We are pleased to report the results of research selected for the 2023 Eikei University of Hiroshima Research Promotion Project.
Our university is implementing the Eikei University of Hiroshima Research Promotion Project with the aim of promoting research activities and improving the quality of education at our university, as well as contributing to the resolution of social issues. We will report on the results of research project that was selected in FY2023 and have completed the research period.
| Principal Investigator | Professor SAGEHASHI Masaki |
| Research theme | Elucidation of the relationship between the number of microplastics including smaller ones and the status of domestic non-fecal wastewater treatment in the Kurose River. |
| Research Result | In this study, we measured microplastics of a size too small (SMPs) to be detected by standard MP monitoring methods, and also with low treatment efficiency in wastewater treatment in the Kurose River, which flows from Higashi-Hiroshima City through Kure City into the Seto Inland Sea. For river water sampling, continuous sampling was conducted using a submersible water pump equipped with a float. On-site pretreatment involved vacuum filtration using a stainless steel (SUS) filter. Those samples were treated at 70°C with potassium persulfate and sodium hydroxide to decompose non-plastic components coexisting with the MPs in the laboratory. After decomposition, the samples were filtered through a polytetrafluoroethylene (PTFE) filter, dried, and analyzed using micro-FT-IR spectroscopy. As a result, samples filtered with a 25 μm SUS filter at the site detected polypropylene (PP), polyethylene (PE), polystyrene (PS), and PET, which were detected in the Kurose River by Hiroshima Prefecture in its microplastic (0.3–5 mm) survey observed in Hiroshima Bay and the Akitsu-Yasuura area. Additionally, the Geographic Information System was used to organize sewerage coverage and population distribution in the watershed. While no clear relationship was observed between population distribution, sewerage coverage rates, and SMPs obtained in this study, the data collected provides a foundation for analyzing such relationships in the future as more measurement results accumulate. |