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Measurement of Soil Gaseous Diffusion Coefficients by a Transient‐State Method with a Time‐dependent Surface Condition
Author(s) -
Rolston D. E.,
Brown B. D.
Publication year - 1977
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1977.03615995004100030013x
Subject(s) - diffusion , flux (metallurgy) , tracer , soil water , diffusion equation , chemistry , argon , soil science , analytical chemistry (journal) , thermodynamics , environmental science , environmental chemistry , physics , economy , organic chemistry , nuclear physics , economics , service (business)
Precise measurement of the gaseous diffusion coefficient in soils is necessary for calculating the flux of gas resulting from soil respiration, denitrification, or fumigation. Gaseous diffusion coefficients of soil columns and a field soil were determined by fitting a solution of the transient‐state diffusion equation for a time‐dependent surface condition to measured N 2 concentration profiles. The time‐dependent surface condition was experimentally imposed by pumping argon at a constant rate into a chamber placed within the soil and on the soil surface. The argon and air mixture exited the chamber through several exit ports. The N 2 concentration at the soil surface and within the soil profile was determined several times within a 5‐hour period after initiation of the argon flow. A solution of the diffusion equation for a non‐constant initial condition can also be used for determining the diffusion coefficient for cases where the initial gas concentration is not constant with depth. Diffusion coefficients for a field soil determined from the transient‐state solutions compared favorably with those determined from laboratory measurements on undisturbed soil cores and field measurements of CO 2 flux.