産業革命から現在までの大気硝酸量の変遷を北極アイスコアから復元～人為窒素酸化物の排出量と大気中の硝酸の存在形態が北極の大気硝酸量を制御することを解明～

2025-05-20 北海道大学,金沢大学,気象庁気象研究所,名古屋大学

アイスコアから復元した硝酸塩量（黒）と周辺国の人為窒素酸化物（NO_x）排出量（オレンジ）の1800-2020年の経年変化（1800-1850年を基準に規格化した値）。タイムラグは、大気酸性度に応じた大気硝酸の輸送されやすさによって説明される。

＜関連情報＞

• https://www.hokudai.ac.jp/news/2025/05/post-1880.html
• https://www.hokudai.ac.jp/news/pdf/250520_pr.pdf
• https://www.nature.com/articles/s41467-025-59208-0

硝酸塩の酸駆動性ガス-粒子分配は工業化時代を経て北極への輸送を制御する Acidity-driven gas-particle partitioning of nitrate regulates its transport to Arctic through the industrial era

Yoshinori Iizuka,Mai Matsumoto,Kaoru Kawakami,Mahiro Sasage,Sakiko Ishino,Shohei Hattori,Ryu Uemura,Hitoshi Matsui,Koji Fujita,Naga Oshima,Andrea Spolaor,Anders Svensson,Bo Møllesøe Vinther,Hiroshi Ohno,Osamu Seki & Sumito Matoba
Nature Communications  Published:19 May 2025
DOI:https://doi.org/10.1038/s41467-025-59208-0

Abstract

Anthropogenic NO_x emissions have altered the biogeochemical nitrogen cycle since the Industrial Revolution, yet Arctic ice core nitrate (NO₃⁻) records are inconsistent with post-1970s NO_x emission reductions. Here we show a NO₃⁻ deposition history covering 1800–2020 using an ice core from the southeastern Greenland dome with high snow accumulation. The ice core NO₃⁻ concentrations are particularly disconnected from NO_x source regions during the peak pollution period and post-1990s. A global chemical transport model reproduced these discordances between total NO₃⁻ and NO_x emissions by altering gaseous HNO₃ and particulate NO₃⁻ (p-NO₃⁻) ratios and subsequently NO₃⁻ lifetime. This result and correlations with acidity parameters recorded in the ice core, suggest that acidity-driven gas-particle partitioning of NO₃⁻ regulates its transport to Arctic regions alongside changes in NO_x emissions. In the future, despite NO_x reductions, the increase in proportion of p-NO₃⁻ with longer atmospheric lifetime becomes crucial to control the Arctic NO₃⁻ burden.