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Altered interactions and joint toxicity between microplastics and zinc induced by activated sludge composting process
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Researchers studied how the composting process ages microplastics made of PET, PP, and PE, and how this aging alters their interactions with the heavy metal zinc. They found that composting increased cracks and oxygen-containing groups on the plastic surfaces, enhancing their capacity to adsorb zinc and increasing the combined toxicity to the model organism C. elegans. The study suggests that aged microplastics in compost may increase heavy metal bioavailability when applied to agricultural soils.
Sludge-derived organic compost is widely recognized as a key carrier of microplastic (MP) input to agricultural soils; however, the accompanied environmental modification, such as aging, and the subsequent environmental impact of MPs are largely unknown. In this study, we investigated the aging of polyethylene terephthalate (PET), polypropylene (PP), and polyethylene (PE) in organic compost of sludge, its effect on the environmental behavior of co-occurring heavy metal zinc (Zn), and their joint toxicity on model organism Caenorhabditis elegans (C. elegans). Cracks and grooves were observed to have formed on the surface of aged MPs (A-MPs), and the abundance of oxygen-containing functional groups increased significantly following composting treatment. The adsorption capacity of A-MPs for Zn was generally enhanced, with A-PET showing the most profound increase. The dissolved organic matter (DOM) released during PET aging primarily consisted of three components, and Zn was preferentially complexed with the protein-like C1 fraction (48.50 %). We found that the aging process enhanced the joint reproductive toxicity of PET and Zn to C. elegans. This may result from accelerated Zn desorption from PET in the nematode's lower pH gut and promoted Zn bioaccumulation. Our results elucidated the relevant mechanism through which oxidative aging in the composting environment remodels MPs' surface properties and enhances heavy metal adsorption and bioavailability. These findings provided a key scientific basis for evaluating the environmental risks of MP-pollutant composites.
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Influence of aged and pristine polyethylene microplastics on bioavailability of three heavy metals in soil: Toxic effects to earthworms (Eisenia fetida)
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Researchers studied how aging affects the ability of polyethylene microplastics to influence the bioavailability of zinc, lead, and cadmium in soil, and the resulting toxicity to earthworms. The study found that aged microplastics had different adsorption properties for heavy metals compared to pristine particles, which altered the bioavailability of these metals and affected earthworm health differently depending on microplastic concentration and aging status.
The evolving interface of aged microplastics and heavy metals: implications for environmental fate and toxicity
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This review examined how microplastics interact with heavy metals in the environment, focusing on how plastics serve as carriers that increase metal mobility and bioavailability. Researchers found that factors like polymer aging, biofilm formation, and water chemistry significantly affect how efficiently microplastics absorb metals, and that the combined exposure creates compounded toxicity including oxidative stress and organ damage in organisms. The findings highlight the need for more research on the long-term and multigenerational effects of these combined pollutants.
Binding between Cu2+/Zn2+ and aged polyethylene and polyethylene terephthalate microplastics in swine wastewaters: Adsorption behavior, and mechanism insights
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This study examined how copper and zinc ions from swine wastewater attach to aged polyethylene and PET microplastics. Aging the microplastics through chemical treatment increased their ability to absorb these heavy metals significantly. The findings are important because livestock wastewater is commonly used as fertilizer, and microplastics in this waste could concentrate heavy metals and deliver them into agricultural soil and potentially into crops.
Metal type and aggregate microenvironment govern the response sequence of speciation transformation of different heavy metals to microplastics in soil
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A five-month soil incubation experiment showed that polyethylene microplastics shifted heavy metals like zinc and cadmium from bioavailable forms toward organic-bound forms in soil aggregates, reducing their immediate availability to plants and organisms. The effect varied by metal type and aggregate size, suggesting microplastics can alter the environmental behavior of multiple co-contaminants simultaneously.
Unraveling the adsorption behavior of Zn(II) on UV-aged PET and PP microplastics: kinetic and isotherm analyses
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This study examined how UV aging changes the ability of PET and polypropylene microplastics to adsorb zinc from water. Researchers found that UV exposure over 30 days increased surface roughness and oxygen-containing functional groups on the plastics, significantly enhancing their capacity to bind zinc ions, which suggests that weathered microplastics in the environment may carry higher concentrations of heavy metals.
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