Small-sized Microplastics Research Articles

Microplastic pollution in Taihu Lake: Spatial distribution from the lake inlet to the lake centre and vertical stratification in the water column

The aim of this study was to analyse the distribution characteristics of microplastics in lakes, assess their potential impacts on ecosystems, and explore effective management and control strategies. Despite a wealth of research focused on lake water, the variations in microplastics with offshore distance and their vertical distribution within the water column are not well understood. Here, we investigated the freshwater continuum from the inlet of Taihu Lake to the centre, and vertically from the surface to the bottom water. The results revealed that the distribution of microplastics (<5 mm in size) exhibited a clear spatial gradient. The microplastic abundance at the lake entrance was 2.12 times greater than that at the centre, and on the lake surface, the microplastic abundance was 1.36–1.69 times higher than that estimated from the water column. Notably, the proportion of small-sized microplastics (<0.1 mm) in the bottom water was 1.72 times higher than that in the surface water. The main types of polymers identified were polyamide (PA) and polyvinyl chloride (PVC), and their main sources may be from clothes washing and industrial activities. The Monte Carlo simulation results indicated that the overall risk of microplastics in surface water was higher than that in the water column, and the contributions of PVC and polyurethane (PU) to the ecological risk were 90.10% and 9.57%, respectively. Therefore, PVC and PU should be the priority of microplastic pollution control. This study provides the first comprehensive evaluation of the spatial ecological risk of microplastics in Taihu Lake, which improves our understanding of the distribution and environmental risks of microplastics in lake systems.

Quantifying microplastics in sediments of Jinzhou Bay, China: Characterization and ecological risk with a focus on small sizes

Small-sized microplastics (MPs) pose greater ecological toxicity due to their larger surface area, which makes them more likely to act as carriers for other pollutants and to be ingested by aquatic organisms. However, traditional visual analysis often neglects small-sized MPs and their associated ecological risk. This study utilized Laser Direct Infrared (LDIR) spectroscopy and traditional visual analysis to examine MPs in 31 sediment samples from Jinzhou Bay, a typical semi-enclosed bay located at the economic center of Dalian, China. The results showed significant heterogeneity in MP distribution, with averages of 1192 and 2361 items/kg dry weight reported by visual analysis and LDIR spectroscopy, respectively. LDIR spectroscopy identified MPs as small as 10 μm, with the majority of MPs (89.21 %) within the 10–250 μm range, and a significant proportion (46.45 %) between 10 and 50 μm among them. However, visual analysis was limited to detecting MPs >50 μm, and significant portions were identified between 50 and 100 μm (49.36 %) and 100–250 μm (31.01 %), missing a substantial fraction of smaller MPs. The predominant polymers identified were polyamide (PA), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and acrylonitrile butadiene styrene (ABS). LDIR spectroscopy demonstrated a strong positive correlation between MP abundance and clay content, a relationship not observed with traditional visual analysis. The Potential Ecological Risk Index (PERI) indicated that over 87 % of sites posed an extremely high risk according to LDIR spectroscopy, compared to 51 % by traditional visual analysis. These discrepancy underscores the underestimation of ecological risks by traditional methods, particularly for small-sized MPs. High-risk polymers such as polyvinyl chloride (PVC), ABS, and polyurethane (PUR) significantly influenced PERI values. These findings highlight the critical need for precise identification and thorough risk assessment of small-sized MPs in environmental studies and offer insights for understanding of MP vertical migration in aquatic environments, particularly in the context of co-settlement with sediments.

