Natural emission of mercury from forest fires in Europe and Mediterranean Region

It is well known that mercury is released to the atmosphere from a multitude of natural and anthropogenic sources. The ratio between the relative contributions from these two source categories may vary with region and time of the year. However, recent studies have highlighted that natural sources in the Mediterranean region provide a significant contribution to the regional atmospheric budget. Major natural sources include emissions from volcanoes, surface waters, top soil and wildfires. Previous studies have provided detailed information on emissions from volcanoes, top soil and surface waters but very little has been done in order to assess the contribution from wildfires of forests in the Mediterranean and European atmosphere. Forest fires in the Mediterranean environment are frequent during dry seasons when large areas of forests are impacted. Considering that every year a large surface areas in Europe is affected by wildfires, Hg emissions from this particular source can be significant in the regional emission budget estimate. Therefore, in order to assess temporal trends of mercury emissions from wildfires in Europe two methodological approaches were used including i) the statistical estimates based on statistical data of forest fires, forests biomass content and emission factors for each vegetation and forest type; and ii) the remote sensing approach which uses satellite observations for estimating the forest biomass as well as the forest surface eroded by wildfires every year. The first approach is suitable for country or regional assessments though significant uncertainty may affect the surface areas estimate, the second approach although provides a well characterised surface area may be affected by uncertainty in characterising the type of forest and vegetation.