs pose serious risks to both human well-being and the equilibrium of ecosystem. The present study outlines the comprehensive characterization, spanning physical and chemical attributes of MPs associated with atmospheric aerosols. Total suspended particulates (TSPs) were collected on a quartz fibre filter by operating a high-volume sampler for 24 h during distinct years (March, 2016 and November, 2020) at a coastal location in the northeast Arabian Sea. Subsequent to the sampling, a series of techniques were applied including density separation. The assessment and scrutiny of the MPs was carried out using stereo-zoom microscopy with supplementary validation using advanced fluorescence microscopy for enhanced precision in identification. Our comparative assessment suggests peroxide treatment followed by density separation could be a robust procedure for the definitive identification and characterization of MPs in the atmosphere. Average total abundance of MPs was found to be 1.30 ± 0.14 n/m3 in 2016 and 1.46 ± 0.12 n/m3 in 2020 with fibres, fragments and films having similar relative contributions (41 %, 31 %, 28 % in 2016 and 40 %, 35 %, 25 % in 2020). Fibres were found to be dominant morphotype followed by fragments and films over the coastal region of the Arabian Sea. In order to unravel the detailed chemical nature of these MPs, spectral analysis using μ-FTIR was carried out. The outcome of the analysis showed prevailing polymers as polyvinyl chloride and polymethyl methacrylate (50545 %) as dominant polymers followed by polyester (15 %), styrene butyl methacrylate (11 %), and polyacetal (9 %). MPs present in the vicinity of the Arabian Sea have potential to supply nutrients and toxicants, consequently can contribute to the modulation of the surface water biogeochemical processes.

Dual-channel fluorescence dye: Fluorescent color-dependent visual detection of microplastics and selective polyurethane

In this study, we developed a dual-channel fluorescent dye ((E)-N'-(4-(diphenylamino)benzylidene)pyrazine-2-carbohydrazide) DPC for visual detection of 8 types of microplastics (MPs; HDPE, MDPE, LDPE, PET, PU, PVC, PS, and PP) and selective PU. The intramolecular charge transfer (ICT) and aggregation-induced emission (AIE) properties of DPC were demonstrated by the spectroscopic analysis, DFT calculations, and Tyndall effect. MPs and nonplastics (cellulose, chitin, sand, shell, and wood) were stained with DPC in water and their respective fluorescence signals in the blue and green channels were analyzed. The staining procedure using DPC was optimized with the concentration of DPC and staining time as parameters. DPC was able to effectively stain 8 types of MPs and only PU in blue and green fluorescence signals, respectively. Furthermore, false positive detections of DPC were minimized through additional ethanol treatment after staining. Moreover, the effects of temperature, pH, and salinity on the staining ability of DPC were investigated. Surprisingly, DPC was able to selectively detect PU through the green fluorescence signal even in a single environment where various MPs existed. Most importantly, DPC is the first fluorescent dye capable of selectively monitoring PU in the green channel as well as staining 8 types of MPs in the blue channel. DPC showed promising potential to be used for MP monitoring on real environmental samples.

Uptake and toxicity of micro-/nanoplastics derived from naturally weathered disposable face masks in developing zebrafish: Impact of COVID-19 pandemic on aquatic life

The unprecedented proliferation of disposable face masks during the COVID-19 pandemic, coupled with their improper disposal, threatens to exacerbate the already concerning issue of plastic pollution. This study evaluates the role of environmentally weathered masks as potential sources of microplastics (MPs) and nanoplastics (NPs) and assesses their adverse impact on the early life stages of zebrafish. Experimental findings revealed that a single disposable mask could release approximately 1.79 × 109 particles, with nearly 70% measuring less than 1 μm, following 60 days of sunlight exposure and subsequent sand-induced physical abrasion. Remarkably, the MPs/NPs (MNPs) emanating from face masks have the potential to permeate the outer layer (chorion) of zebrafish embryos. Furthermore, due to their minute size, these particles can be consumed by the larvae's digestive system and subsequently circulated to other tissues, including the brain. Exposure to mask-derived MNPs at concentrations of 1 and 10 μg/L led to significant cases of developmental toxicity, incited oxidative stress, and prompted cell apoptosis. A subsequent metabolomics analysis indicated that the accumulation of these plastic particles perturbed metabolic functions in zebrafish larvae, primarily disrupting amino acid and lipid metabolism. The outcomes of this research underscore the accelerating possibility of environmental aging processes and physical abrasion in the release of MNPs from disposable face masks. Most importantly, these results shed light on the possible ecotoxicological risk posed by improperly disposed of face masks.

Inter-event and intra-event dynamics of microplastic emissions in an urban river during rainfall episodes

Urban rivers represent the major conduits for land-sourced microplastics in the global oceans, yet the real-time dynamics of their emissions in rivers during rainfall (and runoff) events are poorly understood. Herein, we report the results of high-frequency sampling of microplastic particles (MPs) and fibers (MPFs) in the surface water of an urban river in Japan over the course of three rainfall events (i.e., light, moderate, and heavy rainfalls). The event mean concentrations (EMCs) of MPs amounted to 35,000 items/m3, 929,000 items/m3, and 331,000 items/m3; and the corresponding total loads were 0.5 kg, 19.8 kg, and 35.0 kg for light, moderate and heavy rainfalls, respectively. The inter-event total loads of MPs correlate well with the total rainfall, while the concentrations were linked with the number of antecedent dry days. The dynamic trends show that <2000 μm MPs displayed first flush effects during light to moderate rainfall events (>50% mass discharged with the initial 20-40% of flow). Small-sized MPs (10-40 μm) mobilized rapidly at lower rainfall intensities, whereas MPs over 2000 μm discharged immediately after the peak rainfall intensity. Moreover, <70 μm MPs depicted a surge following heavy rainfall events due to turbulent flow conditions reverting the deposited MPs into suspension. Overall, the three events increased the loads by 4-110 folds, and EMCs by 10-350 folds compared to the concentrations during dry weather while portraying a significant impact on 300-1000 μm MPs. The dynamics of MPs were correlated with those of suspended solids in river water, and the characteristics were comparable to the same of road dust sampled in Japan. Although the dynamic trends between MPs and MPFs in river water were comparable, MPFs were relatively less impacted by rain, likely due to the intervention of separate sewer systems in the study area.

