Cadmium Distribution and Migration as Influenced by Polymer Modifiers in a Loam Soil

This paper studies the influence of four modifiers (organic-inorganic composite modifiers, inorganic polymer compound modifiers, polyacrylate compound modifiers, organic polymer compound modifiers) on soil pH, cation exchange capacity (CEC), Cd concentration and their distribution and migration in the soil profile under high Cd concentration (40 mg/kg) during continuous remediation tub experiment. The results showed that: (1) Four modifiers significantly increased the pH and CEC in each soil layer, and inorganic polymer compound modifiers providing the best results in the 0 �20 cm soil layer. (2) There is an extremely significant negative correlation between the carbonate-bound Cd and exchangeable Cd, with considerable effect in the 0 �20 cm and 20 �40 cm soil layers. The inorganic polymer compound modifiers had the best effect on the soil exchangeable Cd. (3) Both pH and CEC in all soil layers were negatively correlated with exchangeable Cd and positively correlated with other forms. (4) Fourier transform infrared spectrometry (FTIR) analysis showed that the modifiers immobilize soil Cd mainly through chemical precipitation, complexation and adsorption so as to reduce the bioavailability of Cd. Thus, we concluded that four modifiers are suitable for Cd mediation/Cd stabilization purposes.