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Use of stable sulfur isotope systematics for evaluating oxidation reaction pathways and in‐cloud‐scavenging of sulfur dioxide in the atmosphere
Author(s) -
Tanaka Noriyuki,
Rye Danny M.,
Xiao Yitian,
Lasaga Antonio C.
Publication year - 1994
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/94gl00893
Subject(s) - sulfur dioxide , sulfur , chemistry , isotope fractionation , sulfate , kinetic isotope effect , mass independent fractionation , dissolution , stable isotope ratio , fractionation , inorganic chemistry , organic chemistry , physics , deuterium , quantum mechanics
Sulfur dioxide injected into the atmosphere is most likely oxidized into sulfate. Two major oxidation pathways are possible: 1) a homogeneous pathway involving gas reaction with hydroxyl radicals and 2) a heterogeneous pathway involving aqueous dissolution or aerosol reactions (Figure 1.). The relative importance of these reaction pathways conditions is controversial. Sulfur isotope ratios can be used to quantify the relative importance of these reaction pathways. However, its application was severly hampered by the fact that the isotope fractionation factor for the homogeneous pathway was not known (Caron et. al., 1986; Nriagu et. al., 1987). A significant isotope fractionation in the homogeneous SO 2 oxidation is identified for the first time using an ab initio quantum mechanical calculation. By using the sulfur isotope fractionation factors we demonstrate a technique that uses measurements of the sulfur isotope ratio in gaseous SO 2 , aerosol SO 4 and sulfate in wet precipitation to quantify the relative importance of the homogeneous and heterogeneous reaction pathways as well as the in‐cloud scavenging of sulfur dioxide for a set of isotopic observations at New Haven, CT, USA.