Synthesis of metal-doped nanoplastics and their utility to investigate fate and behaviour in complex environmental systems

Research on the distribution and effects of particulate plastic has intensified in recent years and yet, due to analytical challenges, our understanding of nanoplastic occurrence and behaviour has remained comparatively elusive. However, process studies could greatly aid in defining key parameters for nanoplastic interactions within and transfers between technical and environmental compartments. Here we provide a method to synthesize nanoplastic particles doped with a chemically entrapped metal used as a tracer, which provides a robust way to detect nanoplastics more easily, accurately and quantitatively in complex media. We show the utility of this approach in batch studies that simulate the activated sludge process of a municipal waste water treatment plant and so better understand the fate of nanoplastics in urban environments. We found that the majority of particles were associated with the sludge (>98%), with an average recovery of over 93% of the spiked material achieved. We believe that this approach can be developed further to study the fate, transport, mechanistic behaviour and biological uptake of nanoplastics in a variety of systems on different scales. Analytical challenges in detecting nanoplastics have hindered the understanding of their behaviour in environmental systems, but these difficulties can be circumvented by synthesizing metal-doped nanoplastics (where the metal can be measured as a proxy for the plastic) to undertake mechanistic investigations of particle fate, transport and biological interactions in lab and pilot-scale studies.