Improved Raman spectroscopy-based approach to assess microplastics in seafood

Quantitative analysis of microplastics in water environments based on Raman spectroscopy and convolutional neural network

With the increasing interest in microplastics (MPs) pollutants, quantitative analysis of MPs in water environment is an important issue. Vibrational spectroscopy, represented by Raman spectroscopy, is widely used in MP detection because they can provide unique fingerprint characteristics of chemical components of MPs, but it is difficult to provide quantitative information. In this paper, an ingenious method for quantitative analysis of MPs in water environment by combining Raman spectroscopy and convolutional neural network (CNN) is proposed. It is innovatively proposed to collect the average mapping spectra (AMS) of the samples to improve the uniformity of Raman spectroscopy detection, and to increase the effective detection range of concentration by filtering different volumes of the same MP solutions. In order to verify the universality and effectiveness of the proposed method, 6 different sizes of Polyethylene (PE) MPs were used as detection objects and mixed into 5 different actual water environments. The R2 and RMSE of CNN for identifying the concentration of PE solutions could reach 0.9972 and 0.033, respectively. Meanwhile, by comparing machine learning models such as Random Forest (RF) and Support Vector Machine (SVM) were compared, and CNN combined with Raman spectroscopy has significant advantages in identifying the concentration of MPs.

A critical review on male-female reproductive and developmental toxicity induced by micro-plastics and nano-plastics through different signaling pathways

It is widely accepted that humans are constantly exposed to micro-plastics and nano-plastics through various routes, including inhalation of airborne particles, exposure to dust, and consumption of food and water. It is estimated that humans may consume thousand to millions of micro-plastic particles, equating to several milligrams per day. Prolonged exposure to micro-plastics and nano-plastics has been linked to negative effects on different living organisms, including neurotoxicity, gastrointestinal toxicity, nephrotoxicity, and hepatotoxicity, and developmental toxicities. The main purpose of this review is to explore the effect of micro-plastics and nano-plastics on the male and female reproductive system, as well as their offspring, and the associated mechanism implicated in the reproductive and developmental toxicities. Micro-plastics and nano-plastics have been shown to exert negative effects on the reproductive system of both male and female mammals and aquatic animals, including developmental impacts on gonads, gametes, embryo, and their subsequent generation. In addition, micro-plastics and nano-plastics impact the hypothalamic-pituitary axes, leading to oxidative stress, reproductive toxicity, neurotoxicity, cytotoxicity, developmental abnormalities, poor sperm quality, diminishes ovarian ovulation and immune toxicity. This study discusses the so many different signaling pathways associated in the male and female reproductive and developmental toxicity induced by micro-plastics and nano-plastics.

Visualization and characterisation of microplastics in aquatic environment using a home-built micro-Raman spectroscopic set up

Microplastics (MP) which are tiny plastic particles of sizes range from 1 μm (μm) to 5 mm (mm), have become a growing cause of concern due to their widespread presence in the environment and their potential impacts on ecosystems and human health. Marine organisms have the potential to consume microplastics, which could lead to physical injuries, blockages, or the transfer of harmful substances up the food chain. Humans may indirectly consume microplastics through contaminated seafood and water, although the complete scope of health risks is currently under investigation. An essential step in gaining a comprehensive understanding of microplastic pollution in waterbodies is the identification of microplastics, which is also crucial for further development of effective environmental regulations to address its adverse impacts. Majority of the researchers are accomplishing it globally using commercial platforms based on Raman spectroscopy. However, the development of indigenous Raman systems, which can enable microplastic identification, particularly in developing nations, is the need of the hour due to the outrageous cost of commercial platforms. In the current study, a custom-designed micro-Raman spectroscopy system was developed to detect and characterize microplastics from waterbodies. The developed system enabled visualization, size measurement and characterization of microplastics. Experimental parameters were fine-tuned, and a standardized Raman database was established for each type of plastic. This system exhibited high resolution which was capable of analysing microparticles of size up to 5 μm. Principal component analysis was carried out on the experimental Raman data, demonstrating good classification amongst different kinds of plastics. The performance of the developed system in analysing real samples was evaluated through experiments conducted on water samples obtained from the shore of Malpe Beach in Udupi district. The results revealed the presence of polyethylene and polyethylene terephthalate in the samples, along with the detection of pigments like copper phthalocyanine and indigo blue.

