Soil Science Society of America Journal, March, 2013, Vol.77(2), p.362(10)
Understanding soil-gas phase properties and processes is important for finding solutions to critical environmental problems such as greenhouse gas emissions and transport of gaseous-phase contaminants in soils. Soil-air permeability, ka (?m2), is the key parameter governing advective gas movement in soil and is controlled by soil physical characteristics representing soil texture and structure. Models predicting ka as a function of air-filled porosity (?) often use a reference-point measurement, for example, ka,1000 at ?1000 (where the measurement is done at a suction of -1000 cm H2O). Using ka measurements from two Danish arable fields, each located on natural clay gradients, this study presents a pore tortuosity-disconnectivity analysis to characterize the soil-gas phase. The main objective of this study is to investigate the effect of soil-moisture condition, clay content, and other potential drivers of soil texture and structure on soil-gas phase characteristics based on a ka-based pore tortuosity parameter, Xa [= log(ka/ka,1000)/log(?/?,1000)]. Results showed that Xa did not vary significantly with soil matric potential (in the range of -10 to -1000 cm H2O), but the average Xa across moisture conditions showed a strong linear relation (R2 = 0.74) to clay content. The Xa, further showed promising relations to specific surface area, Rosin-Rammler particle size distribution indices, ? and ? (representing characteristic particle size and degree of sorting, respectively), and the Campbell water retention parameter, b. Considering clay as a main driver of soil-gas phase characteristics, we developed expressions linking clay content and ka,1000 at ?1000 and discussed the effect of clay content on general ka-? behavior.
Grading (Building materials) -- Usage ; Soil Permeability -- Analysis ; Soil Research