Sébastien Lange, Univ. Laval, Dept et génie agro., Pav. de l'envirotron, Sainte Foy, QC G1K 7P4, Canada and Suzanne Allaire, Dept. des Sols et de Genie Agro., "Pav. Envirotron, Univ. Laval", "Pav. Envirotron, Univ. Laval", Ste-Foy, QC G1K 7P4, CANADA.
Gas
diffusion and
soil
physicals properties in large soil monoliths
Lange Sébastien et Allaire Suzanne
Département des sols et de génie agro-environnemental
Université Laval, Québec, Canada
Gas diffusion in soil is affected by
different soil properties including structure, texture, water and air contents.
Gas diffusion has rarely been measured at scale larger than a few centimetres.
The objective of this study is to experimentally determine relative gas
diffusion coefficient with large undisturbed soil cores (0.45 m diameter and 0.4 m depth) as affected by
soil physicals properties. Three intact replicates of an organic soil and a
fine sandy soil were extracted from fields. A gas injection chamber and a
subdivided flux chamber were installed at each end of the monoliths. Neon was
injected and its concentration was maintained constant in the injection chamber
for 48 hrs. Atmospheric pressure was maintained throughout the system to avoid
convective fluxes. Gas samples were withdrawn in 5 sections, 3 depths and 7
heights in each columns many times until gas was detected in sufficiently high
concentration in at least one section of the flux chamber. Samples were
analysed on GC. Soil samples were taken from the monoliths for water content,
structure, granulometry, organic carbon content, and bulk density measurements
at the same sections and depths. Observations were completed on macroporosity
and other heterogeneities (stones, roots, worms, etc.). Diffusion coefficient
will be calculated for the different sections and depths. Variability in
diffusion within monoliths, between replicates and between soils will be
discussed. Stepwise regressions and cross correlation statistical analysis will
be used to relate diffusion and soil physical properties. Application of these
findings to interpretation of field studies and the use of small samples will
be discussed.