Effects of Weathering on the Sorption Behavior and Toxicity of Polystyrene Microplastics in Multi-solute Systems

Wai Kit Ho, Japhet Cheuk Fung Law, Tong Zhang, Kelvin Sze-Yin Leung*

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

70 Citations (Scopus)
30 Downloads (Pure)


Recent studies have demonstrated that weathering modifies the physicochemical properties and sorption behavior of microplastics (MPs). However, little is known about the effects of such weathering on the simultaneous sorption by MPs of different organic pollutants in multi-solute systems. In this study, the role of cosolute properties in the formation of solute multilayers with a hydrophobic primary solute (4-MBC) on pristine and various weathered polystyrene MPs (PSMPs) was examined. Three weathered PSMPs were studied namely, UV-irradiated PS (UV-PS), microbially degraded PS (MD-NPS), and UV-irradiated PS with subsequent microbial degradation (MD-UV-PS). The weathered PSMPs generally exhibited higher degree of oxygenated functionalities with less surface hydrophobicity than pristine particles. Our findings showed that the formation of solute multilayers with hydrophobic cosolutes was drastically suppressed in UV-PS due to more severe competition at hydrophobic sorption sites. Nevertheless, hydrophilic cosolutes contributed to solute multilayer formation with 4-MBC on PSMPs after UV irradiation, probably due to the stronger sorption of hydrophilic compounds to the oxidized surfaces of these particles via enhanced H-bonding. Strikingly, the sorption of 4-MBC by MD-UV-PS was notably enhanced when hydrophobic cosolutes were present. The observed synergistic sorption indicates that adhered biofilms and/or organic matter on MD-UV-PS could sorb the hydrophobic cosolute molecules, and eventually promote sorption of 4-MBC. Our further toxicity tests revealed that such solute multilayers formed on PSMPs inhibited microalgal growth. These results suggest that the fate and biological effects of MP-mediated chemical exposure could be strongly affected by weathering processes and coexistence of multiple organic contaminants in natural environments.

Original languageEnglish
Article number116419
Number of pages10
JournalWater Research
Publication statusPublished - 15 Dec 2020

Scopus Subject Areas

  • Ecological Modelling
  • Water Science and Technology
  • Waste Management and Disposal
  • Pollution

User-Defined Keywords

  • Algal toxicity
  • Microplastic
  • Multi-solute system
  • Organic UV filter
  • Sorption
  • Weathering


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