Abstract
Microplastic fibres (MPFs) are increasingly being reported as one of the dominant forms of microplastic pollution in aquatic environments. Clothing and textiles produced from synthetic fibres such as polyester (PES), polyacrylic (PAC) and nylon (PA) are considered some of the main sources of MPFs. However, there has been little focus on the environmental fate and effects of MPFs compared to microplastic particles and fragments. In the current study, the environmental fate of MPFs was studied by long-term UV degradation studies using a suite of 5 MPFs with different physical and chemical characteristics (PES, PAC and PA) under freshwater and marine conditions. A detailed chemical characterisation of the pristine test materials was conducted, using GC-MS, LC-MS and ICP-MS to identify the type of additive chemicals present. Degradation studies were conducted in sterile synthetic freshwater (algal culture medium, TG201) and sterile-filtered seawater. Exposures were conducted in 35 mL quartz glass tubes using an Atlas Suntest CPS+ with Xenon lamp generating 65 W/m2 light intensity and fitted with a daylight filter (300-400 nm). The endpoints studied after 5 and 10 months were changes in MPF size (light microscopy and SEM), polymer chemistry and surface properties (ATR-FTIR), and the leaching and degradation of additives (colorants, UV-stabilizers, softeners). The release of additive chemicals and their possible photodegradation to intermediate products was investigated as part of the UV degradation studies. In addition, we investigate the potential for the same suite of MPFs and their leachates to elicit toxicological responses in a marine microalga. Effects on algal production, photosynthetic activity and lipid content were assessed as a function of polymer type, fibre length, concentration, as well as the additive chemical profiles of the different MPF leachates.