Solubility of lead in precipitation as a function of raindrop size

This paper presents first results concerning the solubility of Pb in precipitation 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 centrifuge and analysed by graphite-furnace atomic absorption spectrometry. Relative solubilities of Pb higher than 45% were found for all drop sizes. Different interdependencies between the concentration of soluble and insoluble Pb as a function of raindrop size were found for several rain events. The solubility of Pb in precipitation mainly depends on the Pb compounds which are located at the scavenged aerosol particles. The chemical composition of aerosol particles depends on their size and their sources. Previous experiments by Ebertet al. (1997,Atmospheric Environment31, 239–246) have indicated a relationship between the concentration of a species in precipitation as a function of raindrop size and the size of the scavenged aerosol particles. Therefore, different soluble concentrations of Pb are found as a function of raindrop size, depending on the soluble Pb compounds located at the scavenged aerosol particles.