Impacts of meteorological factors on hydrogen sulfide concentration downwind of geothermal power plants

Hydrogen sulfide (H₂S) concentration in the city of Reykjavik, downwind of geothermal power plants has been studied with respect to meteorological factors as the odor and other effects are starting to become a nuisance. The main sources of H₂S in Reykjavik City were the Nesjavellir and Hellisheidi Geothermal Power Plants, which are both less than 35km east of the city. The H₂S concentration in Reykjavik was correlated with the H₂S emissions from the power plants but was also heavily influenced by weather conditions. The results showed that the H₂S concentration at the Grensasvegur Measuring Station was elevated when the wind direction was from 54° to 125°, especially when the wind direction was stable for several hours. The H₂S concentration in Reykjavik was highest when the wind speed in the city was between 1.5 and 4ms^-1, and decreased rapidly with higher wind speeds. H₂S concentration showed correlation with the air temperature in the city below 3°C and the concentration rose as the temperature decreased, and the air became more stable and was highest when there was a temperature inversion. The quantitative effects of precipitation on H₂S concentration could not be determined in this study although the events with the highest H₂S concentration occurred when there was no precipitation. The results showed that favorable conditions for high H₂S events can be expected in Reykjavik 2-6 times per year and events with H₂S concentration exceeding 50μgm^-3 might be expected on average about 2 times per year. The results also indicate that events with high H₂S concentration can be predicted by using a current weather forecast.