Abstract:
The objectives of this research are to assess the transport of Cu2+ and Pb2+ through the unsaturated zone of agricultural area and apply the mathematical model explain the mechanism their movements. The research was divided into 3 parts. In the first part, soil samples were collected from agricultural areas to analyze the physical and chemical characteristics of the soil. The results showed that their soil types were mostly sandy loam with pH of 5.3 and PZC of 5.04. The analysis of 8 types of chemical fertilizers found that fertilizer of 15-15-15 had the highest Cu about 25 mg/kg and both fertilizer of 15-15-15 and of 16-8-8 had the highest Pb about 25 mg/kg equally. In the second part, the rainy column found that bromide (Br-) transported faster than in the summer column at every depths. The values of dispersivity in the summer column were higher than the rainy column. Finally, the column experiments were conducted to describe the transport of Cu and Pb at pH 3 and 5 of the summer columns and at pH 5 of the rainy column. The movement of Pb2+ is faster than Cu2+ in all depths. In other word, Cu2+ has higher retardation factor (R) than that of lead. The retardation factor was affected from pH and water content at each depth. Data from breakthrough curves (BTCs), which obtained from column tests, was used to assess the sorption distribution coefficient (Kd) using HYDRUS-1D. The fitted results derived from the model well described the observed data, BTCs of Pb2+ and Cu2+, with R2 ranged from 0.9023 to 0.9768. According to the final part, the finding is that the Kd value is decreased as increasing travelling distances and water contents.