The in situ pH of hydrothermal fluids at mid-ocean ridges

Kang Ding, William E. Seyfried, Zhong Zhang, Margaret K. Tivey, Karen L. Von Damm, Albert M. Bradley

Research output: Contribution to journalArticle

52 Scopus citations


Here we report the first in situ pH of hydrothermal vent fluids at mid-ocean ridges. Measurements were made during dives with DSV Alvin to the Main Endeavour Field (Juan de Fuca Ridge) and the East Pacific Rise at 21°N, and 9°-10°N using solid-state electrochemical sensors. Vent fluid temperature and pressure ranged from 180 to 384 °C and 220 to 250 bar, respectively. pH(in situ) of the highest temperature vent fluid is only slightly acidic (5.1-5.4), although sharply lower values occur at the seawater/vent-fluid interface. Knowledge of pH(in situ) is essential for unravelling the complex geochemical and biogeochemical processes controlling the evolution of seafloor hydrothermal systems.

Original languageEnglish (US)
Pages (from-to)167-174
Number of pages8
JournalEarth and Planetary Science Letters
Issue number1-2
StatePublished - Aug 30 2005


  • Hydrothermal fluid
  • In situ pH
  • Mid-ocean ridges

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