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 35 km 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 4 m s−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 50 μg m−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.