The formation and size distribution of nanoparticles emitted from hydrothermal vents: A laboratory-based approach

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K11621
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 63010:Environmental dynamic analysis-related
• Research Institution: Osaka University
• Principal Investigator: Nakayama Noriko 大阪大学, 理学研究科, 助教 (60431772)
• Co-Investigator(Kenkyū-buntansha): 中嶋 悟 大阪大学, 理学研究科, 教授 (80237255)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: ナノ粒子 / 微量金属元素 / 金属硫化物ナノ粒子 / 海洋化学 / 地球化学 / 物質循環 / 水熱反応実験 / 水圏環境

Outline of Final Research Achievements

Our observations showed that trace metals in seawater can exist in the form of nanoparticles for an extended period and can be transported long-range, suggesting a vital role of metal nanoparticles in the marine biogeochemical cycling of trace metals. However, the formation and removal mechanisms of the nanoparticles remain unexplored. It is due primarily to the difficulty in measuring trace concentration and size distribution of trace metal nanoparticles in the ocean. In order to explore the possible formation mechanism, we performed a series of laboratory experiments, which simulated mixing hydrothermal fluid in supercritical fluid condition into seawater, which we considered as a nanoparticle-forming process. We found that nanoparticles were formed through the process, and the supercritical fluid condition is a vital factor. We also found that different seawater-rock reaction temperatures resulted in different size distributions of formed nanoparticles.

Free Research Field

地球環境科学

Academic Significance and Societal Importance of the Research Achievements

海洋や湖沼といった水圏環境において、生物活動に必須な栄養素である微量金属元素が、どのような形状・サイズ分布・化学組成・化学状態で水中に供給され、どのようにして沈降や除去を免れて水中に存在しているのかについて、未だ推定の域を出ていない。本研究の成果は、これまで考えられてきた水圏生態系を支える微量金属元素の物質循環学に、ナノ粒子態という存在状態の概念を新たに認識させるという学術的意義がある。