Microplastics (MPs) that have accumulated in the environment are emerging as contaminating pollutants due to their interactions with metal ions. MPs change the migration and transformation of metal ...ions in the environment and afterward impact their environmental presence. Therefore, it is necessary to evaluate the interaction characteristics and mechanisms between Cd2+and MPs for assessing the ecological impacts of MPs. The traditional sequencing batch equilibrium test demonstrated that the sorption of Cd2+ onto MPs was related to the type of MPs present, the pH value of the solution, the ionic strength of the participants and the presence of humic acid. The sorption dynamics and isotherm experiment illustrated that the interactions were controlled by surface sorption and distribution effects. The specific surface area and surface charge were the main factors in managing the sorption process. FTIR spectra and a 2D-COS analysis showed that different functional groups played an important role in the sorption of Cd2+onto MPs. The results from this work afford new insights on how MPs may play an important role in the fate and transport of heavy metals and present a new analysis method for evaluating the environmental behavior of MPs and their role in transporting other contaminants.
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•The Cd-MPs interaction process was highly dependent on solution pH, ionic strength and humic acid.•The sorption was controled by surface sorption and distributional effects.•The 2D-COS analysis stated functional groups played an important role for sorption of Cd2+ on MPs.
Microplastics (MPs) are presumed to be inert during aging under ambient conditions. In this study, four types of virgin MPs, including polystyrene (PS), phenol-formaldehyde resin (PF), polyethylene ...(PE), and polyvinyl chloride (PVC), were aged under simulated solar light irradiation. Surprisingly, several environmentally persistent free radicals (EPFRs), which are considered to be a type of emerging contaminant, were detected on the irradiated PS and PF, rather than PE and PVC, by electron paramagnetic resonance (EPR) spectroscopy. Depending on the photoaging duration time, the characteristic g-factors of the EPFRs produced on PS and PF were 2.0044–2.0049 and 2.0043–2.0044, respectively. The generated EPFRs on PS and PF decayed rapidly at the initial stage and then slowly disappeared with the elapsed aging time. Analyses by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC) suggested that MPs might experience chemical chain scission, O2/H2O addition, and EPFR formation under the light irradiation. Accompanying with the formation of EPFRs, reactive oxygen species, such as O2 •– and •OH, were also observed. The findings provide a novel insight to evaluate the potential hazards of MPs to organisms and ecosystems.
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•Microplastic aging in simulated multiple actions generated by plasma was studied.•Physical and chemical properties of microplastic were characterized after aging.•Aging degree was ...positively related to plasma oxidation intensity and duration.•Aged microplastic provided more sites for adsorption of tetrabromobisphenol.•Enahnced adsorption of microplastic exhibited synergistic toxicity to alge growth.
Microplastics (MPs) are becoming one class of pollutants with high global concerns. Information regarding aging behaviors of MPs in complicated natural conditions is still lacking due to the very slow aging processes. In this study, discharge plasma oxidation was applied to simulate the various radical oxidation and physical effects naturally occurring in the environment to shed light on the aging behaviors and mechanisms of MPs, with polyvinyl chloride microplastic (PVC-MP) as a model. The surface morphology, particle size, specific surface area, crystallinity, and chemical compositions of PVC-MP were comprehensively characterized as a result of aging. The aging degree indicated by carbonyl index and oxygen-to-carbon ratio increased with the plasma oxidation intensity and duration. The aged PVC-MP was characterized as more O-containing functional groups, smaller particle size, larger specific surface area, higher hydrophilicity, and higher crystallinity. Consequently, the aged PVC-MP provided more sites for adsorption of tetrabromobisphenol (TBBPA) in solutions by forming hydrogen-bonds, and electrostatic force. The changes in the properties of the aged PVC-MP, and the strong adsorption with TBBPA led to unexpected synergistic toxic effects to Scenedesmus obliquus. The results provide direct evidences of aging processes of MPs and the potential environmental risks due to aging in the environment.
Microplastics may experience photoaging and breakdown into nanoplastics in aquatic environment as a result of long-term light irradiation. However, the underlying mechanisms responsible for the ...photodegradation of microplastics are largely overlooked. In this study, the photodegradation of microplastics, utilizing polystyrene microplastic (PS-MP) as a model, was investigated under irradiation with simulated solar light for as long as 150 d. A large amount of reactive oxygen species (ROS), including O2•−, 1O2, H2O2 and •OH, were detected in the PS-MP suspension due to light irradiation, which displayed significant relationships with the generated environmentally persistent free radicals (EPFRs). Distinct photoaging of PS-MP was observed with increased surface roughness and decreased particle size. However, these photoaging effects were significantly inhibited by ROS quenchers, suggesting that the generation ROS played a vital role in the PS-MP phototransformation. In addition, ROS induced formation of more oxidative functional groups on the PS-MP, thus enhancing the negative surface potential and the stability of PS-MP in water. This study elucidated the mechanism of formation of ROS by simulated solar light irradiated MPs and their subsequent roles in the phototransformation of MP, thus expanding current knowledge on the fate of MPs in aquatic environments.
