Statistical assessment and modeling of the effects of weather conditions on H_2S plume dispersal from Icelandic geothermal power plants

摘要

Episodes of high atmospheric load of hydrogen sulfide (H_2S), where the concentration is over 50 μg m~(-3) hourly average value, occur about 80 times a year in Reykjavik (data from 2007 to 2009). H_2S originates mainly from two geothermal power plants 25-30 km (south-)east of Reykjavik, at Hellisheidi and Nes-javellir. Certain weather-dependent dispersion conditions, such as wind, cloud cover and air temperature, allow the transport of emissions towards Reykjavik and the neighboring cities, causing local air pollution. High concentrations of H_2S occur within a narrow range of weather conditions, namely slow (mean value 2±1 ms~(-1)) easterly (114° ± 23°) winds, together with cold air temperatures (median value -3℃) and preferably no, or little, cloud cover. A classification of weather types shows the preferred occurrence of high H_2S concentrations in connection with low atmospheric exchange and autochthonous weather. Stable atmospheric stratification and inversions enable the transport of H_2S emissions to Reykjavik. The measured concentrations, the short lived peaks in concentration and different values at nearby measurement stations, indicate a very narrow plume, which fits well with a Gaussian plume distribution model.