High-throughput microplastic assessment using polarization holographic imaging

Microplastic (MP) pollution has emerged as a global environmental concern due to its ubiquity and harmful impacts on ecosystems and human health. MP assessment has therefore become increasingly necessary and common in environmental and experimental samples. Microscopy and spectroscopy are widely employed for the physical and chemical characterization of MPs. However, these analytical methods often require time-consuming pretreatments of samples or expensive instrumentation. In this work, we develop a portable and cost-effective polarization holographic imaging system that prominently incorporates deep learning techniques, enabling efficient, high-throughput detection and dynamic analysis of MPs in aqueous environments. The integration enhances the identification and classification of MPs, eliminating the need for extensive sample preparation. The system simultaneously captures holographic interference patterns and polarization states, allowing for multimodal information acquisition to facilitate rapid MP detection. The characteristics of light waves are registered, and birefringence features are leveraged to classify the material composition and structures of MPs. Furthermore, the system automates real-time counting and morphological measurements of various materials, including MP sheets and additional natural substances. This innovative approach significantly improves the dynamic monitoring of MPs and provides valuable information for their effective filtration and management.

A rapid and portable fluorescence spectroscopy staining method for the detection of plastic microfibers in water

We propose a simple technique for microplastic detection based on their interaction with a hydrophilic and anionic fluorescent dye 1,3,6,8 pyrene tetrasulfonate (PTSA). Synthetic microfibers derived from surgical face masks (an abundantly generated plastic waste post COVID) were considered as model microplastics. The interactions between microfibers and the dye were studied as a function of physiological parameters (pH, contact time and temperature), external agents, dye dosage and polymer variants. A pocket-sized photometer (by Lovibond Tintometer group) was employed for the detection and further validated using advanced equipment set-ups (fluorescence microscope, Fourier transform infrared spectroscopy and benchtop spectrofluorometer). Risk assessment studies were conducted on Artemia salina as a model organism. As a risk mitigation strategy, dye recovery followed by sunlight mediated degradation were performed. The detection study was performed in real water samples collected from fresh, estuarine and seawater samples spiked with microfibers. As an outcome, an optimized standard operational conditions were determined for the effective detection of synthetic microfibers. The data obtained could have scientific and industrial impact, in particular for experts working in the broad arena of clean water, who are specifically interested in developing cost-effective solutions for effective detection and biomonitoring of emerging pollutants.

Labelling of micro- and nanoplastics for environmental studies: state-of-the-art and future challenges

Studying microplastics and nanoplastics (MNP) in environmental matrices is extremely challenging, and recent developments in labelling techniques may hold much promise to further our knowledge in this field. Here, we reviewed MNP labelling techniques and applications to provide the first systematic and in-depth insight into MNP labelling. We classified all labelling techniques for MNP into four main types (fluorescent, metal, stable isotope and radioisotope) and discussed per type the synthesis methods, detection methods, influencing factors, and the current and future applications and challenges. Direct labelling of environmental MNP with fluorescent dyes and metals enables simple visualisation and selective detection of MNP to improve detection efficiency. However, it is still an open question how to avoid co-labelling of non-plastic (i.e. non-target, matrix) materials. Labelling of MNP that are intentionally added in the environment may allow semi-automatic detection of MNP particles with high accuracy and sensitivity during studies on e.g. transport and degradation. The detection limit of labelled MNP largely depends on particle size and the type of matrix. Fluorescent labelling allows efficient detection of microplastics, whereas metal labelling is preferred for nanoplastics research due to a potentially higher sensitivity. A major challenge for fluorescent and metal labelling is to develop techniques that do not alter the inherent MNP properties or only do so minimally, in particular the surface properties. Stable and radioactive isotope labelling (13C and 14C, but also 15N, 2H) of the polymer itself allows to preserve inherent MNP properties, but have been largely ignored. Overall, labelling of MNP holds great promise for advancing our fundamental understanding of the behaviour of plastics, notably the smallest fractions, in the environment.

Toxic effects of polystyrene microbeads and benzo[α]pyrene on bioaccumulation, antioxidant response, and cell damage in goldfish Carassius auratus

Microplastics (MP) are harmful, causing stress in aquatic species and acting as carriers of hydrophobicity. In aquatic environments, benzo[α]pyrene (BaP) is an endocrine-disrupting chemical that accumulates in the body and causes toxic reactions in living organisms. We investigated the effects of single and combined microbead (MB) and BaP environments on goldfish antioxidant response and apoptosis. For 120 h, goldfish were exposed to single (MB10, MB100, and BaP5) and combined (MB10+BaP5 and MB100+BaP5) environments of 10 and 100 beads/L of 0.2 µm polystyrene MB and 5 µg/L BaP. We measured MB and BaP bioaccumulation as well as plasma parameters including ALT, AST, and glucose. The level of oxidative stress was determined by evaluating lipid peroxidation (LPO) and total antioxidant capacity (TAC) in plasma, as well as antioxidant-related genes for superoxide dismutase and catalase (SOD and CAT) and caspase-3 (Casp3) mRNA expression in liver tissue. The TUNEL assay was used to examine SOD in situ hybridization and apoptosis in goldfish livers. Except for the control group, plasma LPO levels increased at the end of the exposure period in all experimental groups. TAC increased up to 24 h of exposure and then maintained a similar level until the trial ended. SOD, CAT, and Casp3 mRNA expression increased substantially up to 120 h as the exposure concentration and time increased. The TUNEL assay revealed more signals and apoptotic signals in the combined exposure environments as a consequence of SOD in situ hybridization than in single exposure environments. These results suggest that combined exposure to toxic substances causes oxidative stress in organisms, which leads to apoptosis.

Diverse and high pollution of microplastics in seasonal snow across Northeastern China

Snow scavenging is recognized as one of the major sinks for atmospheric microplastics (MPs). However, little is known about the properties of MPs in large-scale surface snow. Using Nile Red staining and micro-Fourier transform infrared spectroscopy, we identified the shapes, sizes, and polymer components of MPs in seasonal snow across northeastern (NE) China, a major industrial area. The average concentration of MPs was (4.52 ± 3.05) × 104 MPs L-1, and the highest contamination (6.65 ± 3.89) × 104 MPs L-1 was observed in Changbai Mountains, which was the highest concentration observed in surface snow to the extent of literature. The majority of snow MPs were smaller than 50 μm and composed primarily of fragments. Ethylene vinyl acetate and polyethylene were the dominant contributors to their chemical components. Investigation with positive matrix factorization revealed that the MPs were primarily generated by debris from packaging materials, followed by industrial and construction activities. In addition, the winter atmospheric circulation over the northwestern Siberian and Mongolian plateaus likely dominated the wide-range dispersion and deposition of the MPs across NE China. These results provide a first comprehensive perspective of MPs from sources to removal associated with snow in a large geographic region.