Release Characteristics of Small-Sized Microplastics in Bottled Drinks Using Flow Cytometry Sorting and Nile Red Staining

Small-sized microplastics (MPs) pose concerns about potential risks to both the environment and human health. However, research on MP pollution is hampered by limitations in the detection techniques. Also, few studies have provided insight into the release of small-sized MPs from disposable polyethylene terephthalate (PET)-bottled drinks for outdoor usage. Thus, PET bottles’ potential to release small MPs sized 1–100 μm outdoors was studied in relation to physical and chemical parameters (temperature, sunlight irradiation, and drink characteristics) using flow cytometry and Nile Red dye. The results showed that temperatures below 80 °C had little effect on the release of MPs from PET bottles. Sunlight irradiation and alkalinity were prone to promote the generation of MPs, mostly 1–5 μm in size. Moreover, the combined impact test implied that two pairings—acidity with temperature and alkalinity with sunlight—positively affected MP release, with maximum releases of 21,622 ± 2477 particles/L and 31,081 ± 7173 particles/L, respectively. Based on the rapid quantification of small-sized MPs using flow cytometry after Nile Red selection, the results hereby presented will assist researchers in reducing MP release and aid them in the evaluation of MPs’ contamination of aquatic environments.

Preferential adsorption of medium molecular weight proteins in extracellular polymeric substance alleviates toxicity of small-sized microplastics to Skeletonema costatum

Extracellular polymeric substances (EPS) secreted by organisms tend to encapsulate microplastics (MPs), forming an EPS-corona that affects the fate of MPs in marine ecosystems. However, the impact of the EPS-corona on the biotoxicity of MPs to marine organisms remains poorly understood. Herein, the effect of the EPS-corona on the toxicity of polystyrene (PS) MPs of different sizes (0.1 and 1 µm) to Skeletonema costatum (S. costatum) was investigated. The preferential adsorption of medium molecule weight (∼55 kDa) proteins onto PS MPs mainly contributed to the EPS-corona formation, decreasing the surface charge negativity of small-sized PS MPs (0.1 µm) by 72.4 %. Nitrogen (N) and oxygen (O) moieties in polysaccharides and proteins were identified as the preferential adsorption sites in the EPS-PS MPs interaction. Density functional theory (DFT) calculations confirmed the nuclear magnetic resonance spectroscopy (NMR) results, revealing that the binding mode between EPS and PS MPs was mainly hydrogen bonding. In addition, EPS-corona increased the cell density of S. costatum by 35.5–36.0 % when exposed to small-sized PS MPs (0.1 µm, 25–50 mg/L). These findings provide new insights into how EPS-corona affects the environmental fate and ecological risks associated with micro- and nano-sized plastics in marine ecosystems.

Pilot-scale performance of gravity-driven ultra-high flux fabric membrane systems for removing small-sized microplastics in wastewater treatment plant effluents

The ubiquitous nature and environmental impacts of microplastic particles and fibers demand effective solutions to remove such micropollutants from sizable point sources, including wastewater treatment plants and road runoff facilities. While advanced methods, e.g., microfiltration and ultrafiltration, have shown high removal efficiencies of small-sized microplastics (<150 μm), the low flux encountered in these systems implies high operation costs and makes them less effective in high-capacity wastewater facilities. The issue presents new opportunities for developing cheap high-flux membrane systems, deployable in low-to high-income economies, to remove small-sized microplastic and nanoplastics in wastewater. Here, we report on developing an ultra-high flux gravity-driven fabric membrane system, assessed through a laboratory-scale filtration and large-scale performance in an actual wastewater treatment plant (WWTP). The method followed a carefully designed water sampling, pre-treatment protocol, and analytical measurements involving Fourier transform infrared (FTIR) spectroscopy and laser direct infrared (LDIR) imaging. The result shows that the ultra-high flux (permeance = 550,000 L/m2h⋅bar) fabric membrane system can effectively remove small-sized microplastics (10–300 μm) in the secondary effluent of an actual WWTP at high efficiency greater than 96 %. The pilot system demonstrated a continuous treatment capacity of 300,000 L/day through a 1 m2 surface area disc, with steady removal rates of microplastics. These findings demonstrate the practical, cheap, and sustainable removal of small-sized microplastics in wastewater treatment plants, and their potential value for other large-scale point sources, e.g., stormwater treatment facilities.

