Screening of suspected micro(nano)plastics in the Ebro Delta (Mediterranean Sea)

Abstract

This is the first work reporting the use of a double suspect-screening to assess most common polymers and additives in micro(nano)plastics (NPLs/MPLs) found in environmental waters. The method consisted of water filtration followed by ultrasonic-assisted extraction with toluene and analysis employing size exclusion chromatography using an advanced polymer chromatography column coupled to high-resolution mass spectrometry with an atmospheric pressure photoionisation source by negative ionisation conditions (LC(APC)-APPI(-)-HRMS). The identification of NPL/MPLs polymers has been based on increasing confirmation level, including the monomers characterisation by the Kendrick Mass Defect and confirmation and quantification when standards were available. In parallel, the identification of main additives in NPL/MPLs composition, as well organic contaminants adsorbed onto the plastic particles were carried out by analysis of the extracts by LC(C18)-APPI (+/-)-HRMS. To assess the impact of plastic pollution it is necessary to assess the composition in terms of polymers but also the additives. This screening approach has been employed to study composition of NPL/MPLs in the Ebro Delta. Two sampling campaigns including freshwater and seawater samples have been investigated to assess plastic composition in the top 5 cm. Polystyrene (PS), polyethylene (PE), polyisoprene (PI), polybutadiene (PBD), polypropylene (PP) and polysiloxanes were the most detected polymers and PP and PE, sizing between < 1000 and 2000 Da, were found at concentrations reaching up to 7000 ng/L in some areas. The pentadecanoic acid, 1,2,3-benzotriazoles, 2-ethylhexanoic acid (2-EHA), and phthalates such as dimethyl phthalate, mono(2-ethylhexyl) phthalate (MEHP) and the phthalimide were more frequently detected plastic additives. Finally, series of organic contaminants were as well detected in the particulate fraction. These organic contaminants cannot be associated to plastic compositions but can be associated to their adsorption to the particulate matter, in particular to NPL/MPLs, due to their non-polar character. Among these organic contaminants, the more frequently detected were pharmaceutical compounds, food additives and pesticides.

Keywords: HRMS; Microplastics; Nanoplastics; Quantification; Size exclusion chromatography; Suspect screening.