Assessing the inconsistency of microplastic measurements in foods and beverages

The widespread occurrence of microplastics (MPs) in the food chain has gained substantial recognition as a pressing concern, highlighting the inevitability of human exposure through ingestion of foodborne MPs, coupled with the release of MPs from plastic packaging. However, there are notable disparities in the reported numbers of MPs in foods and beverages, warranting a thorough investigation into the factors contributing to these discrepancies. Table salt is one of the major sources of MPs, and there was an approximately hundred-fold difference between the reviewed studies that reported the highest and lowest number of MPs. In addition, more noticeable discrepancies were discovered between studies on MPs released from teabags. One study reported that approximately 15 billion MPs were released into a cup of tea from a single teabag, whereas another research paper found only approximately 106.3 ± 14.6 MP/teabag after brewing. This comprehensive review focuses on the inconsistencies observed across studies examining MPs, shedding light on the plausible factors underlying these variations. Furthermore, the review outlines areas in analytical procedures that require enhancement and offers recommendations to promote accuracy and standardization in future research efforts, such as employing analytical methods capable of confirming the presence of MPs, using appropriate filter sizes, considering representative sample sizes when extrapolation is involved, and so on. By pinpointing the detection processes leading to the inconsistent results observed in MP studies, this comparative analysis will contribute to the development of reliable analytic methods for understanding the extent of microplastic contamination in the human food chain.

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.

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.

Endoplasmic reticulum stress exacerbates microplastics-induced toxicity in animal cells

Human and animal exposure to microplastics (MPs) contained in food is inevitable because of their widespread existence in the environment. Nevertheless, MPs toxicity studies in ruminants often lack attention. Here, we assessed the cytotoxicity of polystyrene microplastics (PS MPs) on goat mammary epithelial cells (GMECs). Compared to controls, PS MPs treatment significantly reduced cell viability, altered cell morphology and disrupted organelle integrity. Detection of membrane potential and reactive oxygen species (ROS) suggested that PS MPs induced mitochondrial dysfunction and oxidative stress. Further transcriptome analysis also confirmed alterations in these pathways. In addition, several genes related to endoplasmic reticulum (ER) homeostasis were significantly regulated in the transcriptional profile. Subsequent experiments confirmed that PS MPs induce ER stress via the PERK/eIF2α/CHOP pathway, accompanied by intracellular Ca2+ overload. Meanwhile, downstream activation of the Bax/Bcl-2 pathway and caspase cascade released apoptotic signals, which led to apoptosis in GMECs. Interestingly, the addition of PERK inhibitor (ISRIB) attenuated PS MPs-induced ER stress and apoptosis, which suggests that ER stress may exacerbate PS MPs-induced cytotoxicity. This work reveals the impact of MPs on mammalian cytotoxicity, enriches the mechanisms for the toxicity of MPs, and provides insight for further assessment of the risk of MPs in food.

Are Microplastics a Macro Issue? A Review on the Sources of Contamination, Analytical Challenges and Impact on Human Health of Microplastics in Food

In recent years, human populations' exposure to microplastics via foods is becoming a topic of concern. Although microplastics have been defined as "emerging contaminants", their occurrence in the environment and food is quite dated. This systematic review aims to investigate the discrepancies which are characterizing the research in the microplastics field in foods, with particular regard to sample preparations, microplastics' concentrations and their effect on humans. For the selection of papers, the PRISMA methodology was followed. Discrepancies in the methodological approaches emerged and in the expression of the results as well, underlying the urgency in the harmonization of the methodological approaches. Uncertainties are still present regarding the adverse effects of microplastics on the human body. The scientific evidence obtained thus far is, in fact, not sufficient to demonstrate a concrete negative effect. This review has clearly underlined the need to standardise laboratory approaches to obtain useful results for better food safety management.

Recent Study of Separation and Identification of Micro- and Nanoplastics for Aquatic Products

Micro- and nanoplastics (MNPs) are polymeric compounds widely used in industry and daily life. Although contamination of aquatic products with MNPs exists, most current research on MNPs focuses on environmental, ecological, and toxicological studies, with less on food safety. Currently, the extent to which aquatic products are affected depends primarily on the physical and chemical properties of the consumed MNPs and the content of MNPs. This review presents new findings on the occurrence of MNPs in aquatic products in light of their properties, carrier effects, chemical effects, seasonality, spatiality, and differences in their location within organisms. The latest studies have been summarized for separation and identification of MNPs for aquatic products as well as their physical and chemical properties in aquatic products using fish, bivalves, and crustaceans as models from a food safety perspective. Also, the shortcomings of safety studies are reviewed, and guidance is provided for future research directions. Finally, gaps in current knowledge on MNPs are also emphasized.

