Identification and Quantification of Nanoplastics in Surface Water and Groundwater by Pyrolysis Gas Chromatography-Mass Spectrometry

Rapid detection of colored and colorless macro- and micro-plastics in complex environment via near-infrared spectroscopy and machine learning

To better understand the migration behavior of plastic fragments in the environment, development of rapid non-destructive methods for in-situ identification and characterization of plastic fragments is necessary. However, most of the studies had focused only on colored plastic fragments, ignoring colorless plastic fragments and the effects of different environmental media (backgrounds), thus underestimating their abundance. To address this issue, the present study used near-infrared spectroscopy to compare the identification of colored and colorless plastic fragments based on partial least squares-discriminant analysis (PLS-DA), extreme gradient boost, support vector machine and random forest classifier. The effects of polymer color, type, thickness, and background on the plastic fragments classification were evaluated. PLS-DA presented the best and most stable outcome, with higher robustness and lower misclassification rate. All models frequently misinterpreted colorless plastic fragments and its background when the fragment thickness was less than 0.1mm. A two-stage modeling method, which first distinguishes the plastic types and then identifies colorless plastic fragments that had been misclassified as background, was proposed. The method presented an accuracy higher than 99% in different backgrounds. In summary, this study developed a novel method for rapid and synchronous identification of colored and colorless plastic fragments under complex environmental backgrounds.

Limits, challenges, and opportunities of sampling groundwater wells with plastic casings for microplastic investigations

Investigating microplastics (MPs) in groundwater suffers from problems already faced by surface water research, such as the absence of common protocols for sampling and analysis. While the use of plastic instruments during the collection, processing, and analysis of water samples is usually avoided in order to minimize unintentional contamination, groundwater research encompassing MPs faces unique challenges. Groundwater sampling typically relies on pre-existing monitoring wells (MWs) and water wells (WWs) that are often constructed with polyvinyl chloride (PVC) casings or pipes due to their favorable price-performance ratio. Despite the convenience, however, the suitability of PVC casings for MP research is questionable. Unfortunately, the specifics of these wells are often not detailed in published studies. Current literature does not indicate significant pollution risks from PVC casings, suggesting these wells might still be viable for MP studies. Our preliminary analysis of the existing literature indicates that if PVC exceeds 6 % of the total MP concentration, it is likely that casings and pipes made of PVC are a source of pollution. Above this threshold, additional investigations in MWs and WWs with PVC casings and pipes are suggested.

Mechanistic study on the increase of Microcystin-LR synthesis and release in Microcystis aeruginosa by amino-modified nano-plastics

Ecological risk of micro/nano-plastics (MPs/NPs) has become an important environmental issue. Microcystin-leucine-arginine (MC-LR) produced by Microcystis aeruginosa (M. aeruginosa) is the most common and toxic secondary metabolites (SM). However, the influencing mechanism of MPs and NPs exposure on MC-LR synthesis and release have still not been clearly evaluated. In this work, under both acute (4d) and long-term exposure (10d), only high-concentration (10 mg/L) exposure of amino-modified polystyrene NPs (PS-NH2-NPs) promoted MC-LR synthesis (32.94 % and 42.42 %) and release (27.35 % and 31.52 %), respectively. Mechanistically, PS-NH2-NPs inhibited algae cell density, interrupted pigment synthesis, weakened photosynthesis efficiency, and induced oxidative stress, with subsequent enhancing the MC-LR synthesis. Additionally, PS-NH2-NPs exposure up-regulated MC-LR synthesis pathway genes (mcyA, mcyB, mcyD, and mcyG) combined with significantly increased metabolomics (Leucine and Arginine), thereby enhancing MC-LR synthesis. PS-NH2-NPs exposure enhanced the MC-LR release from M. aeruginosa via up-regulated MC-LR transport pathway genes (mcyH) and the shrinkage of plasma membrane. Our results provide new insights into the long-time coexistence of NPs with algae in freshwater systems might pose a potential threat to aquatic environments and human health.

Co-photoaging inhibited the heteroaggregation between polystyrene nanoplastics and different titanium dioxide nanoparticles

Heteroaggregation between nanoplastics (NPs) and titanium dioxide nanoparticles (TiO2NPs) determines their environmental fates and ecological risks in aquatic environments. However, the co-photoaging scenario of NPs and TiO2NPs, interaction mechanisms of TiO2NPs with (aged) NPs, as well as the dependence of their heteroaggregation on TiO2NPs facets remain elusive. We found the critical coagulation concentration (CCC) of polystyrene nanoplastics (PSNPs) with coexisting RTiO2NPs was 1.9 - 2.2 times larger than that with coexisting ATiO2NPs, suggesting a better suspension stability of PSNPs+RTiO2NPs. In addition, CCC of TiO2NPs with coexisting photoaged PSNPs (APSNPs) was larger 1.7 - 2.2 times than that with PSNPs coexisting, indicating photoaging inhibited their heteroaggregation due to increasing electrostatic repulsion derived from increased negative charges on APSNPs and the polymer-derived dissolved organic carbon. Coexisted TiO2NPs promoted oxidation of PSNPs with the action of HO· and O2·- under UV light, leading to inhibited heteroaggregation. Moreover, Van der Waals and Lewis-acid interaction dominated the formation of primary heteroaggregates of PSNPs-TiO2NPs (ESE = ‒2.20 ∼ ‒2.78 eV) and APSNPs-TiO2NPs (ESE = ‒3.29 ∼ ‒3.67 eV), respectively. The findings provide a mechanistic insight into the environmental process of NPs and TiO2NPs, and are significant for better understanding their environmental risks in aquatic environments.

Mechanisms of ingested polystyrene micro-nanoplastics (MNPs) uptake and translocation in an in vitro tri-culture small intestinal epithelium

Micro and nanoplastics (MNPs) are now ubiquitous contaminants of food and water. Many cellular and animal studies have shown that ingested MNPs can breach the intestinal barrier to reach the circulation. To date however, the cellular mechanisms involved in intestinal absorption of MNPs have not been investigated with physiologically relevant models, and thus remain unknown. We employed in vitro simulated digestion, a tri-culture small intestinal epithelium model, and a panel of inhibitors to assess the contributions of the possible mechanisms to absorption of 26 nm carboxylated polystyrene (PS26C) MNPs. Inhibition of ATP synthesis reduced translocation by only 35 %, suggesting uptake by both active endocytic pathways and passive diffusion. Translocation was also decreased by inhibition of dynamin and clathrin, suggesting involvement of clathrin mediated endocytosis (CME) and fast endophilin-mediated endocytosis (FEME). Inhibition of actin polymerization also significantly reduced translocation, suggesting involvement of macropinocytosis or phagocytosis. However, inhibition of the Na+-H+ exchanger had no effect on translocation, thus ruling out macropinocytosis. Together these results suggest uptake by passive diffusion as well as by active phagocytosis, CME, and FEME pathways. Further studies are needed to assess uptake mechanisms for other environmentally relevant MNPs as a function of polymer, surface chemistry, and size.

Routine method for the analysis of microplastics in natural and drinking water by pyrolysis coupled to gas chromatography-mass spectrometry

The presence of microplastics (MPs) in water intended for human consumption represents a growing concern due to their ubiquity in the aquatic environments and the potential adverse effects on human health. In this context, validated and standardized analytical methods are required to minimize uncertainties associated with the determination of MPs in water, especially during the drinking water treatment process. In this study, a simple water sampling and extraction procedure and analysis using pyrolysis with gas chromatography coupled to mass spectrometry (Py-GC-MS) was developed to determine 7 types of polymers in water. Quality parameters associated with the method were evaluated, including limits of detection (MDL) and quantitation (MQL), linearity, precision, accuracy, and extended uncertainty. The developed methodology was validated by participating in the EUROQCHARM interlaboratory exercise, and the Z-scores were within the acceptable range for 4 of the 5 polymers tested. Finally, MPs were determined in river water, reclaimed water, and drinking water from the urban area of Barcelona and total concentrations ranged from 11.3 µg/L to 77.1 µg/L. The proposed methodology allows for simple (direct filtration of 100-500 mL of water with a 13 mm glass fiber filter), quantitative (µg/L), and rapid (with a total analysis time of 20 min per sample, including both pyrolysis and GC-MS) analysis of MPs in water intended for drinking.

