船舶通過による予想外のメタン排出量を観測(Ships trigger high and unexpected emissions of the greenhouse gas methane)

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2025-07-03 チャルマース工科大学

スウェーデンのチャルマース工科大学の研究によれば、船舶が浅海域を航行する際の圧力変化と水のかき混ぜにより、海底に蓄積されたメタンが突発的に大気中へ放出される現象が確認された。特に港湾や河口での排出量は周囲の最大20倍に達し、燃料種に関係なく発生する。従来の温室効果ガス観測では見落とされていたこの現象は、船型や航行頻度に依存し、地球規模でのメタン収支の再評価が求められる重要な発見である。

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船舶航行が引き起こす沿岸域のメタン排出 Coastal methane emissions triggered by ship passages

Amanda T. Nylund,Johan Mellqvist,Vladimir Conde,Kent Salo,Rickard Bensow,Lars Arneborg,Jukka-Pekka Jalkanen,Anders Tengberg & Ida-Maja Hassellöv
Communications Earth & Environment  Published:15 May 2025
DOI:https://doi.org/10.1038/s43247-025-02344-8

船舶通過による予想外のメタン排出量を観測(Ships trigger high and unexpected emissions of the greenhouse gas methane)

Abstract

Estuarine and coastal areas are important sources of methane emitted to the atmosphere through diffusion or ebullition. These processes can be triggered by pressure changes and water column mixing, which can be induced by ships. However, the contribution of ship-triggered emissions is unknown and missing in current emission inventories. Here we show evidence of extensive ship-induced methane emissions and an estimated methane flux (11.1 mmol m−2 day−1) from Neva Bay shipping lane. The flux is 10–1000 times higher than reported global estuarine/coastal fluxes, and of similar magnitude as aquatic methane emission hotspots. Our results indicate that ship-induced pressure changes (30–60 mbar) trigger methane emission, comparable with observed emissions induced by tidal pressure changes. The ship-triggered methane emissions corresponded to a 22% increase of emitted carbon dioxide equivalents, compared to the combustion related exhausts. Our results demonstrate the need to include shipping lanes when assessing estuarine/coastal methane emissions.

1904環境影響評価
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