Component identification for the SERS spectra of microplastics mixture with convolutional neural network

With the increasing interest in microplastics (MPs) pollutants, relevant detection technologies are also developing. In MPs analysis, vibrational spectroscopy represented by surface-enhanced Raman spectroscopy (SERS) is widely used because they can provide unique fingerprint characteristics of chemical components. However, it is still a challenge to separate various chemical components from the SERS spectra of MPs mixture. In this study, it is innovatively proposed to combine the convolutional neural networks (CNN) model to simultaneously identify and analyze each component in the SERS spectra of six common MPs mixture. Different from the traditional method, which requires a series of spectral preprocessing such as baseline correction, smoothing and filtering, the average identification accuracy of MP components is as high as 99.54 % after the unpreprocessed spectral data is trained by CNN, which is better than other classical algorithms such as support vector machine (SVM), principal component analysis linear discriminant analysis (PCA-LDA), partial least squares discriminant analysis (PLS-DA), Random Forest (RF), and K Near Neighbor (KNN), with or without spectral preprocessing. The high accuracy shows that CNN can be used to quickly identify MPs mixture with unpreprocessed SERS spectra data.

Unveiling the noxious effect of polystyrene microplastics in aquatic ecosystems and their toxicological behavior on fishes and microalgae

Microplastic (MP) particles are considered noxious pollutants due to their presence in aquatic habitats at almost every level of the food chain. Thus, the entry of MP particles into marine waterbodies has triggered a common research interest. Until recently, the toxicity of polystyrene towards aquatic creatures in comparison to other polymers has not been widely investigated. This article provides an extensive overview of the occurrence of microplastic particles, the route of polystyrene (PS) in the aquatic ecosystem, the PS properties characterization, and its noxious effects on the aquatic biota, particularly fishes and microalgae. Alarming high levels of polystyrene were found in urban, coastal, and rural surface waters and sediments. The fast-screening technique began with a stereoscope to determine the polystyrene particles' shape, size, and color on the organism. SEM and complemented by micro FTIR or Raman spectroscopy were used to evaluate MP's polymer structures. The findings present evidence suggesting that polystyrene buildup in fish can have long-term and unknown consequences. Meanwhile, the presence of polystyrene on microalgae causes a decrease in chlorophyll concentration and photosynthetic activity, which may disrupt photosynthesis by interfering with the electron characters and leading to the production of reactive oxygen species (ROS).

Occurrence of nano/microplastics from wild and farmed edible species. Potential effects of exposure on human health

The occurrence of nano/microplastics (N/MPs) has become a global concern due to their risk on the aquatic environment, food webs and ecosystems, thus, potentially affecting human health. This chapter focuses on the most recent evidence about the occurrence of N/MPs in the most consumed wild and farmed edible species, the occurrence of N/MPs in humans, the potential impact of N/MPs on human health as well as future research recommendations for assessing N/MPs in wild and farmed edible species. Additionally, the N/MP particles in human biological samples, which include the standardization of methods for collection, characterization, and analysis of N/MPs that might allow evaluating the potential risk of the intake of N/MPs in human health, are discussed. Thus, the chapter consequently includes relevant information about the content of N/MPs of more than 60 edible species such as algae, sea cucumber, mussels, squids, crayfish, crabs, clams, and fishes.

Adverse impacts of high-density microplastics on juvenile growth and behaviour of the endangered tri-spine horseshoe crab Tachypleus tridentatus

The impacts of high-density microplastics, namely polyamine 6,6 (nylon), polymethyl methacrylate (PMMA) and polyethylene terephthalate (PET), on growth and behaviour of the endangered tri-spine horseshoe crab Tachypleus tridentatus were investigated for 100 days. Negative changes in wet weight and prosomal width of the juveniles were observed in all treatments of microplastics, but significant difference was only detected in prosomal width between control and PMMA. T. tridentatus became significantly less active upon exposure to nylon and PET. The extent of burrowing by T. tridentatus did not significantly differ among the treatments but was overall significantly reduced towards day 100. T. tridentatus exposed to PET significantly showed the lowest survival probability (30 %), compared to the other treatments (70-90 %). In conclusion, high-density microplastics compromised growth and behaviour of juvenile horseshoe crabs. Among the polymers that were tested, PET was considered more harmful and associated with higher mortality.

