The comparative study by Raman spectroscopy of the plastic tide in the three ports of the Mediterranean Sea

Abstract

This paper summarizes the field studies on marine microplastics (MPs) carried out in the autumn season in four various localisations within three ports chosen at the Mediterranean Sea near the French Riviera and the West Coast of Italy (within the Ligurian Sea). It considers the transport problem and the fate of the MPs introduced to the sea by analysing beach debris found on the shore after the stormy weather. Monitored ports included Saint-Tropez, Portoferraio and Porto Ercole, in which two different places were monitored. The aim is to approach the plastic tide phenomena by concentrating on a selected fraction of all MPs presented on the seashore. The final identification of debris was performed using Raman spectroscopy, providing a high-resolution signal. The PE, PP and PS contents were compared as the most frequent and representative polymers. Finally, we tackle the pending issue of the compound leakage from the MPs taking the environmentally aged particles from Portoferraio for further laboratory experiments and discuss an innovative approach with a low detection limit based on the electrochemical methods.

Keywords: Electrochemical analysis; Marine microplastics; Mediterranean Sea; Polymer leakage; Raman spectroscopy.

Fig. 1

The qualitative identification (by Raman spectroscopy) of all samples in three ports and four localizations

Fig. 2

The relative content of particular polymer types in selected localizations: a Porto Ercole (1), b Porto Ercole (2), c Portoferraio and d Saint-Tropez

Fig. 3

An overview of Raman spectra for the most numerous samples collected in Saint-Tropez: a PE and b PP

Fig. 3

An overview of Raman spectra for the most numerous samples collected in Saint-Tropez: a PE and b PP

Fig. 4

The summary of colour percentage in a overall and in b Porto Ercole (1), c Porto Ercole (2), d Portoferraio and e Saint-Tropez

Fig. 5

SEM images of the PIN-Au NPs composite, where a shows the survey image of the whole surface and b shows a detailed image of the structured coating of the GC electrode

Fig. 6

Cyclic voltammetry curves for leaching solution of a sample 3 and b sample 13 recorded in 0.1 M LiClO₄ using WE: GC coated with PIN-Au NPs, RE: sat. Ag|AgCl|KCl, CE: Pt mesh, and c blanc solution 0.1 M LiClO₄ exposed on the air