Atmospheric SO_2 oxidation by NO_2 plays no role in the mass independent sulfur isotope fractionation of urban aerosols

摘要

Modern anthropogenic aerosols usually exhibit low but significant Delta 33S signatures (-0.6 to 0.5460) whose origin still remains unclear. While isotope fractionation factors associated with the oxidation of SO2 by O-2+ TMI (Transition Metal Ion), H2O2 or OH cannot lead to such extreme Delta S-33-values, an increasing number of studies points to the significant role of NO2 as a contributing oxidant, especially in the urban environment.