Microplastics in seawater: sampling strategies, laboratory methodologies, and identification techniques applied to port environment

Abstract

The European Interreg Italy-France 2014-2020 Maritime Project SPlasH! (Stop to Plastics in H 2 O!) focused on the study of microplastics (MPs) in the marine port environment to evaluate their presence, abundance, and mechanisms of diffusion to the open sea. In the framework of this project, a worldwide review of 74 studies was carried out, providing an overview of MP investigation techniques, focusing on sampling strategies, laboratory methodologies, and identification of MPs collected in seawater, and specifically evaluating their applicability to the marine port environment. Nets were the most commonly used device for MP surface sampling, but their use can be difficult in narrow spaces within the port basins, and they must be coupled to discrete sampling devices to cover all port basins. In the laboratory, density separation (NaCl, ZnCl 2 , NaI, sodium lauryl sulfate (SLS)), filtration (polycarbonate, polyamide, glass, cellulose, ANOPORE inorganic membrane filters), sieving, visual sorting, and digestion methods (acidic, enzymatic, alkaline, oxidative) were used to separate MPs from seawater. Digestion becomes essential with water samples with great inorganic and organic loads as deriving from a port. Although many studies are based only on visual MP identification under a microscope, analytical identification techniques unequivocally determine the particle nature and the identity of the plastic polymers and are necessary to validate the visual sorting of MPs. Fourier-transform infrared spectroscopy (FTIR) is the most used analytical identification technique.

A Practical Overview of Methodologies for Sampling and Analysis of Microplastics in Riverine Environments

“…Based on the relatively low concentrations of MPs in the environment, their sampling on the water surface generally requires water filtration or collection of large sample volumes employing mostly neuston, plankton, and manta nets ( Figure 2) of different mesh sizes, considered as volumereduced or nondiscrete sampling devices in which the volume of water is reduced until only the particles of interest for further processing in a laboratory remain [34]. MPs' small sizes demand sampling devices that allow the collection of a large volume of water in order to reduce the spatial and temporal variations adequately [15].…”

“…Alternatively, discrete sampling devices (Niskin bottles, rosettes, integrating water sampler (IWS), buckets, bottles, and steel samplers; KC Denmark A/S Research equipment, Silkeborg, Denmark) can be used to collect bulk samples [34]. In bulk sampling, a known and recorded volume of the sample is collected without reducing it.…”

“…Moreover, this type of sampling is rapid and can help to reduce any risk of contamination, given that the time of handling of the sample and the time of exposition of it to the surrounding environment are shortened. However, disadvantages consist of a limited amount of samples that can be collected, stored, and processed [34].…”

Microplastics and their potential effects on the aquaculture systems: a critical review

“…2019; Cutroneo et al . 2020; Li et al . 2020b), and the content of the MPs reaches 43 000 particles per km 2 in more than 95% of detected sites in five Great Lakes in the United States (Eriksen et al .…”

The Importance of Biofilms to the Fate and Effects of Microplastics

“…A recently proposed size schema separates microplastics in marine environments into the following categories: nano (1-1000 nm)-, micro (1-1000 μm)-, meso (1-10 mm)-, and macroplastics (≥1 cm). Size schemes are proposed to address the sampling problems encountered in the field, but these schemes are lacking since it is difficult to provide a microplastic sample that is spatially representative of a specific environmental space [26][27][28][29].…”