Denitrification Rates in a Marine Sediment as Measured by the Acetylene Inhibition Technique

Abstract

A method has been developed for measurement of denitrification activity in sediments by application of the acetylene inhibition technique. Acetylene-saturated water was injected, at close intervals, into sediment cores which were then incubated for a few hours at the in situ temperature. Frozen segments of the cores were assayed for accumulation of N 2 O by a combined gas extraction and detection system. The segments were thawed under a stream of helium from which N 2 O (and other gases) was collected in a liquid N 2 trap, and the quantity of N 2 O was measured by gas chromatography. The maximum rate of denitrification in a coastal marine sediment was 35 nmol of N per cm 3 of sediment per day at 2.5°C, and the rate of denitrification for the total sediment was 0.99 nmol of N per m 2 per day.