Behavioral impairments and disrupted mitochondrial energy metabolism induced by polypropylene microplastics in zebrafish larvae

Polypropylene microplastics (PP-MPs) are emerging pollutant commonly detected in various environmental matrices and organisms, while their adverse effects and mechanisms are not well known. Here, zebrafish embryos were exposed to environmentally relevant concentrations of PP-MPs (0.08-50 mg/L) from 2 h post-fertilization (hpf) until 120 hpf. The results showed that the body weight was increased at 2 mg/L, heart rate was reduced at 0.08 and 10 mg/L, and behaviors were impaired at 0.4, 10 or 50 mg/L. Subsequently, transcriptomic analysis in the 0.4 and 50 mg/L PP-MPs treatment groups indicated potential inhibition on the glycolysis/gluconeogenesis and oxidative phosphorylation pathways. These findings were validated through alterations in multiple biomarkers related to glucose metabolism. Moreover, abnormal mitochondrial ultrastructures were observed in the intestine and liver in 0.4 and 50 mg/L PP-MPs treatment groups, accompanied by significant decreases in the activities of four mitochondrial electron transport chain complexes and ATP contents. Oxidative stress was also induced, as indicated by significantly increased ROS levels and significant reduced activities of CAT and SOD and GSH contents. All the results suggested that environmentally relevant concentrations of PP-MPs could induce disrupted mitochondrial energy metabolism in zebrafish, which may be associated with the observed behavioral impairments. This study will provide novel insights into PP-MPs-induced adverse effects and highlight need for further research.

Monitoring Poly(methyl methacrylate) and Polyvinyl Dichloride Micro/Nanoplastics in Water by Direct Solid-Phase Microextraction Coupled to Gas Chromatography-Mass Spectrometry

A simple, sustainable, and sensitive monitoring approach of micro/nanoplastics (MNPs) in aqueous samples is crucial since it helps in assessing the extent of contamination and understanding the potential risks associated with their presence without causing additional stress to the environment. In this study, a novel strategy for qualitative and quantitative determination of MNPs in water by direct solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was proposed for the first time. Spherical poly(methyl methacrylate) (PMMA) and irregularly shaped polyvinyl dichloride (PVDC) were used to evaluate the feasibility and performance of the proposed method. The results demonstrated that both PMMA and PVDC MNPs were efficiently extracted by the homemade SPME coating of nitrogen-doped porous carbons (N-SPCs) and exhibited sufficient thermal decomposition in the GC-MS injection port. Excellent extraction performances of N-SPCs coating for MNPs are attributed to hydrophobic cross-linking, electrostatic forcing, hydrogen bonding, and pore trapping. Methyl methacrylate was identified as the marker for PMMA, while 1,3-dichlorobenzene and 1,3,5-trichlorobenzene were the indicators for PVDC. Under the optimal extraction and decomposition conditions, the proposed method exhibited ultrahigh sensitivity, with a limit of detection of 0.0041 μg/L for PMMA and 0.0054 μg/L for PVDC. Notably, a programmed temperature strategy for the GC-MS injector was developed to discriminate and eliminate the potential interferences of intrinsic indicator compounds. Owing to the integration of sampling, extraction, injection, and decomposition into one step by SPME, the proposed method demonstrates exceptional sensitivity, eliminating the necessity for complex sample pretreatment procedures and the use of organic solvents. Finally, the proposed method was successfully applied in the determination of PMMA and PVDC MNPs in real aqueous samples.

Reducing microplastics in tea infusions released from filter bags by pre-washing method: Quantitative evidences based on Raman imaging and Py-GC/MS

Microplastics released from plastic-based filter bags during tea brewing have attracted widespread attention. Laser confocal micro-Raman and direct classical least squares were used to identify and estimate micron-sized microplastics. Characteristic peaks from pyrolysis-gas chromatography/mass spectrometry of polyethylene terephthalate, polypropylene, and nylon 6 were selected to construct curves for quantification submicron-sized microplastics. The results showed that microplastics released from tea bags in the tea infusions ranged from 80 to 1288 pieces (micron-sized) and 0 to 63.755 μg (submicron-sized) per filter bag. Nylon 6 woven tea bags released far fewer microplastics than nonwoven filter bags. In particular, a simple strategy of three pre-washes with room temperature water significantly reduced microplastic residues with removal rates of 76 %-94 % (micron-sized) and 80 %-87 % (submicron-sized), respectively. The developed assay can be used for the quantitative evaluation of microplastics in tea infusions, and the pre-washing reduced the risk of human exposure to microplastics during tea consumption.

Recent developments of (bio)-sensors for detection of main microbiological and non-biological pollutants in plastic bottled water samples: A critical review

The importance of water in all biological processes is undeniable. Ensuring access to clean and safe drinking water is crucial for maintaining sustainable water resources. To elaborate, the consumption of water of inadequate quality can have a repercussion on human health. Furthermore, according to the instability of tap water quality, the consumption rate of bottled water is increasing every day at the global level. Although most people believe bottled water is safe, it can also be contaminated by microbiological or chemical pollution, which can increase the risk of disease. Over the last decades, several conventional analytical tools applied to analyze the contamination of bottled water. On the other hand, some limitations restrict their application in this field. Therefore, biosensors, as emerging analytical method, attract tremendous attention for detection both microbial and chemical contamination of bottled water. Biosensors enjoy several facilities including selectivity, affordability, and sensitivity. In this review, the developed biosensors for analyzing contamination of bottled water were highlighted, as along with working strategies, pros and cons of studies. Challenges and prospects were also examined.

Oxidative stress and metabolic process responses of Chlorella pyrenoidosa to nanoplastic exposure: Insights from integrated analysis of transcriptomics and metabolomics

Oxidative stress is a universal interpretation for the toxicity mechanism of nanoplastics to microalgae. However, there is a lack of deeper insight into the regulation mechanism in microalgae response to oxidative stress, thus affecting the prevention and control for nanoplastics hazard. The integrated analysis of transcriptomics and metabolomics was employed to investigate the mechanism for the oxidative stress response of Chlorella pyrenoidosa to nanoplastics and subsequently lock the according core pathways and driver genes induced. Results indicated that the linoleic acid metabolism, glycine (Gly)-serine (Ser)-threonine (Thr) metabolism, and arginine and proline metabolism pathways of C. pyrenoidosa were collectively involved in oxidative stress. The analysis of linoleic acid metabolism suggested that nanoplastics prompted algal cells to secrete more allelochemicals, thereby leading to destroy the immune system of cells. Gly-Ser-Thr metabolism and arginine and proline metabolism pathways were core pathways involved in algal regulation of cell membrane function and antioxidant system. Key genes, such as LOX2.3, SHM1, TRPA1, and proC1, are drivers of regulating the oxidative stress of algae cells. This investigation lays the foundation for future applications of gene editing technology to limit the hazards of nanoplastics on aquatic organism.

Environmental nanoplastics quantification by pyrolysis-gas chromatography-mass spectrometry in the Pearl River, China: First insights into spatiotemporal distributions, compositions, sources and risks

Nanoplastics (NPs, size <1000 nm) are ubiquitous plastic particles, potentially more abundant than microplastics in the environment; however, studies highlighting their distribution dynamics in freshwater are rare due to analytical limitations. Here, we investigated spatiotemporal levels of nine polymers of NPs in surface water samples (n = 30) from the full stretch of the Pearl River (sites, n = 15) using pyrolysis gas chromatography-mass spectrometry (Py-GC/MS). Six polymers were detected, including polystyrene (PS), polyvinyl chloride (PVC), nylon/polyamide 66 (PA66), polyester (PES), poly(methyl methacrylate) (PMMA) and polyethylene (PE), where three polymers showed high detection frequencies; PS (100 % in winter and summer), followed by PVC (73 % in winter and 87 % in summer) and PA66 (53 % in winter and 67 % in summer). The spatiotemporal distribution revealed the sites related to aquaculture (AQ) and shipping (SHP) showed higher NP levels than those of human settlement (HS) and wastewater treatment plants (WWTPs) (p = 0.004), and relatively high average levels of NPs in the urban sites compared to rural sites (p = 0.04), albeit showed no obvious seasonal differences (p = 0.78). For instance, the average PS levels in the Pearl River were in the following order: AQ 411.55 µg/L > SHP 81.75 µg/L > WWTP 56.66 µg/L > HS 47.75 µg/L in summer and HS 188.1 µg/L > SHP 103.55 µg/L > AQ 74.7 µg/L > WWTP 62.1 µg/L in winter. Source apportionment showed a higher contribution through domestic plastic waste emissions among urban sites, while rural sites showed an elevated contribution via aquaculture, agriculture, and surface run-off to the NP pollution. Risk assessment revealed that NPs at SHP and AQ sites posed a higher integrated risk in terms of pollution load index (PLI) than those at WWTP and HS sites. Regarding polymer hazard index (HI), 80 % of sampling sites in summer and 60 % of sampling sites in winter posed level III polymer risk, with PVC posing the highest risk. This study provides novel insights into the seasonal contamination and polymer risks of NP in the Pearl River, which will help to regulate the production and consumption of plastics in the region. ENVIRONMENTAL IMPLICATIONS: The contamination dynamics of field nanoplastics (NPs) in freshwater resources remain little understood, mainly attributed to analytical constraints. This study aims to highlight the spatiotemporal distribution of NPs in the Pearl River among various land use types, urban-rural comparison, seasonal comparison, their compositional profiles, potential sources, interaction with environmental factors, and ecological and polymer hazard assessments of investigated polymers in the full stretch of the Pearl River from Liuxi Reservoir to the Pearl River Delta (PRD) region. This study, with a comparatively large number of samples and NP polymers, will offer novel insights into the contamination profiles of nano-sized plastic particles in one of the important freshwater riverine systems in China.

