Release study of microplastic fibres and heavy metals from disposable surgical face masks in aqueous medium: the effect of physio-chemical factors and shear forces

Abstract

Since the COVID-19 pandemic broke out, there has been a dramatic surge in the usage of disposable face masks, and even though the pandemic has passed, discarded masks persist in aquatic systems where they continue to release microplastic fibres. These masks are composed of plastic nonwoven fabrics and can potentially contribute polypropylene (PP) microplastics to the environment. This investigation aimed to assess the potential for these PP microplastics to be released into the water by disposable surgical face masks under different parameters. This study systematically assesses various factors that may affect the release of microplastic fibres into the natural aquatic environment. The initial investigation focused on the impact of various hydro–chemical parameters, including pH levels (4, 7, and 9), ionic strength (IS) at 10, 50, and 100 mM, and humic acid (HA) concentrations (0.1, 1, and 10 mg L⁻¹), to analyse the overall release pattern of microplastic fibres from facemasks. The experimental findings demonstrate that pH, ionic strength, and humic acid significantly influenced the release pattern of the fibres, with the highest release observed at pH 9, 10 mM IS, and 0.1 mg L⁻¹ HA. At higher IS and HA concentrations, the release of microplastic fibres was lower compared to that at lower concentrations. This study also emphasises the impact of varying shear stress levels on the release dynamics of fibres and co-contaminants like heavy metals (HMs) from disposable surgical facemasks over different time intervals. Furthermore, the release pattern of the microplastic fibres was examined in various natural water systems, including lakes and seawater. Future studies will extend this work to longer exposure durations to better capture the long-term release dynamics of microplastic fibres from masks.