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Titel |
Unified Measurement System (UMS) for the Gas Dispersion Coefficient, Permeability and Diffusion Coefficient, and their Interrelations in Differently-Textured, Variably-Saturated Soil |
VerfasserIn |
S. Hamamoto, P. Moldrup, K. Kawamoto, T. Komatsu, D. E. Rolston |
Konferenz |
EGU General Assembly 2009
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 11 (2009) |
Datensatznummer |
250024819
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Zusammenfassung |
The transport of gaseous compounds in soil occurs by gas diffusion, advection, and
dispersion. These gas transport processes are controlled by the soil-gas diffusion coefficient
(Dp), air permeability (ka) and soil-gas dispersion coefficient (DH), respectively.
Among the three main gas transport parameters, the DH and how it is linked to
soil types, moisture conditions and other gas transport parameters, are the least
understood. In this study, a unified measurement system (UMS) that enables sequential
measurement of gas transport parameters (i.e., Dp, ka and DH) on the same soil core
was developed. Using different particle size fractions of non-aggregated (Toyoura
sand) and aggregated (Nishi-Tokyo loam) soils, the effects of soil structure, particle
(aggregate) size and column scale (5-cm i.d. and 30-cm or 60-cm length) on the
three gas transport parameters were investigated and possible links between gas
transport parameters were identified. In the arterial pore region (APR) for both
soils (soil-air content (É) < around 0.45 m3 m-3, corresponding to the total
pore volume for Narita sand and the inter-aggregate pore volume for Nishi-Tokyo
loam), measured gas dispersivity (λ = DH/u0, u0: pore-air velocity) for both soils
decreased with increasing É. However, for Nishi-Tokyo loam at higher É, the λ
values increased again with higher É, suggesting that the gas movement becomes
more dispersive since intra-aggregate pores with a smaller and complicated pore
structure act as additional tortuous gas pathways. In the APR for both soils, strong
linear relations between the gas dispersivity (λ), the pore tortuosity-connectivity
factor (X) calculated from the measured Dp and the log-transformed ka were found. |
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