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[SVC32-P35] Hydrogen sulfide concentrations at hot springs areas around volcanoes, as measured by miniature monitor in development
Keywords:volcanic gas, hydrogen sulfide, gas measuring instrument
Some residents and workers stay for long periods in hot spring areas around volcanoes where hydrogen sulfide is present in the air. We could not find any examples of measurements of the hydrogen sulfide concentrations in such places. Therefore, we measured them on site. Seven hot spring sites around the volcano were selected where residents and workers stay long-term, and the hourly mean hydrogen sulfide concentrations in the air at the breathing positions of the residents and workers were measured continuously. Measurements were carried out three times per location in 2022, for a period of 9 to 16 days per measurement. The results showed that the hourly average values ranged from 0.05 to 3.96 ppm. Ten residents and workers at each location were interviewed about their health status, and none of them were aware of any adverse health effects such as chronic sore throat, respiratory discomfort such as runny nose, or continuous eye pain.
Environmental standards have not been set for hydrogen sulfide in air. The guideline value of 0.11 ppm (24-hour average value) in the European Air Quality Guidelines 2nd Edition (WHO, 2000) exists as a standard for health effects due to long-term exposure. However, no experiments or observations have been carried out on humans to determine what health effects occur when this standard is exceeded. Other standards have been established for workers based on findings from human exposure experiments. American Conference of Governmental Industrial Hygienist (ACGIH) Threshold Limit Values (TLV) are 1 ppm for a time-weighted average (TWA) of 8 hours per day, 40 hours per week and 5 ppm for a 15-minute Short-Term Exposure Limit (STEL).
The measurements were mainly carried out using a prototype under development as part of the NEDO research and development ‘Development of an IoT Hydrogen Sulfide Monitoring System’. This instrument is being developed to improve the efficiency of environmental impact assessment of geothermal power plants. Combining a periodic calibration function with a conventional electrochemical gas sensor designed for ppm-order measurements, the sensor enables long-term continuous measurement of hydrogen sulfide in the low-concentration range, with low susceptibility to noise and drift. The measurement range is around 0.01 to 5 ppm, and a certain level of accuracy has been confirmed by comparison with conventional measurement methods for environmental impact assessment. The instrument is easy to carry, measuring 32 cm x 26 cm x 16 cm and weighing just under 3 kg. It can be operated for more than three days on four AA alkaline batteries and can also be used for long-term measurements over several months by using an external power supply.
In the future, the plan is to test dozens of these instruments operating simultaneously around volcanoes in order to visualize the distribution of hydrogen sulfide concentrations in volcanic gases.
This paper is based on results obtained from a project, JPNP21001, subsidized by the New Energy and Industrial Technology Development Organization (NEDO).
Environmental standards have not been set for hydrogen sulfide in air. The guideline value of 0.11 ppm (24-hour average value) in the European Air Quality Guidelines 2nd Edition (WHO, 2000) exists as a standard for health effects due to long-term exposure. However, no experiments or observations have been carried out on humans to determine what health effects occur when this standard is exceeded. Other standards have been established for workers based on findings from human exposure experiments. American Conference of Governmental Industrial Hygienist (ACGIH) Threshold Limit Values (TLV) are 1 ppm for a time-weighted average (TWA) of 8 hours per day, 40 hours per week and 5 ppm for a 15-minute Short-Term Exposure Limit (STEL).
The measurements were mainly carried out using a prototype under development as part of the NEDO research and development ‘Development of an IoT Hydrogen Sulfide Monitoring System’. This instrument is being developed to improve the efficiency of environmental impact assessment of geothermal power plants. Combining a periodic calibration function with a conventional electrochemical gas sensor designed for ppm-order measurements, the sensor enables long-term continuous measurement of hydrogen sulfide in the low-concentration range, with low susceptibility to noise and drift. The measurement range is around 0.01 to 5 ppm, and a certain level of accuracy has been confirmed by comparison with conventional measurement methods for environmental impact assessment. The instrument is easy to carry, measuring 32 cm x 26 cm x 16 cm and weighing just under 3 kg. It can be operated for more than three days on four AA alkaline batteries and can also be used for long-term measurements over several months by using an external power supply.
In the future, the plan is to test dozens of these instruments operating simultaneously around volcanoes in order to visualize the distribution of hydrogen sulfide concentrations in volcanic gases.
This paper is based on results obtained from a project, JPNP21001, subsidized by the New Energy and Industrial Technology Development Organization (NEDO).