Regional source discrimination of atmospheric aerosols in Europe using the isotopic composition of lead

Pb²⁰⁶/Pb²⁰⁷ and Pb²⁰⁸/Pb²⁰⁷ isotope ratios were measured in a series of daily atmospheric aerosol samples collected in southern Sweden between 9 February and 30 May 1988. The ratios were observed to vary considerably, depending on the origin of air. 5-day back-trajectories were used to classify the samples according to source region: Northwest, Western Europe, East, Eastern Europe, or a combination of two regions. Significant differences in the isotope ratios were found. Unique signatures based on the Pb²⁰⁶/Pb²⁰⁷ and Pb²⁰⁸/Pb²⁰⁷ ratios could be assigned for each region. The signatures were generally consistent with isotope ratios of Swedish and other European gasolines, and with literature values of the isotope ratios of economically significant lead ores used in Europe. A comparison was made between the regional signatures and the Pb²⁰⁶/Pb²⁰⁷ ratios observed in Arctic aerosol samples. Excellent agreement was observed between the Arctic Pb²⁰⁶/Pb²⁰⁷ ratios (1.160) and an average source signature (1.156) calculated from observations in this study using equal contributions from Western Europe, Eastern Europe, and the East as predicted by a chemical transport model.