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•ROS formed in PS-MP suspension under 150 d simulated sunlight irradiation.•ROS played a vital role in PS-MP phototransformation.•ROS induced formation of more oxidative functional groups on PS-MP surfaces.•Photoaging enhanced the stability of PS-MP in water.
•Photodegradation behaviors of MPs in the presence of clays were firstly explored.•Clay minerals, particularly kaolinite, significantly enhanced the MP photoaging.•The aging of PET was more prominent ...than PVC.•Clay facilitated the production of •OH, greatly contributing to MP degradation.•Photodegradation mechanism of MPs mediated by clay minerals was disclosed.
It is well known that microplastics (MPs) may experience weathering and aging under ultraviolet light (UV) irradiation, but it remains unclear if these processes are impacted by natural components, such as clay minerals. In this study, we systematically investigated the photodegradation behaviors of polyvinyl chloride (PVC) and poly (ethylene terephthalate) (PET), two utmost used plastics, in the presence of clay minerals (kaolinite and montmorillonite). The results demonstrated that the clay minerals, particularly kaolinite, significantly promoted the MPs photodegradation, and the aging of PET was more prominent. The photodegradation was the most distinct at pH 7.0, regardless of the presence or absence of the clay minerals. The results of electron paramagnetic resonance and inhibition experiments of reactive oxygen species indicated that the minerals, particularly kaolinite, remarkably facilitated production of •OH, which was the key species contributing to the photodegradation of MPs. Specifically, UV irradiation facilitated the photo-ionization of MPs, producing hydrated electrons and MP radical cations (MP+). The Lewis base sites prevalent on the clay siloxane surfaces could stabilize the MP radical cations and prevent their recombination with hydrated electrons, which promoted the generation of •OH under aerobic conditions, and facilitated the degradation of MP. Two-dimensional (2D) Fourier transformation infrared (FTIR) correlation spectroscopy (COS) analysis and ultra-high-performance liquid chromatography coupled to a Q Exactive Orbitrap HF mass spectrometer were used to identify the sequential changes of functional groups, and the degradation products of the MPs. This study improves our understanding on the aging of MPs in the complex natural environment.
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Plastics pollution in global soil systems is becoming a severely global issue and potential threat to terrestrial ecosystem serves and human health. Herein, in order to determine the degradability ...and ecological effects of polyethylene (PE) films, we measured the weight loss and characterization of PE films and analyzed variation in microbial community. The results of weight loss, SEM and FTIR spectra exhibited that PE films had unique degradation performance under different conditions. Simultaneously, we investigated the effects of PE films on the microbial community, and the microbiota colonizing on plastics. PE films may change the soil microbial community composition in soil, and hold the post of unique matrix for microbial colonization. These results indicate that the degradation of PE films and microbial community composition in soil can be affected by different conditions (soil layer, time and plants). By assessing the alteration of microbial community composition and PE films in soil, this work will contribute to enhance our understanding on the potential risks of plastics on soil ecosystems and provide a scientific basis for understanding the ecological effect of plastics on soil functions.
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•Degradation characteristics of PE films in soil were assessed.•PE films have different effects on microbial community under different conditions.•Compared with soil, PE films surfaces have unique microbial community composition.•The interactions between PE films and soil microbial community were explored.
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•SPC activated by discharge plasma is used to remove plasticizer from wastewater.•Plasticizer removal efficacy under various experimental conditions is evaluated.•Roles of active ...species in plasticizer removal are evaluated.•Mineralization process and byproducts formation are explored.•Enhancement mechanisms on plasticizer removal in such a system are discussed.
Phthalates, as additives in the plastic production process, were able to enter the water environment, causing huge risks to ecological environment and human health. The potential of phthalates elimination in aqueous using sodium percarbonate (SPC) activated by discharge plasma (marked as “SPC + plasma”) was evaluated, with dimethyl phthalate (DMP) as a model pollutant. Experimental results showed that about 92.1% of DMP was eliminated in the “SPC + plasma” system with the treatment time of 30 min, which was 30.7% higher than that in sole plasma system, and the synergetic intensity for DMP elimination reached up to 127.0; and the energy yield was also raised by 131%. H2O2 and OH radicals formation were promoted but ozone concentration decreased in the “SPC + plasma” system. Appropriate SPC dosage benefited DMP elimination, and the synergetic intensity increased from 2.0 to 127.0 as the SPC dosage increased from 0.06 mmol L−1 to 0.12 mmol L−1. OH radicals, O2·−, 1O2, and CO3·− played crucial roles in DMP elimination, and the roles of O2·− and 1O2 were strengthened in the “SPC + plasma” system. Ultraviolet–visible spectroscopy measurement, total content of organic carbon, atomic force microscopy and three-dimensional fluorescence analysis demonstrated that DMP molecular structure was destroyed during treatment, and some smaller molecular fractions were generated. The main intermediates included phthalic acid monomethyl ester, phthalic acid, o-phthalic anhydride, acetic acid, formic acid, and oxalic acid. The possible enhancement mechanisms for DMP elimination in the “SPC + plasma” system were proposed.
