Mercury emissions from forest fires in Europe and Northern Africa

The assessment of mercury emissions from major natural sources and their variations with meteorological conditions is considered one of the major priority among all those involved in estimating the relative contribution of major natural sources compared to industrial sources and ultimately to evaluate the mercury flux released to the atmosphere on regional and global scale. The aim of this study was to estimate the contribution of wildfires to the total mercury released to the atmosphere in the Mediterranean region. Mercury emissions from wildfires in Europe and Northern Africa region were estimated by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. MODIS data stream have been used regionally for measuring biomass production with global coverage at 500 m resolution, while the burned surface was mapped using a recently developed algorithm that uses multitemporal land surface reflectance data. As emission coefficient a literature value was adopted. Mercury emissions are in the range of estimates reported in recent papers and show a growing trend when compared to the global mercury budget. The uncertainty analysis shows that our estimates depend dramatically from the emission factor - which in our case is undifferentiated for each forest type and time of the year -, from the estimate of burned surface, from the assessment of burned phytomass, from the wildfire dynamics and the quality of data coverage.