A photoluminescence strategy for detection nanoplastics in water and biological imaging in cells and plants

Nanoplastics exposure poses a significant threat to the environment and human health, and accurate measurement of nanoparticles in aqueous solutions remains challenging. In this work, we synthesized the cationic fluorescent probe 4-[1-Cyano- 2-[4-(Diethylamino)-2-hydroxyphenyl]ethenyl]-1-ethylpyridinium (PCP) through a straightforward procedure for the rapid and accurate detection and labeling of nanoplastics in aqueous solutions. PCP binds to nanoplastics through electrostatic and hydrophobic interactions with restricted intramolecular rotation and exhibits enhanced fluorescence emission. Using carboxylation-modified polystyrene nanoplastics as a model, PCP could accurately detect concentrations as low as 0.525 mg∙L-1 in aqueous solution and perform wash-free semi-quantitative direct observation. The method demonstrated good reproducibility and recovery in actual sample spiking experiments. In addition, PCP-labeled nanoplastics were successfully used to visualize the uptake and distribution of cells and Arabidopsis thaliana when exposed to different concentrations of nanoplastics. This work provides a simple and sensitive method for efficiently identify, track, and quantify nanoplastics without requiring additional pretreatment and complex instrumentation, making it an ideal tool for accurately quantifying nanoplastics in aqueous solutions and studying the biological interactions of nanoplastics.

Quantitative image analysis of microplastics in bottled water using artificial intelligence

The ubiquitous occurrence of microplastics (MPs) in the environment and the use of plastics in packaging materials result in the presence of MPs in the food chain and exposure of consumers. Yet, no fully validated analytical method is available for microplastic (MP) quantification, thereby preventing the reliable estimation of the level of exposure and, ultimately, the assessment of the food safety risks associated with MP contamination. In this study, a novel approach is presented that exploits interactive artificial intelligence tools to enable automation of MP analysis. An integrated method for the analysis of MPs in bottled water based on Nile Red staining and fluorescent microscopy was developed and validated, featuring a partial interrogation of the filter and a fully automated image processing workflow based on a Random Forest classifier, thereby boosting the analysis speed. The image analysis provided particle count, size and size distribution of the MPs. From these data, a rough estimation of the mass of the individual MPs, and consequently of the MP mass concentration in the sample, could be obtained as well. Critical materials, method performance characteristics, and final applicability were studied in detail. The method showed to be highly sensitive in sizing MPs down to 10 μm, with a particle count limit of detection and quantification of 28 and 85 items/500 mL, respectively. Linearity of mass concentration determined between 10 ppb and 1.5 ppm showed a regression coefficient (R2) of 0.99. Method precision was demonstrated by a repeatability of 9-16% RSD (n = 7) and within-laboratory reproducibility of 15-27% RSD (n = 21). Accuracy based on recovery was 92 ± 15% and 98 ± 23% at a level of 0.1 and 1.0 ppm, respectively. The quantitative performance characteristics thus obtained complied with regulatory requirements. Finally, the method was successfully applied to the analysis of twenty commercial samples of bottled water, with and without gas and flavor additives, yielding results ranging from values below the limit of detection to 7237 (95% CI [6456, 8088]) items/500 mL.

Rapid identification of micro and nanoplastics by line scan Raman micro-spectroscopy

Microplastic pollution has become an environmental problem that cannot be ignored in our society. Raman spectroscopy technology has been widely used in the field of microplastics detection due to its non-contact, non-destructive chemical specificity. Traditional point confocal Raman micro-spectroscopy technology uses single-point detection, resulting in long measurement times to scan the large areas of interest of typical samples. In this paper, we present a line scan confocal Raman micro-spectroscopy tool for fast detection and identification of microplastic particles. We show size and composition identification of particles and imaging over large areas. Compared with point confocal Raman imaging, the line scan confocal Raman technology increases the imaging speed by 1-2 orders of magnitude.

Distribution, screening and biochemical characterization of indigenous microalgae for bio-mass and bio-energy production potential from three districts of Pakistan

Abstract Trend of biofuel production from microalgal triacylglycerols is enhancing, because this substrate is a good sustainable and advantageous alternative to oil and gas fuel. In the present study, indigenous micro algal isolates were screened from water (n=30) and soil (n=30) samples collected from three districts of Punjab, Pakistan to evaluate their biofuel production potential. The samples were inoculated on BG – 11 agar medium plates by incubating at room temperature of 25°C providing 1000 lux for 16h light cycle followed by 8h of dark cycle for 15 d. Water samples were found to be rich in microalgae and 65.33% microalgae (49 isolates) were isolated from Faisalabad district. On the basis of microscopic morphology microalgal isolates (n=180) were selected and subjected to lipid detection by Nile red staining assay. Nile red positive isolates (n=23) were processed for biochemical (lipid, protein and carbohydrates) characterization. AIN63 isolate showed higher lipids (17.4%) content as detected by micro vanillin assay. Algal isolate AIN128 showed best protein contents (42.91%) detected by Bradford assay and AIN172 isolate showed higher carbohydrate contents (73.83%) as detected by anthrone assay. The selected algal isolates were also analyzed by Fourier transform infrared (FTIR) spectroscopy for confirmation of carbohydrate, protein and lipid analysis. These indigenous algae have the potential for in-vitro biofuel production from agricultural waste.

Occurrence and distribution of plastic particles (10-25,000 μm) and microfibers in the surface water of an urban river network in Japan

Urban rivers remain the key conduits conveying land-sourced plastics into the ocean. However, detailed information is limited on the concurrent evaluation over a wide array of particle size-specific abundances, characteristics, and distribution patterns of plastics in riverine environments. Therefore, this study provides a comprehensive assessment of plastic pollution in an urban river network in Japan by analyzing mesoplastics (5000-25,000 μm), large microplastics (300-5000 μm), small microplastics (SMPs, 10-300 μm), and microplastic-fibers (MPFs, 10-5000 μm) concurrently, for the first time. Sampling was conducted at seven stations in the Kamo and Katsura Rivers flowing across metropolitan Kyoto City. The analytical procedures involved infrared spectroscopy and fluorescence-staining microscopy. The concentrations of plastics were moderate compared to the global reports and gradually increased along the river flow (3550-15,840 items/m3; 180-13,180 μg/m3), mostly due to urban discharges via non-point sources. The number concentrations increased with decreasing particle size, marking 99.94% of SMPs, including 50% smaller than 40 μm. Conversely, mass concentrations decreased, exhibiting 96% larger than 1000 μm (64% mesoplastics including 20% around 5000 μm), along with 2% SMPs. Polyethylene (PE) and polyvinyl alcohol were distinct among SMPs, with PE indicating higher susceptibility to fragmentation compared to polypropylene and other polymer types. MPF concentrations were homogeneous throughout the watershed (1470-3600 items/m3; 520-1060 μg/m3), with a higher proportion of fibers smaller than 1000 μm (86%), apparently originating from polyethylene terephthalate/nylon/acrylic-like textile fibers. The proportion of MPFs surpassed particles within 100-3000 μm and was considerably high around 300 μm (> 98%). The river network of Kyoto conveys billions of tiny microplastics to the Yodo River, the primary water resource downstream, within a dry day.

