UV degradation of natural and synthetic microfibers causes fragmentation and release of polymer degradation products and chemical additives

Lisbet Sørensen,Anette Synnøve Groven,Ingrid Alver Hovsbakken,Oihane Del Puerto,Daniel F Krause,Antonio Sarno,Andy M Booth

doi:10.1016/j.scitotenv.2020.143170

Lisbet Sørensen, Anette Synnøve Groven + Show 5 more

Open Access

https://doi.org/10.1016/j.scitotenv.2020.143170

Copy DOI

Abstract

A high proportion of the total microplastic (MP) load in the marine environment has been identified as microfibers (MFs), with polyester (PET) and polyamide (PA) typically found in the highest abundance. The potential for negative environmental impacts from MPs may be dependent on their degree of degradation in the environment, which is influenced by both intrinsic properties (polymer type, density, size, additive chemicals) and extrinsic environmental parameters. Most polymer products break down slowly through a combination of environmental processes, but UV degradation can be a significant source of degradation. The current study aimed to investigate the effect of UV irradiance on the degradation of natural (wool) and synthetic (PET and PA) MFs. Degradation of MFs was conducted in seawater under environmentally relevant accelerated exposure conditions using simulated sunlight. After 56 days of UV exposure, PA primarily exhibited changes in surface morphology with no significant fragmentation observed. PET and wool fibers exhibited both changes in surface morphology and fragmentation into smaller particles. A range of molecular degradation products were identified in seawater leachates after UV exposure, with increasing abundance over the duration of the experiment. Furthermore, a variety of additive chemicals were shown to leach from the MFs into seawater. While some of these chemicals were also susceptible to UV degradation and some are expected to biodegrade rapidly, others may be persistent and contribute to the overall load of chemical pollution in the marine environment.

Highlights

Textile washing has been identified as a major source of MPFs to the environment (Browne et al, 2011), the level of MPF release is dependent on factors such as polymer type, fabric type, type of washing machine, washing program and type of detergent (De Falco et al, 2018; Hartline et al, 2016; Napper and Thompson, 2016; Salvador Cesa et al, 2017)
After UV exposure, both polyamide (PA) and polyester (PET) fibers showed signs of degradation at the fiber surface when investigated by scanning electron microscopy (SEM) (Fig. 1)
A different form of degradation was observed for wool fibers, where the surface fibrils appeared to be smoothed during UV exposure

Summary

Introduction

Textile washing has been identified as a major source of MPFs to the environment (Browne et al, 2011), the level of MPF release is dependent on factors such as polymer type, fabric type (including fiber, yarn, weave and finishing), type of washing machine, washing program and type of detergent (De Falco et al, 2018; Hartline et al, 2016; Napper and Thompson, 2016; Salvador Cesa et al, 2017). Focus has been given recently to the potential effects of additive and production chemicals leaching from plastic into water (Zimmermann et al, 2019). UV-degradation may cause formation of watersoluble polymer degradation products, but this process has yet to be investigated for textile polymers

Methods

Results

Conclusion