CARBONYL SULFIDE IN 2 ESTUARIES AND SHELF WATERS OF THE WESTERN NORTH-ATLANTIC OCEAN

Dissolved carbonyl sulfide (OCS) was determined in the water column an d sediment porewaters of two estuaries in the eastern United States, a nd in surface waters of the western North Atlantic shelf during summer 1990. Concentrations of OCS in shelf waters averaged 0.4 nmol l-1, wh ereas estuarine concentrations ranged from 0.3 to 12.1 nmol l-1. In an oxic waters, OCS concentrations increased sharply, and porewater conce ntrations exceeded 7000 nmol l-1. The mechanisms leading to the produc tion of OCS in sediments have not been identified, but include organic matter regeneration, pyrite oxidation, and sulfate reduction. Elevate d OCS concentrations in estuaries must be due to a balance between pro duction by the photolysis of dissolved organic sulfur compounds and se diment-water exchange, and losses by sea-air exchange and hydrolysis. Sea-air fluxes of OCS from estuarine and shelf waters are orders of ma gnitude higher than those from the oligotrophic ocean. Since OCS is a precursor of sulfate aerosols in the stratosphere, these results sugge st that further studies are needed to quantify the role that the coast al environment may play in the planet's radiation balance.