1 Department of Building, Civil and Environmental Engineering, Concordia University, Montreal, QC H3G 1M8, Canada.
2 Department of Building, Civil and Environmental Engineering, Concordia University, Montreal, QC H3G 1M8, Canada. Electronic address: chunjiang.an@concordia.ca.
3 Institute for Energy, Environment and Sustainable Communities, University of Regina, Regina, SK S4S 0A2, Canada.
4 Fisheries and Oceans Canada, Ecosystem Science, Ottawa, ON K1A 0E6, Canada.
5 Northern Region Persistent Organic Pollutant Control (NRPOP) Laboratory, Faculty of Engineering and Applied Science, Memorial University, St. John's, NL A1B 3X5, Canada.

The COVID-19 pandemic has driven explosive growth in the use of masks has resulted in many issues related to the disposal and management of waste masks. As improperly disposed masks enter the ocean, the risk to the marine ecological system is further aggravated, especially in the shoreline environment. The objective of this study is to explore the changing characteristics and environmental behaviors of disposable masks when exposed to the shoreline environment. The transformation of chain structure and chemical composition of masks as well as the decreased mechanical strength of masks after UV weathering were observed. The melt-blown cloth in the middle layer of masks was found to be particularly sensitive to UV irradiation. A single weathered mask can release more than 1.5 million microplastics to the aqueous environment. The physical abrasion caused by sand further exacerbated the release of microplastic particles from masks, with more than 16 million particles released from just one weathered mask in the presence of sand. The study results indicate that shorelines are not only the main receptor of discarded masks from oceans and lands, but also play host to further transformation of masks to plastic particles.