Effects of nanoplastic exposure routes on leaf decomposition in streams

Polystyrene nanoparticles (PS NPs) released from plastic products have been demonstrated to pose a threat to leaf litter decomposition in streams. Given the multitrophic systems of species interactions, the effects of PS NPs through different exposure routes on ecosystem functioning remain unclear. Especially dietary exposure, a frequently overlooked pathway leading to toxicity, deserves more attention. A microcosm experiment was conducted in this study to assess the effects of waterborne and dietary exposure to PS NPs on the litter-based food chain involving leaves, microbial decomposers, and detritivores (river snails). Compared to waterborne contamination, dietary contamination resulted in lower microbial enzyme activities and a significantly higher decrease in the lipid content of leaves. For river snails, their antioxidant activity was significantly increased by 20.21%-69.93%, and their leaf consumption rate was significantly reduced by 16.60% through the dietary route due to the lower lipid content of leaves. Besides, the significantly decreased nutritional quality of river snails would negatively influence their palatability to predators. The findings of this study indicate that dietary exposure to PS NPs significantly impacts microbial and detritivore activities, thus affecting their functions in the detritus food chain as well as nutrient cycling.

Limited exposure of captive Australian marsupials to plastics

The global concern regarding the ubiquitous presence of plastics in the environment has led to intensified research on the impact of these materials on wildlife. In the Australian context, marsupials represent a unique and diverse group of mammals, yet little is known about their exposures to plastics. This study aimed to assess the contamination levels of seven common plastics (i.e., polystyrene (PS), polycarbonate (PC), poly-(methyl methacrylate) (PMMA), polypropylene (PP), polyethylene terephthalate (PET), polyethylene (PE), and polyvinyl chloride (PVC)) in both the diet and faeces of kangaroos, wallabies and koalas sampled from a sanctuary in Northeastern Australia. Quantitative analysis was performed by pressurized liquid extraction followed by double-shot microfurnace pyrolysis coupled to gas chromatography mass spectrometry. Interestingly, the analysis of the food and faeces samples revealed the absence of detectable plastic particles; with this preliminary finding suggesting a relatively limited exposure of captive Australian marsupials to plastics. This study contributes valuable insights into the current state of plastic contamination in Australian marsupials, shedding light on the limited exposures and potential risks, and highlighting the need for continued monitoring and conservation efforts. The results underscore the importance of proactive measures to mitigate plastic pollution and protect vulnerable wildlife populations in Australia's unique ecosystems.

Formation of nanoparticles during accelerated UV degradation of fleece polyester textiles

Micro- and nanoplastics have emerged as critical pollutants in various ecosystems, posing potential environmental and human health risks. Washing of polyester textiles has been identified as one of the sources of nanoplastics. However, other stages of the textile life cycle may also release nanoparticles. This study aimed to examine nanoparticle release during UV degradation of polyester textiles under controlled and real-world conditions. Fleece polyester textiles were weathered under simulated sunlight for up to two months, either in air or submerged in water. We conducted bi-weekly SEM image analyses and quantified released nanoparticles using nanoparticle tracking analysis (NTA). At week 0, the fiber surface appeared smooth after prewashing. In the air group, nanoparticles appeared on the fiber surface after UV-exposure. In the group of textiles submerged in water, the surfaces developed more pits over time. The cumulative nanoparticle emission from the weathered textiles ranged from 1.4 × 1011 to 4.0 × 1011 particles per gram of fabric in the air group and from 1.6 × 1011 to 4.4 × 1011 particles per gram of fabric in the water group over two months. The predominant particle size fell into the 100 to 200 nm range. The estimated mass of the released nanoparticles was 0.06-0.26 g per gram of fabric, which is lower than the amount released during the washing of new textiles. Additionally, Scanning Transmission X-ray Microscopy (STXM) images indicated that the weathered nanoparticles underwent oxidation. Overall, the research offers valuable insights into nanoparticle formation and release from polyester textiles during UV degradation.

A powerful method for In Situ and rapid detection of trace nanoplastics in water-Mie scattering

The pervasive presence of nanoplastics (NPs) in environmental media has raised significant concerns regarding their implications for environmental safety and human health. However, owing to their tiny size and low level in the environment, there is still a lack of effective methods for measuring the amount of NPs. Leveraging the principles of Mie scattering, a novel approach for rapid in situ quantitative detection of small NPs in low concentrations in water has been developed. A limit of detection of 4.2 μg/L for in situ quantitative detection of polystyrene microspheres as small as 25 nm was achieved, and satisfactory recoveries and relative standard deviations were obtained. The results of three self-ground NPs showed that the method can quantitatively detect the concentration of NPs in a mixture of different particle sizes. The satisfactory recoveries (82.4% to 110.3%) of the self-ground NPs verified the good anti-interference ability of the method. The total concentrations of the NPs in the five brands of commercial bottled water were 0.07 to 0.39 μg/L, which were directly detected by the method. The proposed method presents a potential approach for conducting in situ and real-time environmental risk assessments of NPs on human and ecosystem health in actual water environments.

Microplastics and non-natural cellulosic particles in Spanish bottled drinking water

This investigation explored the presence of microplastics (MPs) and artificial cellulosic particles (ACPs) in commercial water marketed in single use 1.5 L poly(ethylene terephthalate) bottles. In this work we determined a mass concentration of 1.61 (1.10-2.88) µg/L and 1.04 (0.43-1.82) µg/L for MPs and ACPs respectively in five top-selling brands from the Spanish bottled water market. Most MPs consisted of white and transparent polyester and polyethylene particles, while most ACPs were cellulosic fibers likely originating from textiles. The median size of MPs and ACPs was 93 µm (interquartile range 76-130 µm) and 77 µm (interquartile range 60-96 µm), respectively. Particle mass size distributions were fitted to a logistic function, enabling comparisons with other studies. The estimated daily intake of MPs due to the consumption of bottled water falls within the 4-18 ng kg-1 day-1 range, meaning that exposure to plastics through bottled water probably represents a negligible risk to human health. However, it's worth noting that the concentration of plastic found was much higher than that recorded for tap water, which supports the argument in favour of municipal drinking water.

Assessing the current state of plastic pollution research in Antarctica: Knowledge gaps and recommendations

Antarctica stands as one of the most isolated and pristine regions on our planet. Regardless, recent studies have evidenced the presence of plastic pollution in Antarctic environments and biota. While these findings are alarming and put into perspective the reach of plastic pollution, it is necessary to assess the current knowledge of plastic pollution in Antarctica. In the present review, an updated literature review of plastic pollution in multiple Antarctic environmental compartments and biota was conducted. Studies were cataloged based on environmental compartments (e.g., sediments, seawater, soil, atmosphere) and biota from different ecological niches. A detailed analysis of the main findings, as well as the flaws and shortcomings across studies, was conducted. In general terms, several studies have shown a lack of adequate sampling and analytical procedures for plastic research (particularly in the case of microplastics) and standard procedures; thus, compromising the reliability of the data reported and comparability across studies. Aiming to guide future studies and highlight research needs, a list of knowledge gaps and recommendations were provided based on the analysis and discussion of the literature and following standardized procedures.

Mass quantification of nanoplastics at wastewater treatment plants by pyrolysis-gas chromatography-mass spectrometry

Municipal wastewater treatment plants (WWTPs) play a crucial role in the collection and redistribution of plastic particles from both households and industries, contributing to their presence in the environment. Previous studies investigating the levels of plastics in WWTPs, and their removal rates have primarily focused on polymer type, size, shape, colour, and particle count, while comprehensive understanding of the mass concentration of plastic particles, particularly those <1 µm (nanoplastics), remains unclear and lacking. In this study, pyrolysis gas chromatography-mass spectrometry was used to simultaneously determine the mass concentration of nine selected polymers (i.e., polyethylene (PE), polypropylene (PP), polystyrene (PS), poly(ethylene terephthalate) (PET), nylon 6, nylon 66, polyvinylchloride (PVC), poly(methyl methacrylate) (PMMA) and polycarbonate (PC)) below 1 µm in size across the treatment processes or stages of three WWTPs in Australia. All the targeted nanoplastics were detected at concentrations between 0.04 and 7.3 µg/L. Nylon 66 (0.2-7.3 µg/L), PE (0.1-6.6 µg/L), PP (0.1-4.5 µg/L), Nylon 6 (0.1-3.6 µg/L) and PET (0.1-2.2 µg/L), were the predominant polymers in the samples. The mass concentration of the total nanoplastics decreased from 27.7, 18 and 9.1 µg/L in the influent to 1, 1.4 and 0.8 µg/L in the effluent, with approximate removal rates of 96 %, 92 % and 91 % in plants A, B and C, respectively. Based on annual wastewater effluent discharge, it is estimated that approximately 24, 2 and 0.7 kg of nanoplastics are released into the environment per year for WWTPs A, B and C, respectively. This study investigated the mass concentrations and removal rates of nanoplastics with a size range of 0.01-1 µm in wastewater, providing important insight into the pollution levels and distribution patterns of nanoplastics in Australian WWTPs.

