Japan Geoscience Union Meeting 2023

Presentation information

[J] Online Poster

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS17] Ocean Plastics, an earth science perspective

Fri. May 26, 2023 3:30 PM - 5:00 PM Online Poster Zoom Room (12) (Online Poster)

convener:Atsuhiko Isobe(Kyushu University), Kiichiro Kawamura(Yamaguchi University), Yusuke Okazaki(Department of Earth and Planetary Sciences, Graduate School of Science, Kyushu University), Masashi Tsuchiya(Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology)

On-site poster schedule(2023/5/26 17:15-18:45)

3:30 PM - 5:00 PM

[MIS17-P06] Age estimate of polyethylene microplastics collected in oceans: an application to the western North Pacific

Rie Okubo1, Aguru Yamamoto1, Akihiro Kurima1, Terumi Sakabe1, Yoichiroh Ide1, *Atsuhiko Isobe2 (1.Asahi Kasei, 2.Kyushu University)

Keywords:microplastics, carbonyl index

Microplastic ages defined as the exposure time to ultraviolet (UV) radiation were estimated using the carbonyl index computed by infrared spectrometry, UV erythemal radiation (UVER or UV index) in meteorological records, and ambient seawater temperature in oceanographic records. A set of accelerated and outdoor exposure experiments were conducted to find a relationship among temporally integrated UVER, ambient temperature, and carbonyl index. Thereafter, ages (exposure time to UV radiation) of microplastics with Miyakojima Island as the reference point were computed. The microplastics collected in the western North Pacific demonstrated that their ages in the open ocean were concentrated within a range between 1 and 3 years, while the ages estimated in the nearshore waters were ranged between 0 and 5 years. The spatial distribution of ages suggested that microplastics generated mostly on land degrade continuously even in the ocean, and that microplastics in the offshore waters were removed from the upper ocean to subsurface layers via biological processes within a timescale of a few years.