Near Field Sinks and Distribution of H2S from Two Geothermal Power Plants in Iceland

Abstract

Geothermal power production has been expanding in SW-Iceland during the last few decades. The simultaneously increasing emission of hydrogen sulfide (H2S) has resulted in increased public concern. In this study H2S was measured in the atmosphere and sulfur in vegetation and precipitation near field of two geothermal power plants, the Nesjavellir and Hellisheidi Power Plants, in southwest Iceland to determine the H2S distribution and its sinks from the atmosphere. Sinks of atmospheric H2S, up to 35 km from the Power Plants, were identified and an attempt made to quantify them. Calculations and data analysis indicated that oxidation and uptake in surface water were the largest sinks in the area and washout with precipitation was the smallest sink. Other sinks were uptake by vegetation, uptake by soil and washout in steam at the source. The total estimated depletion of the H2S from the atmosphere was 256 tons/year which was insignificant compared to the total emission which was over 20,000 tons in 2012. About 99% of the H2S emissions from the Power Plants were thus transported out of the study area as H2S. The results from atmospheric measurements of H2S showed that the H2S concentration was influenced by weather conditions and terrain. The shape of the H2S plumes observed at the same location was similar between events, indicating repeated patterns of plume distribution. Plumes were found to follow mountain passes and accumulate alongside a mountain range.