Aging assessment of microplastics (LDPE, PET and uPVC) under urban environment stressors

Miranda, Mariana N.; Sampaio, Maria J.; Tavares, Pedro B.; Silva, Adrián M.T.; Pereira, M.F.R.

doi:10.1016/j.scitotenv.2021.148914

Cited by 119 publications

(34 citation statements)

References 63 publications

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“…The degree of oxidation of the plastics was indicated by the CI value, which is an effective parameter in field observations for a wide range of materials. − In this study, CI ranged from 0.1 to 23.3 (average 1.4 ± 0.8) for all the samples and was significantly correlated with most of the morphological metrics, including line density, centroid density, wavelength, perimeter, and area of crack patterns (Figure A). The degree of oxidation increased with the degree of crack development, i.e., increasing the amounts of lines and nets.…”

Section: Resultsmentioning

confidence: 64%

Crack Patterns of Environmental Plastic Fragments

Deng

Zheng

et al. 2022

Environ. Sci. Technol.

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Secondary microplastics usually come from the breakdown of larger plastics due to weathering and environmental stress cracking of plastic wastes. In the present study, 5013 plastic fragments were collected from coastal beaches, estuary dikes, and lake banks in China. The fragment sizes ranged from 0.2 to 17.1 cm, and the dominant polymers were polypropylene and polyethylene. Cracks were observed on the surfaces of 49–56% of the fragments. Based on the extracted crack images, we proposed a general crack pattern system including four crack types with specific definitions, abbreviations, and symbols. The two-dimensional spectral analysis of the cracks suggests that the first three patterns showed good regularity and supported the rationality of the pattern system. Some crack metrics (e.g., line density) were closely correlated with the carbonyl index and additives (e.g., phthalate esters) of fragments. For crack investigation in field, we proposed a succinct protocol, in which five crack ranks were established to directly characterize the degree of cracking based on the line density values. The system was successfully applied to distinguish the differences in crack features at two representative sites, which indicates that crack pattern is a useful tool to describe the morphological changes of plastic surfaces in the environment.

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Section: Resultsmentioning

confidence: 64%

Crack Patterns of Environmental Plastic Fragments

Deng

Zheng

et al. 2022

Environ. Sci. Technol.

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“…Several previous works conducted under simulated environmental conditions and on field-collected samples showed that photo and thermal oxidation together with humidity could alter the physicochemical structure of MPs leading to the introduction of oxygen into the polymer chain with the formation of carbonyl (CO) and hydroxyl (OH) functional groups [ 60 , 61 , 62 , 63 ].…”

Section: Discussionmentioning

confidence: 99%

Effects and Impacts of Different Oxidative Digestion Treatments on Virgin and Aged Microplastic Particles

et al. 2022

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Although several sample preparation methods for analyzing microplastics (MPs) in environmental matrices have been implemented in recent years, important uncertainties and criticalities in the approaches adopted still persist. Preliminary purification of samples, based on oxidative digestion, is an important phase to isolate microplastics from the environmental matrix; it should guarantee both efficacy and minimal damage to the particles. In this context, our study aims to evaluate Fenton’s reaction digestion pre-treatment used to isolate and extract microplastics from environmental matrices. We evaluated the particle recovery efficiency and the impact of the oxidation method on the integrity of the MPs subjected to digestion considering different particles’ polymeric composition, size, and morphology. For this purpose, two laboratory experiments were set up: the first one to evaluate the efficacy of various digestion protocols in the MPs extraction from a complex matrix, and the second one to assess the possible harm of different treatments, differing in temperatures and volume reagents used, on virgin and aged MPs. Morphological, physicochemical, and dimensional changes were verified by Scanning Electron Microscope (SEM) and Fourier Transformed Infrared (FTIR) spectroscopy. The findings of the first experiment showed the greatest difference in recovery rates especially for polyvinyl chloride and polyethylene terephthalate particles, indicating the role of temperature and the kind of polymer as the major factors influencing MPs extraction. In the second experiment, the SEM analysis revealed morphological and particle size alterations of various entities, in particular for the particles treated at 75 °C and with major evident alterations of aged MPs to virgin ones. In conclusion, this study highlights how several factors, including temperature and polymer, influence the integrity of the particles altering the quality of the final data.

