ENVIRONMENTALLY RELEVANT PRECURSORS OF CARBONYL SULFIDE IN AQUATIC SYSTEMS

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.