Chemical Composition of Precipitation and River Water in Southern Iceland: Effects of Eyjafjallajökull Volcanic Eruptions and Geothermal Power Plants.

Samples of precipitation have been collected and analysed from four sampling stations in southern Iceland. Sea-salt in the precipitation has the same elemental ratios as in seawater and its concentration decreases with distance from the shore. The sampling station at Mjóanes, at Thingvallavatn Lake, is located around 100 km west of Eyjafjallajökull and during and after its eruption in 2010, the concentration of fluoride in precipitation increased from 10-20 μg/l to 90 μg/l and the annual average concentration elevated from 11 μg/l to 28 μg/l. From 1980 to 1998, pH of rainwater at Írafoss increased due to emissions reductions of anthropogenic sulphur. Since 1998, pH of the precipitation has decreased again at Írafoss. Similar pH changes are seen in Mjóanes, which is close to Írafoss, but not in other sampling stations further away. River water samples collected in the vicinity of the rainwater samplers, from the spring fed river Sog have elevated non-SO4 sulphur concentration from 2005-2010 and decreased δ34S from 2005-2007. Írafoss and Mjóanes are located approximately 12-20 km away from two geothermal power plants, Nesjavellir- and Hellisheidi power plants that emit large quantities of CO2 and H2S, among other gases, to the atmosphere. The data presented here suggest that geothermal power production can cause local environmental effects, like rainwater acidification and increases in dissolved sulphur in rivers in the vicinity of the power plants.