アーカイアン時代の硫黄循環と大気中の酸素の初期史
D E Canfield1, K S Habicht, B Thamdrup
1Danish Center for Earth System Science (DCESS) and Institute of Biology, Odense University, SDU, Campusvej 55, 5230 Odense M, Denmark. dec@biology.ou.dk
まとめ
堆積硫黄の同位体は,初期の地球を明らかにしています.
科学分野:
- 地質化学 地質化学
- 古代気候学 (paleoclimatology) とは,古代気候学 (paleoclimatology) とは,古代気候学 (paleoclimatology) とは,古代気候学 (paleoclimatology) とは,古代気候学 (paleoclimatology) とは
- 微生物学 微生物学とは
背景:
- 大気中の酸素の蓄積の歴史は,生命の初期段階を理解するために重要である.
- 堆積岩の硫黄の同位体は,古代の環境条件の代理を提供している.
研究 の 目的:
- 高温での微生物の硫酸塩還元過程における硫黄同位体の分断を調査する.
- 硫酸塩の還元率が堆積物における同位体シグネチャーの保存にどのように影響するかを決定する.
- アルカインとプロテロゾーイク時代の大気中の酸素と海水の硫酸塩濃度の進化を再構築する.
主な方法:
- 微生物硫酸塩還元実験で88°Cまで硫黄の同位素分離を測定した.
- 古代の岩層からの堆積硫黄イソトープ記録を分析した.
- 同位体保存に対する硫酸塩還元率の影響をモデル化した.
主要な成果:
- 硫黄の同位体分割は88°Cまでの温度で微生物の硫酸縮小過程で観察されました.
- 硫酸塩の還元率は,生物学的硫黄同位体の分断の保存に大きな影響を与えます.
- 堆積硫黄同位体記録は,アーケイア初期 (3.4〜2.8億年前) の海水硫酸塩と大気中の酸素レベルが低いことを示している.
結論:
- 初期のアルカイアの大気と海は,酸素と硫酸塩が限られていた.
- 大気中の酸素と海水の硫酸塩の大幅な蓄積は,初期のプロテロゾーイク (250億~540億年前) に始まった.
- 硫黄同位体の地化学は,地球の初期の生地化学サイクルを再構築するための強力なツールです.
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