Role of Chromium and Vanadium in the Atmospheric Oxidation of Sulfur(IV)

• Oxidation of HSO3- in aqueous solution has been studied in the presence of vanadium(V), chromium(III) and chromium(VI). Based on spectrophotometric kinetics data and product analysis it is concluded that the autoxidation rate of sulfur(IV) in slightly acidic solution is unaffected by the presence of vanadium(V) and chromium(III). Chromate(VI), on the other hand, oxidizes sulfur(IV) in a direct redox process in acidic solution. The overall rate of this reaction decreases with increasing pH and it becomes relatively slow in the atmospherically relevant pH range 4-6. Moreover, chromium(III) dominates strongly over chromium(VI) in the atmospheric aqueous phase. Hence, it is concluded that cations of vanadium vanadium and chromium have no significant influence on the atmospheric aqueous-phase oxidation of sulfur(IV) under most ambient atmospheric conditions. Only in very acidic droplets, direct redox between chromium(VI) and sulfite might be of some importance.

Ämnesord

NATURVETENSKAP  -- Kemi -- Oorganisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Inorganic Chemistry (hsv//eng)

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Meteorologi och atmosfärforskning (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Meteorology and Atmospheric Sciences (hsv//eng)

Nyckelord

Transition metals

Atmospheric oxidation

Sulfur(IV)

tropospheric aqueous phase

transition metals

troposheric aqueous phase

catalysis

kinetics

sulfur(IV) oxidation

atmospheric chemistry

Reaction mechanism

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