Identification and quantification of microplastics in salts by complementary approaches using pyrolysis-gas chromatography/quadrupole-time of flight mass spectrometry (Py-GC/QTOFMS) and laser direct infrared (LDIR) chemical imaging analysis

Microplastics (MPs) and nanoplastics (NPs) have been suspected as contaminants in various foodstuffs, including salts, all over the world. Regarding the different sizes and polymer types, the mass concentrations of actual plastic particles in salt are not very clear. The purpose of this study is to develop a scalable method for qualitative and quantitative analysis of MPs and NPs by using Pyrolysis Gas Chromatography Quadrupole-Time of Flight mass spectrometry (Py-GC/QTOFMS) to detect their mass concentrations in salt samples. The targeted and suspected lists of polymers in salts were compiled based on the combined results of the high-resolution mass spectrometry (HRMS) full scanning with auxiliary MS dataset and the laser direct infrared (LDIR) chemical imaging analysis. The seven targeted MPs with polymer standards, i.e., polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), polypropylene (PP), polystyrene (PS), polyethylene (PE), polyethylene terephthalate (PET), and polycarbonate (PC), were first subjected to a full MS scanning mode of the Py-GC/QTOFMS analysis. Subsequently, the parental masses of their pyrolysis compounds were used as the seeds to generate the related daughter masses. This process established both retention time and mass-pairs matching for the target MS/MS mode for enabling the identification and quantification of the particles. The suspected MPs with a matching degree >0.65 in the LDIR list were explored either by the full scan MS. Only PVC was identified, and PET was suspected. The Py-GC/QTOFMS result is complementary and comparable to the LDIR detection with the matching degree >0.85. We identified that PVC and PET (suspected) can be measured in both commercial and bulk sea salts, and their concentrations in sea salts are much higher than in rock salts, implying heavy contamination of the seawater.

Micro(nano)plastics: invisible compounds with a visible impact

The plastic related research has been an epicentre in recent times. The presence and spread of micro (nano) plastics (MNPs) are well-known in the terrestrial and aquatic environment. However, the focus on the fate and remediation of MNP in soil and groundwater is limited. The fate and bioaccumulation of ingested MNPs remain unknown within the digestive tract of animals. There is also a significant knowledge gap in understanding the ubiquitous organic environmental pollutants with MNPs in biological systems. Reducing plastic consumption, improving waste management practices, and developing environmentally friendly alternatives are some of the key steps needed to address MNP pollution. For better handling and to protect the environment from these invisible substances, policymakers and researchers urgently need to monitor and map MNP contamination in soil and groundwater.

Identification and quantification of nanoplastics in different crops using pyrolysis gas chromatography-mass spectrometry

Quantitative studies of nanoplastics (NPs) abundance on agricultural crops are crucial for understanding the environmental impact and potential health risks of NPs. However, the actual extent of NP contamination in different crops remains unclear, and therefore insufficient quantitative data are available for adequate exposure assessments. Herein, a method with nitric acid digestion, multiple organic extraction combined with pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) quantification was used to determine the chemical composition and mass concentration of NPs in different crops (cowpea, flowering cabbage, rutabagas, and chieh-qua). Recoveries of 74.2-109.3% were obtained for different NPs in standard products (N = 6, RSD <9.6%). The limit of detection (LOD) and the limit of quantitation (LOQ) were 0.02-0.5 μg and 0.06-1.5 μg, respectively. The detection method for NPs exhibited good external calibration curves and linearity with 0.99. The results showed that poly (vinylchloride) (PVC), poly (ethylene terephthalate) (PET), polyethylene (PE), and polyadiohexylenediamine (PA66) NPs could be detected in crop samples, although the accumulation levels associated with the various crops varied significantly. PVC (N.D.-954.3 mg kg-1, dry weight (DW)) and PE (101.3-462.9 mg kg-1, DW) NPs were the dominant components in the samples of all four crop species, while high levels of PET (414.3-1430.1 mg kg-1, DW) NPs were detected in cowpea samples. Furthermore, there were notable differences in the accumulation levels of various edible crop parts, such as stems (60.2%) > leaves (39.8%) in flowering cabbage samples and peas (58.8%) > pods (41.2%) in cowpea samples. This study revealed the actual extent of NP contamination in different types of crops and provided crucial reference data for future research.

Polyethylene nanoparticles at environmentally relevant concentrations enhances neurotoxicity and accumulation of 6-PPD quinone in Caenorhabditis elegans

The exposure risk of 6-PPD quinone (6-PPDQ) has aroused increasing concern. In the natural environment, 6-PPDQ could interact with other pollutants, posing more severe environmental problems and toxicity to organisms. We here examined the effect of polyethylene nanoplastic (PE-NP) on 6-PPDQ neurotoxicity and the underling mechanisms in Caenorhabditis elegans. In nematodes, PE-NP (1 and 10 μg/L) decreased locomotion behavior, but did not affect development of D-type neurons. Exposure to PE-NP (1 and 10 μg/L) strengthened neurotoxicity of 6-PPDQ (10 μg/L) on the aspect of locomotion and neurodegeneration induction of D-type motor neurons. Exposure to PE-NPs (10 μg/L) caused increase in expressions of mec-4, asp-3, and asp-4 governing neurodegeneration in 10 μg/L 6-PPDQ exposed nematodes. Moreover, exposure to PE-NP (10 μg/L) increased expression of some neuronal genes (daf-7, dbl-1, jnk-1, and mpk-1) in 6-PPDQ exposed nematodes, and RNAi of these genes resulted in susceptibility to neurotoxicity of PE-NP and 6-PPDQ. 6-PPDQ could be adsorbed by PE-NPs, and resuspension of PE-NP and 6-PPDQ after adsorption equilibrium exhibited similar neurotoxicity to co-exposure of PE-NP and 6-PPDQ. In addition, exposure to PE-NP (1 and 10 μg/L) increased 6-PPDQ accumulation in body of nematodes and increased defecation cycle length in 6-PPDQ exposed nematodes. Therefore, 6-PPDQ could be adsorbed on nanoplastics (such as PE-NPs) and enhance both neurotoxicity and accumulation of 6-PPDQ in organisms.

Fast and portable fluorescence lifetime analysis for early warning detection of micro- and nanoplastics in water

The presence of plastic fragments in aquatic environments, particularly at the micro- and nano-scale, has become a significant global concern. However, current detection methods are limited in their ability to reveal the presence of such particles in liquid samples. In this study, we propose the use of a fluorescence lifetime analysis system for the detection of micro- and nanoplastics in water. This approach relies on the inherent endogenous fluorescence of plastic materials and involves the collection of single photons emitted by plastic fragments upon exposure to a pulsed laser beam. Briefly, a pulsed laser beam (repetition frequency = 40 MHz) shines onto a sample solution, and the emitted light is filtered, collected, and used to trace the time distributions of the photons with high temporal resolution. Finally, the fluorescence lifetime was measured using fitting procedures and a phasor analysis. Phasor analysis is a fit-free method that allows the measurement of the fluorescence lifetime of a sample without any assumptions or prior knowledge of the sample decay pattern. The developed instrument was tested using fluorescence references and validated using unlabelled micro- and nano-scale particles. Our system successfully detected polystyrene particles in water, achieving a remarkable sensitivity with a detection limit of 0.01 mg/mL, without the need for sample pre-treatment or visual inspection. Although further studies are necessary to enhance the detection limit of the technique and distinguish between different plastic materials, this proof-of-concept study suggests the potential of the fluorescence lifetime-based approach as a rapid, robust, and cost-effective method for early warning detection and identification of plastic contaminants in aquatic environments.

