SOLUBILITY OF LEAD IN PRECIPITATION AS A FUNCTION OF RAINDROP SIZE

This paper presents first results concerning the solubility of Pb in p recipitation as a function of raindrop size. Raindrops were collected according to their size by freezing them in liquid nitrogen (Guttalgor method). Soluble and insoluble fractions of Pb were separated by a ce ntrifuge and analysed by graphite-furnace atomic absorption spectromet ry. Relative solubilities of Pb higher than 45% were found for all dro p sizes. Different interdependencies between the concentration of solu ble and insoluble Pb as a function of raindrop size were found for sev eral rain events. The solubility of Pb in precipitation mainly depends on the Pb compounds which are located at the scavenged aerosol partic les. The chemical composition of aerosol particles depends on their si ze and their sources. Previous experiments by Ebert et al. (1997, Atmo spheric Environment 31, 239-246) have indicated a relationship between the concentration of a species in precipitation as a function of rain drop size and the size of the scavenged aerosol particles. Therefore, different soluble concentrations of Pb are found as a function of rain drop size, depending on the soluble Pb compounds located at the scaven ged aerosol particles. (C) 1998 Elsevier Science Ltd. All rights reser ved.