Aerosol Regional Background in Developing Countries

Abstract

To determine the aerosol regional background in three experimental sites in Brazil, South Africa and India modelled and measured surface concentrations of black carbon, organic carbon, sulphate, nitrate and ammonium were analysed. The South American site is characterised by a seasonal variation of the observed aerosol components. Measured ammonium and sulphate compare well with the model results. The model overestimates the elemental and organic carbon concentrations in the dry season, probably due to overestimation of the biomass burning emission inventories. In India modelled and measured concentrations in the wet season are very similar in level. In the dry season the observed concentrations are much higher than modelled due to air masses passing over New Delhi before arriving at the site. The South African site is influenced mainly by the local anthropogenic sources, thus the model estimates are substantially lower than the measured levels. A strong underestimation of modelled NO3 concentration is evident in all sites: in warm environment nitrogen shifts from the aerosol to the gas phase, and condenses on larger particles and the model does not take this into account.