Impacts of extreme weather events on microplastic distribution in coastal environments

Coco Ka Hei Cheung; Christelle Not

doi:10.1016/j.scitotenv.2023.166723

Impacts of extreme weather events on microplastic distribution in coastal environments

Sci Total Environ. 2023 Dec 15:904:166723. doi: 10.1016/j.scitotenv.2023.166723. Epub 2023 Sep 1.

Authors

Coco Ka Hei Cheung¹, Christelle Not²

Affiliations

¹ Department of Earth Sciences, The University of Hong Kong, Pokfulam, Hong Kong; The Swire Institute of Marine Science, The University of Hong Kong, Pokfulam, Hong Kong. Electronic address: ccc62000@connect.hku.hk.
² Department of Earth Sciences, The University of Hong Kong, Pokfulam, Hong Kong; The Swire Institute of Marine Science, The University of Hong Kong, Pokfulam, Hong Kong. Electronic address: cnot@hku.hk.

PMID: 37659554
DOI: 10.1016/j.scitotenv.2023.166723

Abstract

Microplastic pollution is a pressing environmental threat to the ecosystem, which can be influenced by varying weather factors. With arising weather extremes in recent years, it is crucial to assess the weather effects on coastal microplastic pollution. In this study, we conducted a year-long baseline survey on beach sediment and surface seawater in Hong Kong, and additional surveys after rainstorm and typhoon events. Our data reveals that microplastic abundance was 5 times higher in wet season over dry season. Yet, the seasonal variation was insignificant when considering only the baseline condition, suggesting the role of extreme weather as the main driver of the seasonal variation in microplastic distribution. Typhoons and rainstorms induced 5.1 to 36.4 times and 1.9 to 11.7 times more microplastics in beach sediment, respectively, and 3.5 to 6.0 times and 2.5 to 4.3 times more microplastics in surface seawater, respectively. The larger microplastic mass in beach sediment and the increased proportion of hard fragments under extreme weather conditions indicate the larger mobility of heavier plastic debris from a wider source. We identified positive correlations between plastic levels and multiple weather factors (including rainfall, wind and tide), suggesting the potential terrestrial inputs of microplastics via surface runoff and wind transport, and the potential redistribution of microplastics from deep to surface sediment via wave agitation. We also identified a strongly positive correlation between macro- and microplastic abundance in beach sediment, suggesting the potential plastic fragmentation under strong wave abrasion, which may intensify the coastal microplastic pollution. This study sheds light on the need for reinforced security of waste management systems to avoid terrestrial plastic inputs under extreme weather forces, as well as the timing of coastal cleanup work in terms of limiting plastic fragmentation and achieving better cleanup efficiency.

Keywords: Coastal pollution; Microplastic; Rainstorm; Typhoon; Weather extremes.