A simulation study of aqueous and gas phase DNAPL migration in shallow unsaturated land elements

Knowledge of DNAPL migration behaviours in shallow unsaturated land elements might be useful in characterizing and deciding suitable remediation techniques for DNAPL contaminated sites. One-dimensional simulations of simultaneous heat, moisture, and gas and aqueous phases DNAPL transport in soil due to diurnal land-atmosphere interactions was carried out The top 0.11-m soil was initially contaminated with uniform DNAPL concentrations in aqueous and gas phases. Two cases of moisture content scenario were presented in the simulations. The results indicated that vegetation cover played significant roles in soil heat and moisture budgets in addition to soil composition and their properties. Vegetation cover significantly reduced the incoming solar radiation to the ground surface resulting to smaller diurnal fluctuations in soil temperature and moisture contents in vegetated lands. The decrease in aqueous phase DNAPL concentrations in the contaminated soil layer and the downward migration depths were relatively bigger in vegetated lands. Rainfall percolation further reduced diurnal soil moisture fluctuations resulting to bigger aqueous phase DNAPL migration depths. Gas phase DNAPL exhibited bigger vertical spreading tendency. Further investigations including other process in the contaminant transport equations, and sensitivity analyses on their relative importance would provide more insight in the matter