Visual detection of microplastics using Raman spectroscopic imaging

As a new type of pollutant in the marine environment and terrestrial ecosystems, microplastics have attracted widespread attention. Assessing the ecological risk of microplastics relies on accurately detecting small-sized particles in the environment. Microplastics exhibit unique "fingerprint" characteristics in Raman spectroscopy, making them suitable for rapid identification. In this study, we achieved visualization of microplastics through pseudo-color images generated by Raman spectroscopy imaging. Pseudo-color imaging maps were generated by selecting characteristic peaks and the classical least-squares fitting method was used to visually represent the distribution of different microplastics. The study explored the potential of Raman spectroscopy and its mapping mode in distinguishing various types of mixed microplastics and demonstrated that this approach can identify microplastics in complex environmental samples. Specifically, a cloud-point extraction followed by membrane filtration method was successfully applied to identifying mixed-component microplastics. In summary, the category, quantity, location, and differentiation of microplastics can be accurately analyzed by Raman spectroscopy, which provides a basis for assessing their ecological risk.

Recent advances on the methods developed for the identification and detection of emerging contaminant microplastics: a review

The widespread use of plastics, popular for their versatility and cost-efficiency in mass production, has led to their essential role in modern society. Their remarkable attributes, such as flexibility, mechanical strength, lightweight, and affordability, have further strengthened their importance. However, the emergence of microplastics (MPs), minute plastic particles, has raised environmental concerns. Over the last decade, numerous studies have uncovered MPs of varying sizes in diverse environments. They primarily originate from textile fibres and cosmetic products, with large plastic items undergoing degradation and contributing as secondary sources. The bioaccumulation of MPs, with potential ingestion by humans through the food chain, underscores their significance as environmental contaminants. Therefore, continuous monitoring of environmental and food samples is imperative. A range of spectroscopic techniques, including vibrational spectroscopy, Raman spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, hyperspectral imaging, and nuclear magnetic resonance (NMR) spectroscopy, facilitates the detection of MPs. This review offers a comprehensive overview of the analytical methods employed for sample collection, characterization, and analysis of MPs. It also emphasizes the crucial criteria for selecting practical and standardized techniques for the detection of MPs. Despite advancements, challenges persist in this field, and this review suggests potential strategies to address these limitations. The development of effective protocols for the accurate identification and quantification of MPs in real-world samples is of paramount importance. This review further highlights the accumulation of microplastics in various edible species, such as crabs, pelagic fish, finfish, shellfish, American oysters, and mussels, shedding light on the extreme implications of MPs on our food chain.

Characterization of microplastics in digestive tract of commercial fish species from the Oman Sea

Microplastics (MPs) content of the digestive tract of two commercial fish from the northern shores of the Oman Sea were investigated. The MPs were characterized by optical microscopy, fluorescent microscopy, and SEM-EDX for their number, shape, size, and color. Polymer composition was analyzes using micro-Raman spectroscopy (RMS). MPs were recovered in all fish samples (100 %), with an average of 43.16 ± 8.23 items/individual in Otolithes ruber, and 29.9 ± 2.73 items/individual in Acanthopagrus latus. The predominant shape of MPs in both fishes was fiber (46 %) with black, transparent, and white colors. The majority of MPs were <1000 μm (75 %), and half of the MPs were smaller than 300 μm in size. Their synthetic nature was confirmed by Nile Red staining and determination of the elemental composition of selected items. Polypropylene (PP) and polyethylene (PE) were the dominant plastic polymers in the fish digestive tracts. This study reveals abundance distribution of MPs in digestive tract of commercial marine fish. High number of ingested MPs can alarm the accumulation of MPs in the northern of Oman Sea ecosystem with anthropogenic activities and raises issues in public health.

Combined approaches for detecting polypropylene microplastics in crop plants

Microplastics (MPs) pollution in the terrestrial environment causes accumulation in crop plants. Consumption of these plants may have negative effects on human health. Therefore, it is crucial to analyze MPs accumulation in the plants. The aim of this study is to determine polypropylene (PP) particles in plants exposed to label-free PP for 75 days. In order to extract PP from organic matter, a two-step alkaline and wet peroxide oxidation chemical digestion method was applied to the roots, stems, and leaves of maize and wheat. The PP particles in the digested solutions were detected by the Nile red staining method, which has not been used previously in the detection of MPs in plants. Nile red stained PP particles mostly accumulated in the roots of wheat and the stems of maize plants. Statistical analysis revealed that the maize deposited more and larger PP particles regardless of the location. Moreover, the presence of PP particles in the digestion solutions was proved by the heating method. The PP particles on the glass slides were transformed into different shapes due to melting.

Spatial distribution of atmospheric microplastics in bulk-deposition of urban and rural environments - A one-year follow-up study in northern Germany

Atmospheric microplastic deposition rates play a crucial role for calculating the input of microplastics in the environment and to further understand pollution patterns. In this study, the spatial and temporal distribution of atmospheric microplastic particles in urban and rural areas of Northern Germany was investigated. Therefore, eleven structurally diverse locations in Hamburg and Mecklenburg-Western Pomerania were equipped with bulk-deposition samplers in triplicates and sampled monthly between August 2019 and July 2020. The resulting 306 samples were treated with hydrogen peroxide (30 %) and sodium hypochlorite (6-14 %) to digest biological organic matter. The filters were subsequently stained with the lipophilic dye Nile Red and underwent visual microplastic identification via fluorescence microscopy. Fragments and fibers were quantified down to a cut-off size of 10 μm. The polymer composition of microplastic particles was investigated along a subset of particles via μ-Raman spectroscopy. The microplastic deposition rate for Northern Germany (89 ± 61 MP/m2/day) is in the same order of magnitude as those reported by previous studies. Significant differences in microplastic deposition rates were found between urban and rural sampling sites. Population density was identified as an important factor for greater amounts of microplastics and higher shares of fibers in urban samples. Special attention was given to the canopy cover at two forested sampling sites and an influence of the comb-out effect on atmospheric microplastic deposition was detected.

