Significance of residual hydrocarbon in sandy soils with and without hysteresis effects

Abstract EN

Soil and groundwater contamination due to accidental spills of hydrocarbons represents a serious environmental problem that threatens groundwater.

The presence of such product as a nonaqueous phase liquid near the water table, or as a trapped residual in the porous media, creates a continuous contamination source that keeps contributing to groundwater contamination for a very long time.

This paper gives a quick estimation of the residual hydrocarbon in porous media based on simple to collect data, including free product thickness in monitoring wells and fluid and porous media properties, along with the influence of hysteresis on this estimation.

Such procedure can be used to come up with a quick quantitative estimation of the components of the spill which is valuable information that can be used in the early stages of remediation planning of contaminated aquifers.

Theoretical estimates of the volume of the spill were made using the hydraulic properties of the soil and assuming a quasi-hydrostatic equilibrium distribution for the hydrocarbon and the water.

The hydrocarbon spill volume is divided into two portions: a.

recoverable hydrocarbon which is the part of the hydrocarbon under positive pressure that will flow into a monitoring well and b.

residual hydrocarbon, which is the portion of the hydrocarbon in the soil and is under negative pressure.

Calculations were carried out to determine the relative amounts of the residual hydrocarbon in sandy soils.

The effects of hysteresis on the estimated residual hydrocarbon were also evaluated and found to be significant.

Similar to published experimental results on well graded and uniform sandy soils, the model predicted that a significant portion of the spill will exist as a residual phase.

This portion could reach 100% of the original spill for small spills, decreasing continuously as the total spill volume increases.