Current health problems, including respiratory disorders, are multifactorial. Among them, the negative impact of the presence of particulate matter (PM) which depend upon their aerodynamical diameter in the atmosphere has now been widely demonstrated. These particles, a major component of aerosols, derive from numerous physical and /or chemical mechanisms. Aerosols can be distinguished into two distinct families: 1) primary aerosols, formed in situ at pollution sources and emitted into the atmosphere, and 2) secondary aerosols, formed in the atmosphere, post-emission, resulting from physical/chemical processes.
While the aerosol final composition is now well documented, the origin(s) and processes controlling the budget of its components are still subject to debate, in particular regarding sulfates. These may have a dual origin: primary or secondary, from the oxidation of sulfur dioxide (SO2) emitted from either anthropogenic (73-80 Tg/an) or natural sources (25-40 Tg/an). Even if anthropogenic emissions of SO2 are now regulated in developed countries, sulfates remain a major component of aerosols.
The aim of this PhD is to constrain both the emission sources of sulfur in the atmosphere of Paris (France) and Montreal (Canada) through the study of stable sulfur isotopes (33S/32S, 34S/32S, 36S/32S), and the secondary oxidation processes that lead to the formation of sulfate through the coupled study of sulfur and oxygen stable isotopes (17O/16O et 18O/16O). Moreover, the study of sulfur and oxygen multi-compositions isotopes enable the study of both the mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) which lead to a better characterization of the transport and secondary oxidation processes of the SO2 in the atmosphere.