From August 31, 2014 to February 27, 2015, a volcanic eruption in Iceland discharged twice as much sulphur dioxide as is emitted by all human activity in a single year. The eruption impacted air quality throughout Sweden with elevated sulphur levels in air and precipitation, especially in northern Sweden.
– The level of airborne sulphur dioxide was greater in the north than in the south, and as the air in northern Sweden is cleaner and less affected by shipping and industry, the difference was even more noticeable, says Sofie Hellsten, researcher at IVL Swedish Environmental Research Institute.
Sulphur dioxide has an acidifying effect on the environment. However, sulphur precipitation has fallen dramatically in Sweden over the past thirty years, and consequently the pressure on acidified lakes and fields has lessened, although the effects of acidification still remain.
During the 2014 eruption, both levels in the air and sulphur deposition increased significantly. In September 2014, air levels were about 25 times higher in northern Sweden compared with the three previous years. In southern and central Sweden, the increase was less – about three times higher in central Sweden and twice as high in southern Sweden.
Sulphur deposition in rainfall, however, was highest during the month of October. Five times higher in northern Sweden, 3.5 times higher in central Sweden and just over twice as high in southern Sweden.
According to dispersion calculations carried out by IVL the eruption contributed more than 80 per cent of the sulphur deposition in rainfall in northern Sweden during the entire time the volcanic eruption lasted.
The emission and its influence on air levels and depositions has been analysed by the IVL-led Throughfall Monitoring Network. The SWETHRO network monitors atmospheric deposition of air pollutants in Sweden and is financed by the Air Quality Management Association and county administrative boards, as well as by the Swedish Environmental Protection Agency.