Temporal and spatial distribution of microplastics in green infrastructures: Rain gardens

Rain gardens, a type of green infrastructure (GI), have been recognized for mitigating flooding and improving water quality from minor storms by trapping stormwater pollutants. Yet, the capability of these systems to retain microplastics (MPs) from stormwater, especially in size <125 μm, remains inadequately understood. This study investigated the spatial and temporal distributions of MPs in three rain gardens located in Newark, New Jersey, USA. The rain gardens have been in operation for ∼7 years and located in different land uses: low-density residential (Site 1), commercial (Site 2), and high-density residential (Site 3). The sediment samples were collected during May 2022, August 2022, and February 2023 at various soil depths and horizontal distances of rain gardens. The MPs were quantified and characterized using Fourier transform infrared (FTIR) spectrometer and a Raman microscope. The overall mean concentration varied between sampling sites, with 469 ± 89.8 pkg−1 in Site 1, 604 ± 91.4 pkg−1 in Site 2, and 997 ± 64.3 pkg−1 in Site 3, with Polypropylene as the dominant polymer, followed by nylon and polyethylene. In the vertical direction, larger MPs (250 μm–5 mm) were effectively retained within the top 5 cm and their concentration declined exponentially with the increasing depths. Small-sized MPs (1–250 μm) were prevalent at deeper depths (≥ 10 cm), and no MPs were found below 15 cm. In the horizontal direction, the highest MP concentration was observed near the stormwater inlet, and the concentration decreased away from the inlet. Over the nine-month period, a notable increase in concentration was observed at all sites. These findings contribute valuable knowledge towards developing effective measures for retaining MPs from stormwater and monitoring GIs in urban environments.

Identification and Visualization of Polystyrene Microplastics/Nanoplastics in Flavored Yogurt by Raman Imaging.

The contamination of food by microplastics has garnered widespread attention, particularly concerning the health risks associated with small-sized microplastics. However, detecting these smaller microplastics in food poses challenges attributed to the complexity of food matrices and instrumental and method limitations. Here, we employed Raman imaging for visualization and identification of polystyrene particles synthesized in polymerization reactions, ranging from 400 to 2600 nm. We successfully developed a quantitative model of particle size and concentration for polystyrene, exhibiting excellent fit (R2 of 0.9946). We established procedures for spiked flavored yogurt using synthesized polystyrene, providing fresh insights into microplastic extraction efficiency. Recovery rates calculated from models validated the method's feasibility. In practical applications, the assessment of the size, type, shape, and quantity of microplastics in unspiked flavored yogurt was conducted. The most common polymers found were polystyrene, polypropylene, and polyethylene, with the smallest polystyrene sizes ranging from 1 to 10 μm. Additionally, we conducted exposure assessments of microplastics in branded flavored yogurt. This study established a foundation for developing a universal method to quantify microplastics in food, covering synthesis of standards, method development, validation, and application.

Size-selective attachment of polyvinyl chloride microplastics on iron oxides in aqueous environments

The interaction of microplastics (MPs) with mineral particles is a crucial process determining the fate of MPs in aquatic environments, but potential size-selective interaction of MPs with minerals is unknown. In this work, strong and multi-layered attachment of a mix of heterogeneously size of polyvinyl chloride (PVC) MPs was observed on all the four types of iron oxides, following an order of Fe3O4-i > Fe3O4-s > γ-Fe2O3 > Fe3O4-n. Electrostatic attraction dominated their strong attachment, while hydrogen bonding and halogen bonding also contributed to MPs-mineral interaction. Importantly, both attachment rates and capacities were more favorable for large-sized PVC MPs (> 1.0 μm) than small-sized MPs (0.6–1.0 μm), due to more available attachment sites and stronger electrostatic attraction. Large-sized MPs preferred to detach from iron oxides before small-sized MPs, confirming by configuration analysis. The attachment accelerated the sedimentation of PVC MPs, while a fraction (i.e., 26.7 %, PVC/iron oxide ratio at 0.2:1) of heteroaggregates floated at the air–water interface associated with bubbles. Natural organic matter decreased MPs-mineral interaction due to competitive adsorption, electrostatic repulsion, and steric hindrance, while the attachment was enhanced with increasing ionic strengths (0–200 mM). These findings contribute to a better understanding of the transport and fate of MPs in aquatic systems.

