Polypropylene Microplastics Research Articles

Leaching of triphenyl phosphate and tri-n-butyl phosphate from polystyrene microplastics: influence of plastic properties and simulated digestive fluids.

Microplastics have gained considerable attention as a growing environmental problem owing to their potential to serve as vectors for harmful chemicals. However, the leaching of these chemicals from microplastics is unclear. In this study, we investigated the leaching of two organophosphate flame retardants, triphenyl phosphate and tri-n-butyl phosphate, from polystyrene microplastics in simulated digestive fluids and water, and polypropylene microplastics were simultaneously used for comparison with polystyrene microplastics. The results indicated that the first-order kinetic model best explained the leaching process, suggesting that leaching was related to the release of organophosphate flame retardant molecules at the polymer surface. Additionally, the size and crystalline state of the microplastics had a significant effect on the leaching, whereas organophosphate flame retardant content had a minimal impact. Simulated digestive fluids facilitated the leaching to a different extent, and under these influencing conditions, leaching percentages from polystyrene microplastics did not exceed 0.51%. Therefore, leaching from PS microplastics may not be an important source of OPFRs in the environment. However, the release of organophosphate flame retardants can be considerably enhanced with the breakdown of polystyrene microplastics to polystyrene nanoplastics.

Combined approaches for detecting polypropylene microplastics in crop plants

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

Mechanistic insight into the role of typical microplastics in chlorination disinfection: Precursors and adsorbents of both MP-DOM and DBPs

Microplastics (MPs) in drinking water are predominantly < 10 µm. The leaching of MPs derived dissolved organic matters (MP-DOM) from 5 µm polypropylene MPs (PP-MPs) and polystyrene MPs (PS-MPs) and the formation of MP-DOM derived disinfection byproducts during chlorination disinfection were first investigated. Comparably, PS-MPs are more vulnerable to chlorination and the primary attacks are on para C in aromatic side-chains via electrophilic Cl-substitution and oxidation by two-electron transfer. The O/C and Cl/C ratio of polystyrene MPs was linear and exponential versus initial available Cl2 concentrations, respectively. The significant PS-DOM leaching was observed with initial available Cl2 of 4.0 mg/L (USEPA recommended upper dose). As the initial available Cl2 concentration increased to 8.0 mg/L, the adsorption of chloro-phenolic-components of 200 Daltons in PS-DOM by 5 µm PS-MPs was observed for the first time. Trichloromethane (TCM) was identified as the dominant disinfection byproduct with a formation potential of 60.3 ± 7.8 and 73.7 ± 9.8 μg/mg for PS-DOM and PP-DOM, respectively. The derived TCM could adsorb onto PS-MPs followed the pseudo-second-order kinetic and Langmuir isotherm models. Extreme chlorination could reduce the maximal adsorption capacity of TCM on 5 µm PS-MPs from 196.68 ± 48.66 to 146.02 ± 32.98 μg/g. Thus, PS-MPs act as precursors and carriers of TCM in chlorination.

First report on the detection of microplastics from the feathers of black-tailed gulls in South Korea

In this study, microplastics, including polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), and polystyrene (PS), adhering to the feathers of all tracked black-tailed gull individuals were studied. PE was detected in the highest number of feathers (n = 26, 35.6 %), followed by PP (n = 21, 28.8 %), PET and other microplastics (n = 16, 21.9 %), and PS (n = 10, 13.7 %). Furthermore, plastic particles of size 50–100 μm were the most common (n = 33, 45.1 %), followed by ≤50 (n = 21, 28.8 %), 100–150 (n = 11, 15.1 %), ≥200 (n = 7, 9.6 %), and 150–200 μm (n = 1, 1.4 %). Microplastic levels did not differ considerably between the Dokdo and Ulleungdo populations. As black-tailed gulls spend >95 % of their time in coastal areas, coastal pollution caused by oil spills and increasing microplastic levels could lead to physical problems, such as the adherence of oil and microplastics onto feathers.

Impact of size and shape in the transport of microplastics by a springtail species

ABSTRACT We investigated the impact of shape (beads, fibers and films) and size (0.5 and 1.0 mm; diameter or length) of polypropylene microplastics (MPs) on MP transport by a springtail species, Folsomia candida in dishes. The percentages of transported beads, fibers and films were 9.10%, 3.18% and 4.10%, respectively. For 1.0 mm MPs, the number of MPs transported was significantly higher for beads than for fibers and films, whereas, for 0.5 mm MPs, the number was significantly higher for fibers than for the other MP types. Additionally, the number of MPs transported was higher for small fibers than for large fibers, whereas it was higher for large beads than for small beads. These results indicate that the effects of F. candida on MP migration depend on MP shape and size. Our results highlight the importance of considering the physical characteristics of MPs while elucidating the interaction between soil fauna and MPs.

