Non-passive Transport of Volatile Organic Compounds Infiltrated from a Surface Disk Source

Abstract

An unsaturated flow and non-passive transport model for water-soluble organic compounds has been implemented in cylindrical coordinates, with a top boundary condition that accounts for different zones of the surface that can be under infiltration or volatilization independently. We simulated two-dimensional infiltration of aqueous mixtures of methanol from a disk source, its redistribution and volatilization in both homogeneous and heterogeneous soils. Simulations showed that the incoming composition significantly affects volumetric liquid content and concentration profiles, as well as the fraction of infiltrated mass of methanol that is released to the atmosphere. Concentration-dependent viscosity had the major impact on the liquid flow. The differences in volumetric liquid content and normalized concentration of methanol became more pronounced during transport through a soil composed of a clay lens embedded within a main matrix of sandy clay loam texture. Dispersion in the liquid-phase was the predominant transport mechanism when dispersivity at saturation was set to 7.8 cm. However, for dispersivity of 1.0 cm, changes in composition led to changes in surface tension inducing significantly higher liquid flow. In this case, liquid-phase advection was the most active transport mechanism for homogeneous soils and highly concentrated infiltrating mixtures.

Relating solute and gas dispersion in gravel at different transport velocities

“…Dispersion in solute is important in case of contaminant transport in both saturated and unsaturated soil [1][2][3], as well as nutrient transport in the root zone [4]. Gas phase dispersion…”

Relating solute and Gas Dispersion in Granite at Different Transport Velocities

“…Solute dispersion is important for contaminant transport in both saturated (groundwater) and unsaturated soil (Thomson, 1997;Silva, 2009;Lewis, 2010), and root zone nutrient transport (Parkinson, 2000). Gas dispersion is important in processes such as radon migration into buildings (Wang, 2002), soil aeration and movement of volatile contaminants at contaminated soil sites (Arands, 1997;Atteia, 2010) and migration and emission of CH 4 at landfills and wetlands (El-Fadel, 1997;De Visscher, 1999;Liang, 2000;Pangala, 2010;Pennock, 2010;Schaufler, 2010).…”

Numerical Investigation of the Impact of Ethanol on Flow in the Vadose Zone

“…Their results showed that the volumetric water content and the concentration profiles together with the volatilization and evaporation fluxes were highly affected by the methanol concentration. A similar model was developed by Silva and Grifoll (2009) to simulate infiltration, redistribution, and volatilization of aqueous mixtures of methanol from a disk source.…”