古代のリン酸危機は本当にあったのか?
Kurt O Konhauser1, Stefan V Lalonde, Larry Amskold
1Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada. kurtk@ualberta.ca
Science (New York, N.Y.)
|March 3, 2007
まとめ
古代の海は,これまで考えられていたよりも多くのリン酸を含んでいた可能性が高い. 実験では,当時豊富に存在していたシリカが,鉄粒子の捕獲にリン酸と競争し,リン酸の除去を減らし,海洋の生産性を高めることが示されている.
科学分野:
- 地質化学 地質化学
- パレオセアノグラフィー
- バイオジオケミストリー バイオジオケミストリー
背景:
- 帯状の鉄の形状は,巨大なアルカイアン時代の鉄の堆積を示しています.
- 以前のモデルでは,鉄酸化水酸化物粒子が海洋のリン酸を除去し,植物プランクトンを制限することを示唆していました.
- これらのモデルは,アルカイア期に溶けたシリカの濃度が高かったことを無視した.
研究 の 目的:
- 古代海のリン酸の利用可能性におけるシリカの役割を調査する.
- 鉄粒子への吸収のためのシリカとリン酸の間の競争を実験的にテストする.
主な方法:
- 古代の海水条件をシミュレートする実験室での実験.
- フェリヒドライト粒子の合成と特徴付け.
- フェリヒドライトのリン酸とシリカの吸収測定.
主要な成果:
- シリカは,フェリヒドライトの吸収部位において,リン酸と効果的に競合することを示した.
- フェリヒドライトとシリカの共降は,粒子のリン酸に対する反応性を低下させた.
- これらの発見は,アルカイアにおける鉄粒子によるリン酸除去の減少を示唆しています.
結論:
- 古代の海は,以前見積もっていたよりも,かなり高いリン酸塩濃度を維持していた可能性が高い.
- シリカは,初期の海洋におけるフォスファートの可用性を調節する上で重要な役割を果たしました.
- 鉄粒子によるリン酸剥離の提案されたモデルは,シリカの影響を含めるように修正する必要がある.
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