Contamination of sea surface water offshore the Tokai region and Tokyo Bay in Japan by small microplastics
Haodong Xu, Haruka Nakano, Tadashi Tokai, Tadashi Miyazaki, Hiroaki Hamada, Hisayuki Arakawa
Abstract
A nested double neuston net was prepared and used to collect samples from the surface of coastal waters around Japan to obtain information about the properties of both small microplastics (SMPs; <350 μm) and large microplastics (LMPs; >350 μm). The SMP concentrations ranged from 1000 to 5900 pieces m−3 in the open ocean and averaged approximately 3000 pieces m−3 in the inner part of Tokyo Bay. The SMP concentrations were around 20–60 times greater than the LMP concentrations. By analyzing the seawater, we obtained a microplastic size distribution that spanned 50–5000 μm. The LMPs mainly comprised packaging-related plastics, such as polyethylene (PE) and polypropylene, while the SMPs were dominated by paint-related plastics. SMPs derived from packaging materials (e.g., PE) may have gradually sank down from the sea surface when they were smaller than 600 μm.