| Autor: |
Phillips, Ronald E., Reddy, K. R., Patrick, W. H. |
| Zdroj: |
Soil Science Society of America Journal; March 1978, Vol. 42 Issue: 2 p272-278, 7p |
| Abstrakt: |
A theoretical analysis of denitrification occurring in submerged soil in a test tube, when assumed to be a zero‐order reaction with available organic carbon nonlimiting, appears to be a first‐order reaction if the effects of diffusion are neglected. In this case, denitrification appears to be a first‐order reaction because denitrification occurs at a faster rate than the diffusive flux can supply NO3‐‐N to the soil. After some length of time, the concentration of NO3‐‐N in the lower portion of the flood‐water‐soil interface will be equal to the concentration in the flood‐water. After which time, denitrification occurs only in the upper portion of the soil sample. When the role of diffusion is neglected, it is generally assumed that denitrification occurs uniformly throughout the soil sample. It is for this reason that denitrification can appear to be a first‐order reaction when it may actually be a zero‐order reaction. The true order of reaction and rate constant of denitrification in a test tube can be evaluated experimentally by eliminating the floodwater above the soil sample; with this experimental geometry some of the confounding effects of diffusion of NO3‐‐N can be minimized. If diffusion is neglected, not only is the order of reaction misjudged but the depth of floodwater above the soil has a significant effect on the magnitude of the calculated rate constant of the apparent first‐order reaction also. |
| Databáze: |
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