When microplastics meet electroanalysis: future analytical trends for an emerging threat

Microplastics are a major modern challenge that must be addressed to protect the environment, particularly the marine environment. Microplastics, defined as particles ≤5 mm, are ubiquitous in the environment. Their small size for a relatively large surface area, high persistence and easy distribution in water, soil and air require the development of new analytical methods to monitor their presence. At present, the availability of analytical techniques that are easy to use, automated, inexpensive and based on new approaches to improve detection remains an open challenge. This review aims to outline the evolution and novelties of classical and advanced methods, in particular the recently reported electroanalytical detectors, methods and devices. Among all the studies reviewed here, we highlight the great advantages of electroanalytical tools over spectroscopic and thermal analysis, especially for the rapid and accurate detection of microplastics in the sub-micron range. Finally, the challenges faced in the development of automated analytical methods are discussed, highlighting recent trends in artificial intelligence (AI) in microplastics analysis.

Identification and detection of microplastic particles in marine environment by using improved faster R-CNN model

Microplastics refer to plastic particles measuring less than 5 mm, which has led to serious environmental problem and the detection of these tiny particles is crucial for understanding the corresponding distribution and impact on the marine environment. In this paper, an improved faster region-based convolutional neural network (R-CNN) model was developed for the identification and detection of microplastic particles. In the proposed model, the residual network-50 (ResNet-50) is employed as the backbone with the replacement of the traditional one to enhance the feature extraction capability and the feature pyramid networks (FPN) module is introduced together for solving the multi-scale target detection. By using the improved Faster R-CNN model, the network model performance is enhanced where the average confidence of detecting unique microplastic particles in the marine environment reaches as high as 99%. Moreover, the microparticles mixture was bounded precisely via the predicted bounding boxes without missing detection and wrong detection. In this way, the successful identification of polystyrene microplastic particles from the particles suspension with similar shapes but various conditions of backgrounds, brightness, distributions and object sizes, was achieved by employing the proposed improved Faster R-CNN model, enabling the accurate detection of microplastic particles in marine environment.

Real-time morphological detection of label-free submicron-sized plastics using flow-channeled differential interference contrast microscopy

Owing to the surge in plastic waste generated during the COVID-19 pandemic, concerns regarding microplastic pollution in aqueous environments are increasing. Since microplastics (MPs) are broken down into submicron (< 1 µm) and nanoscale plastics, their real-time morphological detection in water is necessary. However, the decrease in the scattering cross-section of MPs in aqueous media precludes morphological detection by bright-field microscopy. To address this problem, we propose and demonstrate a differential interference contrast (DIC) system that incorporates a magnification-enhancing system to detect MPs in aqueous samples. To detect MPs in both the stationary and mobile phases, a microfluidic chip was designed, taking into consideration the imaging depth of focus and flow resistance. MPs of various sizes flowing in deionized, tap, and pond water at varying speeds were observed under Static and Flow conditions. Successful real-time morphological detection and quantification of polystyrene beads down to 200 nm at a constant flow rate in water were achieved. Thus, the proposed novel method can significantly reduce analysis time and improve the size-detection limit. The proposed DIC microscopy system can be coupled with Raman or infrared spectroscopy in future studies for chemical composition analysis. ENVIRONMENTAL IMPLICATION: Microplastics (MPs), particularly submicron plastics < 1-µm, can pose a risk to human health and aquatic ecosystems. Existing methods for detecting MPs in the aqueous phase have several limitations, including the use of expensive instruments and prolonged and labor-intensive procedures. Our results clearly demonstrated that a new low-cost flow-channeled differential interference contrast microscopy enables the real-time morphological detection and quantification of MPs down to 200 nm under flowing conditions without sample labeling. Consequently, our proposed rapid method for accurate quantitative measurements can serve as a valuable reference for detecting submicron plastics in water samples.

Atmospheric Microplastics: Perspectives on Origin, Abundances, Ecological and Health Risks

Microplastic (MP) pollution has aroused a tremendous amount of public and scientific interest worldwide. MPs are found widely ranging from terrestrial to aquatic ecosystems primarily due to the over-exploitation of plastic products and unscientific disposal of plastic waste. There is a large availability of scientific literature on MP pollution in the terrestrial and aquatic ecosystems, especially the marine environments; however, only recently has greater scientific attention been focused on the presence of MPs in the air and its retrospective health implications. Besides, atmospheric transport has been reported to be an important pathway of transport of MPs to the pristine regions of the world. From a health perspective, existing studies suggest that airborne MPs are priority pollutant vectors, that may penetrate deep into the body through inhalation leading to adverse health impacts such as neurotoxicity, cancer, respiratory problems, cytotoxicity, and many more. However, their effects on indoor and outdoor air quality, and on human health are not yet clearly understood due to the lack of enough research studies on that and the non-availability of established scientific protocols for their characterization. This scientific review entails important information concerning the abundance of atmospheric MPs worldwide within the existing literature. A thorough comparison of existing sampling and analytical protocols has been presented. Besides, this review has unveiled the areas of scientific concern especially air quality monitoring which requires immediate attention, with the information gaps to be filled have been addressed.

Early screening of suspected microplastics in bottled water in the Santiago Metropolitan Region of Chile

Bottled water has emerged as a possible healthier alternative due to concerns about the quality of drinking water sources. However, recent studies have detected worrying concentrations of environmental contaminants in bottled water, including microplastics. Therefore, it is an emerging need to quantify their concentrations in local suppliers which could differ among countries and regions. In this work, we used fluorescence microscopy with Nile Red for the identification and quantification of potential microplastics in twelve brands of bottled water distributed in the Santiago Metropolitan Region of Chile. The average concentration of microplastics was 391 ± 125 p L-1, while the highest concentration observed was 633 ± 33 p L-1. Microplastics between 5 and 20 μm were the major contributors, a size fraction that has been reported to be susceptible to accumulate in the digestive tract or generate potential alterations in the lymphatic and circulatory systems. The estimated daily intake value for per capita was estimated to be 229 p kg-1 year-1 for people weighing 65 kg and 198 p kg-1 year-1 for those weighing 75 kg.

Effects of microfiber and bead microplastic exposure in the goldfish Carassius auratus: Bioaccumulation, antioxidant responses, and cell damage

We confirmed antioxidant-related gene expression, bioaccumulation, and cell damage following exposure to various microplastics in vivo and in vitro in the goldfish Carassius auratus. Exposure of C. auratus to a 500 µm fiber-type microplastic environment (MF; 10 and 100 fibers/L) and two sizes (0.2 and 1.0 µm) of beads (MB; 10 and 100 beads/L) for 120 h increased superoxide dismutase (SOD) mRNA expression in the liver until 24 h followed by a decrease. Whereas, catalase (CAT) mRNA expression increased from 12 h to the end of the in vivo experiment. In vitro experiments were conducted with diluted microfibers (1 and 5 fibers/L) and microbeads (1 and 5 beads/L) using cultured liver cells. The results of SOD and CAT mRNA expression analysis conducted in vitro showed a tendency similar to those of experiments conducted in vivo. The H2O2 level increased in the high-concentration experimental groups compared with that in the low-concentration groups of 0.2-µm beads. In addition, the H2O2 level increased in both MF and MB groups from 12 h of exposure. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in plasma were used as indicators of liver damage in fish. The ALT and AST levels increased up to 120 h after exposure. Caspase-3 (casp-3) mRNA expression was higher in the MB group than in the MF group. We visually confirmed liver casp-3 mRNA signals using in situ hybridization. The degree of DNA damage in the MF and MB high-concentration groups increased with the exposure time. The tail length and percent of DNA in the tail of the MB group were significantly higher than those of the MF group, confirming that DNA damage was greater in the MB group. Both fiber- and bead-type microplastics induced oxidative stress in C. auratus, but the bead-type induced greater stress than the fiber-type.

