Sulfide concentrations critically affect worker safety and the integrities of underground facilities, such as deep geological repositories for spent nuclear fuel. Sulfide is highly sensitive to oxygen, which can oxidize sulfide to sulfate. This can hinder precise measurement of the sulfide concentration. Hence, a literature review was conducted, which revealed that two methods are commonly used: the methylene blue and sulfide ion-selective electrode (ISE) methods. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used for comparison with the two methods. The sulfide ISE method was found to be superior as it yielded results with a higher degree of accuracy and involved fewer procedures for quantification of the sulfide concentration in solution. ICP-OES results can be distorted significantly when sulfide is present in solution owing to the formation of H2S gas in the ICP-OES nebulizer. Therefore, the ICP-OES must be used with caution when quantifying underground water to prevent any distortion in the measured results. The results also suggest important measures to avoid problems when using ICP-OES for site selection. Furthermore, the sulfide ISE method is useful in determining sulfide concentrations in the field to predict the lifetime of disposal canisters of spent nuclear fuel in deep geological repositories and other industries.

1. Introduction
2. Methods of Measuring Sulfide Ions
    2.1 Methylene Blue Method
    2.2 Sulfide Ion-Selective Electrode
    2.3 Comparing the Methylene Blue and ISEMethods
3. Methods
    3.1 Materials
    3.2 Analytical Instruments
    3.3 First Study: Sulfide and SAOB
    3.4 Second Study: Sulfide Without SAOB
    3.5 Third Study: Methylene Blue Method
    3.6 Fourth Study: Comparison of ISE andMethylene Blue Method
4. Results and Discussion
    4.1 First Study: Field-applicable TitrationMethod (with SAOB)
    4.2 Second Study: Laboratory Titration Method(Without SAOB)
    4.3 Third Study: Methylene Blue Method
    4.4 Fourth Study: Sulfide ISE and MethyleneBlue Comparison
5. Conclusions
Acknowledgements
REFERENCES

• Nakkyu Chae(Seoul National University)
• Samuel Park(Seoul National University)
• Sungyeol Choi(Seoul National University) Corresponding author