Author(s): Takeshi Takemura; Shinya Nishio; Tomoaki Nakamura

Linked Author(s): Takeshi Takemura

Keywords: Microplastics; UAV; NDVI; Sanbanze

Abstract: The Sanbanze, located in the northernmost part of Tokyo Bay, has a large amount of debris, most of which is shell and plant litter, and not much large visible plastic debris. However, it is assumed that microplastics have drifted and accumulated even in the Sanbanze. In this study, we conducted a field survey to understand the accumulation of microplastics in the Sanbanze using images taken by an unmanned aerial vehicle (UAV). The results of spectral reflectance characteristics for all litter in Sanbanze showed that reflectance was lowest at 430 nm and increased with increasing wavelength. In the case of 100% shell litter, reflectance was greater in all wavelength ranges compared to the other litter. On the other hand, in the case of 100% plant litter, reflectance was generally smaller. These results indicate that the reflectance of shell litter is generally larger than that of plant litter and sand, and that the reflectance of plant litter is smaller than that of sand up to a wavelength of 800 nm, after which the reflectance of dead plant litter is larger. Based on these results, we investigated the identification of the debris floating ashore using NDVI calculated from images taken by UAV. As a result, differences were observed between the case of shell litter and the case of plant litter. In the case of this study, the NDVI value ranged from 0.13 to 0.32 for detecting plant litter, and from 0 to 0.12 for detecting shell litter.

DOI: https://doi.org/10.3850/978-90-833476-1-5_iahr40wc-p0500-cd

Year: 2023