Bioaccumulation of polystyrene microplastics and changes in antioxidant and AChE pattern in a freshwater snail (Filopaludina bengalensis) from river Ganga

Microplastic pollution is a leading global problem affecting terrestrial and marine aquatic ecosystems. Due to the stagnant nature of microplastics, the toxic effect of microplastics is more pronounced to benthic organisms than the surface feeder. Hence, the present study effort was to study the microplastic bioaccumulation pattern and changes in the enzymatic and nonenzymatic antioxidant and AChE pattern of freshwater snail Filopaludina bengalensis, which were subjected to 0.5 ppm to 5 ppm levels of polystyrene microsphere (∼ 30 µm) for 27 days. The study showed that microplastics were easily accumulated in the test organism in a dose and time-dependent manner, amounting to 82 ± 6.02 particles /individuals at a 5 ppm dose on the 27th day. However, no mortality was observed at the test microplastic dosages. The enzymatic antioxidant profile (SOD and catalase) showed limited variability and remained stable with increased duration and microplastic dose. However, the nonenzymatic antioxidant profile showed distinct variability with the complete seizing of the DPPH activity on the 27th day at 5 ppm microplastic dose and a gradual decrease of ABTS and FRAP activity at all the dose ranges. Even the AChE activity decreased with higher exposure concentrations. The present study for the first time shows the direct impact of microplastics on a freshwater snail widely available in the Indian subcontinent, indicating the role of microplastic pollution will create havoc in the Ganga river eco-biosystem in the long run.

Global research hotspots and trends on microplastics: a bibliometric analysis

In recent years, microplastics have become an integral part of the terrestrial and aquatic environments, which is one of the major concerns of communities around the world. Therefore, it is necessary to know the current status of studies and feasible potentials in the future. This study, conducted an in-depth bibliometric analysis of publications from 1990 to 2022 to present the influential countries, authors, institutes, papers, and journals on microplastics. Findings reveal that there has been a steady increase in microplastic publications and citations in recent years. And, the number of publications and citations has increased 19 and 35 times since 2015. Besides, we performed a comprehensive keyword analysis to show the significant keywords and clusters in this field. In particular, this study used the TF-IDF method as a text-mining analysis to extract the new keywords used in recent years (i.e., 2020-2022). New keywords can draw the attention of scholars to important issues and provide a basis for future research directions.

Separation and flow cytometry analysis of microplastics and nanoplastics

In recent years, the utilization of flow cytometry for quantitative microplastic analysis has gained prominence. However, the current methods have some drawbacks that need to be improved. The present study aims to enhance the flow cytometry detection protocols for Nile red (NR) stained microplastics, facilitating distinct microplastic and nanoplastic enumeration. By elevating dimethyl sulfoxide (DMSO) concentration to 20%-30% within the solution, NR solubility improved and agglomeration reduced. The analysis of 26 replicates of polystyrene (PS) liquid samples through four distinct dot plots highlighted the superior accuracy of dot plots integrating yellow fluorescence. Through systematic staining of varying NR concentrations across three microplastic liquid samples (polyethylene terephthalate, polyethylene, and polypropylene), the optimal staining concentration was determined to be 15-20 μg/mL. The distributions of agglomerated NR and NR stained PS under two scenarios-dissolved NR and partially agglomerated NR-were compared. Results showed their distinct distributions within the side scatter versus yellow fluorescence dot plot. Counting results from gradient-diluted PS liquid samples revealed a microplastic detection lower limit of 104 particles/mL, with an optimal concentration range of 105-106 particles/mL. Flow cytometric assessment of PS microspheres spanning 150 nm to 40 μm indicated a 150 nm particle size detection minimum. Our investigation validated the efficacy of NR staining and subsequent flow cytometry analysis across eleven types of microplastics. Separation and concentration of microplastics (1.0-50.0 μm) and nanoplastics (0.2-1.0 μm) were achieved via sequential sieving through 50, 1.0, and 0.2 μm filter membranes. We used a combination of multiple filtration steps and flow cytometry to analyze microplastics and nanoplastics in nine simulated water samples. Our results showed that the combined amount of microplastics (1.0-50.0 μm) and nanoplastics (0.2-1.0 μm) after filtration had a ratio of 0.80-1.19 compared to the total microplastic concentration before filtration. This result confirms the practicality of our approach. By enhancing flow cytometry-based microplastic and nanoplastic detection protocols, our study provides pivotal technical support for research concerning quantitative toxicity assessment of microplastic and nanoplastic pollution.

Fluorescent Nanodiamonds for Tracking Single Polymer Particles in Cells and Tissues

Polymer nanoparticles are widely used in drug delivery and are also a potential concern due to the increased burden of nano- or microplastics in the environment. In order to use polymer nanoparticles safely and understand their mechanism of action, it is useful to know where within cells and tissues they end up. To this end, we labeled polymer nanoparticles with nanodiamond particles. More specifically, we have embedded nanodiamond particles in the polymer particles and characterized the composites. Compared to conventional fluorescent dyes, these labels have the advantage that nanodiamonds do not bleach or blink, thus allowing long-term imaging and tracking of polymer particles. We have demonstrated this principle both in cells and entire liver tissues.