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“…• 0.1 M HNO 3 in deionized water (pH ca. 1, sample labeled as HNO 3 ), simulating acidic environments in wastewater conditions (Wang et al 2021) or long-term effects of weaker acidic conditions (e.g., prolonged exposure to acid rains, Miranda et al 2021); • 0.1 M NaOH in deionized water (pH ca. 13, sample labeled as NaOH), to simulate a strongly alkaline environment and enhance alkaline hydrolysis of the polymer, simulating long-term degradation in weaker alkaline conditions (Miranda et al 2021).…”

Section: Physicochemical Ageing Experimentsmentioning

confidence: 99%

“…1, sample labeled as HNO 3 ), simulating acidic environments in wastewater conditions (Wang et al 2021) or long-term effects of weaker acidic conditions (e.g., prolonged exposure to acid rains, Miranda et al 2021); • 0.1 M NaOH in deionized water (pH ca. 13, sample labeled as NaOH), to simulate a strongly alkaline environment and enhance alkaline hydrolysis of the polymer, simulating long-term degradation in weaker alkaline conditions (Miranda et al 2021). This process can also simulate sludge dewatering processes, likely affecting plastic fragments (Liu et al 2022); • 33% H 2 O 2 (sample labeled as H 2 O 2 ), a liquid medium used to simulate thermo-oxidative degradation of plastic (Luo et al 2021;Bhagat et al 2022).…”

Section: Physicochemical Ageing Experimentsmentioning

confidence: 99%

“…Moreover, plastic can likely interact with other chemical stressors during its use life and after its dispersion, especially in urbanized contexts (e.g., in wastewater or sludge treatments). The abovementioned processes, which can further enhance plastic chemical degradation (e.g., alkaline hydrolysis and advanced oxidation processes; Miranda et al 2021;Alimi et al 2022), are generally overlooked in laboratory-based ageing tests.…”

Section: Introductionmentioning

confidence: 99%

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Physicochemical and biological ageing processes of (micro)plastics in the environment: a multi-tiered study on polyethylene

Binda

Zanetti

Bellasi

et al. 2022

Environ Sci Pollut Res

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Pollution by plastic and microplastic impacts the environment globally. Knowledge on the ageing mechanisms of plastics in natural settings is needed to understand their environmental fate and their reactivity in the ecosystems. Accordingly, the study of ageing processes is gaining focus in the context of the environmental sciences. However, laboratory-based experimental research has typically assessed individual ageing processes, limiting environmental applicability. In this study, we propose a multi-tiered approach to study the environmental ageing of polyethylene plastic fragments focusing on the combined assessment of physical and biological processes in sequence. The ageing protocol included ultraviolet irradiation in air and in a range of water solutions, followed by a biofouling test. Changes in surface characteristics were assessed by Fourier transform infrared spectroscopy, scanning electron microscopy, and water contact angle. UV radiation both in air and water caused a significant increase in the density of oxidized groups (i.e., hydroxyl and carbonyl) on the plastic surface, whereby water solution chemistry influenced the process both by modulating surface oxidation and morphology. Biofouling, too, was a strong determinant of surface alterations, regardless of the prior irradiation treatments. All biofouled samples present (i) specific infrared bands of new surface functional groups (e.g., amides and polysaccharides), (ii) a further increase in hydroxyl and carbonyl groups, (iii) the diffuse presence of algal biofilm on the plastic surface, and (iv) a significant decrease in surface hydrophobicity. This suggests that biological-driven alterations are not affected by the level of physicochemical ageing and may represent, in real settings, the main driver of alteration of both weathered and pristine plastics. This work highlights the potentially pivotal role of biofouling as the main process of plastic ageing, providing useful technical insights for future experimental works. These results also confirm that a multi-tiered laboratory approach permits a realistic simulation of plastic environmental ageing in controlled conditions.

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Aging assessment of microplastics (LDPE, PET and uPVC) under urban environment stressors

Cited by 119 publications

References 63 publications

Crack Patterns of Environmental Plastic Fragments

Crack Patterns of Environmental Plastic Fragments

Effects and Impacts of Different Oxidative Digestion Treatments on Virgin and Aged Microplastic Particles

Physicochemical and biological ageing processes of (micro)plastics in the environment: a multi-tiered study on polyethylene

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