EVAPORATION OF PETROLEUM-PRODUCTS FROM CONTAMINATED SOILS

Bioremediation can remove petroleum products from soil that has been c ontaminated by leaking underground storage tanks, but abiotic processe s such as evaporation can contribute significantly to the overall remo val process. The mathematical model described in this paper was develo ped to predict the evaporation rate of volatile liquids from petroleum -contaminated sand. The model is based on simple concepts relating to molecular diffusion embodied in the theory underlying the estimation o f binary diffusivities using measurements made with an Arnold diffusio n cell. The model in its simplified form indicates that the rate of ev aporation for a particular volatile liquid is proportional to the squa re root of the product of diffusivity and partial pressure divided by the molecular weight of the liquid. This in part explains why evaporat ive losses from sand are so much higher for gasoline than for diesel f uel. The model also shows that the time for evaporation is directly pr oportional to the square of the depth dried out and inversely proporti onal to the vapor pressure of the volatile liquid. The model was teste d using gravimetric measurements of the evaporation of n-heptane, unle aded gasoline, and diesel fuel from sand under laboratory conditions.