In situ effects of microplastics on the decomposition of aquatic macrophyte litter in eutrophic shallow lake sediments, China

The toxicity of microplastics (MPs) to aquatic organisms has been extensively studied recently. However, few studies have investigated the effects of MPs in sediments on aquatic ecosystem functioning. In the present study, we conducted an in situ experiment to explore the concentration-dependent effects (0.025%, 0.25%, 2.5%) and size-dependent effects (150–300 μm and 500–1000 μm) of polypropylene microplastics (PP MPs) on Vallisneria natans litter decomposition dynamics, in particular, the process associated with macroinvertebrates, microorganisms, as well as microalgae and/or cyanobacteria. The results showed that exposure to high concentrations and large sizes of PP MPs can accelerate leaf litter biomass loss and nutrition release. Moreover, microbial respiration, microalgal and/or cyanobacteria chlorophyll-a were also significantly affected by PP MPs. However, PP MPs have no effect on the abundance of associated macroinvertebrate during the experiment, despite the collection of five macroinvertebrate taxa from two functional feeding groups (i.e., collectors and scrapers). Therefore, our experiment demonstrated that PP MPs may enhance leaf litter decomposition through effected microbial metabolic activity, microalgal and/or cyanobacteria biomass in the sedimentary lake. Overall, our findings highlight that PP MPs have the potential to interfere with the basic ecological functions such as plant litter decomposition in aquatic environments.

Sub-micron microplastics affect nitrogen cycling by altering microbial abundance and activities in a soil-legume system

Recently, the environmental and agricultural impact of plastic waste has attracted considerable attention. Here, we investigated the impact of sub-micron polyethylene (PE) and polypropylene (PP) microplastics (MPs) on nitrogen cycling, with emphasis on bacterial abundance and diversity in a soil-soybean (Glycine max) system. Exposure to soil containing MPs (50 and 500 mg kg−1) did not affect soybean growth, but significantly increased plant nitrogen uptake, which was confirmed by increased activities of nitrogenase in the soil and glutamine synthetase in soybean root. Additionally, there was an increase in 16S gene copy number and carbon and nitrogen substrate utilization, indicating increased abundance and activity of rhizosphere microbial communities. Moreover, MP contamination affected the taxonomic profile of rhizosphere bacteria, especially the abundance of symbiotic and free-living bacteria involved in nitrogen cycling. Furthermore, qPCR analysis of nitrogen-related genes and Kyoto Encyclopedia of Genes and Genomes analysis of 16S rRNA gene sequencing data revealed an increased abundance of functional genes associated with nitrogen fixation and nitrification. However, the concentration and polymer type of MPs did not have a significant impact in our system. Overall, these results provide insights into the interactions between MPs and rhizosphere bacterial communities in the soil-legume system.

Different microbial assemblage colonized on microplastics and clay particles in aerobic sludge treatment

In this study, a combination of property analysis and high–throughput sequencing was used to investigate the microbial colonization ability and their community structures and functions in polypropylene microplastics (PPMPs), polystyrene microplastics (PSMPs) and montmorillonite (MMT), respectively as the representatives of artificial and natural substrates in aerobic sludge treatment. After 45 d of incubation, the surface properties of substrates were altered with the increased oxygen functional groups and surface roughness, indicating microbial settlement. Moreover, MPs had different microbial structures from that of MMT, and PSMPs exhibited higher microbial diversity and abundance than PPMPs and MMT. Also, these substrates changed the inherent ecological niche in sludge. Especially, the abundance of some pathogens (e.g., Pseudomonas, Klebsiella and Flavobacterium) was increased in MPs, and the disease risk of Kyoto Encyclopedia of Genes and Genomes metabolic pathway (e.g., Infectious diseases: Bacterial, Infectious diseases: Parasitic and Immune diseases) was higher. Also, the presence of MPs inhibited the decomposition of organic matter including soluble chemical oxygen demand and protein compared to natural substrates. The findings revealed the crucial vector role of MPs for microbes and the effect on aerobic sludge treatment, highlighting the necessity of MP removal in sludge.

