Oil Contamination Propagation Patterns in Soils

In recent decades attention to contamination propagation into soils and underground water has been increased which has led to increasing the studies on soil contamination problems and methods of in-situ remediation. Also، soil contamination with petroleum compounds has been one of the most challenging issues. In many countries with petroleum industries، mines of oil exploration، refineries and etc، by reasons، such as leakage from tanks or pipelines of oil transmission due to corrosion and damage، soil will be contaminated by oil pollution. Hence، contaminant propagation in soils and also remediation of the contaminated soils has been considered as a sensitive، complex and critical environmental issue. According to recent studies، it is clear that further study on petroleum contamination propagation pattern in soils and underground water is needed. Therefore، the study about this pattern is main purpose of this research which has been done by means of numerical Finite Element Method (FEM). Following، the theory of pollution propagation and the mechanisms and formulation of this process are expressed. Then، the explanation of modeling has been carried out in terms of geometry، boundary conditions، method of analysis، material parameters and etc. Verification and analysis results have been presented، respectively. Finally، conclusion is given and discussed. In this research، effective parameters on oil contamination propagation in soils and underground water have been investigated. These parameters are soil permeability، relative density of contamination، dispersivity coefficients، diffusion coefficient and ground water table depth. The results show there are different propagation patterns in coarse and fine grain soils. Furthermore، the efficiency of pumping method as an in-situ remediation approach for contaminated soils is studding by authors. The most important conclusions are as following: -In coarse grain soils، downward propagation pattern and in fine grain soils lateral propagation pattern are dominant. -By increasing the longitudinal dispersivity coefficient، contamination patterns will be extended. It is more evident in coarse soils which is due to more void ratios in these types of soils. The results are more sensitive to longitudinal dispersivity coefficients variations with respect to transverse dispersivity coefficients. -The effect of diffusion coefficient has a direct relation with the perimeter of contamination domain