Microplastics in the marine environment: analytical considerations, emerging sources, and protocol validation
Mendes, Ana Rita Marques
Mendes, Ana Rita Marques
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Publication Date
2024-02-02
Type
Thesis
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Abstract
Microplastics particles, with a size range between 1µm to 5 mm are established in all ecosystems, from the poles to the equator, and in a wide range of organisms including mammals, birds, fish, and invertebrates. Microplastics are contaminants and act as vectors for chemical pollutants in the environment. The sources of microplastics are direct, such as microbeads, or indirect, such as fragmentation of larger items of debris. The present work investigated microplastics from the perspective of previously unidentified sources, deposition in intertidal and subtidal sediments, extraction mechanisms from the gastrointestinal tract of marine turtles, and interaction with metal contaminants. Microplastic white fibres were discovered in sediments next to a wastewater treatment plant. These fibres were compared to those found in sewage-related waste and consumer sanitary products like wet wipes and sanitary towels. The study found that 50% of the tested brands labelled as flushable contained a mixture of PET and cellulose, while the rest contained cellulose alone. The accumulation of sewage-related waste and macro-debris (including wet wipes and sanitary towels) intermingled with seaweed biomass was associated with a combined sewer overflow, and the microplastic fibres extracted from this waste were similar to those found in the intertidal sediments close to the WWTP over a ten-month period. The result of this study highlights that wet wipes and sanitary towels flushed down toilets are a significant source of microplastic fibres in the environment. The present work also examined the microplastics content of intertidal and subtidal sediments at 87 locations in habitats designated as Special Areas of Conservation (SACs) and Special Protection Areas (SPAs) on the coastline of Ireland. Microplastic abundance was closely related to distance from known sources and concentrations were greater in intertidal as opposed to subtidal sediments. Colourless, polyethylene fibers and polypropylene fragments were the most abundant microplastic recorded, and finer-grained sediments were shown to entrap more microplastics than coarser sediments. The results demonstrate that an understanding of potential sources of pollution, sediment type, and hydrodynamic conditions are important in terms of microplastic abundance and distribution in marine sediments and for effective waste management strategies and policy aimed at reducing the global plastics problem. This work also developed a new extraction protocol for the removal of microplastics from the digestive tract of turtles using a combination and modification of pre established methods. The results observed from the chymes tested facilitated the development of an improved protocol for microplastic extraction, reducing contamination and enhancing the efficiency of the technique.
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Publisher
NUI Galway