Rate constants for atmospheric trace organics scavenging SO4− in the Fe-catalysed autoxidation of S(IV)

Numerous organic compounds are released into the atmosphere in globally large quantities. Chemical transformation of these compounds under the influence of other atmospheric components has not yet been fully recognised. One of the uncertainties is the importance of the mechanism and kinetics of atmospheric reactions involving organics for the quantitative description of such phenomena as the formation of aerosols and the acidification. Rate constants for scavenging SO4− radical anions by benzene, phenol, α-pinene, myrtenal and cis-pinonic acid in aqueous phase were determined by the method described previously (Atmos. Environ. 37 (2003) 3913) yielding 2.4×109, 8.8×109, 1.2×109, 9.6×108 and 1.6×107 M−1 s−1, respectively. These anions were produced by autoxidation of S(IV) catalysed by Fe ions at pH 3.0 and ionic strength 0.005 M. In the case of myrtenal, the formation of an aldehyde-hydrogen sulphite adduct, non-reactive with respect to oxidizing radicals, was taken into account.