An Open Gas-Flow System for Investigating the Response of Nitrous Oxide Fluxes from Soil Cores to Different Oxygen Concentrations

Abstract

The design of an inexpensive device for creating mixtures of gases in different but known proportions and perfusing them through soil cores is described. Soil in cores were perfused with gas mixtures containing, 0, 2, 10, 33, 81 and 100% O2 plus 0.1% CO2 made up to 100% with He for 48 hours at a rate which ensured that the air-filled pore volume of the soil was replaced once every 3.3 minutes. After this period the N2O emission from the soil was measured. There was significant N2O flux from all soils within the first 12 hours, including those which has been exposed to 100% O2. The amount of N2O emitted over 324 hours increased with decreasing O2 concentration in the perfusing gas mixture, although the initial (0 to 108 hours) rate of N2O emission from the 100% O2 treatment was significantly greater than that of the 33 and 81% O2 treatments. N2O emissions from soil exposed to 0, 2 and 10% O2 were linear with time, whereas the rate of N2O emission from soil exposed to the greater O2 concentrations increased significantly after 210 hours