Abstract

Groundwater pollution by human activities has been reported severally. Movement of leachate is identified as a major process of the phenomenon. Analytical work to replicate the process has been partially successful in soils. The objective therefore was to investigate the one dimensional (1-D) transport of phosphate at the side and centre of a sand column, verify and calibrate the model derived. Phosphate of known concentration was applied to the saturated sand column. A rainfall simulator located 45 cm above the column was showered over the soil. Samples were collected from drum outlets piped from the sides and centre of the column and analyzed at time intervals of 15, 30, 45, and 60 min. The rate of movement of phosphate with respect to depth  in the soil were  0.045, 0.018, 0.013 and 0.013 ppm/cm at the side of the soil column while the rates at the centre  were 0.036, 0.021, 0.014 and 0.001 ppm/cm at 15, 30, 45, and 60 min respectively. The model verified with experimental data showed predicted transport was in close agreement with experimental values with coefficient of correlation (r) ranging from 0.86 to 0.98. The amount of phosphate retained on the soil is higher at the centre than at the side of the soil column. The concentration of phosphate in the leachate generally decreased with depth and time.

Key words: Phosphate transport, column experiment, model, side flow, centre flow.