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Abstract
Maintenance of a constant hydraulic head above a column of clay soil frequently can not generate a constant desired flux although such a constant flux is required for analyzing the breakthrough curve for the diffusion coefficient. Consequently, an automated system for solute transport in a clay soil column was developed. The system includes: (1) a column and tubing, (2) a proportional pump, and (3) a fraction collector. By changing the size of the tubing or speed of pumping, an increasing, decreasing or constant head can be achieved, and a constant or any desired flux obtained simultaneously for various textured soils including clay soil. The ratio of the inside diameter of the column to the mean particle diameter of the soil media was greater than 40 and the media volume was at least 30 times of that of the filtering materials, suggesting that apparatus induced errors in the determination of the dispersion coefficient should be negligible. Placing a micro‐filter at the outlet of the soil column produced a clear filtrate. By adjusting the collection time, a fixed volume of filtrate can be obtained. The flexibility of the set‐up allows maintenance of any required constant flux and permits modifications including the replacement of tracer solution instantaneously and the dilution of the leachate while leaching is in process. If desired, an automatic analytical device and a signal processor can be added to the system.