Effect Of Soil Water Content On N₂O Diffusion Process And Reduction Process

Nitrous oxide is a potent greenhouse gas,it also plays an important role in depletion of the ozone layer in stratospheric ozone depletion.A key pathway of reducing nitrous oxide?N₂O?emission from farmland is strengthen N₂ O to N₂ reduction process,quantification of N₂ O from subsoil is an important method for mitigation measures.However to response of making farmland greenhouse gas emission reduction measures between the reduction mechanism and influencing factors is great significance.This object of this paper is to quantify N₂ O production and clarify the mechanism of N₂ O diffusion and reduction from subsoil.Experimental treatments included 4 gradients about water-filled pore space?WFPS?: 30%,50%,60%,80%.Under specific soil conditions,we quantify the reduction of N₂ O as it diffuses upward in different?WFPS?,Cumulative N₂ O emission during the experiment in the treatments with N₂ O and without N₂ O have different changing trend.Soil moisture content is an important factor affecting N₂ O emissions.Soil surface N₂ O emissions were measured for 22 d,and after the experiment,residual N₂ O in the system was determined.In this study,we investigated:?1?diurnal variation of N₂ O emission;?2?Assess the effects of soil moisture content on N₂ O diffusion.?3?Quantifying N₂ O reduction in subsoil.During the experiment,without adding N₂ O,emissions were lowest in the 30% WFPS and in the dry water content treatment.In the N₂ O addition treatment,emissions were lowest in the treatment with 80%WFPS.Cumulative N₂ O emissions were shown that in the 30%WFPS treatment were not different from emissions in the control treatment.The N₂ O emissions at 60% WFPS were significantly higher than emissions at other treatments,the suitable treatments to N₂ O emissions in WFPS 60%.In order to verify the influence between water contents and N₂ O emissions,we continue do another experiments.Experimental treatments included 3 gradients about water-filled pore space?WFPS?: 30%,75%,100%.We conclude that: during pre-culture,emissions ranged between 0-12?g d-1,emissions were highest in the 75% WFPS.In the 11 d,30% and 75% WFPS treatments were increased,but 100%WFPS gradually decreased.Soil analyses for N as NH4+and as NO3-during beginning and before incubation,Compare with the two stages: concentrations of NO3--N get lower,but NH4+-N get higher,maybe appear to biologically reactive in substrates.Nitrous oxide flux during the experiment in the treatments without and with addition of N₂ O.Without adding N₂ O,the emissions ranged between 0-9 ?gN₂O-N m-2 h-1.Emissions were lowest in the treatment with 100%WFPS treatment.After 18 d,fluxes in both 30% and 100%WFPS treatments had rose to levels,but WFPS 75% treatment declined.After 22 d,they were not changed at all.In the N₂ O addition treatments,emission ranged between 0-12?g N₂O-N m-2 h-1.Emissions were lowest in the treatment with 100%WFPS,highest in the 30%WFPS,During the experiment,emissions in the treatment 30% and 75% WFPS stabilized around 8 ?g N₂O-N m-2 h-1.Emissions in the 100%WFPS treatment gradually increased during the experimental period.Concentrations of NH4+,NO3-were increased for all treatments during the experimental period.concentrations did not differ between treatments with and without applied N₂ O at the end of the experiment.Concentrations of NH4 +were increased with increasing moisture content,and in the end of the experimental,all the treatments were increased.For NO3-,the same trend was observed: concentrations of NO3-decreased with decreasing moisture content.The object of this study is to clarify the mechanism of N₂ O production in subsoil and quantify its production pathway on the agriculture ecosystem and evaluate its environmental effect.