Predicting Drifting Polystyrene Degradation in World Oceans Based on Thermal Decomposition
- Hideki Kimukai, Koshiro Koizumi, Hiroyuki Taguchi, Akifumi Okabe, Kohei Takatama, Seon Yong Chung, Bum Gun Kwon, Masahiko Nishimura, Sibel Mentese, and Katsuhiko Saido*
The accumulation of plastic litter in natural environments has become a serious global issue. Since 1972, mega to micro/nanosized drifting plastics have been determined to be highly a significant pollutant in all oceans worldwide. To clarifying numerous problems such as entanglement or improper ingestion due to drifting and debris plastic, the amounts of currently drifting plastics should be determined. For this purpose, chemicals derived from polystyrene (PS) degradation were analyzed for 4000 sand and water samples taken from around the world including open sea sites (surface to 5000 m depth) during the period from 2000 to 2018. All styrene oligomers (SOs) of styrene (styrene monomer, SM), 2,4-diphenyl-1-butene (styrene dimer, SD2), and 2,4,6-triphenyl-1-hexene (styrene trimer, ST) were found to contain products from PS degradation. On the basis of survey SO values, 1.4 × 109 metric tons (MT) of SO were found to have been released into world oceans between 1950 and 2018. This SO subsequently underwent conversion to 2.7 × 106 MT of PS. Twenty percent underwent degradation, while 1.2 × 107 MT of PS apparently continued to drift about in ocean water. Drifting PS has been clearly shown not only to be crushed into micro/nanoplastic particles but also to degrade into basic structural units of SOs constituting PS.
© 2022 The Authors. Published by American Chemical Society