Microplastics in freshwater sediments: analytical methods, temporal trends, and risk of associated organophosphate esters as exemplar plastics additives

Simeon Onoja, Holly A. Nel, Mohamed Abou Elwafa Abdallah, Stuart Harrad*

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

61 Downloads (Pure)


It has been estimated that over 28 million tonnes of plastics end up in water bodies annually. These plastics degrade into microplastics (MPs), which along with microbeads and MPs from other sources such as wastewater treatment plants continue to threaten the aquatic system. At such small sizes, and corresponding larger surface areas per unit mass/volume, MPs exhibit enhanced capacity for absorbing and desorbing toxic chemicals/additives. Therefore, MPs can serve as vectors through which additives as well as other persistent, bio-accumulative, and toxic chemicals can enter the food chain. Additives are a significant component of most plastic products with some identified as hazardous to health and the environment. One group of additives that has continued to attract interest is organophosphate esters (OPEs), which are used both as flame retardants and plasticizers. Some of these OPEs are suspected carcinogens and endocrine disruptors and have been reported to exert serious toxic effects on freshwater biota. Separate studies on the presence and fate in the freshwater environment of these additives and MPs have emerged recently. However, no studies exist that examine the extent to which plastics additives such as OPEs in sediments are sorbed to MPs as opposed to the sediment itself. This has potentially important implications for the bioavailability of such additives and studies to examine this are recommended. This paper reviews critically the current state-of-knowledge on MPs in freshwater sediments, methods for their analysis, as well as their occurrence, temporal trends, and risks to the freshwater aquatic environment. Moreover, to facilitate the study of additives associated with MPs that have been extracted from sediments, we consider the possible effect of MP isolation methods on the determination of concentrations of associated additives like OPEs.

Original languageEnglish
Article number111830
Number of pages15
JournalEnvironmental Research
Early online date3 Aug 2021
Publication statusPublished - Jan 2022

Bibliographical note

Funding Information:
The authors would like to thank the Petroleum Technology Development Fund ( PTDF ) for provision of a scholarship (Reference: 1372) to Simeon Onoja.

Publisher Copyright:
© 2021


  • Analytical methods
  • Flame retardants
  • Freshwater sediment
  • Microplastics
  • Organophosphate esters (OPEs)
  • Plasticizers

ASJC Scopus subject areas

  • Biochemistry
  • Environmental Science(all)


Dive into the research topics of 'Microplastics in freshwater sediments: analytical methods, temporal trends, and risk of associated organophosphate esters as exemplar plastics additives'. Together they form a unique fingerprint.

Cite this