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.
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.
•BMPs were similar toxicity compared to CMPs.•The toxicity is mPLA > mPE > mPA > mPBS.•The increase of photosynthetic pigments may produce more carbon-based defensive chemicals to accustom the stress ...induced by MPs.•Toxicity of microplastics on microalgae depends on their physicochemical properties.
It has been demonstrated that some conventional microplastics (CMPs) have toxicities to organisms, however, whether biodegradable microplastics (BMPs) have similar potential risks to marine ecosystems remains to be elucidated. Therefore, this study aimed to investigate i) the effects of CMPs (i. e., micro-sized polyethylene (mPE) and polyamide (mPA)) on marine algae Chlorella vulgaris; and ii) the potential effects of BMPs (i.e., micro-sized polylactic acid (mPLA) and polybutylene succinate (mPBS)) on C. vulgaris. The results showed that either CMPs or BMPs inhibited the growth of microalgae compared with the control. The maximum inhibition ratio of the four types of MPs on C. vulgaris were 47.24% (mPE, 1 000 mg/L), 40.36% (mPA, 100 mg/L), 47.95% (mPLA, 100 mg/L) and 34.25% (mPBS, 100 mg/L), respectively. Among them, mPLA showed the strongest inhibitory effect on the growth of C. vulgaris. Interestingly, the MPs can stimulate the contents of pigments (e.g., chlorophyll a, chlorophyll b, and carotenoid), which may be acted as cellular defense to the stress induced by MPs. The results also showed that MPs stimulated the production of EPS. Under the investigated condition, the strongest inhibition on C. vulgaris was induced by mPLA, and followed by mPE, mPA, and mPBS. It was found that the factors such as the physicochemical properties of MPs (e.g., shading effect, the roughness of surface, the increase in potential), the chemical changes (i.e., the release of additives, the increase of oxidative stress) contributed to the inhibitory effects of MPs on microalgae, but the deciding factor remains to be further systematically explored.
Atmospheric transport is an important pathway for the deposition of micro- and nano-plastics in remote areas. However, the sources and fate of atmospheric microplastics remain poorly understood. A ...study on atmospheric transport and deposition in the Pyrenean Mountains highlights the movement of microplastics away from known sources (cities, agriculture, and industry) into remote areas. Following this first evidence of atmospheric microplastic deposition in a pristine location, it is necessary to reconsider previous studies on atmospheric microplastic deposition and behavior in remote areas.
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•Atmospheric transport is an important pathway for microplastics deposition.•Atmospheric microplastics can be identified in the remote area.•Implications for research in the Tibetan Plateau are discussed.
The degradable properties of degradable plastics allow them to form microplastics (MPs) faster. Therefore, degradable MPs may easily be transported in the underground environment. Research on ...degradable MPs transport in porous media is necessary and urgent. In this study, polylactic acid (PLA) and polyvinyl chloride (PVC) were selected to compare the transport differences between degradable and nondegradable MPs under different factors (flow rates, ionic strengths (ISs), pH, and coexisting cations) through column experiments, and UV irradiation was used to further simulate the effect of aging on different types of MPs. Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) were used to characterize functional groups and to determine the surface elements of MPs, respectively. The results showed that MPs were more mobile at higher flow rate, lower IS, higher pH, and monovalent cations. The order of transport capacity of MPs was PVC < aged PVC < PLA < aged PLA. This result was mainly attributed to the more negative Zeta potential and higher dispersion stability of aged PLA and PLA, which were caused by abundant O-functional groups. Compared with PVC, the O/C ratio of PLA increased significantly after aging, indicating that PLA was more prone to aging. The advection-dispersion-equation (ADE) fitted the transport data of MPs well. The interaction energy of MPs and quartz sand was accurately predicted by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. This work contributes to a comprehensive understanding of the transport of degradable MPs in the environment.
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•PLA was easier to transport than PVC.•The greater mobility of PLA was attributed to its abundant O-functional groups.•The mobility of aged MPs was greater than that of the pristine.•Increasing pH and flow rate facilitated the transport of MPs.•Increasing ionic strength and cation valence decreased the mobility of MPs.
Plastic pollution has become a global and persistent challenge, posing threats to ecosystems and organisms. In recent years, there has been a rapid increase in scientific research focused on ...understanding microplastics in the soil‒plant system. This surge is primarily driven by the direct impact of microplastics on agricultural productivity and their association with human activities. In this study, we conducted a comprehensive bibliometric analysis to provide an overview of the current research on microplastics in soil‒plant systems. We systematically analysed 192 articles and observed a significant rise in research interests since 2017. Notably, China has emerged as a leading contributor in terms of published papers, closely followed by Germany and the Netherlands. Through co-authorship network analysis, we identified 634 different institutions that participated in publishing papers in this field, with the Chinese Academy of Sciences having the most collaborations. In the co-occurrence keyword network, we identified four clusters focusing on the diversity of microplastics within the agroecosystem, transportation, and quantification of microplastics in soil, analysis of plastic contamination type and impact, and investigation of microplastic phytotoxicity. Furthermore, we identified ten research priorities, categorized into the effects of microplastics in "soil" and "plant". The research hotspots were found to be the effect of microplastics on soil physicochemical properties and the synergistic phytotoxicity of microplastics with other pollutants. Overall, this bibliometric analysis holds significant value, serving as an important reference point and offering valuable suggestions for future researchers in this rapidly advancing field.
