Characterization of microplastics from antifouling coatings released under controlled conditions with an automated SEM-EDX particle analysis method

Abstract

A significant portion of microplastics in the marine environment originate from antifouling coatings. However, knowledge about release pathways and rates is limited. One such pathway is particle release from ship hull coatings during sailing. This study demonstrates the release of microplastic particles from a typical commercial antifouling coating in simulated low-speed sailing conditions. The self-polishing antifouling yacht coating was exposed to controlled low-speed sailing conditions in artificial seawater. The particle content of the artificial seawater was monitored throughout an automated particle analysis protocol using scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDX). Particle counts, sizes and chemistries were recorded. Over the duration of the exposure, the total particle volume release increased with time. Particle release behaviour can be correlated to the polishing behaviour of antifouling coatings. The equivalent diameter of the majority of the particles was 1–5 $\mu$m. The particles were mainly composed of carbon (around 58%wt.), oxygen (around 32%wt.), copper (0–8%wt.), and zinc (0–2%wt.). Carbon and part of the oxygen can be ascribed to the polymeric binder in the coating. Copper and zinc, on the other hand, can be attributed to the known biocidal pigments in the coating. This study improves our understanding of particle release from antifouling coatings.