Abundance and characterization of microplastic pollution in the wildlife reserve, Ramsar site, recreational areas, and national park in northern Jakarta and Kepulauan Seribu, Indonesia

This is the first study to evaluate the presence and distribution of microplastics in sediments in the regions with a unique degree of complexity, such as wildlife reserve areas, a Ramsar site that connects directly to Greater Jakarta's mainland, recreational islands, and a marine national park. Microplastics of varying sizes and shapes are found in all places, with an increase trend in the abundance toward areas near to the epicenter of human activity. Comparatively to other marine protected areas, the amount of microplastics discovered is comparable; however, there is an upward trend. Season influences microplastic accumulation, with the dry season causing the greater accumulation. Small-sized microplastics and microplastics resulting from large plastic fragments were predominantly discovered. The properties of microplastics in the study region are dominated by polyethylene, polypropylene, polystyrene, polyvinyl chloride, and nylon. Additional in-depth research and waste reduction from all sources that involve all stakeholders are required to reduce the amount of contaminants entering the protected area.

Sequestration and export of microplastics in urban river sediments

In rivers, riverbeds are considered to have dual properties as a short-term sink and a source of further mobilization for microplastics. To better understand the sources, storage, and fate of microplastics in river systems, this study quantified the formation of microplastic hotspots in riverbeds and seasonal variations in microplastic inventories in riverbeds, especially for small-sized microplastics (<330 µm), with a fluorescence-based protocol. This study provides first-hand measured evidence for the sequestration of microplastics in the riverbed under low-flow conditions and its export from the riverbed under high-flow conditions. The results show that riverbeds in urban areas are still hotspots for microplastic pollution and that high inputs of urban microplastics control microplastic load in its downstream areas. Seasonal rainfall exported 34.86 % (equivalent to 4.34 × 1011 items/8.57 t) of microplastic pollution from the riverbed, and its removal capacity may be related to the rainfall intensity. Wider riverbeds are conducive to the formation of microplastic hotspots due to the flow slow down. Most importantly, rainfall-driven scouring of the riverbed can enhance the pollution of small-sized microplastics in the riverbed, especially the smallest-size microplastics (<100 µm). Therefore, this study not only contributes reliable information about the sequestration and export of microplastics in the riverbed, but also provides a possible mechanism to explain the lack of small-sized microplastics (<330 µm) in the ocean.

Vertical distribution and weathering characteristic of microplastics in soil profile of different land use types

After deposition on the topsoil, microplastics (MPs) may be vertically migrated to deeper soil layers over time or eventually enter the groundwater system, leading to more widespread environmental and ecological issues. However, the vertical distribution of MPs in natural soils are not yet fully understood. In this study, we collected soil profiles (0–100 cm) from four different land use types on the west bank of Taihu Lake in China to investigate the vertical distribution and weathering characteristics of MPs. The average abundance of soil MPs followed the pattern of paddy field (490 ± 82 items/kg) > dryland (356 ± 55 items/kg) > tea garden (306 ± 32 items/kg) > woodland (171 ± 27 items/kg) in the 0–10 cm layer, and the abundance of MPs decreased linearly with soil depth (r = −0.89, p < 0.01). Compared to tea garden and woodland, MPs in dryland and paddy field have migrated to deeper soil layers (80–100 cm). The carbonyl index of polyethylene and polypropylene MPs increased significantly with soil depth (r = 0.96, p < 0.01), with values of 0.58 ± 0.30 and 0.54 ± 0.33, respectively. The significant negative correlation between MPs size and carbonyl index confirmed that small-sized MPs in deeper soil layers originated from the weathering and fragmentation of MPs in topsoil. The results of structural equation model showed that roots and soil aggregates may act as filters during the vertical migration of MPs. These findings contribute to a better understanding of the environmental fate of MPs in soil and the assessment of associated ecological risks.

The pollution of microplastics in sediments of the Yangtze River Basin: Occurrence, distribution characteristics, and basin-scale multilevel ecological risk assessment.