Quantitative analysis of nanoplastics in environmental and potable waters by pyrolysis-gas chromatography-mass spectrometry

Nanoplastics are emerging environmental contaminants, but their presence in environmental and potable water remains largely understudied due to the absence of quantitative analytical methods. In this study, we developed and validated a pretreatment method that combines hydrogen peroxide digestion and Amicon® Stirred Cell ultrafiltration (at 100 kDa, approximately 10 nm) with subsequent detection by pyrolysis gas chromatography-mass spectrometry (Pyr-GC/MS). This method allows for the simultaneous identification and quantification of nine selected nanoplastic types, including poly(ethylene terephthalate) (PET), polyethylene (PE), polycarbonate (PC), polypropylene (PP), poly(methyl methacrylate) (PMMA), polystyrene (PS), polyvinylchloride (PVC), nylon 6, and nylon 66, in environmental and potable water samples based on polymer-specific mass concentration. Limits of quantification ranged from 0.01 to 0.44 µg/L, demonstrating the method's ability to quantitatively detect nanoplastics in environmental and potable water samples. Most of the selected nanoplastics were detected at concentrations of between 0.04 and 1.17 µg/L, except for PC, which was consistently below the limit of detection (<0.44 µg/L). The prevalent polymer components in the samples were PE (0.10 - 1.17 µg/L), PET (0.06 - 0.91 µg/L), PP (0.04 - 0.79 µg/L), and PS (0.06 - 0.53 µg/L) nanoplastics. The presented analytical method offers an accurate means to identify, quantify, and monitor nanoplastics in complex environmental and potable water samples. It fills gaps in our understanding of nanoplastic pollution levels, providing a valuable methodology and crucial reference data for future studies.

Sublethal effects induced by different plastic nano-sized particles in Daphnia magna at environmentally relevant concentrations

A growing number of studies have reported the toxic effects of nanoplastics (NPs) on organisms. However, the focus of these studies has almost exclusively been on the use of polystyrene (PS) nanospheres. Herein, we aim to evaluate the sublethal effects on Daphnia magna juveniles of three different NP polymers: PS-NPs with an average size of 200 nm, polyethylene [PE] NPs and polyvinyl chloride [PVC] NPs with a size distribution between 50 and 350 nm and a comparable mean size. For each polymer, five environmentally relevant concentrations were tested (from 2.5 to 250 μg/L) for an exposure time of 48 h. NP effects were assessed at the biochemical level by investigating the amount of reactive oxygen species (ROS) and the activity of the antioxidant enzyme catalase (CAT) and at the behavioral level by evaluating the swimming behavior (distance moved). Our results highlight that exposure to PVC-NPs can have sublethal effects on Daphnia magna at the biochemical and behavioral levels. The potential role of particle size on the measured effects cannot be excluded as PVC and PE showed a wider size range distribution than PS, with particles displaying sizes from 50 to 350 nm. However, we infer that the chemical structure of PVC, which differs from that of PE of the same range size, concurs to explain the observed effects. Consequently, as PS seems not to be the most hazardous polymer, we suggest that the use of data on PS toxicity alone can lead to an underestimation of NP hazards.

Stimulated Raman Scattering Microscopy Reveals Bioaccumulation of Small Microplastics in Protozoa from Natural Waters

Microplastics (MPs) are pollutants of global concern, and bioaccumulation determines their biological effects. Although microorganisms form a large fraction of our ecosystem's biomass and are important in biogeochemical cycling, their accumulation of MPs has never been confirmed in natural waters because current tools for field biological samples can detect only MPs > 10 μm. Here, we show that stimulated Raman scattering microscopy (SRS) can image and quantify the bioaccumulation of small MPs (<10 μm) in protozoa. Our label-free method, which differentiates MPs by their SRS spectra, detects individual and mixtures of different MPs (e.g., polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polystyrene, and poly(methyl methacrylate)) in protozoa. The ability of SRS to quantify cellular MP accumulation is similar to that of flow cytometry, a fluorescence-based method commonly used to determine cellular MP accumulation. Moreover, we discovered that protozoa in water samples from Yangtze River, Xianlin Wastewater Treatment Plant, Lake Taihu and the Pearl River Estuary accumulated MPs < 10 μm, but the proportion of MP-containing cells was low (∼2-5%). Our findings suggest that small MPs could potentially enter the food chain and transfer to organisms at higher trophic levels, posing environmental and health risks that deserve closer scrutiny.

Size-Resolved Identification and Quantification of Micro/Nanoplastics in Indoor Air Using Pyrolysis Gas Chromatography-Ion Mobility Mass Spectrometry

Humans are exposed to differing levels of micro/nanoplastics (MNPs) through inhalation, but few studies have attempted to measure <1 μm MNPs in air, in part due to a paucity of analytical methods. We developed an approach to identify and quantify MNPs in indoor air using a novel pyrolysis gas chromatographic cyclic ion mobility mass spectrometer (pyr-GCxcIMS). Four common plastic types were targeted for identification, namely, (polystyrene (PS), polyethylene (PE), polypropylene (PP), and polymethyl methacrylate (PMMA). The method was applied to size-resolved particulate (56 nm to 18 μm) collected from two different indoor environments using a Micro-Orifice Uniform Deposit Impactors (MOUDI) model 110 cascade impactor. Comprehensive two-dimensional separation by GCxcIMS also enabled the retrospective analysis of other polymers and plastic additives. The mean concentrations of MNP particles with diameters of <10 μm and <2.5 μm in the laboratory were estimated to be 47 ± 5 and 27 ± 4 μg/m3, respectively. In the private residence, the estimated concentrations were 24 ± 3 and 16 ± 2 μg/m3. PS was the most abundant MNP type in both locations. Nontargeted screening revealed the presence of plastic additives, such as TDCPP (tris(1,3-dichloro-2-propyl)phosphate) whose abundance correlated with that of polyurethane (PU). This is consistent with their use as flame retardants in PU-based upholstered furniture and building insulation. This study provides evidence of indoor exposure to MNPs and underlines the need for further study of this route of exposure to MNPs and the plastic additives carried with them.

Identification and quantification of nanoplastics (20-1000 nm) in a drinking water treatment plant using AFM-IR and Pyr-GC/MS

Nanoplastics, owing to their small particle size, pose a significant threat to creatures, deserving heightened attention. Numerous studies have investigated microplastics pollution and their removal efficiency in drinking water treatment plants, none of which have involved nanoplastics due to lacking a suitable analytical method. This study introduced a feasible method of combing AFM-IR and Pyr-GC/MS to identify and quantify nanoplastics (20-1000 nm) for a preliminary understanding of their fate during drinking water treatment processes. Resolving of chemical functional groups and pyrolysis products from AFM-IR and Pyr-GC/MS data demonstrated the presence of PE and PVC nanoplastics in this drinking water treatment plant. The initial influent abundances of PE and PVC nanoplastics were 0.86 μg/L and 137.31 μg/L, with subsequent increase to 4.49 μg/L and 208.64 μg/L in ozonation contact tank unit. Then a gradual decreasing was observed along water process, achieving 98.4% removal of PE nanoplastics and 44.0% removal of PVC nanoplastics, respectively. Although this drinking water treatment plant has exhibited a certain level of nanoplastics removal efficiency, particular attention should be directed to the oxidation unit, which appears to be a significant source of nanoplastics. This study will lay a foundation for revealing nanoplastics pollution in the environment.

Integrating transcriptomics and biochemical analysis to understand the interactive mechanisms of the coexisting exposure of nanoplastics and erythromycin on Chlorella pyrenoidosa

Nanoplastics and antibiotics frequently co-exist in water polluted by algal blooms, but little information is available about interaction between substances. Erythromycin, as a representative of antibiotics, has been frequently detected in aquatic environments. This investigation attempted to reveal the interaction mechanism of nanoplastics and erythromycin on Chlorella pyrenoidosa. Results demonstrated that the joint toxicity of erythromycin and nanoplastics was dynamic and depended on nanoplastics concentration. Antagonistic effects of 1/2 or 1 EC50 erythromycin and nanoplastic concentration (10 mg/L) on the growth of C. pyrenoidosa was observed. The joint toxicity of 1/2 or 1 EC50 erythromycin and nanoplastic concentration (50 mg/L) was initially synergistic during 24-48 h and then turned to antagonistic during 72-96 h. Consequently, antagonistic effect was the endpoint for joint toxicity. Integration of transcriptomics and physiological biochemical analysis indicated that the co-existence of nanoplastics and erythromycin affected the signal transduction and molecular transport of algal cell membrane, induced intracellular oxidative stress, and hindered photosynthetic efficiency. Overall, this study provided a theoretical basis for evaluating the interactive mechanisms of nanoplastics and antibiotics.

