Lead isotopes decipher multiple origins within single PM 10 samples in the atmosphere of Paris
Résumé
The atmospheric concentration of lead (Pb) in France has strongly decreased since its legal reduction in gasoline in 2000. Pb-isotope ratios are effective tracers of its origin. Pb in atmospheric particulate matter with a diameter <10 μm (PM10) in Paris is shown to have a dual origin: (1) an intrinsic fraction (leached by hydrofluoric acid) forms the cores of particles and (2) a labile fraction (complexation with hydrobromic acid) represents generally >90 % (mass) of the bulk Pb and aggregates on pre-existing particles in the atmosphere. Characterisation of the emissions from different pollution sources, however, indicates that Pb is entirely contained in the labile fraction. Our results show that, in air, the intrinsic fraction is consistently more radiogenic (the degree of enrichment being greater in summer), hinting at different origins. The labile fraction clearly identifies industrial activity as its main source, but the intrinsic fraction may result from either a different industrial-pollution source or, more likely, from a natural end-member (i.e. pre-industrial sediment).