Lead isotope composition and host phases in airborne particulate matter from Budapest, Hungary

摘要

Lead is a frequent, potentially toxic pollutant of the urban environment. Its risk assessment in airborne particulate matter requires data both on its speciation and potential sources. In this paper we present results of a detailed mineralogical (XRD and TEM) and geochemical (selective chemical extractions and lead isotope ratio analyses) study of total suspended particulate (TSP) matter samples from Budapest, Hungary, to fulfill these requirements. Total lead concentrations showed significant enrichment in the studied TSP samples as compared to its geochemical background value. It could be associated with several host phases. The potentially mobile fraction of lead, which could also be harmful to humans, can be as high as 16% of the total lead. This is represented by Pb sorbed on the surface of clay minerals and in the form of carbonates (and sulfates). On the other hand, between 20 and 30% of total lead of TSP material is hosted by magnetite, a highly resistant mineral. However, its rapid oxidation during combustion processes to hematite and/or weathering in the acidifying urban environment to ferrihydrite, may result in the enhanced mobilization of lead.The lead isotope composition of the TSP samples suggests the mixing of several sources for this metal, with slight variation among the sampling sites. Despite the phasing out of leaded gasoline, its contribution to the Pb content of the TSP was observed. Our data also supported that the presence of lead of gasoline origin decreases in the airborne TSP during the last decade in Budapest. Another important source for lead is found to be coal combustion linked to domestic and industrial heating. Lead isotope ratio data suggest additional source(s) for this metal, at least in certain localities, but further investigations are necessary to specify them.