In situ osmotic analyzer for the year-long continuous determination of Fe in hydrothermal systems Original Research Article

A submersible osmotically pumped analyzer (Fe-OsmoAnalyzer) has been adapted for the long-term continuous high resolution monitoring of iron(II) and (III) in deep-sea hydrothermal vents. Ferrozine is used as the colorimetric reagent. The detection limit for our analyzer is 0.1 μM for a 0.7 cm pathlength with a linear response up to 50 μM. The Fe-OsmoAnalyzer uses periodic injections of standards and blanks to self calibrate and can operate unattended for over a year collecting data every 15 min. The Fe-OsmoAnalyzer was field tested during a 6 week test deployment at 900 m in Monterey Bay and a year-long deployment at 1100 m off the coast of Hawaii. A second year-long deployment in a low temperature hydrothermal vent on the Juan de Fuca Ridge provided high resolution continuous monitoring of Fe and was able to distinguish tidally influenced fluctuations in Fe concentrations.