Mechanisms of hydrogen sulfide release from coastal marine sediments to the atmosphere

Abstract

In two shallow, coastal areas in Denmark the rates of H₂S release were directly measured by continuously collecting the gas over a known area. Peak emission rates of up to 0.30 and 6.7 mmol H₂S m⁻² h⁻¹ were found with a diurnal average of 0.063 and 1.58 mmol H₂S M⁻² h⁻¹. The release mainly takes place at night since photosynthetic microorganisms efficiently oxidize the sulfide during the day. Only traces of H₂S escape through a stagnant layer of oxic water 10 cm deep. The rate of H₂S release is compared to the diurnal changes in light, temperature, Eh, pH, O₂, and H₂S at the sediment surface and with the rate of sulfate reduction within the sediment.