窒素酸とアンモニアの凝縮による新しい大気粒子の急速な増加
Mingyi Wang1,2, Weimeng Kong3, Ruby Marten4
1Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA, USA.
Nature
|May 15, 2020
まとめ
新しい研究によると 低温で窒素酸とアンモニアが 窒素酸アンモニアの粒子を形成し 都市部での粒子の増殖と生存を大幅に促進しています この過程は,都市や上層大気におけるスモッグの形成を理解するために極めて重要です.
科学分野:
- 大気化学
- 環境科学
- 粒子物理学
背景:
- 新粒子の形成は都市スモッグの重要な要因ですが,都市におけるそのメカニズムは十分に理解されていません.
- 既存のモデルでは 都市部に存在する粒子の濃度が高いため 素早く除去すべきだと考えられています
研究 の 目的:
- 都市の大気条件下での新粒子の形成と成長における窒素酸とアンモニアの役割を調査する.
- これらの蒸気が素粒子の急速な成長と生存率の上昇につながる条件を決定する.
主な方法:
- 実験はCERNのCLOUD室で シミュレートされた大気条件下で行われました
- 窒素酸,アンモニア,温度による粒子の核形成と成長率の分析.
主要な成果:
- +5°C以下では,窒素酸とアンモニアの蒸気は,新しく形成された粒子に凝縮します.
- -15°C以下では,酸塩安定化によって,酸塩粒子の直接核化が行われます.
- 観測された粒子の成長速度は 時速100ナノメートルを超え,以前考えられていたよりもかなり速い.
結論:
- 窒素酸とアンモニアによる粒子の形成と成長は,特に冬の都市環境で粒子の生存率を急速に増加させることができます.
- このメカニズムは,冷たい上部フリートロポスフィアの粒子形成にも関連しています.
- 不均質な都市環境では,温度依存と局所的な源による高成長率を好む一時的な条件が予想されます.
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