Evaluation of vertical distribution characteristics of microplastics under 20 μm in lake and river waters in South Korea

Following the alarming reports of microplastic pollution in the marine environment, increased attention has been given to microplastics in other environmental media. Despite the attention, there is limited research available on the depth-distribution of microplastics in freshwater. Specifically, in the case of water sources used for drinking or tap, the height of intake facilities varies, and it is highly likely that there is a correlation between the vertical distribution of microplastics and these water intake structures. Further, because the size of microplastics varies widely in the environment, the commonly used sampling devices are not suitable for selectively extracting microplastics without causing cross-contamination. Thus, we developed a suitable device for microplastics of size 5-20 µm and studied microplastic distribution in freshwater at various depths by considering various types of microplastics and aqueous systems. Lake and river, two major water sources, were selected for the study of microplastics distribution in water system. The microplastic distribution characteristics in both water systems showed that polypropylene and polyethylene were the most abundant across all depths because of their production volume. Plastic types with higher density were found only at the lower layers, and polystyrene was found in the upper layers because of the environmental effects on its buoyancy caused pore diameter and surface area. The lake and river had higher microplastic distribution in the lower layer and upper layer, respectively. This was because the flow rate in river was higher than that of lake. The higher flow rate reduced the settling velocity in river. Thus, hydrodynamic stability influences the vertical distribution and concentrations of microplastics in the water systems. These results are expected to be used for understanding the behavioral characteristics of microplastics in water systems and to manage water sources.

Toxic effects of sub-acute microplastic (polyamide) exposure on the accumulation, hematological, and antioxidant responses in crucian carp, Carassius carassius

The purpose of this study is to investigate the impact of microplastics (MPs) on fish and to confirm the toxic effects of MPs on fish, as well as to clarify the standard indicators. MPs are present in a large amount in the aquatic environment and can have various adverse effects on aquatic animals. Crucian carp, Carassius carassius (mean weight, 23.7 ± 1.6 g; mean length, 13.9 ± 1.4 cm), were exposed to PA (Polyamide) concentrations of 0, 4, 8, 16, 32 and 64 mg/L for 2 weeks. The PA accumulation profile in C. carassius decreased from the intestine to the gill to the liver. Hematological parameters such as red blood cell (RBC) counts, hemoglobin (Hb), and hematocrit (Ht) notably decreased at high levels of PA exposure. Plasma components such as calcium, magnesium, glucose, cholesterol, total protein, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP) were significantly altered by PA exposure. The activities of superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST) and glutathione (GSH) of liver, gill and intestine significantly increased following PA exposure. The results of this study suggest that MP exposure affects the hematological physiology and antioxidant responses in C. carassius as well as accumulation in specific tissues.

Microplastic emission trends in Turkish primary and secondary municipal wastewater treatment plant effluents discharged into the Sea of Marmara and Black Sea

Wastewater Treatment Plants (WWTPs) are recognized as one of the primary sources of microplastics, a class of contaminants that has lately gained attention. The quantity of MP that WWTPs release into the environment depends on several factors, including the treatment type, season, and population serviced. MP abundance and characterization were explored in 15 WWTP effluent waters, 9 discharged to the Black Sea from Türkiye and 6 to the Marmara Sea, with varying population densities and treatment methods. The mean MP abundance in primary treatment WWTPs (76.25 ± 49.20 MP L-1) was found to be substantially greater than that in secondary treatment WWTPs (20.57 ± 21.56 MP L-1) (p<0.05). MPs in WWTP effluent waters showed significant seasonal and spatial differences (Two Way ANOVA, Tukey, p<0.05). However, no positive correlation was detected between the population serviced and MP abundance in effluent waters. While the fiber was the dominant shape (49.5%) among MPs in effluent waters, ≈80% of the length was <1000 μm. MPs are classified into polymer types as follows: polyethylene terephthalate (34.9%) > polypropylene (32.4%) > polyethylene (19.9%) > polyamide (11%) > polystyrene (1.2%) > polyvinyl chloride (0.6%). With effluent waters from the WWTPs tested, we calculated that 1.24x1010 daily MPs are discharged into the Black Sea while 4.95x1010 MPs are into the Marmara Sea, for a combined annual discharge of 2.26x1013 MPs highlighting that WWTPs are key contributors of MP in Turkish coastal waters.

Fluorescence Correlation Spectroscopy Studies of Dye Diffusion on Fresh and Aged Polyethylene Terephthalate

Microplastics accumulate a wide variety of organic pollutants and thus may serve as efficient vectors for the transport of toxic substances. Much remains to be learned about how organic molecules interact with the surfaces of plastics and how these properties evolve as the microplastics are weathered. In this Letter, we report, for the first time, the application of confocal fluorescence correlation spectroscopy (FCS) to studies of organic molecules adsorbed from aqueous solution onto the surfaces of synthetic secondary microplastics. Both fresh and artificially aged poly(ethylene terephthalate) (PET) plastics are employed. The plastics are artificially aged in a UV-ozone chamber. Raman and infrared spectra confirm the composition of the PET microplastics. Water contact angle and surface roughness measurements reveal, respectively, an increase in wettability and a change in the nature of roughness with aging, consistent with surface oxidation. Rhodamine B (RhB) dye is used as a fluorescent probe in FCS studies and serves as an analogue for organic pollutants commonly found on microplastics. The FCS results reveal the accumulation of dye on the PET surfaces as they age. Dye motion is significantly slower on the plastics than in bulk aqueous solution and occurs by anomalous subdiffusion. The rate of diffusion becomes dramatically slower and more anomalous as the plastics are aged. Surface diffusion is likely slowed by either ionic interactions or hydrogen bonding between the dye and plastic. These results provide new insights critical to the understanding of how microplastics accumulate and transport organic pollutants as they weather in the environment.

Coumarin 6 staining method to detect microplastics

Microplastics have contaminated the ocean in large quantities and are widely distributed throughout the world. Thus, our understanding of the concentration of microplastics in various environments should be increased. However, current methods to detect microplastics require considerable effort and expensive equipment. In this study, we developed a fluorescence staining technique using coumarin 6 and examined its effectiveness. A mixture of acetone and ethanol was used as the solvent, and 10 different types of plastics were able to be stained with coumarin 6. The fluorescence peak for coumarin 6 staining was approximately 500 nm for each plastic type. The optimal immersion time and coumarin 6 concentration for staining were determined to be 60 min and 1 mg L-1, respectively. Using this technique, we were able to stain all of the microplastics obtained from samples collected in Tokyo Bay seawater.

Evidence of microplastics release from polythene and paper cups exposed to hot and cold: A case study on the compromised kinetics of catalase

Microplastics (MPs) have become widespread in the modern world posing a hidden threat to the global environment. However, growing accumulation and devastating impact of MPs on human health and the environment have received least attention. In the current investigation, for the first time MPs have been identified which are released from the daily usable materials like polythene bags (PB) and paper cups (PC) in response to hot and cold water exposure at different time intervals. The impact of these MPs has been assessed on the major antioxidant enzyme, bovine liver catalase (BLC). The binding of MPs caused conformational changes in BLC by decreasing the α-helical content, which results in reduction of the enzymatic activity. Kinetics study revealed nearly ∼1.4-fold compromised catalytic efficiency of catalase in response to MPs. Nevertheless, hepatic catalase activity was also significantly decreased in presence of MPs. Further, materials like glass, porcelain, stainless steel, and high-grade plastics are discovered as greener alternatives to PB and PC.