Biochemical effects of polypropylene microplastics on red tilapia (Oreochromis niloticus) after individual and combined exposure with boron

Toxicity of single pollutants or microplastics (MPs) on organisms have been widely reported. However, their combined toxicity with boron has not been investigated. This study examined effects of individual polypropylene microplastics (PP-MPs) or mixed PP-MPs and boron on biochemical biomarkers in red tilapia (Oreochromis niloticus). O. niloticus were exposed for 21 days to pristine PP-MPs concentrations (10 or 100 mg/L), concentrations of boron alone (30 or 70 mg/L), and identical concentrations of boron in the presence of PP-MPs in laboratory aquaria. Results showed that higher concentrations of individual PP-MPs lead to significantly decreased acetylcholinesterase (AChE) in the brain and malondialdehyde (MDA) in fish liver. In contrast, superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione (GSH) were significantly increased in fish liver exposed to higher concentrations of individual PP-MPs. Mixed concentrations of boron and PP-MPs significantly decreased AChE, GSH, and MDA activity in fish. In contrast, mixed concentrations of boron and PP-MPs significantly increased CAT, SOD, and GPx activity in fish. Findings highlight that PP-MPs may increase adverse effects of boron in O. niloticus. We present evidence that individual MPs in long-term exposure have a significant impact on biomarker responses in O. niloticus.

Long-term aged fibrous polypropylene microplastics promotes nitrous oxide, carbon dioxide, and methane emissions from a coastal wetland soil

Microplastics (MPs) has been suggested that it can greatly affect soil greenhouse gases (GHGs) emissions via altering soil physical, chemical, and biological properties. However, the difference in GHGs emissions, especially for those from coastal wetland soils, between varied aged MPs was rarely explored and the underlying mechanisms of GHGs emissions affected by the aged MPs were poorly understood. Therefore, the implications of fibrous polypropylene MPs (FPP-MPs) exposure on N2O, CO2, and CH4 emissions were examined by a 60-day soil incubation experiment. Compared with the control, the additions of un-aged FPP-MPs with both two rates (0.2 and 2 %) and aged FPP-MPs with a low rate (0.2 %) showed an insignificant effect on N2O emission, while the aged FPP-MPs added with a high rate (2 %) resulted in a remarkably increase in N2O emission, especially for those of the 30-day-aged FPP-MPs. A significant increase in CO2 emission was only observed in the 30-day-aged FPP-MPs treatments, compared with the control, and a higher addition rate produced a higher increase of CO2 emission. Regarding CH4 emission, it was significantly increased by adding aged FPP-MPs, and a longer aging period or/and a higher addition rate generated a higher degree of promotion of CH4 emission. However, compared with the CO2 emission, the quantity of CH4 emission was extremely low. These increased GHGs emissions can be ascribed to the improvements in soil physical structure and other chemical properties (e.g., pH and contents of soil organic matter and dissolved organic carbon) and enhancements in the abundances of denitrification- and carbon mineralization-related microorganisms. Overall, our results highlight the risk of elevated GHGs emissions from the soil polluted with 30-day-aged FPP-MPs, which should not be ignored as long-term aged FPP-MPs continue to increase in coastal wetland soils.

Early clues and molecular mechanism involved in neurodegenerative diseases induced in immature mice by combined exposure to polypropylene microplastics and DEHP

Studies have shown that exposure to either microplastics (MPs) or di-(2-ethylhexyl) phthalic acid (DEHP) alone can cause neurotoxicity in animals, but it remains uncertain whether and to what extent co-exposure to these two substances, which often occur together in reality, can also induce neurotoxicity. This study aimed to investigate the neurotoxicity and molecular mechanisms of combined exposure to DEHP and polypropylene microplastics (synthetic PP-MPs were used), the microplastics most commonly encountered by young children, in immature mice. The results showed that exposure to PP-MPs and/or DEHP did cause neurotoxic effects in immature mice, including induction of neurocognitive and memory deficits, damage to the CA3 region of the hippocampus, increased oxidative stress, and decreased AChE activity in the brain. The severity of the neurotoxicity increased with increasing concentrations of PP-MPs, combined exposure to PP-MPs and DEHP exhibited additive or synergistic effects. Transcriptomic analyses revealed that the PP-MPs and/or DEHP exposure altered the expression profiles of gene clusters involved in the stress response, and in protein processing in endoplasmic reticulum. Quantitative analyses further indicated that PP-MPs and/or DEHP exposure inhibited the activity of the heat shock response mediated by heat shock transcription factor 1, while chronically activated the unfolded protein response, consequently inducing neurotoxicity through neuronal apoptosis and neuroinflammation in the immature mice. As a pioneer study to highlight the neurotoxicity induced by combined exposure to PP-MPs and DEHP in immature mice, this research provides new insights into mitigating the health risks of PP-MPs and DEHP exposure in young children.