A short review on the recent method development for extraction and identification of microplastics in mussels and fish, two major groups of seafood

The prevalence of microplastics in the marine environment poses potential health risks to humans through seafood consumption. Relevant data are available but the diverse analytical approaches adopted to characterise microplastics have hampered data comparison among studies. Here, the techniques for extraction and identification of microplastics are summarised among studies of marine mussels and fish, two major groups of seafood. Among the reviewed papers published in 2018-2021, the most common practice to extract microplastics was through tissue digestion in alkaline chemicals (46 % for mussels, 56 % for fish) and oxidative chemicals (28 % for mussels, 12 % for fish). High-density solutions such as sodium chloride could be used to isolate microplastics from other undigested residues by flotation. Polymer analysis of microplastics was mainly carried out with Fourier-transform infrared (FTIR) spectroscopy (58 % for both mussels and fish) and Raman spectroscopy (14 % for mussels, 8 % for fish). Among these methods, we recommend alkaline digestion for microplastic extraction, and the automated mapping approach of FTIR or Raman spectroscopy for microplastic identification. Overall, this study highlights the need for a standard protocol for characterising microplastics in seafood samples.

Estimation of contamination level in microplastic-exposed crayfish by laser confocal micro-Raman imaging

Crayfish is one of the most important freshwater aquaculture species in China. The potential risks of crayfish consumption caused by environmental microplastic pollution have attracted much attention. In this study, a total of 72 crayfish samples were exposed to the microplastic concentrations of 1 mg/L, 3 mg/L, and 9 mg/L for 7, 14, and 28 days, and microplastic contamination levels in crayfish were then explored by laser confocal micro-Raman (LCM-Raman) imaging and scanning electron microscope (SEM). LCM-Raman imaging showed better performance in microplastics identification. Besides, the average percentage of the contaminated area in visualized LCM-Raman images was used to quantitatively assess contamination levels. Following 28 days of exposure to 9 mg/L microplastics, microplastic accumulation reached about 13,000 particles per crayfish. The results confirmed that LCM-Raman imaging combined with image processing technology could be used to construct a high-performance analytical strategy for the assessment of microplastic contamination in crayfish.

Detection of Environmental Microfiber Pollutants through Vibrational Spectroscopic Techniques: Recent Advances of Environmental Monitoring and Future Prospects

A robust environmental monitoring system is highly essential for the instant detection of environmental microfiber pollutants for the sustainable management of the environment and human health. The extent of microfiber pollution is growing exponentially across the globe in both terrestrial and marine environments. An immediate and accurate environmental monitoring system is crucial to investigate the composition and distribution of these micropollutants. Fourier Transform Infrared Spectroscopy and Raman Spectroscopy are vibrational spectroscopic techniques that have the novel ability to detect microfibers within a minute concentration from diverse environmental samples. The major micropollutants which have been analyzed are polyethylene, polypropylene, nylon 6, polystyrene, and polyethylene terephthalate. After a detailed and critical study of the various aspects of spectroscopic analysis, the review is concluded with a comprehensive discussion of the significance of these robust methods and their application in future aspects for further preventing microfiber pollution in the marine environment. This study highlights the utilities and significance of vibrational spectroscopic detection techniques for the immediate and accurate identification of synthetic microfibers. This review also evaluated the implementation of spectroscopic methods as a precise tool for the characterization and monitoring of microfiber pollutants in the environment.

The onset of surface-enhanced Raman scattering for single-particle detection of submicroplastics

Microplastics represent an emerging environmental problem worldwide, raising ecological and food safety concerns. Compared to microplastics, there is growing evidence of an even higher abundance of submicro- and nanoplastics in the environment, but a reliable monitoring method for detecting these smaller-sized plastics is lacking. Herein we presented the application of surface-enhanced Raman scattering (SERS) for this purpose. Particles of polystyrene (PS; 600 nm) were used as the probe analyte. Gold nanourchins (AuNU; 50 nm), i.e. urchin-shaped nanoparticles with irregular spikes around the core, were used as the SERS-active substrate. The effectiveness of SERS on PS was evaluated at a single-particle level with different numbers of AuNU in order to determine the minimum conditions required for the onset of the SERS effect. Our findings suggest that SERS of a single particle of PS can be induced by as few as 1-5 particles of AuNU, and that the use of excitation wavelength at 785 nm is appropriate to meet the red-shifted surface plasmon resonance of AuNU upon aggregation. These specifications provide additional information for the development of SERS-based tools for detecting plastic particles < 1 µm in food and environmental samples.

