Abstract/Summary

Considerable amounts of polyethylene terephthalate (PET) microplastic fibres are released into the aquatic environment by the laundering of polyester clothing. Microplastic fibres can be ingested by organisms in the environment. Therefore, it has been suggested that microplastic fibres act as vectors for adsorbed contaminants, which are subsequently desorbed in the gut of the organism. We undertook sorption isotherms at pH 6, pH 7, and pH 8 to quantify the sorption of methylmercury (MeHg) to PET fibres. Sorption isotherms were fit to Langmuir, Freundlich, and Brunauer-Emmett-Teller models. Sorption decreased with increasing pH, which can be explained by physisorption on the negatively charged PET surfaces and the greater presence of neutral or negative MeHg species at higher pH. We used the parameters obtained by the model fits to predict the likely concentration of MeHg on PET microplastic fibres in aquatic ecosystems with environmentally realistic MeHg concentrations. We calculated MeHg concentrations on PET microplastic fibres that were four orders of magnitude lower than previously observed concentrations of MeHg in seston (suspended particles comprising algae and bacteria) at the base of the aquatic food web. The results indicate that the presence of PET microplastic fibres in the environment do not elevate the MeHg exposure to organisms which ingest fibres in the environment.