大気中の反応性窒素の主要な源である土壌細菌からのHONO排出は,大気中の反応性窒素の主要な源である
R Oswald1, T Behrendt, M Ermel
1Biogeochemistry Department, Max Planck Institute for Chemistry, Mainz, Germany. robert.oswald@mpic.de
まとめ
土壌の微生物は,重要な大気化合物である窒素酸 (HONO) を大量に放出し,窒素循環に貢献します. 以前は過小評価されていた土壌由来のHONOは,大気中の化学物質と土壌からの窒素の損失に影響を与えます.
科学分野:
- 環境科学 環境科学
- 土壌科学は,土壌科学である.
- 大気化学 大気化学
背景:
- 土壌のニートリート (NO2(-)) から放出される窒素酸 (HONO) のアビオティック放出は,大気中のHONOとヒドロキシルラジカル (OH) の源として提案されました.
- バイオジオケミカルおよび大気中の窒素サイクルにおける土壌由来HONOの定量的な意義は不明のままである.
研究 の 目的:
- 土壌由来HONO排出量の役割と規模を調査する.
- アンモニアを酸化するバクテリアがHONOの放出に直接貢献するかどうかを,均衡の予測を超えて判断する.
主な方法:
- 乾燥地帯や耕作可能な地域の非酸性土壌を用いた実験室での実験.
- HONOと酸化窒素 (NO) を含む反応性窒素排出量の定量化.
- 土壌ベースの酸塩とヘンリーの法則の均衡に関連してHONOの放出の評価.
主要な成果:
- 試験された土壌からのHONOの排出量は,酸化窒素 (NO) の排出量と同等であった.
- アンモニアを酸化するバクテリアは,平衡ベースの予想を上回る量のHONOを直接放出することが判明しました.
- この微生物の放出は,窒素循環のこれまで説明されなかった重要な経路を表しています.
結論:
- 土壌に由来するHONOは,NOに匹敵する反応性窒素排出量の実質的な構成要素です.
- 微生物の活動,特にアンモニア酸化細菌による活動が,大気中のHONOの直接的かつ重要な源である.
- このプロセスは,土壌からの追加の窒素損失と大気中の反応性窒素の源であり,窒素循環のダイナミクスに影響を与えます.
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