Analyzing the impacts of cadmium alone and in co-existence with polypropylene microplastics on wheat growth.

Heavy metals typically coexist with microplastics (MPs) in terrestrial ecosystems. Yet, little is known about how the co-existence of heavy metals and MPs affect crops. Therefore, this study aimed to evaluate the impact of cadmium (Cd; 40 mg/L) alone and its co-existence with polypropylene (PP)-MPs (50 and 100 µm) on seed germination, root and shoot growth, seedling dry weight (DW), and antioxidant enzyme activities of wheat. The study demonstrated that the germination rate of wheat did not vary significantly across treatment groups. Yet, the inhibitory impact on wheat seed germination was strengthened under the co-existence of Cd and PP-MPs, as the effect of a single treatment on seed germination was non-significant. The germination index and mean germination time of wheat seeds were not affected by single or combined toxicity of Cd and PP-MPs. In contrast, Cd and PP-MPs showed synergistic effects on germination energy. Wheat root and shoot length were impeded by Cd alone and in combination with PP-MPs treatments. The DW of wheat seedlings showed significant change across treatment groups until the third day, but on the seventh day, marginal differences were observed. For example, on third day, the DW of the Cd treatment group increased by 6.9% compared to CK, whereas the DW of the 100 µm PP-MPs+Cd treatment group decreased by 8.4% compared to CK. The co-occurrence of Cd and PP-MPs indicated that 50 μm PP-MPs+Cd had an antagonistic impact on wheat seedling growth, whereas 100 μm PP-MPs+Cd had a synergistic impact due to the larger size of PP-MPs. The antioxidant enzyme system of wheat seeds and seedlings increased under single Cd pollution, while the activities of superoxide dismutase, catalase, and peroxidase were decreased under combined pollution. Our study found that Cd adversely affects wheat germination and growth, while the co-existence of Cd and PP-MPs have antagonistic and synergistic effects depending on the size of the PP-MPs.

DOSE DEPENDENT EFFECTS OF TWO POLYMERIC MATERIALS AND SIMILARITIES WITH CERTAIN DRUGS

Polymeric materials became of crucial interest in the research area over the recent years due to worldwide production increase of these materials not always being followed by knowledge of their possible detrimental effects. Therefore, in the present study we analyzed the different effects of polymeric materials at various exposure times. Our results focused on some general effects in terms of anxiety and swimming performance over 120h of exposure and multiple repeated doses of both Polyethylene and Polypropylene microplastics. Polyethylene showed an anxiogenic potential, while Polypropylene exhibited an anxiolytic potential at the first two doses. In terms of swimming performance, an increase of specific parameters was observed throughout the repeated doses in the case of Polyethylene, whereas in the case of Polypropylene they decrease. These results were compared with those from the specialized existing literature on the effects of some of the most common hallucinogenic and psychoactive substances. Our results highlight that the mechanism of action of the aforementioned materials is different and show toxic effects from the first dose. Polyethylene has a similar outcome to the one in the case of some substances, especially hallucinogenic, such as LSD, mescaline, MDMA, phencyclidine, and nicotine. On the other hand, polypropylene has a similar effect to psychoactive drugs, cannabidiol, tetrahydrocannabinol, but also MDMA at certain doses. Bases on these observations, further studies should be conducted on the similarities of the detrimental effects.

Deleterious Effects of Polypropylene Microplastic Ingestion in Nile Tilapia (Oreochromis niloticus).

