Seawater solutions of environmentally relevant organosulfur compounds,
commercial humic acid (HA), and natural dissolved organic matter (DOM
) were incubated with and without UV light in order to determine the c
arbonyl sulfide (COS) producing capabilities of these compounds. COS d
ark-and photo-production rate constants were determined for dilute sol
utions of the organosulfur compounds (mu mol l(-1)) and HA/DOM (mg l(-
1)). Dissolved COS was determined using a purge and cryogenic trap met
hod followed by GC/FPD detection. COS was produced in considerable amo
unts both non-photochemically and photochemically from the reduced for
m of free acid of glutathione (GSH) and photochemically from cysteine
(CYS). Other organosulfur compounds yielded little or no COS. Photosen
sitizers, such as commercial HA and natural DOM, photo-catalyzed COS p
roduction from several of the chemicals tested and from unknown COS pr
ecursors in the seawater samples. HA itself was found to contain COS p
recursors. We propose that reactions of thiyl radicals with carbonyl c
ompounds play an important role in COS formation from the organosulfur
compounds studied. (C) 1997 Elsevier Science B.V.