Is CS₂ a precursor for atmospheric COS?

Abstract

THE stratospheric sulphate layer¹ may play a major part in the Earth's global radiation budget^2,3. Recent measurements^4–6 indicated that carbonyl sulphide (COS) has an appreciable concentration, ranging from 0.3 to 0.5 p.p.b. in the Earth's troposphere. The gas is relatively inert^7,8 in the troposphere and may therefore diffuse to the stratosphere where, through photolysis^7–9, it may provide a major source of sulphate for the formation of the stratospheric sulphate layer. Thus, the origin of atmospheric COS is of particular interest in the stratospheric sulphur cycle. Kurylo¹⁰ suggested that the reaction of carbon disulphide (CS₂) with OH might form COS as a reaction product. We investigate this possibility here through global COS budget analysis in the light of new atmospheric and laboratory measurements. Recent measurements showed that CS₂ has a tropospheric concentration of around 0.1 p.p.b.⁵. The gas has previously been detected in seawater samples by Lovelock¹¹.