Parametric assessment of infiltration of some NAPLs in soil porous media

Abstract
Background and objectives: Human activities imposed several contaminations to the environment. Although environmental contaminations can be categorized into inorganic and organic contaminations, but the so-called non-aqueous phase liquids (NAPLs) are considered among the most hazardous pollutants in environment and can potentially cause severe damage to our environment. The contaminated soils not only may transfer the pollutants to the human chain food, but may transmit the contaminants to the groundwater and drinking water. Furthermore, the contaminated soil would limit the use of available lands for agricultural purposes. Environmental contamination, particularly soil is one of the most important challenges in recent years. Non-aqueous phase liquids (NAPLs) have significant influences on environmental contaminations. Understanding infiltration characteristics of these compounds into the soils is very important because it assists to remediate contaminated soils and manage to reduce NAPL recharge into groundwater. The main objective of this research was to quantitatively investigate the influence of infiltration of some NAPLs including crude oil and kerosene into soil.
Materials and methods: Consequently, the required soil samples were collected from neighboring Tehran oil refinery. The saturated hydraulic conductivity, cumulative infiltration and the infiltration rates were obtained by using Darcy’s law and Philip, Kostiakov and Green-Ampt infiltration models, respectively. The performance of predictive infiltration models were evaluated using RMSE and R2 statistics.
Results: The obtained results showed that similar to water, the wetting front length and cumulative infiltration for both examined NAPL components were nonlinearly increased. The largest NAPLs infiltration rates as well as that of water were observed during the initial experimental periods. The hydraulic conductivity of crude oil and kerosene were obtained to be 0.0058, 0.280 cm/min, respectively.
Conclusion: Quantitative assessment of kerosene infiltration into the soil indicated that for NAPLs, when time moves towards infinity, the basic intake rate doesn’t resemble the soil saturated hydraulic conductivity. This can be attributed to the fact that at the final stage of infiltration process, the sorptivity plays a significant role in infiltration of these components. Overall observations show that that based on the calculated RMSE statistic, the Green-Ampt and Philip models can well predict the NAPLs infiltration into the soil. Some NAPL characteristics including type of compounds, composition, surface tension, viscosity and specific gravity were appeared to significantly influence the infiltration process.
Conclusion: Quantitative assessment of kerosene infiltration into the soil indicated that for NAPLs, when time moves towards infinity, the basic intake rate doesn’t resemble the soil saturated hydraulic conductivity. This can be attributed to the fact that at the final stage of infiltration process, the sorptivity plays a significant role in infiltration of these components. Overall observations show that that based on the calculated RMSE statistic, the Green-Ampt and Kostiakov models can well predict the NAPLs infiltration into the soil. Some NAPL characteristics including type of compounds, composition, surface tension, viscosity and specific gravity were appeared to significantly influence the infiltration process.