A new underwater in-situ microplastics detection system based on micro-Raman spectroscopy: Development and sea trials

Abstract

In-situ underwater observation for marine microplastics (MPs) study has long been desired but challenged by the difficulty in achieving continuous MPs enrichment and MPs analysis in underwater environments. Herein, a novel underwater system for in-situ detection of MPs was introduced. An innovative design with a filter mesh flipped 180° driven by a stepper motor was adopted to ensure the self-cleaning of the filter mesh and continuous MPs enrichment, reducing the frequency of manual maintenance required for the system. A special-designed optical detection chamber based on micro-Raman spectroscopy featured a 13 × 10 mm imaging field of view and a 50 µm imaging resolution was developed to gather morphology and composition information of MPs. During sea trials, the system successfully detected polypropylene (PP) microplastic and other suspended substances in seawater including microalgae, organic substances, and sands. This study lays the groundwork for future research into underwater in-situ investigation of marine MPs pollution.