The increasing prevalence of microplastics in the environment has become a concern for various ecosystems, including wetland ecosystems. Here, we investigated the effects of three popular ...microplastic types: polyethylene, polylactic acid, and tire particles at 5 °C and 25 °C on the sediment microbiome and metabolome at the 3% (w/w) level. Results indicated that temperature greatly influenced catalase and neutral phosphatase activities, whereas the type of microplastic had a more significant impact on urease and dehydrogenase activities. The addition of microplastic, especially tire particles, increased microbial diversity and significantly altered the microbial community structure and metabolic profile, leading to the formation of different clusters of microbial communities depending on the temperature. Nonetheless, the effect of temperature on the metabolite composition was less significant. Functional prediction showed that the abundance of functional genes related to metabolism and biogeochemical cycling increased with increasing temperature, especially the tire particles treatment group affected the nitrogen cycling by inhibiting ureolysis and nitrogen fixation. These observations emphasize the need to consider microplastic type and ambient temperature to fully understand the ecological impact of microplastics on microbial ecosystems.
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•Evaluated the effects of polyethylene, polylactic acid, and tire particles (microplastics - MPs) on sediment.•MPs, especially tire particles, increased microbial diversity at higher temperatures.•Temperature influenced microbial diversity dynamics and had less of an effect on metabolites.•Comparatively, tire particle treatments had unique microbial communities and different metabolites.
Microplastics are ubiquitous contaminants in aquatic habitats globally, and wastewater treatment plants (WWTPs) are point sources of microplastics. Within aquatic habitats microplastics are colonized ...by microbial biofilms, which can include pathogenic taxa and taxa associated with plastic breakdown. Microplastics enter WWTPs in sewage and exit in sludge or effluent, but the role that WWTPs play in establishing or modifying microplastic bacterial assemblages is unknown. We analyzed microplastics and associated biofilms in raw sewage, effluent water, and sludge from two WWTPs. Both plants retained >99% of influent microplastics in sludge, and sludge microplastics showed higher bacterial species richness and higher abundance of taxa associated with bioflocculation (e.g. Xanthomonas) than influent microplastics, suggesting that colonization of microplastics within the WWTP may play a role in retention. Microplastics in WWTP effluent included significantly lower abundances of some potentially pathogenic bacterial taxa (e.g. Campylobacteraceae) compared to influent microplastics; however, other potentially pathogenic taxa (e.g. Acinetobacter) remained abundant on effluent microplastics, and several taxa linked to plastic breakdown (e.g. Klebsiella, Pseudomonas, and Sphingomonas) were significantly more abundant on effluent compared to influent microplastics. These results indicate that diverse bacterial assemblages colonize microplastics within sewage and that WWTPs can play a significant role in modifying the microplastic-associated assemblages, which may affect the fate of microplastics within the WWTPs and the environment.
Degraded plastic debris has been found in nearly all waters within and nearby urban developments as well as in the open oceans. Natural removal of suspended microplastics (MPs) by deposition is often ...limited by their excess buoyancy relative to water, but this can change with the attachment of biological matter. The extent to which the attached biological ballast affects MP dynamics is still not well characterised. Here, we experimentally demonstrate using a novel OMCEC (Optical Measurement of CEll colonisation) system that the biological fraction of MP aggregates has substantial control over their size, shape and, most importantly, their settling velocity. Polyurethane MP aggregates made of 80% biological ballast had an average size almost twice of those containing 5% biological ballast, and sank about two times slower. Based on our experiments, we introduce a settling velocity equation that accounts for different biological content as well as the irregular fractal structure of MP aggregates. This equation can capture the settling velocity of both virgin MPs and microbial-associated MP aggregates in our experiment with 7% error and can be used as a preliminary tool to estimate the vertical transport of MP aggregates made of different polymers and types of microbial ballast.
