August Microplastic Pollutants in sediments around the coastline of Ireland

90% of samples analysed showed traces of microplastics

Researchers from Earth and Ocean Sciences and the Ryan Institute at NUI Galway have carried out an extensive study on the microplastic content of sediments at 87 locations in habitats designated as Special Areas of Conservation (SACs) and Special Protection Areas (SPAs) around the coastline of Ireland. Microplastics were detected in 79 of the 87 locations studies representing 90% of samples analysed.

Dr Liam Morrison led the study, which has been published in the international journal Marine Pollution Bulletinand was co-authored by NUI Galway PhD student Ana Mendes and Postdoctoral Researcher Dr Nessa Golden. Microplastics were detected in samples from 79 of the 87 locations studies representing 90% of samples analysed.

The study showed that microplastic abundance was closely related with distance from known sources and concentrations were greater in intertidal (on the shore, between tides) as opposed to subtidal (below the level of the lowest tide) sediments. The abundance of microplastics in the intertidal zone is partly influenced by movement of the sea, including wave action, tides, and currents, whereas the subtidal zone is a much more stable environment and could be considered a sink for microplastics.

It was found that the most common plastic type or polymer was polypropylene (PP) (34%) followed by polyethylene terephthalate (PET) (26%) and polyethylene (PE) (26%), comprising of a total of 86% of all the microplastic detected. The dominant colour observed was clear followed by blue, white and black and the appearance of clear PE/PET fibres may indicate grey-water sources (wastewater from sinks, showers, baths and primarily washing machines), as PE/PET is common in clothing, while PP clear fibres are likely from commercial and/or recreational fishing materials.

A relationship between sediment grain size, microplastic abundance and distance from known sources (river/waterways, urban settlements, and wastewater treatment facilities) was established. A higher concentration of microplastics in finer sediments (such as mudflats) within a 2 km distance from a known source, was observed with microplastic concentration decreasing with an increase in sediment grain size or as sediments get coarser (such as sandy beaches) and/or distance from a possible source of microplastics.

The results demonstrate that an understanding of potential sources of pollution, sediment type (sandy beaches to mudflats) and hydrodynamic conditions (waves and currents) are very important in terms of MP abundance and distribution in marine sediments and in terms of effective waste management strategies and policy aimed at reducing the global plastics problem.

Dr Morrison said: “This study provided a broader assessment of microplastic abundance by representing 87 inshore locations around Ireland. In addition, Ireland is the highest producer of plastic waste per person in the EU and the fourth worst in recycling rate, according to the latest data released by Eurostat.

“Owing to their great diversity, ranging from size and other properties, microplastics can effectively penetrate through food webs where absorption and desorption of pollutants and associated chemicals can occur, creating a complex range of potential hazards for biota and humans”

This study provides an insight into the state of microplastic debris in Irish coastal sediments and a baseline for further research and policy making towards marine litter and in particular micro-litter in Ireland.

Read the full study in Marine Pollution Bulletin here: https://www.sciencedirect.com/science/article/abs/pii/S0025326X21008365

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