Quantification, identification and source discrimination of anthropogenic microfibres in marine and freshwater bodies: a forensic approach

Kechi-Okafor, Chimdia Nwanneka Adaeze (2023) Quantification, identification and source discrimination of anthropogenic microfibres in marine and freshwater bodies: a forensic approach. Doctoral thesis, Northumbria University.

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Abstract

Microfibres (MFs) – fibres with length <5 mm - are pervasive and pose a danger to aquatic environments. Typically, studies on MF pollution have focused on identifying synthetic fibres; however, forensic science studies have consistently demonstrated that anthropogenic natural MFs are more abundant than their synthetic counterparts. This discrepancy could be due to the different methodological approaches to MF characterisation. Accurate characterisation is critical, as natural MFs may be equal in their environmental threat. Therefore, it is essential to adopt appropriate methods that distinguish between all fibre types that result in accurate quantification. This study aims to address these gaps by using forensic methods to investigate the occurrence of MFs in marine and freshwater environments and a lesser-known pathway to them, namely in the form of tumble drying.

Conventional forensic methodological approaches, including the use of polarising light microscopy (PLM), an instrument capable of distinguishing between all fibre types, were used to identify and characterise MFs collected from marine and freshwater environments along the Kenyan-Tanzanian coast and Lake Victoria respectively. Additionally, the study evaluated lint filters and dryer sheets designed to capture MFs during tumble drying while drying cotton and polyester T-shirts together and quantified the amount of MFs released.

Conventional forensic methodological approaches revealed that natural MFs are dominant, constituting 55% and 78% of marine and freshwater samples, respectively. Among the natural fibres, cotton MFs were the most abundant in all sampled locations. Fine filters captured more MFs than coarse filters during sampling.

Over 90% of the MFs released from vented tumble dryers were cotton, demonstrating the important role of the garment itself to shed fibres that influences their prevalence in the environment rather than the quantities of fibre production.

Natural fibres cannot be excluded from MF pollution discourse as they are as pervasive as their synthetic counterparts. Central to the discussion of MF pollution is the shedding capacity of textile materials i.e. what is shed by a material influences its prevalence in the environment, and quantifying this, is primarily reliant on the pore size of capturing devices used.

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