Microplastic (MP) appears to be omnipresent in the atmosphere, raising concerns about dispersion across environmental compartments, ecological consequences and human health risks by inhalation. To ...date, data on the sources of atmospheric MP and deposition to river catchment areas are still sparse. We, therefore, took aerosol and total atmospheric deposition samples in the catchment area of the large German river Weser to estimate microplastic deposition fluxes (DFs) at six specific sites and airborne MP concentrations. Sampling in rural, suburban, and urban environments and wastewater treatment plants (WWTPs) was performed, aiming at a variation in airborne MP pollution and elucidating potential MP source areas. Aerosol samples were taken twice in April and October while monthly total deposition samples were collected over a period from March to October. Microplastics were detected in all analysed aerosol samples by Raman spectroscopy down to 4 μm, and in all 32 total deposition samples by μFT-IR down to 11 μm. Average MP number concentrations of 91 ± 47 m−3 were found in aerosol samples. The measured total MP number DFs ranged between 10 and 367 N m−2 day−1 (99 ± 85 mean ± SD) corresponding to total deposition of 0.05 ± 0.1 kg ha−1 per year and to an estimated 232 metric tons of plastic being deposited in the Weser River catchment annually. MP number DFs were higher in urban than rural sites. An effect of WWTPs on the MP abundance in air was not observed. Polypropylene, polyethylene, polyethylene terephthalate, polyvinyl chloride, polystyrene, and silicone fragments were found as the predominant polymer types in total deposition samples, while polyethylene particles dominated in aerosol samples. The results suggest that proximity to sources, especially to cities, increase the numbers of MP found in the atmosphere. It further indicates that atmospheric MP considerably contributes to the contamination of both aquatic and terrestrial habitats.
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•Average airborne MP concentration of 91 ± 47 particles per m3 (>4 μm)•Average total MP deposition rate of 99 ± 85 particles per m2 per day (>11 μm)•Atmospheric deposition must be considered as a diffuse MP source.•Proximity to sources, especially to cities, increase MP numbers in the atmosphere.•PP and PE fragments predominate in air in Central and Northwest Germany.
Rivers are viewed as major pathways of microplastic transport from terrestrial areas to marine ecosystems. However, there is paucity of knowledge on the dispersal pattern and transport of ...microplastics in river sediments. In this study, a three dimensional hydrodynamic and particle transport modelling framework was created to investigate the dispersal and transport processes of microplastic particles commonly present in the environment, namely, polyethylene (PE), polypropylene (PP), polyamide (PA), and polyethylene terephthalate (PET) in river sediments. The study outcomes confirmed that sedimental microplastics with lower density would have higher mobility. PE and PP are likely to be transported for a relatively longer distance, while PA and PET would likely accumulate close to source points. High water flow would transport more microplastics from source points, and high flow velocity in bottom water layer are suggested to facilitate the transport of sedimental microplastics. Considering the limited dispersal and transport, the study outcomes indicated that river sediments would act as a sink for microplastic pollutants instead of being a transport pathway. The patchiness associated with the hotspots of different plastic types is expected to provide valuable information for microplastic source tracking.
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•Microplastics with lower density have high mobility in sediments.•Dense microplastics prone to accumulate close to source points in river sediments.•High bottom water velocity result in longer transport of sedimental microplastics.•Limited transport of benthic microplastics makes river sediments function as a sink.•Patchiness in microplastics hotspots provide valuable data for source tracking.
Capsule: Modelling of transport processes of microplastics to understand their dispersal and fate in aquatic environments.
Microplastics are widespread contaminants, virtually present in all environmental compartments. However, knowledge on sources, fate and environmental concentration over time and space still is ...limited due to the laborious and varied analytical procedures currently used. In this work we critically review the methods currently used for sampling and detection of microplastics, identifying flaws in study design and suggesting promising alternatives. This work provides insights on bulk sample collection, separation, digestion, identification and quantification, and mitigation of cross-contamination. The sampling of microplastics will improve in representativeness and reproducibility through the determination of bulk sample volume, filter's pore size, density separation and digestion solutions, but also through use of novel methods, such as the enhancement of visual identification by staining dyes, and the generalized use of chemical characterization.
•Methods of sampling and detection of microplastics vary between groups.•Sampling and separation of microplastics needs to be standardized.•Removal of organic matter through digestion improves identification.•Visual inspection can be improved, chemical identification is essential.•Mitigation of cross-contaminations is required to validate the results.
