In order to investigate hydrothermal processes in detail, an in situ submersible chemical analyzer (GAMOS) was developed for the determination of dissolved manganese in seawater.
First, a flow through analytical method has been developed for the determination of trace amounts of manganese (Mn (II)) in seawater by applying luminol-hydrogen peroxide chemiluminescence (CL) detection. The method was very simple and almost all of the metal ions did not interfere with the CL detection except for iron species. The iron species were thoroughly removed from the sample solutions by passing through a 8-quinolinol immobilized chelating resin column. The lower and upper limits of Mn detection were 0.029 nM and 4 ƒÊM, respectively. The relative standard deviation was 0.58 % at 10 nM of Mn(II). The method permitted the selective and sensitive determination of sub-nM levels of Mn in seawater sample without any selective preconcentration procedures.
Second, the first in situ flow-through chemical analyzer using chemiluminescence (CL) method in deep sea up to a depth of 5200 m was developed. The analyzer called GAMOS (Geochemical Anomalies MOnitoring System) determines concentration of dissolved manganese continuously in seawater automatically. A detection limit of 0.78 nM was obtained. The performance of GAMOS was carefully cleared by using high pressure test chambers to complete the system for deep-sea operation. The GAMOS was then used successfully for deep-sea hydrothermal plume observation by towing it from a research vessel.
Third, by attaching GAMOS to the submersible Shinkai 6500, the author successfully surveyed the RM24 site, a hydrothermal active site in the southern East Pacific Rise. Large spatial and temporal variety in the hydrothermal field was observed. Anomalies of manganese concentration and temperature (dT) were observed coincidentally, but the relationship between them is not consistently proportional. Wide variation in Mn/dT was observed, which implies diversity between geochemical flux and heat flux, probably depending on the type of venting in the hydrothermal fields.