Development and Verification of Test Protocol for Available Soil Metals Using Mixed-Bed Ion-Exchange Resin Capsule.

Objective of this study was to establish a test protocol for available soil metals using ion-exchange resin-capsule by packing Chelex 100(Bio-Rad) into polyester cloth to form a tight sphere. The resin-capsule was inserted into saturated pastes for 4 days under controlled environment. The resin-capsule was removed from the soil and thoroughly washed with distilled water. Metals were stripped from each resin-capsule with 50mL of 2M HCl and analyzed using AAS or ICP. Recovery of added metals were ranged from 94% to 101% irrespective of metal and its concentration(0~100 mg kg^-1). Significant relationships were existed between resin adsorption quantity(RAQ) of metals and respective metal concentration in soil solution. Metal extraction followed first order kinetics with relatively low rate constants. Activation energies and enthalpies of activation were considered to be lower than those of surface-controlled processes. This revealed that the resin-capsule extracted available metals from soil solution and the overall process could be governed by mechanisms of ion exchange and slow diffusion. Available metal concentrations using the resin-capsule showed significant relationships with those determined using 0.1N HCl and 0.5M KNO₃ extraction. However, further calibration work is needed for practical application and standardization of this procedure as test protocol for available soil metals.