Spectroscopic techniques for authentication of animal origin foods

Milk and milk products, meat, fish and poultry as well as other animal derived foods occupy a pronounced position in human nutrition. Unfortunately, fraud in the food industry is common, resulting in negative economic consequences for customers as well as significant threats to human health and the external environment. As a result, it is critical to develop analytical tools that can quickly detect fraud and validate the authenticity of such products. Authentication of a food product is the process of ensuring that the product matches the assertions on the label and complies with rules. Conventionally, various comprehensive and targeted approaches like molecular, chemical, protein based, and chromatographic techniques are being utilized for identifying the species, origin, peculiar ingredients and the kind of processing method used to produce the particular product. Despite being very accurate and unimpeachable, these techniques ruin the structure of food, are labor intensive, complicated, and can be employed on laboratory scale. Hence the need of hour is to identify alternative, modern instrumentation techniques which can help in overcoming the majority of the limitations offered by traditional methods. Spectroscopy is a quick, low cost, rapid, non-destructive, and emerging approach for verifying authenticity of animal origin foods. In this review authors will envisage the latest spectroscopic techniques being used for detection of fraud or adulteration in meat, fish, poultry, egg, and dairy products. Latest literature pertaining to emerging techniques including their advantages and limitations in comparison to different other commonly used analytical tools will be comprehensively reviewed. Challenges and future prospects of evolving advanced spectroscopic techniques will also be descanted.

Developmental and reproductive toxic effects of exposure to microplastics: A review of associated signaling pathways

Microplastics (MPs), small pieces of plastic (∼5 mm), are released into the environment not only as a result of the decomposition of large-sized plastics but also from day-to-day use of plastic products. Chronic exposure to MPs has been attributed to harmful effects on aquatic organisms and rodents. Effects include gastrointestinal toxicity, hepatotoxicity, neurotoxicity, and reproductive and developmental toxicities. Exposure to MPs may also potentially affect human health. Herein, we reviewed the impact of MPs on male and female reproductive systems and the associated mechanisms involved in the reproductive and developmental toxicities of MPs. We performed a literature search in Google Scholar and PubMed using the following keywords: MPs and reproductive toxicity; MPs and developmental studies; MPs and infertility; MPs and aquatics; and MPs and rodents. Evidence of MPs accumulation has been reported in many organs of humans and experimental models. The harmful effects of MPs have been manifested in male and female reproductive systems of mammalian and aquatic animals, including developmental effects on gametes, embryos, and their offspring. This review describes various signaling pathways involved in MPs-associated male and female reproductive and developmental toxicities.

Preliminary Findings of the High Quantity of Microplastics in Faeces of Hong Kong Residents

Microplastics are recognised as a ubiquitous and hazardous pollutant worldwide. These small-sized particles have been detected in human faeces collected from a number of cities, providing evidence of human ingestion of microplastics and their presence in the gastrointestinal tract. Here, using Raman spectroscopy, we identified an average of 50 particles g⁻¹ (20.4–138.9 particles g⁻¹ wet weight) in faeces collected from a healthy cohort in Hong Kong. This quantity was about five times higher than the values reported in other places in Asia and Europe. Polystyrene was the most abundant polymer type found in the faeces, followed by polypropylene and polyethylene. These particles were primarily fragments, but about two-thirds of the detected polyethylene terephthalate were fibres. More than 88% of the microplastics were smaller than 300 µm in size. Our study provides the first data on the faecal level, and thus the extent of ingestion, of microplastics in Hong Kong’s population. This timely assessment is crucial and supports the recently estimated ingestion rate of microplastics by Hong Kong residents through seafood consumption, which is one of the highest worldwide. These findings may be applicable to other coastal populations in South China with similar eating habits.

