トロポスフィアの上部の条件下でのイソプレンからの新しい粒子の形成
Jiali Shen1,2, Douglas M Russell3, Jenna DeVivo4
1Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki, Helsinki, Finland.
Nature
|December 5, 2024
まとめ
熱帯上層熱帯圏の新粒子の形成は,イソプレン酸化有機分子 (IP-OOM) によって引き起こされる. 硫酸濃度が低い場合でも これらの分子は核化し急速に成長し 新しい大気粒子を形成します
科学分野:
- 大気化学
- エアロゾール科学
- 気候科学
背景:
- 熱帯上の熱帯圏で観測された全般的な新粒子形成 (NPF).
- この地域では夜間高濃度のイソプレンが検出されましたが,前駆体蒸気は知られませんでした.
- イソプレンは熱帯雨林から放出される 生物学的揮発性有機化合物です
研究 の 目的:
- トロポスフィアの新粒子の形成におけるイソプレンの役割を調査する.
- イソプレン由来粒子の核形成と成長機構を決定する.
- 気温,硫酸,NOxなどの大気条件がNPFに与える影響を評価する.
主な方法:
- CERN CLOUD室で行われた実験室での実験
- 模擬上層熱帯条件: -30°Cと -50°Cの温度
- イソプレンとヒドロキシルラジカルの反応と,その後のイソプレン酸化有機分子 (IP-OOM) の核形成/成長について調査した.
主要な成果:
- 確認されたNPFは,上層熱帯温度でイソプレンとの水素基反応によって開始されます.
- イソプレン酸化有機分子 (IP-OOM) は,追加の蒸気なしで観測された上層熱帯濃度で核化されています.
- 核化の速度は硫酸またはヨウ素酸化物によって大きく増加し,最大30cm−3s−1に達した.
- IP-OOMは素粒子 (3−60 nm h−1) の急速な成長を促進した.
- NPFと成長は,上層熱帯 NOx濃度の存在で持続しました.
結論:
- 熱帯雨林からのイソプレン放出は,熱帯上層熱帯圏における重要な新粒子の形成を促すことができます.
- イソプレンで酸素化された有機分子は,この地域のNPFの主要な前駆体です.
- この発見は,イソプレンがエアロゾールに大きく貢献し,気候への影響を及ぼす可能性を示唆しています.
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