Colour and size influences plastic microbead underestimation, regardless of sediment grain size

Research output: Contribution to journalArticlepeer-review


  • Holly Nel
  • Tatenda Dalu
  • Ryan J. Wasserman
  • Jeffrey W. Hean

Colleges, School and Institutes


The quantification of microplastics in environmental samples often requires an observer to determine whether a particle is plastic or non-plastic, prior to further verification procedures. This implies that inconspicuous microplastics with a low natural detection may be underestimated. The present study aimed at assessing this underestimation, looking at how colour (white, green and blue), size (large; ~1000 μm and small; <400 μm) and grain size fraction may affect detection. Sediment treatments varying in grain size were inoculated with known quantities of low-density polyethylene microbeads extracted from commercially bought facial scrubs. These microbeads varied in colour and size. Once extracted using a density separation method microbeads were counted. An overall underestimation of 78.59% may be a result of observer error and/or technical error. More specifically, the results suggested that microbeads varying in colour and size have a different detection probability and that these microbead features are more important in underestimation likelihoods than grain sizes.


Original languageEnglish
Pages (from-to)567-570
Number of pages4
JournalScience of the Total Environment
Early online date19 Nov 2018
Publication statusPublished - 10 Mar 2019


  • Analytical methods, Detection probability, Microplastics, Observer error