In:
Vadose Zone Journal, Wiley, Vol. 11, No. 1 ( 2012-02)
Abstract:
Soil‐gas diffusivity ( D p / D o ) and its dependency on soil matric potential (ψ) is important when taking regulative measures (based on accurate predictions) for climate gas emissions and also risk‐mitigating measures (based on upper‐limit predictions) of gaseous‐phase contaminant emissions. Useful information on soil functional pore structure, e.g., pore network tortuosity and connectivity, can also be revealed from D p / D o –ψ relations. Based on D p / D o measurements in a wide range of soil types across geographically remote vadose zone profiles, this study analyzed pore connectivity for the development of a variable pore connectivity factor, X , as a function of soil matric potential, expressed as pF (=log |−ψ|), for pF values ranging from 1.0 to 3.5. The new model takes the form of X = X * ( F / F *) A with F = 1 + pF −1 , where X * is the pore network tortuosity at reference F ( F* ) and A is a model parameter that accounts for water blockage. The X –pF relation can be linked to drained pore size to explain the lower probability of the larger but far fewer air‐filled pores at lower pF effectively interconnecting and promoting gas diffusion. The model with X* = 2 and A = 0.5 proved promising for generalizing D p / D o predictions across soils of wide geographic contrast and yielded results comparable to those from widely used predictive models. The X –pF model additionally proved valuable for differentiating between soils (providing a unique soil structural fingerprint for each soil layer) and also between the inter‐ and intraaggregate pore regions of aggregated soils. We further suggest that the new model with parameter values of X * = 1.7 and A = 0 may be used for upper limit D p / D o predictions in risk assessments of, e.g., fluxes of toxic volatile organics from soil to indoor air at polluted soil sites.
Type of Medium:
Online Resource
ISSN:
1539-1663
,
1539-1663
DOI:
10.2136/vzj2011.0096
Language:
English
Publisher:
Wiley
Publication Date:
2012
detail.hit.zdb_id:
2088189-7