Metabolic equilibrium and reproductive resilience: Freshwater gastropods under nanoplastics exposure

Nanoplastics (NPs) have gained increasing attention due to their widespread presence in aquatic environments and potential adverse effects on organisms. The interaction between NPs and freshwater gastropods can lead to a range of physiological and reproductive disturbances. In this study, we investigated the adverse effects of NPs (two size: 20 nm and 100 nm; three concentrations: 0.5, 50 and 100 ppm) on energy metabolism and reproductive fitness in freshwater gastropods Lymnean stagnalis after 21 days exposure. Briefly, the condition index negatively correlated with increasing NPs concentrations for both sizes. Bioaccumulation revealed a concentration-dependent trend in the 100 nm group, and the highest accumulation appeared in the 100 ppm group, compared to all the rest groups. This phenomenon could be attributed to the larger surface area which facilitates stronger attachment to tissues, while smaller particles could be cleared more readily from body. Carbohydrate and protein reserves remained largely unaffected at all concentrations. However, 100 nm NPs triggered stress responses, increasing lipid production, and 20 nm NPs potentially interfered with mitochondrial function, affecting electron transport system activity. Despite the variations observed in lipid levels and energy cost, the ratio of available energy to energy cost remained stable across for both NPs sizes, and this resilience suggests that cellular energy allocation endured undisturbed, hinting at mechanisms that enable gastropods to maintain their metabolic equilibrium. Reproductively, NPL-exposed groups had fewer clutches, with clutches per collection time decreasing over time for both sizes. In terms of egg development, shell growth and hatching rates remained unaffected, suggesting resilience in aquatic ecosystems.In conclusion, this study underscores the substantial impact of NPs on freshwater gastropods, raising ecological and reproductive concerns. The intricate interplay between nanoparticle size, concentration, and physiological responses highlights the complexity of NPs interactions in aquatic ecosystems, necessitating further research and regulatory measures.

Photo-oxidation of Micro- and Nanoplastics: Physical, Chemical, and Biological Effects in Environments

Micro- and nanoplastics (MNPs) are attracting increasing attention due to their persistence and potential ecological risks. This review critically summarizes the effects of photo-oxidation on the physical, chemical, and biological behaviors of MNPs in aquatic and terrestrial environments. The core of this paper explores how photo-oxidation-induced surface property changes in MNPs affect their adsorption toward contaminants, the stability and mobility of MNPs in water and porous media, as well as the transport of pollutants such as organic pollutants (OPs) and heavy metals (HMs). It then reviews the photochemical processes of MNPs with coexisting constituents, highlighting critical factors affecting the photo-oxidation of MNPs, and the contribution of MNPs to the phototransformation of other contaminants. The distinct biological effects and mechanism of aged MNPs are pointed out, in terms of the toxicity to aquatic organisms, biofilm formation, planktonic microbial growth, and soil and sediment microbial community and function. Furthermore, the research gaps and perspectives are put forward, regarding the underlying interaction mechanisms of MNPs with coexisting natural constituents and pollutants under photo-oxidation conditions, the combined effects of photo-oxidation and natural constituents on the fate of MNPs, and the microbiological effect of photoaged MNPs, especially the biotransformation of pollutants.

Internalization, physiological responses and molecular mechanisms of lettuce to polystyrene microplastics of different sizes: Validation of simulated soilless culture

Microplastics (MPs) exists widely in the environment, and the resulting pollution of MPs has become a global environmental problem. Plants can absorb MPs through their roots. However, studies on the mechanism of the effect of root exposure to different size MPs on vegetables are limited. Here, we use Polystyrene (PS) MPs with different particle sizes to investigate the internalization, physiological response and molecular mechanism of lettuce to MPs. MPs may accumulate in large amounts in lettuce roots and migrate to the aboveground part through the vascular bundle, while small particle size MPs (SMPs, 100 nm) have stronger translocation ability than large particle size MPs (LMPs, 500 nm). MPs can cause physiological and biochemical responses and transcriptome changes in lettuce. SMPs and LMPs resulted in reduced biomass (38.27 % and 48.22 % reduction in fresh weight); caused oxidative stress (59.33 % and 47.74 % upregulation of SOD activity in roots) and differential gene expression (605 and 907 DEGs). Signal transduction, membrane transport and alteration of synthetic and metabolic pathways may be the main causes of physiological toxicity of lettuce. Our study provides important information for understanding the behavior and fate of MPs in edible vegetables, especially the physiological toxicity of MPs to edible vegetables, in order to assess the potential threat of MPs to food safety and agricultural sustainable development.

Polyethylene nanoplastics cause reproductive toxicity associated with activation of both estrogenic hormone receptor NHR-14 and DNA damage checkpoints in C. elegans

As the most commercial polymer, the polyethylene nanoparticle (PE-NP) has been discharged into the environment and poses potential risks to organisms. However, the possible reproductive toxicity of PE-NP and underlying mechanisms remain largely unknown. In this study, Caenorhabditis elegans was employed as the animal model to effects of PE-NP (100 nm) and their leachates on reproduction and underlying mechanisms. Nematodes were exposed to PE-NP at 0.1-100 μg/L from L1-larvae to adult day 1 (approximately 4.5 days). Both brood size and number of fertilized eggs in uterus were decreased by 10 and 100 μg/L PE-NP, but could not be affected by their leachates. In addition, number of mitotic cells, length, and area of gonad were reduced by 10 and 100 μg/L PE-NP, but were not altered by their leachates. Accompanied with alteration in expressions of genes (egl-1, ced-9, ced-4, and ced-3) governing cell apoptosis, germline apoptosis was enhanced by PE-NP. Meanwhile, DNA damage was involved in the enhancement germline apoptosis after PE-NP exposure. PE-NP further increased expression of nhr-14 encoding estrogenic hormone receptor, and RNAi of nhr-14 suppressed PE-NP reproductive toxicity. Moreover, RNAi of nhr-14 decreased expression of egl-1, ced-4, ced-3, and mrt-2 in PE-NP exposed nematodes. Therefore, exposure to PE-NPs rather than in their leachates potentially caused reproductive toxicity by activating both estrogenic hormone receptor NHR-14 and DNA damage checkpoints (CLK-2, HUS-1, and MRT-2) in nematodes. These findings provide important insights into the exposure risk of PE-NPs on reproduction of environmental organisms.

Emergence of nanoplastics in the aquatic environment and possible impacts on aquatic organisms

Plastic production on a global scale is instrumental in advancing modern society. However, plastic can be broken down by mechanical and chemical forces of humans and nature, and knowledge of the fate and effects of plastic, especially nanoplastics, in the aquatic environment remains poor. We provide an overview of current knowledge on the environmental occurrence and toxicity of nanoplastics, and suggestions for future research. There are nanoplastics present in seas, rivers, and nature reserves from Asia, Europe, Antarctica, and the Arctic Ocean at levels of 0.3-488 microgram per liter. Once in the aquatic environment, nanoplastics accumulate in plankton, nekton, benthos through ingestion and adherence, with multiple toxic results including inhibited growth, reproductive abnormalities, oxidative stress, and immune system dysfunction. Further investigations should focus on chemical analysis methods for nanoplastics, effect and mechanism of nanoplastics at environmental relevant concentrations in aquatic organisms, as well as the mechanism of the Trojan horse effect of nanoplastics.

Quantification of nanoplastics uptake and transport in lettuce by pyrolysis gas chromatography-mass spectrometry

Nanoplastics (NPs) can enter the edible parts of crop and threaten human health, which attract widespread attention. However, the precise quantification of NPs in crop is still a tremendous challenge. Herein, a method with Tetramethylammonium hydroxide (TMAH) digestion, dichloromethane extraction combined with pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) quantification was present to quantify polystyrene (PS) NPs uptake in lettuce (Lactuca sativa). 25% of TMAH was optimized as extraction solvent and 590 °C was selected as pyrolysis temperature. Recoveries of 73.4-96.9% were obtained for PS-NPs at spiking level of 4-100 μg/g in control samples (RSD < 8.6%). The method exhibited good intra-day and inter-day reproducibility, detection limits of 34-38 ng/g and linearity with 0.998-0.999. The reliability of Py-GC/MS method was verified by europium-chelated PS using inductively coupled plasma mass spectrometry (ICP-MS). To simulate different environmental conditions, hydroponic culture and soil incubated lettuce were exposed to different concentrations of NPs. Higher levels of PS-NPs were detected in roots and very few was transferred to the shoots. NPs in lettuce were confirmed by laser scanning confocal microscopy (LSCM). The developed method provides new opportunities for the quantification of NPs in crops.

A review on constructive classification framework of research trends in analytical instrumentation for secondary micro(nano)plastics: What is new and what needs next?

Secondary micro(nano)plastics generated from the degradation of plastics pose a major threat to environmental and human health. Amid the growing research on microplastics to date, the detection of secondary micro(nano)plastics is hampered by inadequate analytical instrumentation in terms of accuracy, validation, and repeatability. Given that, the current review provides a critical evaluation of the research trends in instrumental methods developed so far for the qualitative and quantitative determination of micro(nano)plastics with an emphasis on the evolution, new trends, missing links, and future directions. We conducted a meta-analysis of the growing literature surveying over 800 journal articles published from 2004 to 2022 based on the Web of Science database. The significance of this review is associated with the proposed novel classification framework to identify three main research trends, viz. (i) preliminary investigations, (ii) current progression, and (iii) novel advances in sampling, characterization, and quantification targeting both micro- and nano-sized plastics. Field Flow Fractionation (FFF) and Hydrodynamic Chromatography (HDC) were found to be the latest techniques for sampling and extraction of microplastics. Fluorescent Molecular Rotor (FMR) and Thermal Desorption-Proton Transfer Reaction-Mass Spectrometry (TD-PTR-MS) were recognized as the modern developments in the identification and quantification of polymer units in micro(nano)plastics. Powerful imaging techniques, viz. Digital Holographic Imaging (DHI) and Fluorescence Lifetime Imaging Microscopy (FLIM) offered nanoscale analysis of the surface topography of nanoplastics. Machine learning provided fast and less labor-intensive analytical protocols for accurate classification of plastic types in environmental samples. Although the existing analytical methods are justifiable merely for microplastics, they are not fully standardized for nanoplastics. Future research needs to be more inclined towards secondary nanoplastics for their effective and selective analysis targeting a broad range of environmental and biological matrices.