The effect of daily ingestion of polypropylene microplastic on the health of tilapia, Oreochromis niloticus, was evaluated. 60 fish (± 200g) were placed in 6 aquariums (n = 10, 100L each), constituting the following treatments: Control (without the addition of polymer), fed with 100 and 500µg of polypropylene/kg of body weight (b.w.), respectively. After 30 days of feeding, the animals were submitted to blood collection for hemogram and biochemical study and later euthanized for gut microbiological analysis, somatic index of liver, spleen, heart, kidney, stomach, and intestine. In the serum biochemical study, an increase in cholesterol and serum Aspartate Aminotransferase (AST) activity levels was observed in animals treated with 500µg of polypropylene. Tilapia-fed polypropylene in the diet showed an increase in thrombocyte and total leukocyte counts, marked by a significant increase in the number of circulating lymphocytes. The results of the somatic study revealed a significant increase in the stomach, liver, and heart of tilapia fed with the polymer. Increase in the number of Gram-negative microorganisms and decrease in mesophilic aerobic microorganisms were observed in the gut of fish exposed to the polymer, including a dose-response effect was observed for these analyses. Therefore, tilapias fed daily with diets containing polypropylene for 30 consecutive days showed deleterious effects, resulting in systemic inflammatory disturbs by altering liver functions, leukocyte profile, and organ morphometry, as well as changes in the intestinal microbiota. Such results demonstrate the impairment of fish health, highlighting the need for further studies that evaluate the impact of microplastics on aquatic organisms.

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

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

Impacts of polypropylene microplastics on lipid profiles of mouse liver uncovered by lipidomics analysis and Raman spectroscopy

Microplastics (MPs) are emerging contaminants, and there are only limited studies reporting the impacts of some MPs on liver lipid metabolism in animals. In this study, we investigated the accumulation of polypropylene-MPs in mouse liver and unraveled the change in lipid metabolic profiles by both lipidomics and Raman spectroscopy. Polypropylene-MP exposure did not cause obvious health symptoms, but hematoxylin-eosin staining showed pathological changes that polypropylene-MPs induced lipid droplet accumulation in liver. Lipidomics results showed a significant change in lipid metabolic profiles and the most influenced categories were triglycerides, fatty acids, free fatty acids and lysophosphatidylcholine, implying the effects of polypropylene-MPs on the hemostasis of lipid droplet biogenesis and catabolism. Most altered lipids contained unsaturated bonds and polyunsaturated phospholipids, possibly affecting the fluidity and curvature of membrane surfaces. Raman spectroscopy confirmed that the major spectral alterations of liver tissues were related to lipids, evidencing the altered lipid metabolism and cell membrane components in the presence of polypropylene-MPs. Our findings firstly disclosed the impacts of polypropylene-MPs on lipid metabolisms in mouse liver and hinted at their detrimental disturbance on membrane properties, cellular lipid storage and oxidation regulation, helping our deeper understanding on the toxicities and corresponding risks of polypropylene-MPs to mammals.

Mechanistic vision on polypropylene microplastics degradation by solar radiation using TiO2 nanoparticle as photocatalyst

Microplastics are emerging contaminants owing to their occurrence and distribution in everywhere the ecosystem and leading to major environmental problems. Management methods are more suitable for larger-sized plastics. Here, the current study elucidates that, TiO2 photocatalyst under sunlight irradiation actively mitigates polypropylene microplastics (pH 3, 50 h) in an aqueous medium. End of post-photocatalytic experiments, the weight loss percentage of microplastics was 50.5 ± 0.5%. Fourier transforms infrared (FTIR) and nuclear magnetic resonance spectroscopy (1H NMR) spectroscopy results revealed the formation of peroxide and hydroperoxide ions, carbonyl, keto and ester groups at the end of the post-degradation process. Ultraviolet–Visible Diffuse Reflectance spectroscopic (UV – DRS) results showed variation in the optical absorbance of polypropylene microplastics peak values at 219 and 253 nm. Increased the weight percentage of oxygen level due to the oxidation of functional groups and decreased the weight percentage of carbon content in electron dispersive spectroscopy (EDS), probably owing to breakdown of long-chain polypropylene microplastics. In addition, scanning electron microscopy (SEM) microscopic analysis showed the surface having holes, cavities, and cracks on irritated polypropylene microplastics. The overall study and their mechanistic pathway strongly confirmed the formation of reactive oxygen species (ROS) with help of the movement of electrons by photocatalyst under solar irradiation which aids the degradation of polypropylene microplastics.

