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.
Microplastic pollution is an increasingly important environment problem. Many studies show the occurrence of microplastics in our environmental system. However, the freshwater system is less ...understood, especially in northwest China. We investigated the occurrence and characteristics of microplastics in the Wei River Basin, which is located in northwestern China. The Wei River is the largest tributary of the Yellow River and runs through three major provinces. In the Wei River, the concentration of microplastics in the surface waters varied from 3.67 to 10.7 items /L and in the sediments, the abundance of microplastics varied from 360 to 1320 items/kg. Fiber (50.1%)was the dominant types in water samples and sediments. The small size (<0.5 mm)(68.1%)were the main size of microplastics in Wei River. The types of microplastics were polyethylene, Polyvinyl chloride and polystyrene, as identified using a Fourier transform infrared spectrometer. This study could be a valuable reference for better understanding the microplastics pollution in inland northwestern China.
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•Microplastics were investigated in Wei River in the northwest of China.•The microplastics in the water samples of the Wei River are lower than the microplastics in the sediments.•Fiber and small size (<0.5 mm) were the dominant types and size in water samples and sediments of Wei River.
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.
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.
After being discarded into the environment, the microplastics (MPs) will undergo weathering effects. However, the low degradation rate of MPs in natural processes greatly limits the understanding of ...long-term aging behavior. By critically reviewing 82 articles in Web of Science from 2015 to 2020, the paper summarized different laboratory technologies including light irradiation, chemical oxidation, heat treatment and γ-ray irradiation to simulate and accelerate the aging of MPs, and evaluated the feasibility by comparison with natural processes. The advantages of laboratory technologies are that aging conditions can be artificially controlled and that the labor and time costs can be saved, whereas the laboratory system is too simple to simulate complex aging processes in the environment. We further reviewed the potential impacts of aging process on the risks of MPs (i.e. physical injury, combined toxicity with external pollutants and chemical risk of additives and low-molecular products). The overall risks are seemingly enhanced by aging process due to the high ingestion by organisms, the strong interaction with pollutants and the release of MP-derived organic compounds. Further studies on the aging behavior of MPs should be focused on the laboratory techniques that can simulate multiple processes of natural aging, the long-term fragmentation behavior of MPs, the effect of aging on growth rate of biofilm in MPs and ingestion property by organisms, and the relationship between aging property of MPs and release rate of chemicals in leachates.
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•Natural and laboratory-accelerated aging processes of microplastics were reviewed.•Advantage of laboratory process is artificially-controlled condition and time-cost saved.•Light irradiation is the mostly selected technology to accelerate the microplastic aging.•Aging increases the risks of microplastics from physical, combined and leachate toxicities.•Laboratory technology that can simulate multiple aging factors should be developed.
•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.
Microplastics are widespread in the environment and might transport readily by ocean currents, wind and atmospheric deposition. Simultaneously, antibiotics and heavy metals could often be detected in ...the environment. They are both positively charged, it is necessary to clarify the interactions of these pollutants with microplastics when they were coexist. In this study, the most commonly used polystyrene (PS) was selected as a representative microplastic. This study investigated the effect of Cd(II) on the sorption of TYL by PS in different coexistence systems. The results showed that: in the composite system, when TYL and Cd(II) coexist, the presence of Cd(II) could inhibit the sorption of TYL by PS, and the inhibitory effect increases with the increase of the concentration of Cd(II), indicating that competitive sorption dominates the sorption. When PS adsorbed Cd(II) first and then adsorbed TYL, the presence of Cd(II) was conducive to the sorption of TYL, and the sorption strengthened with the increase of Cd(II) concentration, indicating that the complexation between TYL and Cd(II) enhanced the sorption of TYL. In addition, initial pH values and ionic strength were essential in the sorption process. Therefore, this study could provide an important basis for evaluating the environmental behavior and ecological risk of microplastics in the process of compound pollution.
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•The effect of Cd(II) on the sorption of TYL by PS was first studied.•The Cd(II) addition inhibited the sorption of TYL by PS in coexist systems.•The Cd(II) addition enhanced the sorption of TYL by PS when Cd(II) first sorbed by PS.•Competition and complexation interactions were involved in the sorption process.
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