大規模な火山によるSO2酸化と硫酸エアロゾールの堆積がケノゾイク北米で発生した
Huiming Bao1, Shaocai Yu, Daniel Q Tong
1Department of Geology and Geophysics, Louisiana State University, Baton Rouge, Louisiana 70803-4101, USA. bao@lsu.edu
Nature
|June 19, 2010
まとめ
北アメリカにおけるケノゾイク中期の火山噴火は,硫酸エアロゾールの堆積を引き起こした. 塩基性雲水の条件は,今日の酸性雲とは異なり,オゾンによる二酸化硫黄の酸化を好みました.
科学分野:
- 地質化学 地質化学
- 大気科学 大気科学
- 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
背景:
- 火山噴火によって大気中に相当量の二酸化硫黄 (SO2) が放出されます.
- SO2が硫酸エアロゾールに酸化すると,地球の放射線バランス,オゾン,生物の生産性に影響を及ぼします.
- SO2の酸化経路を理解することは,過去の火山活動と大気条件の解釈の鍵です.
研究 の 目的:
- 亜亜紀中期のタフ質堆積物における硫黄と三重酸素同位素を用いたSO2酸化経路の調査.
- 硫酸エロゾールによる過去の大気条件と火山噴火の影響を再構築するために.
主な方法:
- 硫黄と三重酸素同位体の分析は,タフ層の堆積物から抽出された大気中の硫酸塩.
- 大気中の硫黄の化学反応と輸送モデルを3次元で利用した.
- 硫酸塩の堆積現象とその化学的サインを識別する.
主要な成果:
- 北米北部のハイ・プレーンで,ケノゾーイク中期 (3400万~700万年前) の間に7つの噴火に関連する硫酸エアロゾール堆積が確認された.
- 2つの灰床は,2つの異なる二次硫酸塩と類似した硫酸塩混合パターンを示しました.
- モデリングは,観察された硫酸塩のシグネチャーには,最初はアルカリの雲水とオゾン主導のSO2酸化が必要であることを示しました.
結論:
- 北部のハイプレーンのケノゾイク中期の雲水は,現在の弱酸性条件とは対照的に,しばしばアルカリ性であった可能性が高い.
- オゾンが優勢であるSO2酸化経路は,これらの過去の火山のイベントの間に一般的であった.
- 大陸の堆積物にある大気中の二次硫酸塩は,過去の火山活動と大気化学に関する貴重な地質アーカイブを提供します.
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