Both biodegradable and nondegradable plastics are widely used. However, their interactions with petroleum hydrocarbons (PHs) have not been sufficiently studied. In this study, a type of biodegradable ...polylactic acid (PLA) and five types of nondegradable microplastics polyamide (PA), polyethylene (PE), polyethylene terephthalate (PET), polystyrene (PS), and polyvinyl chloride (PVC) were selected to investigate the sorption and desorption mechanisms of PHs. The sorption kinetics of the six types of microplastics followed a pseudo-second-order kinetics model (R2 ranged from 0.956 to 0.999) and indicated that chemical sorption dominated the sorption process. The key rate-controlling steps of the sorption of PHs on microplastics were intraparticle diffusion and liquid film diffusion. The sorption capacity of PHs on microplastics followed the order of PA > PE > PS > PET > PLA > PVC. The difference in sorption capacity might be due to the crystallinity, and rubber or glass state of the microplastics. In addition, all types of microplastics exhibited reversible sorption without noticeable desorption hysteresis. No obvious differences were observed in the sorption and desorption of PHs between biodegradable and nondegradable microplastics. Both biodegradable and nondegradable microplastics could sorb/desorb PHs and serve as transportation vectors.
•Kinetics and isotherms were elucidated.•The sorption conformed to pseudo-second-order model.•Sorption capacity followed the order PA > PE > PS > PET > PLA > PVC.•The desorption was reversible, without hysteresis.•PLA displayed similar sorption and desorption mechanisms as PA, PE, PET, PVC, and PS.
Microplastics (MP) are receiving increased attention as a harmful environmental pollutant, however information on the reproduction toxicity of MP in terrestrial animals, especially mammals, is ...limited. In this experiment, we investigated the impact of polystyrene microplastics (micro-PS) on the reproductive system of male mice. Healthy Balb/c mice were exposed to saline or to different doses of micro-PS for 6 weeks. The results showed that micro-PS exposure resulted in a significant decrease in the number and motility of sperm, and a significant increase in sperm deformity rate. We also detected a decrease in the activity of the sperm metabolism-related enzymes, succinate dehydrogenase (SDH) and lactate dehydrogenase (LDH), and a decrease in the serum testosterone content in the micro-PS exposure group. We found that micro-PS exposure caused oxidative stress and activated JNK and p38 MAPK. In addition, we found that when N-acetylcysteine (NAC) scavenges ROS, and when the p38 MAPK-specific inhibitor SB203580 inhibits p38MAPK, the micro-PS-induced sperm damage is alleviated and testosterone secretion improves. In conclusion, our findings suggest that micro-PS induces reproductive toxicity in mice through oxidative stress and activation of the p38 MAPK signaling pathways.
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•Micro-PS resulted in a significant decrease in the quantity and quality of sperm in mice.•Micro-PS exposure caused oxidative stress in testes.•Micro-PS exposure activated JNK and P38 MAPK.•Blocking oxidative stress or P38 MAPK can alleviate micro-PS-induced sperm damage.
Microplastics have become a contaminant of increasing concern in soils. Although biodegradable plastics were considered as alternatives of traditional plastics, some evidence showed that ...biodegradable plastics might produce more microplastics. Until now, the effect of biodegradable microplastics on soil functions and processes, as well as microbial communities is uncertain. Based on high throughput sequencing, enzymatic activity assay and dynamic analysis of soil carbon and nitrogen, we investigated the effects of biodegradable polylactic acid microplastics (PLA MPs) on soil microbiota and related ecological processes under conditions of high or low carbon content. The results showed that PLA MPs had no significant effect on the overall diversity and composition of bacterial communities or related ecosystem functions and processes. However, co-occurrence network analysis revealed that PLA MPs impacted the interactions between constituent species, which might have legacy effect on soil bacterial communities and functions. Our data also revealed that PLA MPs could trade off the priming effect of carbon source. Our results provided an integrated picture in understanding the effects of PLA MPs on soil microbes, properties and ecological functions, which will help to further understand the effects of MPs on terrestrial ecosystems.
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•2% PLA MPs did not impact soil nutrient pool and ecological functions.•A faster ammonia transformation rate was observed in PLA MPs amended soil.•The interaction among bacteria has been changed with the addition of PLA MPs.•Different effect of PLA MPs on soil under different carbon content was observed.
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