In recent years, petroleum products and byproducts have been widely used chemicals in soil habitats, which change the soil properties and quality of groundwater due to solubility, volatility and biodegradability of these pollutants. The aim of this research was to investigate the impacts of kerosene and gas oil pollutants on the breakthrough curve (BTC), soil water retention curve (SWRC) and some physical and chemical properties of the laboratorycontaminated soils. For this purpose, some water-saturated soils were artificially contaminated in the pulse condition inside some glass cylinders by applying half and one pore volume of these pollutants. Furthermore, parametric investigations of the soil retention curves were performed using RETC software by Van Genukhten, and Brooks-Corey equations in the various suctions and the soil properties were determined before and after pollution during a 3-month period. The BTC revealed that kerosene flowed out of the soil with a sharper gradient and greater velocity than gas oil, especially on introduction of one volume of kerosene (triple times more than the 0.5 volume). The RETC results regarding the Van Genukhten model demonstrated slightly lower water-holding capacity in the contaminated samples than the unpolluted one. Contamination not only diminished the saturation moisture (H s ), but also reduced the residual moisture (H r ) and the SWRC gradient (n), while BrooksCorey equation represented only one set of data for all conditions. It can be concluded that all apparent physical and chemical properties of soil have been changed by spill of petroleum hydrocarbon on the soil surface. Evaluation of both equations demonstrated more accurate prediction of the SWRC's parameter by Van Genukhten compared to Brooks-Corey. The results of this research can be generalizable for the assessment of petroleum pollution impacts on the quality and changes of soil properties in terms of pulse contamination for approximately the same condition on a wider scale.

Soil and ground water resource pollution by petroleum compounds and chemical solvents has multiple negative environmental impacts. The aim of this research was to investigate the impacts of kerosene and gas oil pollutants on some physical and chemical properties, breakthrough curve (BTC), and water retention curve (SWRC) of silty clay soil during a 3-month period. Therefore, some water-saturated soils were artificially contaminated in the pulse condition inside some glassy cylinders by applying half and one pore volume of these pollutants, and then parametric investigations of the SWRC were performed using RETC software for Van Genukhten and Brooks-Corey equations in the various suctions and the soil properties were determined before and after pollution during 3 months. The results showed that gas oil and kerosene had a slight effect on soil pH and caused the cumulative enhancement in the soil respiration, increase in the bulk density and organic matter, and reduction in the soil porosity and electrical and saturated hydraulic conductivity. Furthermore, gas oil retention was significantly more than kerosene (almost 40%) in the soil. The survey of SWRC indicated that the contaminated soil samples had a little higher amount of moisture retention (just under 15% in most cases) compared to the unpolluted ones during this 3-month period. The parametric analysis of SWRC demonstrated an increase in the saturated water content, Θ s, from nearly 49% in the control sample to just under 53% in the polluted ones. Contaminants not only decreased the residual water content, Θ r, but also reduced the SWRC gradient, n, and amount of α parameter. The evaluation of both equations revealed more accurate prediction of SWRC's parameters by Van Genukhten compared to those of Brooks and Corey.