Effect of time and electrical potential gradient on the buffer capacity of soils, as measured using an electrokinetic method

The buffer capacity of soils is a property of interest in the field of environmental remediation, and is related to chemical properties such as the nature of soil humic material and the variable charged surfaces of clays and hydrated oxides. An electrokinetic technique has been proposed as a method for the determination of the buffer capacity of soils, making use of the electrolytic reactions of water that arise after the application of an electrical field. Such reactions produce hydronium and hydroxyl ions, which are continually entering the soil. A study was made of the effect of the duration of the electrokinetic process (24, 48 and 72 h), as well as of the electrical potential gradient applied to the soil (1.2 and 1.8 V/cm), in the determination of the buffer capacity of a soil of volcanic origin. It was observed that time had a significant effect on the value obtained for the buffer capacity in a basic medium (fβ–), and that both variables had a significant effect on that obtained in an acid medium (fβ+). Moreover, the buffer capacity of two soils of volcanic origin obtained using the electrokinetic technique was compared with that obtained using the traditional volumetric method. The results obtained using both techniques showed good agreement.