Cation-π mechanism promotes the adsorption of humic acid on polystyrene nanoplastics to differently affect their aggregation: Evidence from experimental characterization and DFT calculation

Multiple water-chemistry factors determine nanoplastics aggregation and thus change their bioavailability and ecological risks in natural aquatic environments. However, the dominant factors and their interactive mechanisms remain elusive. In this study, polystyrene nanoplastics (PSNPs) showed greater colloidal stability in Li Lake water compared to ultrapure water. The RDA and PARAFAC results suggested that dissolved organic carbon, humic acid (HA) in particular, Ca2+, and pH are critical factors influencing PSNPs aggregation. Batch experiments showed that the critical coagulation concentration (CCC) of PSNPs was increased with pH increase; HA increased the CCC of PSNPs in NaCl by 2.6-fold but decreased that in CaCl2 by 1.8-fold. Moreover, cations increased the adsorption of HA on PSNPs. The DFT results suggested that HA-cations complexes (EAE = -1.10 eV and -0.51 eV for HA-Ca2+ and HA-Na+, respectively) but not HA alone (EAE = -0.33 eV) are the main scenarios for their adsorption on PSNPs, and a cation-π mechanism between PSNPs and HA-cations complexes dominates PSNPs aggregation in this scenario. The findings are significant for better understanding the environmental process and fate of nanoplastics in aquatic environments. ENVIRONMENTAL IMPLICATION: Nanoplastics are kinds of emerging contaminants. Nanoplastic aggregation determines their bioavailability and toxic risks to ecological health. Herein, the hydrodynamic sizes of PSNPs in local Li Lake water was tested and a redundancy analysis was performed to examine the key water-chemistry factors driving PSNPs aggregation. Moreover, the mechanisms in PSNPs aggregation driven by multiple dominant water-chemistry factors including cations, pH, and DOC were firstly unveiled by combining experimental characterization and theoretical computations. This work improves our understanding of the environmental fate of nanoplastics and provides a theoretical basis for the risk assessment and control of nanoplastics in real aquatic environments.

Particle transfer mediates dermal exposure of consumers to plasticizers in eraser and pen accessories

Dermal exposure to chemicals released from daily consumer products is a rising concern, particularly for children who are susceptible to unintentional hand-to-mouth transfer and related chemical exposure risk. However, chemical transfer induced by tiny particles of intact products has yet to be adequately addressed. The objective of the present study was to determine the potentiality of particles release from intact erasers and pen grips upon dermal contact by measuring the migration rates of the embedded plasticizers (phthalates and its alternatives). The results showed that billions of particles were released from erasers (0.6-1.2 × 109) and pen grips (0.2-1.6 × 108) upon dermal contact at ambient temperature, with sizes mainly smaller than 1 μm. The composition of eraser leachates was identical to that of the corresponding bulk eraser, as confirmed by Fourier-transform infrared spectroscopy and pyrolysis. Migrated hydrophobic plasticizers may be used as indicators of particle release from erasers and pen grips. The potentiality of particle release was negatively correlated with the total plasticizer contents (r = -0.51; p < 0.05) for both erasers and pen grips. These findings indicated that particles directly released from school supplies and accessories could be a non-negligible source of human exposure to plasticizers.

Hydrophobicity-driven self-assembly of nanoplastics and silver nanoparticles for the detection of polystyrene microspheres using surface enhanced Raman spectroscopy

Microplastics (MPs) and Nanoplastics (NPs) accumulated in the environment have been identified as a major global issue due to their potential harm to wildlife. Current research in the detection of MPs is well established. However, the detection of NPs remains challenging. The aim of this paper is to investigate the detection of polystyrene (PS) NPs on a super-hydrophobic substrate using surface-enhanced Raman spectroscopy (SERS) technology after high-speed centrifugation of PS NPs and AgNPs. The hydrophobic substrate reduces the contact area of droplet, concentrating PS NPs and AgNPs on a small spot, which eliminates the random distribution of nano particles. The condensed PS NPs and AgNPs improve the SERS intensity, reproductivity and detection sensitivity. The results show that SERS measurement on a hydrophobic substrate could significantly improve the detection sensitivity of PS NPs, with the detection limits of PS NPs as low as 0.5 mg/L (500 nm PS NPs) and 1 mg/L (100 nm PS NPs). The study provides an effective and rapid method for the detection of NPs at trace concentration, demonstrating more possibility for the future detection of trace NPs in the aquatic environment.

Desalination, Water Re-use, and Halophyte Cultivation in Salinized Regions: A Highly Productive Groundwater Treatment System

Groundwater salinization is a problem affecting access to water in many world regions. Though desalination by conventional reverse osmosis (RO) can upgrade groundwater quality for drinking, its disadvantages include unmanaged brine discharge and accelerated groundwater depletion. Here, we propose a new approach combining RO, forward osmosis (FO), and halophyte cultivation, in which FO optimally adjusts the concentration of the RO reject brine for irrigation of Salicornia or Sarcocornia. The FO also re-uses wastewater, thus, reducing groundwater extraction and the wastewater effluent volume. To suit different groundwater salinities in the range 1-8 g/L, three practical designs are proposed and analyzed. Results include specific groundwater consumption (SGC), specific energy consumption (SEC), wastewater volume reduction, peak RO pressure, permeate water quality, efficiency of water resource utilization, and halophyte yield. Compared to conventional brackish water RO, the results show superior performance in almost all aspects. For example, SGC is reduced from 1.25 to 0.9 m3 per m3 of drinking water output and SEC is reduced from 0.79 to 0.70 kW h/m3 by a FO-RO-FO system treating groundwater of salinity 8 g/L. This system can produce 1.1 m3 of high-quality drinking water and up to 4.9 kg of edible halophyte per m3 of groundwater withdrawn.

Extraction of Common Small Microplastics and Nanoplastics Embedded in Environmental Solid Matrices by Tetramethylammonium Hydroxide Digestion and Dichloromethane Dissolution for Py-GC-MS Determination

Determination of microplastics and nanoplastics (MNPs), especially small MPs and NPs (<150 μm), in solid environmental matrices is a challenging task due to the formation of stable aggregates between MNPs and natural colloids. Herein, a novel method for extracting small MPs and NPs embedded in soils/sediments/sludges has been developed by combining tetramethylammonium hydroxide (TMAH) digestion with dichloromethane (DCM) dissolution. The solid samples were digested with TMAH, and the collected precipitate was washed with anhydrous ethanol to eliminate the natural organic matter. Then, the MNPs in precipitate were extracted by dissolving in DCM under ultrasonic conditions. Under the optimized digestion and extraction conditions, the factors including sizes and concentrations of MNPs showed insignificant effects on the extraction process. The feasibility of this sample preparation method was verified by the satisfactory spiked recoveries (79.6-91.4%) of polystyrene, polyethylene, polypropylene, poly(methyl methacrylate), polyvinyl chloride, and polyethylene terephthalate MNPs in soil/sediment/sludge samples. The proposed sample preparation method was coupled with pyrolysis gas chromatography-mass spectrometry to determine trace small MPs and NPs with a relatively low detection limit of 2.3-29.2 μg/g. Notably, commonly used MNPs were successfully detected at levels of 4.6-51.4 μg/g in 6 soil/sediment/sludge samples. This proposed method is promising for evaluating small solid-embedded MNP pollution.