Different microplastics in anaerobic paddy soils: Altering methane emissions by influencing organic matter composition and microbial metabolic pathways

Microplastics are widespread in farmland and threaten soil ecology. However, how different microplastics affect methane emission in paddy soil are still unclear. To address this knowledge gap, three typical microplastics, polyethylene, polypropylene, and polyvinyl chloride were added to paddy soil with different doses (0.01%, 0.1%, and 1%), and a 50-day incubation experiment was conducted. Compared with polyethylene and polypropylene microplastics, 1% of polyvinyl chloride microplastic resulted in the highest increase in methane production. According to the integrated liquid phase analysis, all three microplastics contributed to the accumulation of humus in the soil solution. Differential microbial taxa analysis indicated that some denitrifying bacteria such as Gemmatimonadetes and Omnitrophicaeota were significantly enriched in 1% polyethylene and polypropylene microplastics groups on day 30, and Rice Cluster I methanogens archaea were enriched specially in the 1% polyvinyl chloride microplastic group. The predicted soil metabolic functions suggested that polyethylene and polyvinyl chloride microplastics enhanced oxidative phosphorylation and amino acid reduction pathways. Macromolecular humus induced by microplastics may play a critical role in the dynamic equilibrium of anaerobic systems in paddy soils. These findings highlighted the threat of microplastics in agricultural fields greenhouse gas emissions. The identified quinone reductive metabolic pathways may provide potential strategies to reduce methane emissions.

Matrix Matters: novel insights for the extraction, preparation, and quantitation of microplastics in a freshwater mesocosm study

The extraction and characterization of secondary microplastics, those formed through subjection to the environment, must continuously improve in accuracy and applicability in order to generate robust microplastics exposure and risk assessments. Currently, there is a dearth of reliable extraction and quantitation methods for solid microplastic particles in sediment with chemical specificity. Herein we present advances in methodologies to extract and quantify microplastic particles from sediment, utilizing an outdoor mesocosm to model a freshwater coastal environment. Model secondary microplastics of crosslinked polyurethane (PU) were studied in comparison to model secondary polypropylene (PP) microplastics. Techniques to characterize particles in sediment included pyrolysis gas chromatography mass spectrometry (py GC/MS), stereoscope microscopy, and scanning electron microscopy. To complement particle analysis, plastic-associated leachable molecules were extracted from sediment and analyzed semi-quantitatively by high performance liquid chromatography with high-resolution mass spectrometry (HPLC/HR-MS). After developing and optimizing extraction and analytical methods we quantitated PU microparticles by count and weight and discovered that model PU particles fell from the water column into the sediment over the course of a year, while no PP particles were located in sediment samples. In addition, target small molecules associated with the crosslinked PU were identified in sediment by HPLC/HR-MS but leachable molecules associated with polypropylene could not be identified in sediment samples. We share the new py GC/MS method to quantify highly crosslinked PUs in complex environmental matrices containing both inorganic and organic components. In the process of generating robust extraction methods for microplastics in sediment, we discovered important considerations for the quantitation of microplastics by py GC/MS and the impacts of sample matrix on the quantitation of PU and PP specifically. We provide guidance for the preparation of microplastics from complex environmental matrices (e.g., sediment and soil) for analysis by py GC/MS.Graphical

Combined toxicity influence of polypropylene microplastics and di-2-ethylhexyl phthalate on physiological-biochemical characteristics of cucumber (Cucumis sativus L.)

Microplastics and di-2-ethylhexyl phthalate (DEHP) are prevalent and emerging pollutants in agro-ecosystem, raising concerns due to their widespread co-presence. Nevertheless, their combined toxicity on terrestrial plants remains largely unexplored. This study investigated the impact of polypropylene microplastics (MPs), DEHP, and their mixture on the physiological and biochemical characteristics of cucumber seedlings. The changes of membrane stability index (MSI), antioxidase activities, photosynthetic pigments and chlorophyll fluorescence in cucumber seedlings were assessed. The results demonstrated that MPs alone significantly inhibited MSI, photosynthetic pigments (Chl a, Chl b, and Chl a + b), Fm and qp of cucumber seedlings, and significantly promoted the carotene content and antioxidant enzyme activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) in cucumber seedlings. While DEHP alone significantly inhibited MSI and photosynthetic pigments of cucumber seedlings, and significantly promoted antioxidant enzyme activities in cucumber seedlings. Moreover, the combined toxicity of MPs and DEHP was found to be less pronounced than that of the single action of MPs and DEHP. The interaction between DEHP and MPs may contribute to the reduced toxicity. Abbott's modeling revealed that the combined toxicity systems were all antagonistic (RI < 1). Two-factor analysis and principal component analysis further confirmed that the treatment of MPs alone contributed the most to the toxicological effects of the physiological properties of cucumbers. In summary, this study highlighted the importance of understanding the combined effects of MPs and DEHP on plant physiology, providing insights for the development of effective treatments for emerging pollutants in agricultural ecosystems.