Microplastics (MPs) pollution in the Yangtze River Basin (YRB) of China has grown to be a serious issue, yet there is a lack of understanding of the environmental risks of MPs in the sediment of the entire basin. This work revealed the spatial distribution characteristics of MPs in YRB sediments, and it methodically assessed the ecological risks of MPs by taking into consideration their abundance, toxic effects, and polymer types. The results showed a high heterogeneity in the abundance of MPs in YRB sediments, with an average of 611 particles/kg dry weight (DW) sediment. Small-sized MPs (<1mm), fibrous, transparent-colored and polypropylene (PP) accounted for the majority with 71.6%, 68%, 37% and 30.8%, respectively. Correlation analysis indicated significant influences of human activities such as population, industrial structure, and urban wastewater discharge on the abundance and morphological types of MPs in sediments. Based on chronic toxicity data exposed to sediments, a predicted no-effect concentration (PNEC) of 539 particles/kg DW was calculated using the species susceptibility distribution (SSD). Multiple deterministic risk assessment indices indicated that MPs in YRB sediments exhibited primarily low pollution load levels, moderate-to-low potential ecological risk levels, and high levels of polymer pollution. However, probabilistic risk assessment revealed an overall low risk of MPs in YRB sediments. Monte Carlo simulation results demonstrated that polyvinyl chloride (PVC) and polycarbonate (PC) made a great contribution to ecological risk and should be considered as priority control pollutants in MPs. In addition, various assessments showed that the ecological risk of MPs in river sediments was higher than that in lake reservoir sediments. This is the first study to comprehensively assess the ecological risk of MPs in sediments of the YRB, which improves the understanding of the basin-wide occurrence characteristics and environmental risks of MPs in freshwater systems.

A microfluidic approach for label-free identification of small-sized microplastics in seawater

Marine microplastics are emerging as a growing environmental concern due to their potential harm to marine biota. The substantial variations in their physical and chemical properties pose a significant challenge when it comes to sampling and characterizing small-sized microplastics. In this study, we introduce a novel microfluidic approach that simplifies the trapping and identification process of microplastics in surface seawater, eliminating the need for labeling. We examine various models, including support vector machine, random forest, convolutional neural network (CNN), and residual neural network (ResNet34), to assess their performance in identifying 11 common plastics. Our findings reveal that the CNN method outperforms the other models, achieving an impressive accuracy of 93% and a mean area under the curve of 98 ± 0.02%. Furthermore, we demonstrate that miniaturized devices can effectively trap and identify microplastics smaller than 50 µm. Overall, this proposed approach facilitates efficient sampling and identification of small-sized microplastics, potentially contributing to crucial long-term monitoring and treatment efforts.

Hydrostatic pressure drives microbe-mediated biodegradation of microplastics in surface sediments of deep reservoirs: Novel findings from hydrostatic pressure simulation experiments

Microplastics originate from the physical, chemical, or biological degradation of plastics in the environment. Once ingested by organisms at the bottom of the food chain, microplastics are passed on to organisms at higher trophic levels, posing a threat to human health. The distribution of microplastics and the metabolic pathways involved in their microbial degradation in surface sediments of drinking water reservoirs are still poorly understood. This study analyzed the occurrence patterns of microplastics and microbial community structure associated with microplastic biodegradation in surface sediments from a deep reservoir at various hydrostatic pressures. Based on the results of Fourier-transform and laser direct infrared spectroscopy, elevating the pressure resulted in altered sizes and shapes of microplastics in sediment samples with the presence of microorganisms. The influence of hydrostatic pressure on small-sized microplastics (20–500 μm) was pronounced. For instance, high pressure accelerated the breakdown of fibers, pellets, and fragments into smaller-sized microplastics. In particular, the mean size of polyethylene terephthalate microplastics decreased from 425.78 μm at atmospheric pressure to 366.62 μm at 0.7 Mpa. Metagenomic analysis revealed an increase in the relative abundances of plastic-degrading genera, such as Rhodococcus, Flavobacterium, and Aspergillus, in response to elevated pressures. Eight functional genes for biodegradation of polystyrene, polyethylene, and polyethylene terephthalate microplastics were annotated, including paaK, ladA, tphA3. Of these, tphA3 gene abundance was negatively influenced by hydrostatic pressure, providing direct evidence for the pathway by which microbial metabolism of polyethylene terephthalate led to decreased microplastic size under high pressure conditions. This study presents novel insights into hydrostatic pressure-driven microbial community structure, functional gene abundance, and key metabolic pathways associated with biodegradation of microplastics in reservoir sediments.

