EDXRF and TXRF analysis of aerosol particles and the mobile fraction of soil in Botswana

Surface soil and airborne particles were sampled at two locations in Botswana, Serowe and Gaborone. EDXRF and TXRF were used to analyse the soil samples for elemental concentrations and the mobile (bio-available) fractions of the soil. EDXRF was also used for analysis of the aerosol particles in two size fractions, PM_2.5 and PM_2.5-10. To extract the mobile fraction, the soil samples were leached in ammonium acetate solution at pH 7. Most of the elements in the soils were found to have very low mobility at the two locations. In order to identify elements for which the major sources in the fine and coarse airborne particles are anthropogenic, elemental concentrations in the soil were used to calculate enrichment factors of airborne particles with respect to titanium in soil. From the calculated enrichment factors, it appears that the elements attributed to bio-mass burning and those attributed to car exhausts have strong anthropogenic sources in Serowe and Gaborone, respectively.