Influence of acidic environments on electrokinetic and adsorptive behavior of iron oxide rich soils

The effects of acidic environments on natural Fe oxide rich soils were examined in the laboratory. Experimental evidence indicates that sustained exposure to pH levels within the range of acidic rainfall may cause substantial changes in the physical/chemical properties of these soils. The significant effect observed was the decrease in magnitude or the reversal of the electrical potential exhibited. For example, the zero point of charge shifted from a pH of 1.5 for the unamended soil to a pH of 8.8 as the soil was aged in the lowest pH solution (pH 1.0). The adsorption of `free' and complexed heavy metal ions (Zn and Zn-EDTA) increased significantly due to acid aging and it is proposed that increased weathering of Fe due to acidic rainfall will accelerate the natural podzolization process. Generally, soils not exposed to acidic conditions tended to behave in a ‘clay-like’ manner while those soils aged in an acidic environment tended increasingly toward an Fe hydroxide/oxide behavior as the pH level of soil exposure was decreased.