Strong complexation between heavy metals and organic complexing agents makes the heavy metals difficult to be removed by classical chemical precipitation. In this study, a novel decomplexation method ...was developed using discharge plasma oxidation, which was followed by alkaline precipitation to treat water containing heavy metal–organic complex, that is, Cu–ethylenediaminetetraacetic acid (Cu–EDTA). The decomplexation efficiency of Cu complex reached up to nearly 100% after 60 min’s oxidation by discharge plasma, which was accompanied by 82.1% of total organic carbon removal and energy efficiency of 0.62 g kWh–1. Presence of free Cu2+ favored Cu–EDTA decomplexation, whereas the presence of excessive EDTA depressed this process. Cu–EDTA decomplexation was mainly driven by the produced 1O2, O2 •–, O3, and •OH by discharge plasma. Cu–EDTA decomplexation process was characterized by UV–vis, ATR–FTIR, total organic carbon, and three-dimensional fluorescence diagnosis. The main intermediates including Cu–EDDA, Cu–IDA, Cu–NTA, small organic acids, NH4 +, and NO3 – were identified, accompanied by Cu2+ releasing. The followed precipitation process removed 78.1% of Cu2+, and Cu-associated precipitates included CuCO3, Cu2CO3(OH)2, CuO, and Cu(OH)2. A possible pathway of Cu complex decomplexation and Cu2+ removal in such a system was proposed.
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•Photoaging under simulated sunlight irradiation enhanced the OP of PF-MP.•Simulated sunlight led to the increased generation of EPFRs and ROS in PF-MP.•The generated active species ...in PF-MP contributed to the elevated OP of PF-MP.•The PF-MP with an increased OP induced a higher cytotoxicity.
Phenol-formaldehyde resin microplastic (PF-MP) is one of the major inhalable microplastics in environments released from the manufacture, processing and usage of PF materials. The associated toxicities of PF-MP might be affected by photoaging. In this study, the dynamic evolutions of the oxidative potential (OP) and redox-active species, including environmentally persistent free radicals (EPFRs), reactive oxygen species (ROS), peroxides and conjugated carbonyls, as well as the associated cytotoxicity of PF-MP were systematically investigated as a result of the simulated sunlight irradiation. As the photoaging time extended, the OP of PF-MP increased. The contents of the produced conjugated carbonyls, ROS and PF-bound EPFRs due to light irradiation increased as well, and displayed significant correlations with the OP (Spearman r > 0.6, p < 0.05). The photoaged PF-MP distinctly increased the cellular ROS and reduced the cell viability of human lung epithelial adenocarcinoma cells (A549). The cytotoxicity of PF-MP showed a similar trend with the OP level in PF-MP, suggesting that the produced active species induced the in vitro toxicities. The results not only highlight the adverse health effects of photoaged PF-MP, but also provide new perspectives for the environmental risks of airborne MPs.
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•Aging in soil lead the surface of PS-MP being wrapped by soil particles.•The wrapping effects of soil particles induced the formation of protective layer.•Protective layer increased ...the particle size of PS-MP and decreased its ingestion.•The aging of PS-MP in the soil decreased its toxicity to earthworms.
The recent discovery of microplastics contaminants in most ecosystems has raised major health issues, yet knowledge on their impact on soil organisms is limited, especially their toxicity evolution with aging. Herein, the toxicity of polystyrene microplastic (PS-MP) to earthworm (Eisenia fetida) along with aging was investigated. Results showed that the 28 d-LC50 (50% lethal concentration) of PS-MP was 25.67 g kg−1, whereas that increased to 96.47 g kg−1 after PS-MP initially aged in soil for 28 days, indicating the toxicity of PS-MP decreased with aging. Laser scanning confocal microscope and scanning electron microscope (SEM) found that the toxicity of PS-MP to earthworm may be due to the ingestion of PS-MP by earthworms and the physical damage (e.g., epidermis abrasion and setae loss) of PS-MP to earthworms. Similarly, the levels of reactive oxygen species, antioxidant enzyme activities and malondialdehyde content increased with PS-MP concentrations from 0.1 to 1.5 g kg−1, but decreased with aging from 7 to 28 days. The integrated biomarker response index also confirmed that the toxicity of PS-MP decreased with aging. SEM found that PS-MP were progressively covered by soil particles during soil aging, inducing the formation of protective layer and increasing the particle size of PS-MP, which prevented direct contact with earthworms and decreased the ingestion of PS-MP, in turn decreased PS-MP toxicity. Overall, our study provides valuable insights for elucidating the effect of aging on the toxicity of microplastics.
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