The main task in the NATAIR project was developing datasets for modelling air pollutant concentration levels from both anthropogenic and natural sources. Volcanic activity is one of the most important natural sources of pollutants for the atmosphere, especially with respect to sulphur species. Volcanogenic sulphur species have been deeply studied because of their influence on the Earth’s irradiative budget, but they are also important sources of primary and secondary aerosols. During the project, an update of the available data, a speciation and an analysis of patterns were carried out, in relation to volcanic emissions. Moreover, current methodologies for estimating emissions were reviewed, and new calculation methods have been developed.
Volcanic sulphur fluxes from the Global Emissions Inventory Activity (GEIA) was one of the reviewed emissions databases, since it provides data from 49 continuously emitting and 25 sporadically emitting volcanoes from the seventies to 1997. Furthermore, this available SO2 data can be extrapolated to all the active volcanic bodies by means of several parameters, such as the Volcanic Explosivity Index (related to the height of eruption columns and the volume of material ejected) or the Volcanic Sulphur Dioxide Index (related only to SO2). In addition, in the framework of the aforementioned project, a database of emissions in Europe was compiled. Most of the analysed data came from spectrometric data obtained through correlation spectrometers (COSPEC), but in some cases, these data were obtained from satellite methods, especially via Total Ozone Mapping Spectrometer (TOMS).
From all the studied European volcanic bodies, Italian and Icelandic ones were the most deeply studied. A data analysing related to two decades of emissions led to a time-averaged emission of 110 kt/year for Stromboli. In addition, SO2 flux from Vulcano (a volcanic island) was estimated to be 6.9 kt/year. An estimated SO2 flux of 1,225 kt/year was estimated for the period 1964-2004 in Iceland, with data from individual eruptions. Additionally, a wide variation in SO2/HCl ratios was found in mount Etna, from values near 4 along non-eruptive periods to values around 8 for the eruptive period which took place from October 2002 to February 2003.
Another important pollutant which is emitted from volcanic bodies consists of particulate matter, which can come from pyroclastic material, volcanic gases or low-temperature reactions. Big particle flux variations were observed for individual sources, even during the same phase of activity. An estimated value of 0.5-0.8 kg/s for sulphate flux was obtained, whereas SO2 flux reached 56.4 kg/s.
In conclusion, this study has clarified some aspects concerning the composition and fluxes coming from volcanic emissions, making use of available continuous monitoring data and semiquantitative estimations. Nevertheless, air pollution monitoring activities should be carefully planned in order to improve the understanding of volcanic emissions.
D. Gaudioso, D.; Badalamenti, F.; Capasso, G.; Di Figlia, M.G.; Napoletani, G.; Romano, D. and and Vitullo, M. (2008): Overview of emissions from volcanoes and other geothermal activities in Europe.