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A 75-year history of microplastic fragment accumulation rates in a semi-enclosed hypoxic basin

The Science of The Total Environment 2022 46 citations ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count. Score: 45 ? 0–100 AI score estimating relevance to the microplastics field. Papers below 30 are filtered from public browse.

Hirofumi Hinata, Michinobu Kuwae, Issei Masumoto, Hirofumi Hinata, Hirofumi Hinata, Hirofumi Hinata, Issei Masumoto, Michinobu Kuwae, Michinobu Kuwae, Narumi K. Tsugeki, Yukinori Tani Hirofumi Hinata, Hirofumi Hinata, Hirofumi Hinata, Issei Masumoto, Hirofumi Hinata, Issei Masumoto, Yukinori Tani Narumi K. Tsugeki, Hirofumi Hinata, Hirofumi Hinata, Hirofumi Hinata, Kenki KASAMO, Hirofumi Hinata, Yoshio HATADA, Kenki KASAMO, Yoshio HATADA, Hayato Kawamata, Hayato Kawamata, Atsuomi Mase, Hirofumi Hinata, Hirofumi Hinata, Yoshiaki Suzuki, Atsuomi Mase, Kenki KASAMO, Kenki KASAMO, Kazuya Sukenaga, Kazuya Sukenaga, Hirofumi Hinata, Yoshiaki Suzuki, Hirofumi Hinata, Yoshio HATADA, Yoshio HATADA, Yukinori Tani

Summary

A sediment core from a semi-enclosed hypoxic basin revealed a 75-year record of increasing microplastic fragment accumulation rates, with the pace accelerating in line with global plastic production growth. The study also found that biological activity and ocean dynamics influenced microplastic sinking and deposition patterns.

Polymers

PE PP PS

Study Type Environmental

Plastic budgets in the marine environment and their long-term trends are yet to be fully understood. Measuring the accumulation rates in bottom sediments is crucial to solving the riddle of missing ocean plastics. Previous studies based on coastal sediment cores have found that accumulation rates have increased with increases in plastic production and/or regional populations. However, the correlations between the rates and bioactivities or ocean dynamics, which are crucial for modeling the microplastic sinking process, have not been examined. We revealed a 75-year microplastic fragment (0.3-5.0 mm) accumulation rate history in a hypoxic basin, Beppu Bay, Japan, based on multi-core analysis and Pb dating of the sediment which was cross-checked by time control with Cs radioactivity peaks. We found that a long-term linear increasing trend with an approximately 20-year variation overlapped with significant peaks around 1990 and 2014 with the first polypropylene microplastic fragment detected from a 1958.8-1961.0 CE sediment layer. The maximum rate was 203 pieces m y with an abundance of 86 pieces kg-dry in 2014. Smaller fragments in the size range of 0.3-2.0 mm have been consistently dominant in terms of the accumulation rate throughout the 1955-2015 period, accounting for 85.3 % of the total accumulation rate. The three major polymers (polyethylene, polypropylene, and polystyrene) accounted for 96.6 % of the total rate. The rate was highly and positively correlated with the chlorophyll-a accumulation rate and concentration in the sediment. Based on the microplastic accumulation rates and concentration in the seawater, the mean sinking velocity of microplastics was estimated to be in the order of 10 m d. Our results will contribute to significant progress in modeling the microplastic sinking process by offering the first field measurement-based mean sinking velocity and significant correlations between the rate and bioactivity-related signals.

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