Waste Management, 2011, Vol.31(12), pp.2464-2472
► The effects of soil physical properties on gas transport parameters were investigated. ► Higher values of and exhibited in the ‘+gravel’ than the ‘−gravel’ fraction at same soil–air content ( ). ► Recent power law models for (WLR) and (RPL) were modified. ► Model parameters were linearly related to easily measurable dry bulk density ( ). Landfill sites are emerging in climate change scenarios as a significant source of greenhouse gases. The compacted final soil cover at landfill sites plays a vital role for the emission, fate and transport of landfill gases. This study investigated the effects of dry bulk density, , and particle size fraction on the main soil–gas transport parameters – soil–gas diffusivity ( / , ratio of gas diffusion coefficients in soil and free air) and air permeability ( ) – under variably-saturated moisture conditions. Soil samples were prepared by three different compaction methods (Standard and Modified Proctor compaction, and hand compaction) with resulting values ranging from 1.40 to 2.10 g cm . Results showed that and values for the ‘+gravel’ fraction (〈35 mm) became larger than for the ‘−gravel’ fraction (〈2 mm) under variably-saturated conditions for a given soil–air content ( ), likely due to enhanced gas diffusion and advection through less tortuous, large-pore networks. The effect of dry bulk density on and was most pronounced for the ‘+gravel’ fraction. Normalized ratios were introduced for all soil–gas parameters: (i) for gas diffusivity / , the ratio of measured to in total porosity ( ), (ii) for air permeability / , the ratio of measured to at 1235 kPa matric potential (=pF 4.1), and (iii) for soil–air content, the ratio of soil–air content ( ) to total porosity ( ) (air saturation). Based on the normalized parameters, predictive power-law models for ( / ) and ( / ) models were developed based on a single parameter (water blockage factor for and for ). The water blockage factors, and , were found to be linearly correlated to values, and the effects of dry bulk density on and for both ‘+gravel’ and ‘−gravel’ fractions were well accounted for by the new models.
Air Permeability ; Gas Diffusivity ; Dry Bulk Density ; Landfill Final Cover ; Engineering ; Chemistry
View record in ScienceDirect (Access to full text may be restricted)