NITROUS-OXIDE PRODUCTION IN THE TROPICAL ATLANTIC-OCEAN

Atmospheric and oceanic nitrous oxide (N2O) measurements were carried out in 1986 in the tropical Atlantic (5° - 12°N, 20° - 22°W). The average N2O concentration in the air was 311 ± 6 ppb. Surface waters were found to be supersaturated (123-132%). The N2O production in highly supersaturated deep waters enabled us to estimate the oceanic source of atmospheric N2O to 11.3 ml m-2 y-1. The eddy diffusion coefficient in the upper thermocline is estimated to be 0.2 cm2 s-1 to support the vertical transport of N2O from the deep layers to the sea surface. The chemical environment (oxygen - nitrate) indicates that the nitrification is the most probable process of N2O formation, but in certain cases assimilatory nitrate reduction may be an additional cause. © 1990.