Predicting Model of Arsenic Transport and Transformation in Soil Columns and Ground Water Contamination (Case study: Gorgan Plain, Iran)

Today, the quality of soil and water resources is affected by various pollutants. From the important chemical pollutants are heavy metals such as Arsenic. Arsenic is a metalloid that its unauthorized amounts in soil and ground water is a serious threat to human life .A mathematical and computer model of arsenic transport and transformation in a soil column from the surface to the groundwater is presented in this study. The flow and the corresponding moisture content and the concentration of a contaminant are considered here in as continuous functions of both space and time. The model simulates different species of arsenic such as arsenit, arsenat, and organic arsenic. This computer model is based on the mass balance equation,including convective transport, dispersive transport,surface adsorption, oxidation and reduction, volatilization, chemical and biological transformation. The governing equations are solved numerically by the implicit finite difference method. For the validation of model under transient states ,the data sets collected from Gorgan site, Golestan province.The simulation results are in good agreement with measured values. With this study and its results the distribution of arsenic in soil column to ground water table can be predicted. The simulation results indicate as the total time from the beginning to the end of simulation increases , the concentration of Arsenic approaches the measured values , as indicated in the result