The protective layer formed by soil particles on plastics decreases the toxicity of polystyrene microplastics to earthworms (Eisenia fetida). (April 2022)

• Record Type: Journal Article
• Authors: Liu, Jinbo; Qin, Jianjun; Zhu, Lang; Zhu, Kecheng; Liu, Ze; Jia, Hanzhong; Lichtfouse, Eric
• Is Part Of: Environment international. Volume 162(2022)
• Publication Date: 2022-04
• Subjects: Polystyrene -- Microplastics -- Earthworm -- Soil -- Toxicity -- Aging; Environmental protection -- Periodicals; Environmental health -- Periodicals; Environmental monitoring -- Periodicals; Environmental Monitoring -- Periodicals; Environnement -- Protection -- Périodiques; Hygiène du milieu -- Périodiques; Environnement -- Surveillance -- Périodiques; Environmental health; Environmental monitoring; Environmental protection; Periodicals; 333.705
• DOI: 10.1016/j.envint.2022.107158
• Languages: English
• ISSNs: 0160-4120

Abstract

Graphical abstract: Highlights: 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. Abstract: 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.