An in-situ, real-time Device for Hg Monitoring in Deep Waters

Mercury (Hg) in water partially occurs in the form of dissolved atomic vapor, the so-called Dissolved Gaseous Mercury (DGM). DGM can range from 2.5 to 25% of Total Hg (THg). DGM plays an important role in the Hg transfer through the air-water interface. The presented device measures the DGM concentration with the limit of detection 0.05 ng/L in the sample of water (250 mL) taken from a maximum depth of 300 m (limit is imposed by the anodized aluminum watertight sampling cylinder strength and acceptable pressure at the input of the internal solenoid valves). A full process cycle, made-up of sampling, measuring and restoring macro-stages, needs about 20 minutes to be completed and the DGM concentration values are immediately transmitted out for user analysis. Continuous automatic cycle processes can be executed since intra/inter contaminations are carefully avoided. The device is mounted on board of the “V-FIDES” Autonomous Underwater Vehicle (AUV)¹ also equipped with a multi-parametric probe measuring physical sea water parameters (pH, salinity, oxygen, etc.).