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•MPs were ubiquitous but low in the commercial seaweed nori.•The size and shape of MPs in nori varied dramatically across different processing stages.•Polyester was the predominant ...component of MPs in commercially packaged nori.•Polypropylene was the most commonly detected polymer in factory-processed nori.•Microfibers were proved to adhere to the surface of nori in the laboratory.
Microplastics have been reported to attach to the marine macroalgae which act as the vector for microplastic transfer in the marine food web. In this study, the edible seaweed nori (Pyropia spp.) was chosen as a target species. The microplastic contaminant situations in nori were analyzed in both its final commercial products and the intermediate products across different processing stages. The abundance of microplastics ranged from 0.9 to 3.0 items/g (dw) among 24 brands of commercially packaged nori samples. With the development of nori processing stages, an enlarged size fraction of greater microplastics (1–5 mm) was observed. Compared with commercially packaged nori samples, the proportions of polypropylene, polyethylene and poly (ethylene-propylene) copolymers increased, whereas that of polyester decreased in factory-processed nori. Additionally, we further simulated and quantified the number of fluorescent polyester fibers (concentrations: 0, 1000, 5000, 10,000 fibers/L) attach to the algal pieces of Pyropia yezoensis under laboratory conditions. The average abundance of microfibers on the nori was positively and quantitatively related to their abundances in seawater (p < 0.01). To our best knowledge, this is the first work that shows the prevalence of microplastics in the commercial seaweed nori and relates to their potential sources during the processing phase.
In recent years, reports of plastic debris in the gastrointestinal (GI) tract of fish have been well documented in the scientific literature. This, in turn, increased concerns regarding human health ...exposure to microplastics through the consumption of contaminated fish. Most of the available research regarding microplastic toxicity has focused on marine organisms through direct feeding or waterborne exposures at the individual level. However, little is known about the trophic transfer of microplastics through the aquatic food chain. Freshwater zooplankton Daphnia magna (hereafter Daphnia), and the fathead minnow Pimephales promelas (FHM), are well-known model species used in standard toxicological studies and ecological risk assessments that provide a simple model for trophic transfer. The aim of this study was to assess the tissue translocation, trophic transfer, and depuration of two concentrations (20 and 2000-part ml−1) of 6 μm polystyrene (PS) microplastics particles between Daphnia and FHM. Bioconcentration factors (BCF) and bioaccumulation factors (BAF) were determined. Fluorescent microscopy was used to determine the number of particles in the water media and within the organs of both species. Throughout the five days of exposure, PS particles were only found within the GI tract of both species. The BCF for Daphnia was 0.034 ± 0.005 for the low concentration and 0.026 ± 0.006 for the high concentration. The BAF for FHM was 0.094 ± 0.037 for the low concentration and 0.205 ± 0.051 for the high concentration. Between 72 and 96 h after exposure all microplastic particles were depurated from both species. The presence of food had a significant effect on the depuration of microplastic particles from Daphnia but not for FHM. Based on the low BCF and BAF values for both species, rapid depuration rates, and null translocation of microplastic particles to organs and tissues from the GI tract, there is a low probability that microplastics will bioconcentrate and bioaccumulate under environmental conditions.
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•There was minimal uptake (<1%) of PS microplastics by Daphnia and fathead minnow.•Microplastics were quantified in the gut and did not translocate to other organs.•Microplastics had short retention times and were fully depurated within 72–96 h.•Low BCF and BAF values were found for Daphnia and fathead minnow, respectively.•Food presence significantly increased depuration of microplastics in Daphnia.
Low uptake, null translocation, and short retention time, indicate a low probability that 6 μm PS microplastics will bioconcentrate and bioaccumulate under environmentally relevant conditions.
Microplastics (MP) are detected in aquatic environments worldwide, yet detection is often limited to larger sized MP. To address this data gap, the abundance of MP 3–500 μm was assessed in the Los ...Angeles River, the San Gabriel River, and the Long Beach Harbor (CA, USA), three areas with highly urbanized surroundings. Whole surface water samples were taken, subjected to a hydrogen peroxide digestion and MP counts were compared between unstained visual examination and Nile Red staining identification techniques. The largest concentration of MP was found in the Los Angeles River, where 13,622 MP m−3 were found using unstained visual examination and 641,292 MP m−3 were found utilizing Nile Red staining. The protocol used to detect smaller sized MP is low cost, time efficient, and reproducible. This work highlights the need for more extensive sampling of smaller sized MP globally and universal testing and reporting standards for MP detection.
•Validated a cost and time effective method for detection of MP sized 3–500 μm•H2O2 digestion and Nile Red staining was the most effective method.•High concentration of 3–20 μm and 20–63 μm MP size classes in urban surface water
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