大西洋のプラごみ、推定総量上回る量が存在か　研究

【パリＡＦＰ＝時事】大西洋に、1950年以降に廃棄されたプラスチックの推定総量を超えるプラスチックごみが浮遊している可能性があることが、18日に英科学誌ネイチャー・コミュニケーションズに掲載された英国立海洋学センターの研究で明らかになった。（写真は資料写真）
　世界の海洋には１億５０００万トンのプラスチックが、多くはマイクロプラスチック粒子の形で存在すると推定されている。しかし、海洋にどの程度プラスチックごみが存在するかを正確に測ることは困難だ。
　この問題を改善するため、英国立海洋学センターの研究チームは、大西洋の１万キロに及ぶ範囲の１２か所からサンプルを採取。水深１０～１００メートルのポリエチレン、ポリプロピレン、ポリスチレンという海洋プラスチックごみで最も多くみられる３種類を調査した。
　研究チームは１９５０年以降のプラスチックごみの発生傾向に基づき、大西洋に現存するプラスチックごみの量が１７００万～４７００万トンだと推定した。４７００万トンという数は、１９５０年以降に大西洋に捨てられたとみられるプラスチックごみの総量を上回っている。
　論文の筆頭著者カチェリーナ・パボートサバ氏は、「かなりの緊急性」をもって、海洋プラスチックごみのレベルを調査する必要があると強調した。【翻訳編集ＡＦＰＢＢＮｅｗｓ】
〔ＡＦＰ＝時事〕（2020/08/20-14:11）

There may be more plastic floating just beneath the surface of the Atlantic ocean today than the estimated total weight of plastic waste dumped in it since 1950, new research showed Tuesday.
The findings, based on analysis of samples of the three most common plastic materials and computer modelling, highlight the unseen scale of the pollution clogging the world's second largest ocean.
Earth's oceans contain an estimated 150 million tonnes of plastic, often in the form of microplastic particles.
These tiny fragments have been detected in every ocean on the planet and even at the bottom of the world's deepest trench.
Despite its ubiquitousness, ocean plastic is hard to accurately measure.
To remedy this, researchers from Britain's National Oceanography Centre analysed the plastic collected in samples from 12 sites spanning 10,000 kilometres of Atlantic Ocean.
They then assessed the abundance of the three most common ocean plastics: polyethylene, polypropylene and polystyrene at depths of between 10 and 100 metres below the surface.
Based on plastic generation trends dating back to 1950, the researchers estimated that the Atlantic now contains between 17 and 47 million tonnes of plastic.
That upper figure is higher than all estimated plastic input into the Atlantic since the middle of the last century.
Accessing remote open ocean is generally challenging and requires well-funded research programmes, lead author Katsiaryna Pabortsava told AFP.
Similarly, there is a logistical and technological challenge in continuous monitoring plastics in the open ocean.
The research found that the upper 200 metres of the Atlantic -- home to the vast majority of its sea life -- contained up to 20 million tonnes of microplastic.
- 'Numerous sources' -
Pabortsava said her study, published in Nature Communications, highlighted the need to better assess ocean plastic levels with considerable urgency.
It is thought around eight million tonnes of plastic enter the ocean every year, causing as-yet unknown damage on the marine food chains that hundreds of millions of people directly rely upon for food and income.
Pabortsava said that even though plastic can be recycled, waste management strategies were failing to stem the flow reaching the ocean.
Sources of plastic are numerous and go beyond littering, she said.
For example, a lot of plastic can come from the household activities (e.g. washing synthetic clothing), or from erosion of car tyres, and surface paints.
Coastal erosion from waste dumps could be a significant source of plastics flowing into the ocean, she added.