Preliminary study to characterize microplastics in the coastal environment using multiple analytical approaches

沿岸環境におけるマイクロプラスチックの特性評価

Battulga, B. ; 安藤 麻里子  ; 小嵐 淳   

Battulga, B.; Atarashi-Andoh, Mariko; Koarashi, Jun

プラスチックごみは、世界の生態系で新たな汚染物質として認識されている。しかしながら、様々な分析に基づいてマイクロプラスチックの特性を評価する方法は未確立である。本研究では、茨城県内および新潟県内の河川において、大きさ,色,組成の異なる様々なマイクロプラスチック試料を採取し、顕微鏡分析や分光学的な分析、同位体分析などの様々な分析手法を駆使して、マイクロプラスチックの特性評価を試みた。その結果、マイクロプラスチックの形態や組成が季節によって異なること、プラスチックの素材が同じでもその安定炭素同位体組成が異なること、放射性セシウムがバイオフィルムの形成を介してマイクロプラスチックに付着していること、などを明らかにした。これらの複合的な分析手法に基づくマイクロプラスチックの特性評価は、マイクロプラスチックの状態や環境中における物質循環への寄与を解明するために有効である。

Plastic debris has been recognized as an emerging contaminant in the global ecosystem. Although microplastics (MPs) have received special attention from the scientific community owing to their widespread distribution, application of highly sensitive techniques to evaluate the characteristics of MPs is still under consideration. In this study, we demonstrate multiple analytical approaches including microscopic, spectroscopic, and isotopic analyses to track MP characterization obtained from coastal river environment. We selected two sampling sites from coastal areas in Japan and collected visible plastic samples. At the same time, surface water and coastal sand samples were collected to evaluate the seasonal variations in MP occurrence and composition. Seasonal differences in occurrence and morphotypes of MPs were detected in both sampling sites, suggesting variations in geographical patterns and consumption of plastic materials in the studied region. We also found differences in carbon isotopic composition between the MPs composed of the same polymer (i.e., polyethylene and polypropylene) but with different colors. Preliminary results of Cs activity concentrations revealed that plastics serve as carriers for radionuclides mediated by biofilms in the coastal river environment. Furthermore, occurrences and differences in the composition of the MPs in the study areas indicate that point and nonpoint sources of MPs strongly affect their concentration in the aquatic environment.