Trade-off of abiotic stress response in floating macrophytes as affected by nanoplastic enrichment

Nanoparticles have been found in large-scale environmental media in recent years, causing toxic effects in various organisms and even humans through food chain transmission. The ecotoxicological impact of microplastics on specific organisms is currently receiving much attention. However, relatively little research to date has examined the mechanisms through which nanoplastic residue may exert an interference effect on floating macrophytes in constructed wetlands. In our study, the aquatic plant Eichhornia crassipes was subjected to 100 nm polystyrene nanoplastics at concentrations of 0.1, 1 and 10 mg L^-1 after 28 days of exposure. E. crassipes can decrease the concentration of nanoplastics in water by 61.42∼90.81% through phytostabilization. The abiotic stress of nanoplastics on the phenotypic plasticity (morphological and photosynthetic properties and antioxidant systems as well as molecular metabolism) of E. crassipes was assessed. The presence of nanoplastics reduced the biomass (10.66%∼22.05%), and the functional organ (petiole) diameters of E. crassipes decreased by 7.38%. The photosynthetic efficiency was determined, showing that the photosynthetic systems of E. crassipes are very sensitive to stress by nanoplastics at a concentration of 10 mg L^-1. Oxidative stress and imbalance of antioxidant systems in functional organs are associated with multiple pressure modes from nanoplastic concentrations. The catalase contents of roots increased by 151.19% in the 10 mg L^-1 treatment groups compared with the control group. Moreover, 10 mg L^-1 concentrations of the nanoplastic pollutant interfere with purine and lysine metabolism in the root system. The hypoxanthine content was reduced by 6.58∼8.32% under exposure to different concentrations of nanoplastics. In the pentose phosphate pathway, the phosphoric acid content was decreased by 32.70% at 10 mg L^-1 PS-NPs. In the pentose phosphate pathway, the phosphoric acid content was decreased by 32.70% at 10 mg L^-1 PS-NPs. Nanoplastics disturb the efficiency of water purification by floating macrophytes, which reduces the chemical oxygen demand (COD) removal efficiency (from 73% to 31.33%) due to various abiotic stresses. This study provided important information for further clarifying the impact of nanoplastics on the stress response of floating macrophytes.

Occurrence and size distribution study of microplastics in household water from different cities in continental Spain and the Canary Islands

The purpose of this study was to investigate the occurrence of microplastics (MPs) in drinking water in Spain by comparing tap water from different locations using common sampling and identification procedures. We sampled tap water from 24 points in 8 different locations from continental Spain and the Canary Islands by means of 25 μm opening size steel filters coupled to household connections. All particles were measured and spectroscopically characterized including not only MPs but also particles consisting of natural materials with evidence of industrial processing, such as dyed natural fibres, referred insofar as artificial particles (APs). The average concentration of MPs was 12.5 ± 4.9 MPs/m³ and that of anthropogenic particles 32.2 ± 12.5 APs/m³. The main synthetic polymers detected were polyamide, polyester, and polypropylene, with lower counts of other polymers including the biopolymer poly(lactic acid). Particle size and mass distributions were parameterized by means of power law distributions, which allowed performing estimations of the concentration of smaller particles provided the same scaling parameter of the power law applies. The calculated total mass concentration of the identified MPs was 45.5 ng/L. The observed size distribution of MPs allowed an estimation for the concentration of nanoplastics (< 1 µm) well below the ng/L range; higher concentrations are not consistent with scale invariant fractal fragmentation. Our findings showed that MPs in the drinking water sampled in this work do not represent a significant way of exposure to MPs and would probably pose a negligible risk for human health.

Effects of petroleum-based and biopolymer-based nanoplastics on aquatic organisms: A case study with mechanically degraded pristine polymers

Mismanaged plastic litter submitted to environmental conditions may breakdown into smaller fragments, eventually reaching nano-scale particles (nanoplastics, NPLs). In this study, pristine beads of four different types of polymers, three oil-based (polypropylene, PP; polystyrene, PS; and low-density polyethylene, LDPE) and one bio-based (polylactic acid, PLA) were mechanically broken down to obtain more environmentally realistic NPLs and its toxicity to two freshwater secondary consumers was assessed. Thus, effects on the cnidarian Hydra viridissima (mortality, morphology, regeneration ability, and feeding behavior) and the fish Danio rerio (mortality, morphological alterations, and swimming behavior) were tested at NPLs concentrations in the 0.001 to 100 mg/L range. Mortality and several morphological alterations were observed on hydras exposed to 10 and 100 mg/L PP and 100 mg/L LDPE, whilst regeneration capacity was overall accelerated. The locomotory activity of D. rerio larvae was affected by NPLs (decreased swimming time, distance or turning frequency) at environmentally realistic concentrations (as low as 0.001 mg/L). Overall, petroleum- and bio-based NPLs elicited pernicious effects on tested model organisms, especially PP, LDPE and PLA. Data allowed the estimation of NPLs effective concentrations and showed that biopolymers may also induce relevant toxic effects.

Efficiency and mechanism of micro- and nano-plastic removal with polymeric Al-Fe bimetallic coagulants: Role of Fe addition

The occurrence of microplastics (MPs) and even nanoplastics (NPs) in tap water has raised considerable attention. As a pre-treatment and also the most important process in drinking water treatment plants, coagulation has been widely studied to remove MPs, but few studies focused on the removal pattern and mechanism of NPs, especially no study paid attention to the coagulation enhanced by prehydrolysed Al-Fe bimetallic coagulants. Therefore, in this study, polymeric species and coagulation behaviour of MPs and NPs influenced by Fe fraction in polymeric Al-Fe coagulants were investigated. Special attention was given to the residual Al and the floc formation mechanism. The results showed that asynchronous hydrolysis of Al and Fe sharply decreases the polymeric species in coagulants and that the increase of Fe proportion changes the sulfate sedimentation morphology from dendritic to layered structures. Fe weakened the electrostatic neutralization effect and inhibited the removal of NPs but enhanced that of MPs. Compared with monomeric coagulants, the residual Al decreased by 17.4 % and 53.2 % in the MP and NP systems (p < 0.01), respectively. With no new bonds detected in flocs, the interaction between micro/nanoplastics and Al/Fe was merely electrostatic adsorption. According to the mechanism analysis, sweep flocculation and electrostatic neutralization were the dominant removal pathways of MPs and NPs, respectively. This work provides a better coagulant option for removing micro/nanoplastics and minimizing Al residue, which has promising potential for application in water purification.

Cocktail effects of emerging contaminants on zebrafish: Nanoplastics and the pharmaceutical diphenhydramine

Nanoplastics (NPLs) became ubiquitous in the environment, from the air we breathe to the food we eat. One of the main concerns about the NPLs risks is their role as carrier of other environmental contaminants, potentially increasing their uptake, bioaccumulation and toxicity to the organisms. Therefore, the main aim of this study was to understand how the presence of polystyrene NPLs (∅ 44 nm) will influence the toxicity (synergism, additivity or antagonism) of the antihistamine diphenhydramine (DPH), towards zebrafish (Danio rerio) embryos, when in dual mixtures. After 96 hours (h) exposure, at the organismal level, NPLs (0.015 or 1.5 mg/L) + DPH (10 mg/L) induced embryo mortality (90%) and malformations (100%) and decreased hatching (80%) and heartbeat rates (60%). After 120 h exposure, NPLs (0.015 or 1.5 mg/L) + DPH (0.01 mg/L) decreased larvae swimming distance (30-40%). At the biochemical level, increased glutathione S-transferases (55-122%) and cholinesterase (182-343%) activities were found after 96 h exposure to NPLs (0.015 or 1.5 mg/L) + DPH (0.01 mg/L). However, catalase (CAT) activity remained similar to the control group in the mixtures, inhibiting the effects detected after the exposure to 1.5 mg/L NPLs alone (increased 230% of CAT activity). In general, the effects of dual combination - NPLs + DPH (even at concentrations as low as 10 μg/L of DPH) - were more harmful than the correspondent individual exposures, showing the synergistic interactions of the dual mixture and answering to the main question of this work. The obtained results, namely the altered toxicity patterns of NPLs + DPH compared with the individual exposures, show the importance of an environmental risk assessment considering NPLs as a co-contaminant due to the potential NPLs role as vector for other contaminants.

Tracking nanoplastics in freshwater microcosms and their impacts to aquatic organisms

In this work, we used palladium-doped polystyrene NPLs (PS-NPLs with a primary size of 286 ± 4 nm) with an irregular surface morphology which allowed for particle tracking and evaluation of their toxicity on two primary producers (cyanobacterium, Anabaena sp. PCC7120 and green algae, Chlamydomonas reinhardtii) and one primary consumer (crustacean, Daphnia magna). the concentration range for Anabaena and C. reinhardtii was from 0.01 to 1000 mg/L and for D. magna, the range was from 7.5 to 120 mg/L.EC_50 s ranged from 49 mg NPLs/L for D. magna (48hEC_50 s) to 248 mg NPLs/L (72hEC_50 s for C. reinhardtii). PS-NPLs induced dose-dependent reactive oxygen species overproduction, membrane damage and metabolic alterations. To shed light on the environmental fate of PS-NPLs, the short-term distribution of PS-NPLs under static (using lake water and sediments) and stirring (using river water and sediments) conditions was studied at laboratory scale. The results showed that most NPLs remained in the water column over the course of 48 h. The maximum percentage of settled particles (∼ 30 %) was found under stirring conditions in comparison with the ∼ 10 % observed under static ones. Natural organic matter increased the stability of the NPLs under colloidal state while organisms favored their settlement. This study expands the current knowledge of the biological effects and fate of NPLs in freshwater environments.