Exploring the potential of cellulose benzoate adsorbents modified with carbon nanotubes and magnetic carbon nanotubes for microplastic removal from water

As global plastic production continues to increase, the issue of microplastic pollution cannot be ignored. In this paper, we explore the potential of cellulose benzoate based adsorbents for removing small-sized microplastics from water. By esterifying cellulose in an ionic liquid, AmimCl, we successfully synthesized cellulose benzoate based adsorbents, which were verified using FTIR, XRD, and solid-state NMR technology. When tested for their ability to remove polystyrene (PS) microplastics from water, cellulose benzoate exhibited a significant improvement in removal efficiency compared to the original cellulose, with the percentage increasing from 9.0% to 68.3%. This improvement can be attributed to their aromatic ring structure that allows for π-π interaction, as well as a higher zeta potential, leading to stronger electrical attraction. When cellulose benzoate was further modified with carbon nanotubes (CNTs) or magnetic carbon nanotubes (MCNTs), its PS removal efficiency further increased to above 97%, owing to the increased zeta potential and the reduction in particle size, which enhances its dispersion in water. Kinetic and isotherm modeling revealed that MCNT-modified cellulose benzoate exhibited superior adsorption rate and capacity, indicating its better performance as an adsorbent. These findings offer a promising approach for microplastic removal and present a new application for lignocellulosic biomass.

Seasonal pulse effect of microplastics in the river catchment-From tributary catchment to mainstream

Rivers have received extensive attention as a major pathway for microplastics (<5000 μm) from land to ocean. This study investigated the seasonal variation of microplastic contamination in surface water of the Liangfeng River catchment, a tributary of the Li River in China, based on a fluorescence-based protocol, and further explored the migration process of microplastic in the river catchment. The abundance of microplastics (50–5000 μm) was (6.20 ± 0.57)–(41.93 ± 8.13) items/L, of which 57.89–95.12% were small-sized microplastics (<330 μm). The microplastic fluxes in the upper Liangfeng River, lower Liangfeng River, and upper Li River were (14.89 ± 1.24) × 1012, (5.71 ± 1.15) × 1012, and (1.54 ± 0.55) × 1014 items/year, respectively. The 3.70% of microplastic load in the mainstream came from the tributary input. Fluvial processes can effectively retain 61.68% of microplastics in the surface water of river catchments, especially for small-sized microplastics. The rainy season is the main period of microplastic retention (91.87%) in the tributary catchment by fluvial processes, while exporting 77.42% of one-year microplastic emissions from the tributary catchment into the mainstream. This study is the first to reveal the transport characteristics of small-sized microplastics in river catchments based on flux variation, which not only can partly explain the “missing small-sized microplastic fraction” in the ocean, but also contribute to improving microplastic model.

Simple and High-sensitivity Analysis of Small Microplastics with Phase Separation by Using Water/isopropanol/chloroform

Phase separation using a water/isopropanol/chloroform mixture generated a small amount of the extraction phase, in which a small portion of microplastics was concentrated. Based on these results, we examined the development of a simple high-sensitivity technique for the analysis of small-sized microplastics with phase separation using a water/isopropanol/chloroform mixture as the extractant.

