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[SVC33-P01] Simple method for determination of dissolved hydrogen sulfide in spring water suitable for field operation
Keywords:hydrogen sulfide, hot spring, geothermal fluids
Some volcanic hot springs and mineral springs contain a relatively high concentration of hydrogen sulfide (H2S). Since H2S is supplied as a gaseous component from the volcanic hydrothermal system, the content of H2S in spring water and its fluctuation may lead to an understanding of the structure of the underground hydrothermal system in the hot spring/volcanic area.
As an official analysis method for dissolved H2S in spring water, there is a method described in "Standard Methods of Analysis for Mineral Springs, Japan," where H2S is fixed as CdS and then determined by iodimetry. However, this method requires a volumetric pipet or flask when collecting sample water. In addition, it is necessary to handle the obtained CdS precipitate quantitatively through whole analytical procedures. Therefore, this method is not suitable for fieldwork in mountainous areas with various restrictions. In this study, we devised a new method to determine dissolved H2S in spring water, suitable for fieldwork that does not require a volumetric pipet and flask, and evaluated its practicality.
The newly devised analytical method in this study is described below. At the sampling site, spring water is injected into the reaction container filled with the Cd-Li solution containing a known amount of cadmium acetate (Cd(CH3COO)2) and lithium chloride (LiCl), an internal standard. H2S in the spring water immediately reacts with Cd2+ to generate CdS precipitate. The reaction container with the post-reaction solution with the CdS precipitate is brought back to the laboratory. The post-reaction solution is filtered, and then the Cd2+ and Li+ concentrations in the filtrate are determined by ICP emission spectrometry and flame emission spectrometry, respectively. The volumetric mixing ratio of spring water and the Cd-Li solution at the time of sampling can be known from the Li+ concentration of the filtrate, assuming the Li+ concentration in the spring water is negligible. The amount of CdS precipitate can be known from the difference between the Cd2+ content in the filtrate and the initial Cd-Li solution. Thes, the H2S concentration in the spring water can be calculated. A volumetric pipet and flask are not required for this series of procedures. In addition, since it is possible to use a disposable syringe made of polypropylene with excellent portability and impact resistance and lightweight for both the sampler and the reaction container, this method is suitable for fieldwork in mountainous areas.
As an official analysis method for dissolved H2S in spring water, there is a method described in "Standard Methods of Analysis for Mineral Springs, Japan," where H2S is fixed as CdS and then determined by iodimetry. However, this method requires a volumetric pipet or flask when collecting sample water. In addition, it is necessary to handle the obtained CdS precipitate quantitatively through whole analytical procedures. Therefore, this method is not suitable for fieldwork in mountainous areas with various restrictions. In this study, we devised a new method to determine dissolved H2S in spring water, suitable for fieldwork that does not require a volumetric pipet and flask, and evaluated its practicality.
The newly devised analytical method in this study is described below. At the sampling site, spring water is injected into the reaction container filled with the Cd-Li solution containing a known amount of cadmium acetate (Cd(CH3COO)2) and lithium chloride (LiCl), an internal standard. H2S in the spring water immediately reacts with Cd2+ to generate CdS precipitate. The reaction container with the post-reaction solution with the CdS precipitate is brought back to the laboratory. The post-reaction solution is filtered, and then the Cd2+ and Li+ concentrations in the filtrate are determined by ICP emission spectrometry and flame emission spectrometry, respectively. The volumetric mixing ratio of spring water and the Cd-Li solution at the time of sampling can be known from the Li+ concentration of the filtrate, assuming the Li+ concentration in the spring water is negligible. The amount of CdS precipitate can be known from the difference between the Cd2+ content in the filtrate and the initial Cd-Li solution. Thes, the H2S concentration in the spring water can be calculated. A volumetric pipet and flask are not required for this series of procedures. In addition, since it is possible to use a disposable syringe made of polypropylene with excellent portability and impact resistance and lightweight for both the sampler and the reaction container, this method is suitable for fieldwork in mountainous areas.