Microplastics: Finding a consensus on the definition.

Polymer science is one of the most revolutionary research areas of the last century, instigated by the discovery of Bakelite, the first synthetic plastic. Plastic, once a revolutionary material, has gradually become a global environmental threat with ubiquitous distribution. The term 'microplastics' coined in 2004, is used to describe the smaller plastic particles recorded, however there is still no all-inclusive definition that accurately encompasses all criteria that could potentially describe what a microplastic is. Here, the authors focus on the currently reported methods for describing and identifying microplastics and propose a new definition that incorporates all the important descriptive properties of microplastics. This definition not only focuses on size and origin, but also considers physical and chemical defining properties. While this manuscript may promote debate, it aims to reach a consensus on a definition for microplastics which can be useful for research, reporting and legislative purposes.

Microplastics in coastal sediments from Southern Portuguese shelf waters.

Microplastics are well-documented pollutants in the marine environment that result from fragmentation of larger plastic items. Due to their long chemical chains, they can remain in the environment for long periods of time. It is estimated that the vast majority (80%) of marine litter derives from land sources and that 70% will sink and remain at the bottom of the ocean. Microplastics that result from fragmentation of larger pieces of plastic are common to be found in beaches and in the water surface. The most common microplastics are pellets, fragments and fibres. This work provides original data of the presence of microplastics in coastal sediments from Southern Portuguese shelf waters, reporting on microplastic concentration and polymer types. Microplastic particles were found in nearly 56% of sediment samples, accounting a total of 31 particles in 27 samples. The vast majority were microfibers (25), identified as rayon fibres, and fragments (6) identified as polypropylene, through infrared spectroscopy (µ-FTIR). The concentration and polymer type data is consistent with other relevant studies and reports worldwide.

Evidence of microplastics in samples of zooplankton from Portuguese coastal waters.

Records of high concentrations of plastic and microplastic marine debris floating in the ocean have led to investigate the presence of microplastics in samples of zooplankton from Portuguese coastal waters. Zooplankton samples collected at four offshore sites, in surveys conducted between 2002 and 2008, with three different sampling methods, were used in this preliminary study. A total of 152 samples were processed and microplastics were identified in 93 of them, corresponding to 61% of the total. Costa Vicentina, followed by Lisboa, were the regions with higher microplastic concentrations (0.036 and 0.033 no. m⁻³) and abundances (0.07 and 0.06 cm³ m⁻³), respectively. Microplastic: zooplankton ratios were also higher in these two regions, which is probably related to the proximity of densely populated areas and inputs from the Tejo and Sado river estuaries. Microplastics polymers were identified using Micro Fourier Transformed Infrared Spectroscopy (µ-FTIR), as polyethylene (PE), polypropylene (PP) and polyacrylates (PA). The present work is the first report on the composition of microplastic particles collected with plankton nets in Portuguese coastal waters. Plankton surveys from regular monitoring campaigns conducted worldwide may be used to monitor plastic particles in the oceans and constitute an important and low cost tool to address marine litter within the scope of the Marine Strategy Framework Directive (2008/56/EC).

Organic pollutants in microplastics from two beaches of the Portuguese coast.

Microplastics pose a threat to coastal environments due to their capacity to adsorb persistent organic pollutants (POPs). These particles (less than 5 mm in size) are potentially dangerous to marine species due to magnification risk over the food chain. Samples were collected from two Portuguese beaches and sorted in four classes to relate the adsorption capacity of pollutants with color and age. Polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and DDTs were analysed on pellets through gas chromatography mass spectrometry (GC-MS), and types of plastic were identified using Fourier transformed infra-red spectroscopy (micro-FTIR). Microplastics were mostly polyethylene and polypropylene. Regarding sizes, some fibres ranged from 1 to 5 µm in diameter and were 500 µm in length. The majority of samples collected had sizes above 200 µm. Black pellets, unlike aged pellets, had the highest concentrations of POPs except for PAHs in Fonte da Telha beach. PAHs with higher concentrations were pyrene, phenantrene, chrysene and fluoranthene. Higher concentrations of PCBs were found for congeners 18, 31, 138 and 187. Further investigation is necessary to understand the relationship between plastic degradation and adsorption for different pollutants.