5:15 PM - 7:15 PM
[MIS02-P03] Age Distribution Analysis of Microplastics Collected in Urban River
Keywords:microplastic, rivers, terrestrial area, age
This study examines the accumulated time in which microplastics (MPs) in the ocean have been exposed to UV radiation, which we will refer to as their ‘age’. Okubo et al. (2023) established a method to estimate polyethylene (PE) age based on the intensity of infrared absorption spectra, the estimated experienced water temperature, and UV intensity. However, there is no previous research on age estimation for MPs in rivers, and age distribution in terrestrial environments remains an open question. Therefore, we collected MPs flowing downstream in the Mikasa River near Onojo City, Fukuoka Prefecture, Japan, and analyzed their age.
MPs samples were collected in August and December 2024 using a device with a 0.3mm mesh attached to a metal ring. We successfully collected 103 MPs in approximately 8 hours of observation. The most common shape of MPs we collected was fragment, and the most common types were polypropylene (PP) and polyethylene (PE). We found a wide age distribution of PEs, between 1 and 19 years. This age distribution is broader and older than the age distribution of MPs in the ocean, which is about 1-5 years. We propose two possible explanations for finding much older MPs in rivers than in the oceans. First, younger plastics are flowing from rivers to the sea while they are still large, so the majority of the young MPs do not remain in the river. Second, plastic debris tends to stay in terrestrial areas for a long time, gets exposed to UV radiation and degrades before flowing into the river when rainfalls occur. In the future, We plan to collect more MPs ages in both rivers and oceans to study how plastic debris flows from rivers to oceans based on age distribution.
MPs samples were collected in August and December 2024 using a device with a 0.3mm mesh attached to a metal ring. We successfully collected 103 MPs in approximately 8 hours of observation. The most common shape of MPs we collected was fragment, and the most common types were polypropylene (PP) and polyethylene (PE). We found a wide age distribution of PEs, between 1 and 19 years. This age distribution is broader and older than the age distribution of MPs in the ocean, which is about 1-5 years. We propose two possible explanations for finding much older MPs in rivers than in the oceans. First, younger plastics are flowing from rivers to the sea while they are still large, so the majority of the young MPs do not remain in the river. Second, plastic debris tends to stay in terrestrial areas for a long time, gets exposed to UV radiation and degrades before flowing into the river when rainfalls occur. In the future, We plan to collect more MPs ages in both rivers and oceans to study how plastic debris flows from rivers to oceans based on age distribution.