Differential staining lowers the false positive detection in a novel volumetric measurement technique of microplastics

A novel method for the volumetric detection of microplastics in various environmental (soil, water) and food (fish, meat) matrices was developed. The method is based on the Nile Red staining of microplastics while eliminating probable interference by other organic polymers such as lignin, chitin, cellulosic materials, and other organic substances using a mixture of three water-based dyes (Calcofluor White, Evans Blue, and 4,6-diamidino-2-phenylindole [DAPI]). The excitation/emission 'sweet spot' was determined for water based blue dyes to detect them in a single channel for effective elimination of probable contaminations. Detection of microplastic particles using the Nile Red method was validated by comparing with traditional detection of microplastics via Fourier transform infrared spectroscopy (FTIR). Volumetric measurements of the microplastics present in environmental samples were made possible using Z-stack confocal microscopy images backed by threshold-based 3D segmentation. Regularly shaped microplastic materials were used to validate the volumetric measurement method. The proposed volumetric determination method will be very useful for screening microplastics in diverse media and improving the prevailing method using FTIR.

A gold nanoparticle doped flexible substrate for microplastics SERS detection

Due to overuse of plastic products, decomposed microplastics (MPs) are widely spread in aquatic ecosystems, and will cause irreparable harm to the human body through the food chain. Traditional MP detection methods require cumbersome sample pre-processing procedures and complex instruments, so there is an urgent demand to develop methods to achieve simple on-site detection. Herein, a simple, sensitive, accurate, and stable MP detection method based on surface-enhanced Raman scattering (SERS) is investigated. Considering the hydrophobic problems of MPs, gold nanoparticle (AuNP) doped filter paper as a flexible SERS substrate is applied to capture MPs in the fiber pores. Benefitting from the electromagnetic (EM) hot spots generated by AuNPs, the Raman signal of MPs can be effectively enhanced. Meanwhile, the flexible SERS substrate has good sensitivity to a minimum detectable concentration of 0.1 g L^-1 for polyethylene terephthalate (PET) in water, and the maximum enhancement factor (EF) can reach 360.5. Furthermore, the practicability of the developed method has been proved by the successful detection of MPs in tap water and pond water. This research provides an easy process, high sensitivity, and good reproducibility method for MP detection.

Effects of temperature and particle concentration on aggregation of nanoplastics in freshwater and seawater

Microplastics have become a significant environmental problem worldwide. Compared with microplastics, nanoplastics are apparently more abundant and harmful but their environmental processes are less well understood. The fate and ecological impacts of nanoplastics in aquatic environments are largely determined by their aggregation properties, which were investigated here using pure water and artificial seawater prepared in the laboratory, as well as river water and coastal seawater collected from subtropical Hong Kong. The tests were carried out at an environmentally realistic temperature range (15-35 °C) with particle concentrations over four orders of magnitude (0.1-100 mg L^-1). Under these experimental conditions, parameters of dynamic light scattering were used to determine the extent of aggregation and colloidal stability of polystyrene nanospheres (nPS), a common test model of nanoplastics. Our results showed that aggregation of nPS was minimal in pure water and river water, but became strong under the ionic strength of artificial seawater and coastal seawater, in which 70 nm nPS could aggregate to > 2000 nm, and this aggregation clearly increased with increase in temperature and particle concentration. The aggregates with increasing size and decreasing colloidal stability were deposited more quickly. Findings from this study imply an increased risk of nanoplastics to marine benthic organisms through the aggregation and deposition processes, particularly in warmer waters.

Applying Raman imaging to capture and identify microplastics and nanoplastics in the garden

The characterisation of microplastics is still a challenge, and the challenge is even greater for nanoplastics, of which we only have a limited knowledge so far. Herewith we employ Raman imaging to directly visualise microplastics and nanoplastics which are released from the trimmer lines during lawn mowing. The signal-noise ratio of Raman imaging is significantly increased by generating an image from hundreds or thousands of Raman spectra, rather than from a single spectrum, and is further increased by combining with the logic-based and PCA-based algorithms. The increased signal-noise ratio enables us to capture and identify microplastics and particularly nanoplastics, including plastic fragments or shreds (with diameters / widths of 80 nm - 3 µm) and nanoparticles (with diameters of < 1000 nm) that are released during the mimicked mowing process. Using Raman imaging, we estimate that thousands of microplastics (0.1-5 mm), and billions of nanoplastics (< 1000 nm), are released per minute when a line trimmer is used to mow lawn. Overall, Raman imaging provides effective characterisation of the microplastics and is particularly suitable for nanoplastics.