安定した同位体である水銀は,大気源を海洋に制限する
Martin Jiskra1,2, Lars-Eric Heimbürger-Boavida3,4, Marie-Maëlle Desgranges5
1Environmental Geosciences, University of Basel, Basel, Switzerland. martin.jiskra@unibas.ch.
Nature
|September 30, 2021
まとめ
人間による海産物の摂取は,有毒な水銀 (Hg) に曝露する主な原因です. この研究では,水銀 (Hg) の吸収と水銀 (Hg) の堆積が,海洋水銀にとって同様に重要な経路であることを明らかにしています.
科学分野:
- 環境化学
- 海洋生物化学
- 同位体地化学
背景:
- 人間が有毒な水銀 (Hg) に曝露するのは,主に海産物の摂取によるものです.
- 地球システムモデルは,大気中の水銀の堆積が海洋水銀の主要な源であり,ガス状水銀 (Hg) の吸収はそれほど重要ではないことを示しています.
- 海中のHg(II) 堆積とHg(0) ガス交換に関する現在の観測は限られており,水銀の海洋源を理解する上で不確実性が生じています.
研究 の 目的:
- 大気中の水銀の沈殿経路を海洋生態系に定量化するために.
- 海水における総水銀 (tHg) に対して,Hg (II) の堆積とHg (0) の吸収の相対的貢献を調査する.
- 地球上の水銀同位体データを分析し,水銀循環の緯度変動を理解する.
主な方法:
- 安定した水銀 (Hg) の同位体で,大西洋と地中海海水の総水銀 (tHg) を測定した.
- 安定した同位体質量バランスモデル (Δ200Hg) を適用して堆積経路を推定する.
- 粒子のHg,堆積物,生物を含む世界の海洋Hgイソトープデータの収集と分析.
主要な成果:
- 海水のtHgイソトープ組成は,表面と深層のサンプルで,Hg(0) とHg(II) 末端間の中位 Δ200Hgシグネチャーで類似していました.
- 海水で示されたHg同位体の質量バランス tHgは,大気中の42%のHg(II) 総堆積と58%のHg(0) 総吸収の混合物から得られます.
- 緯度Δ200Hgのグラデントが観測され,より高い緯度における海洋によるより大きなHg0の吸収が示唆された.
結論:
- 大気中のHg(0) の地球規模の海洋吸収量は,Hg(II) の堆積量と同等である.
- この発見は,水銀の分散に関する以前の仮定に異議を唱え,水銀汚染からの海洋生態系の回復を理解する上で重要な意味を持つ.
- 水銀の安定した同位体は,海洋環境における複雑な生地化学サイクルプロセスを解明するための強力なツールを提供します.
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