Carbonyl sulfide in two estuaries and shelf waters of the western North Atlantic Ocean

Abstract

Dissolved carbonyl sulfide (OCS) was determined in the water column and sediment porewaters of two estuaries in the eastern United States, and in surface waters of the western North Atlantic shelf during summer 1990. Concentrations of OCS in shelf waters averaged 0.4 nmol l −1, whereas estuarine concentrations ranged from 0.3 to 12.1 nmol l −1. In anoxic waters, OCS concentrations increased sharply, and porewater concentrations exceeded 7000 nmol l −1. The mechanisms leading to the production of OCS in sediments have not been identified, but include organic matter regeneration, pyrite oxidation, and sulfate reduction. Elevated OCS concentrations in estuaries must be due to a balance between production by the photolysis of dissolved organic sulfur compounds and sediment-water exchange, and losses by sea-air exchange and hydrolysis. Sea-air fluxes of OCS from estuarine and shelf waters are orders of magnitude higher than those from the oligotrophic ocean. Since OCS is a precursor of sulfate aerosols in the stratosphere, these results suggest that further studies are needed to quantify the role that the coastal environment may play in the planet's radiation balance.