Composition and source apportionment of atmospheric aerosols in Portugal during the 2003 summer intense forest fire period

摘要

The summer of 2003 was characterized by an intense heat wave across Europe that resulted in a large number of deaths and intense and extended forest fires. In Portugal, during this period more than 300000 ha of forests were destroyed by fire, during a short period, emitting enormous quantities of pollutants to the atmosphere. These emissions have presumably important effects in terms of regional human health and on the atmospheric radiation balance. During the summer of 2003 aerosol samples were taken in the Aveiro region, Portugal, and analysed for total mass and a series of inorganic and organic compounds, including tracers of biomass burning such as potassium and levoglucosan. Based on air mass trajectories, the aerosol size distribution, the levels of particulate mass and the aerosol composition, observed during periods with and without forest fires, the contribution of forest fires to the regional aerosol load is inferred. The absolute and relative variability of the aerosol inorganic and organic components are used to evaluate the importance of forest fire emissions as sources responsible for the presence in the summer atmosphere of compounds such as particulate tracers. The results permit also to have, at least, a semi quantitative estimation of the emission factors of biomass burning tracers such as potassium and levoglucosan to the organic aerosol load in air mass plumes resulting from forest fires. The calculation of emission factors from natural forest fires (without the bias of laboratory and prescribed burnings) is a useful complement for a correct inventory of the impact of these nowadays common summer events on the contamination of regional and global atmosphere.