Evaluation of levels and sources of microplastics and phthalic acid esters and their relationships in the atmosphere of highly industrialized and urbanized Gebze, Türkiye

The presence of microplastics (MPs) in the atmosphere and their relationship with other pollutants have been gaining attention due to both their ubiquity and threatening human health. As well phthalic acid esters (PAEs) regarding as plasticizers for being added in plastic materials are key role for plastic pollution. In this study, the concentrations and sources of airborne MPs together with major PAEs and their relationships were investigated for four seasons. MP particles <20 μm, constituting the majority of the samples, were successfully revealed by NR fluorescent analysis. As a result of the μATR-FTIR analyzes, it was seen that besides different polymer derivatives, dye-pigment types, some minerals and compounds, and abundant semi-synthetic fibers and natural fibers were also present. MPs concentration were found in the range of 7207-21,042 MP/m³ in summer, 7245-32,950 MP/m³ in autumn, 4035-58,270 MP/m³ in winter and 7275-37,094 MP/m³ in spring. For the same period, the concentrations of PAEs ranged from 9.24 to 115.21 ng/m³ with an average value of 38.08 ± 7.92 ng/m³. PMF was also applied and four factors were extracted. Factor 1, accounts 52.26 % and 23.27 % of the total PAEs and MPs variances, was attributed to PVC sources. Factor 2, explaining 64.98 % of the total MPs variance had the highest loading of MPs and moderate loadings of relatively low molecular weight of PAEs, was attributed to plastics and personal care products. Factor 3, explaining the 28.31 % of the total PAEs variance was laden with BBP, DnBP, DiBP and DEP and was attributed to various plastic input during the sampling campaign coming from the industrial activities. The last factor accounts for 11.65 % of the total PAEs variance and was dominated by DMEP and it was linked to a source of the activities performed in the laboratories of the university.

Formation, behavior, properties and impact of micro- and nanoplastics on agricultural soil ecosystems (A Review)

Micro and nanoplastics (MPs and NPs, respectively) in agricultural soil ecosystems represent a pervasive global environmental concern, posing risks to soil biota, hence soil health and food security. This review provides a comprehensive and current summary of the literature on sources and properties of MNPs in agricultural ecosystems, methodology for the isolation and characterization of MNPs recovered from soil, MNP surrogate materials that mimic the size and properties of soil-borne MNPs, and transport of MNPs through the soil matrix. Furthermore, this review elucidates the impacts and risks of agricultural MNPs on crops and soil microorganisms and fauna. A significant source of MPs in soil is plasticulture, involving the use of mulch films and other plastic-based implements to provide several agronomic benefits for specialty crop production, while other sources of MPs include irrigation water and fertilizer. Long-term studies are needed to address current knowledge gaps of formation, soil surface and subsurface transport, and environmental impacts of MNPs, including for MNPs derived from biodegradable mulch films, which, although ultimately undergoing complete mineralization, will reside in soil for several months. Because of the complexity and variability of agricultural soil ecosystems and the difficulty in recovering MNPs from soil, a deeper understanding is needed for the fundamental relationships between MPs, NPs, soil biota and microbiota, including ecotoxicological effects of MNPs on earthworms, soil-dwelling invertebrates, and beneficial soil microorganisms, and soil geochemical attributes. In addition, the geometry, size distribution, fundamental and chemical properties, and concentration of MNPs contained in soils are required to develop surrogate MNP reference materials that can be used across laboratories for conducting fundamental laboratory studies.

Quantification of Polymer Surface Degradation Using Fluorescence Spectroscopy

One solution to minimizing plastic pollution is to improve reuse and recycling strategies. Recycling, however, is limited by the overall degradation of plastics being used, and current techniques for monitoring this plastic degradation fail to observe this in its early stages, which is key for optimizing reusability. This research seeks to develop an inexpensive, reproducible, and nondestructive technique for monitoring degradation of polyethylene (PE) and polypropylene (PP) materials using Nile red as a fluorescent probe. Changes in Nile red's fluorescence spectra were observed upon exposure to stained, aged PE and PP samples. As the surface hydrophobicity of the plastic decreases, Nile red's fluorescence signal undergoes a corresponding signal shift to longer wavelengths (lower energy). The trends seen in the fluorescent profile were related to more commonly used measurements of plastic degradation, namely, the carbonyl index from infrared spectroscopy and bulk crystallinity from calorimetry. Results demonstrate clear trends in fluorescence spectra shifts as related to the chemical and physical changes to the plastics, with trends dependent on the polymer type but independent of polymer film thickness. The strength of this technique is divided into two defined fits of the fluorescence signal; one fit characterizes the degradation throughout the whole range of degradative oxidation and the other is tailored to provide insight into the early stages of degradation. Overall, this work establishes a characterization tool that assesses the extent of plastics' degradation, which may ultimately impact our ability to recover plastics and minimize plastic waste.

Toxic effects of microplastic (Polyethylene) on fish: Accumulation, hematological parameters and antioxidant responses in Korean Bullhead, Pseudobagrus fulvidraco

Plastic waste discharged into the aquatic environment decomposes into microplastics (MP), which have toxic effects on fish species. Korean bullhead, Pseudobagrus fulvidraco is widely distributed in freshwater ecosystems in Korea, and it is important as an ecological indicator species to evaluate MP toxicity in Korea. In this study, the accumulation and physiological effects of juvenile P. fulvidraco exposed to microplastics (Polyethylene: PE-MPs with white surface and spherical shape) at control (0 mg/L), 100, 200, 5000 and 10,000 mg/L for 96 h were confirmed. Exposure to PE-MPs showed significant bioaccumulation of P. fulvidraco, and the accumulation profile was in the order of gut > gills > liver. Hematological parameters such as the red blood cell (RBC), hemoglobin (Hb) and hematocrit (Ht) were significantly decreased over 5000 mg/L In plasma components, calcium, magnesium and total protein were significantly decreased over 5000 mg/L, whereas glucose, cholesterol, aspartate aminotransferase (AST), alanine transaminase (ALT) and alkaline phosphatase (ALP) were significantly increased over 5000 mg/L or at 10,000 mg/L In antioxidant responses, superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) were significantly increased over 5000 mg/L, whereas glutathione (GSH) was significantly decreased over 5000 mg/L. The results of this study suggest that acute exposure to PE-MPs induced all physiological changes in a concentration-dependent manner, and it affects the hematological parameters, plasma components and antioxidant response of juvenile P. fulvidraco after accumulation in specific tissues.