Microplastic pollution in the offshore sea, rivers and wastewater treatment plants in Jiangsu coastal area in China

Offshore areas are particularly important in recognizing microplastics pollution because they are sinks of land imports and sources of ocean microplastics. This study investigated the pollution and distribution of microplastics in the offshore Sea, rivers and wastewater treatment plants (WWTPs) in Jiangsu coastal area in China. Results showed that microplastics were widely present in the offshore area, with an average abundance of 3.1–3.5 items/m3. Significantly higher abundance was present in rivers (3.7–5.9 item/m3), municipal WWTPs (13.7 ± 0.5 item/m3), and industrial WWTPs (19.7 ± 1.2 item/m3). The proportion of small-sized microplastics (1–3 mm) increased from WWTPs (53%) to rivers (64%) and the offshore area (53%). Polyamide (PA), polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), polystyrene (PS), and rayon (RA) were dominant types of microplastics. Both living and industrial sources contributed to the prevalent microplastics in the offshore Sea. Redundancy analysis showed that small-sized microplastics (1–3 mm) were positively correlated to total phosphorus (TP), while large-sized microplastics (3–5 mm) were positively correlated to TP and NH3–N. The abundance of PE, PP and PVC microplastics were positively correlated to TP and total nitrogen (TN), thus nutrients could be indicators of microplastics pollution in the offshore area.

Size matters either way: Differently-sized microplastics affect amphibian host and symbiotic microbiota discriminately

Concerns about the implications of microplastics (MPs) on aqueous animals have gained widespread attention. It has been postulated that the magnitude of MPs can influence its toxicity. However, little is known about how MPs toxicity changes with particle size. Amphibians are reliable bioindicators of ecosystem health due to their complex life cycles. In this study, we compared the influences of two sizes nonfunctionalized polystyrene microspheres (1 and 10 μm) on the metamorphosis of Asiatic toad (Bufo gargarizans). Acute exposure to MPs at high concentrations led to bioaccumulation in the digestive track and internal organs (i.e., liver and heart) of tadpoles. Long-term exposure to either size, at environmentally-related concentrations (1 and 4550 p/mL), led to growth and development delay in pro-metamorphic tadpoles. Remarkably, developmental plasticity mitigated these deleterious effects prior to the onset of metamorphic climax without compromising survival rate in later stages. MPs with a diameter of 10 μm dramatically altered the gut microbiota (e.g., abundance of Catabacter and Desulfovibrio) of pro-metamorphic tadpoles, whereas MPs with a diameter of 1 μm induced much more intensive transcriptional responses in the host tissues (e.g., upregulation of protein synthesis and mitochondrial energy metabolism, and downregulation of neural functions and cellular responses). Given that the two MPs sizes induced similar toxic outcomes, this suggests that their principal toxicity mechanisms are distinct. Small-sized MPs can travel easily across the intestinal mucosa and cause direct toxicity, while large-sized MPs accumulate in gut and affect the host by changing the homeostasis of digestive track. In conclusion, our findings indicate that MPs can affect the growth and development of amphibian larvae, but their developmental plasticity determines the ultimate detrimental effects. Multiple pathways of toxicity may contribute to the size-dependent toxicity of MPs. We anticipate that these findings will increase our understanding of the ecological effects of MPs.

Species sensitivity distributions of micro- and nanoplastics in soil based on particle characteristics

Micro- and nanoplastics are released into the soil through various anthropogenic activities; however, research on ecological risk assessment (ERA) of soil microplastics is limited. In this study, the species sensitivity distributions (SSDs) of representative groups of soil biota were analyzed to determine their sensitivity to microplastic properties. A total of 411 datasets from apical endpoint data within 74 studies were classified and utilized in SSD estimation. The hazardous concentrations for 5% of species for microplastics was 88.18 (40.71–191.00) mg/kg soil. It has been established that small-sized microplastics are more toxic to soil organisms than larger microplastics. Most microplastics were spherical and polystyrene, exhibiting the most adverse effects among all the microplastic types assessed herein. The results suggest that physical characteristics of microplastics are important toxicity determinants in soil ecosystems. Given the potential for adverse environmental effects, further effective management strategies should urgently be employed in these areas. This study provided an integrated perspective of microplastic ecotoxicity in soil. In addition, SSDs were estimated using larger datasets and for more species than in previous studies. This is the first study to consider microplastic properties for estimating SSD.