まとめ
歯類からのメタンは現代的な炭素を含んでいるが,他の生物学的源は炭素14で枯渇している. 化石燃料は1987年に大気中のメタンの21%を占め,核反応炉が発生源となった.
科学分野:
- 環境科学 環境科学
- 放射化学は放射化学である.
- 大気化学 大気化学
背景:
- メタン (CH4) は,多様な源を持つ強力な温室効果ガスです.
- 炭素14 (14C) 年代測定は,バイオジェニックを化石メタンから区別するために重要です.
- メタンの同位体組成を理解することは,気候変動の研究の鍵です.
研究 の 目的:
- 炭素14測定を用いてメタンの源を区別する.
- 大気中のメタンへの化石炭素の貢献度を定量化するために.
- メタン排出量における原子力発電の役割を評価する.
主な方法:
- 様々な源からのメタンサンプルにおける炭素14の放射線測定分析.
- 大気サンプルにおけるメタン濃度およびデルタ"3C同位体の測定.
- メタンの供給源を区切るために大気輸送モデリング.
主要な成果:
- 類のメタンは現代的な炭素を含み,湿地,沼地,米,ツンドラメタンは14C濃度が低下している.
- 大気中の14CH4は1986年から1987年にかけて増加し,1987年末までに123.3 pMC (北) と120.0 pMC (南) に達した.
- 化石炭素は大気中のメタンの21% (+/- 3%) を含む;圧縮水炉は14CH4の増大する源である.
結論:
- 炭素14の分析により,メタンの源を効果的に区別できます.
- 化石燃料の排出は,大気中のメタンに大きく貢献しています.
- 圧力水炉は,新興の人為的なメタンの源である.
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