Automated quantitative mineralogy and plastics – A new view of the plastic surface in aquatic environments

Plastics are a ubiquitous pollutant, and are rapidly colonized by biofilms that sorb inorganic and organic components, forming the interface between plastics and the environment. This study provides a proof of concept for the use of automated quantitative mineralogy (AQM) to illuminate and analyse the metal and mineral component of the plastisphere on plastics sampled from temperate and tropical aquatic localities. The method is non-destructive and requires minimal sample preparation, providing a 2-dimensional visualisation and semi-quantitative analysis of the arrangement of biogenic and abiogenic components, highlighting potential interactions between these components. Our results also communicate the potential role of plastic structure on mineral retention in relation to environmental parameters that can influence mechanical degradation. AQM provides a novel avenue to understand the minerals associated with plastics, and increases our knowledge of the interfacial composition, which can inform potential interactions, transformations and insights into the long-term fate of plastic pollutants.