MIGRATION OF SILVER, INDIUM, TIN, ANTIMONY, AND BISMUTH AND VARIATIONS IN THEIR CHEMICAL FRACTIONS ON ADDITION TO UNCONTAMINATED SOILS.

Metals (Ag, In, Sn, Sb, and Bi) were added to the surfaces of four soil types in columns and exposed to precipitation in a grass-covered field for 18 months. The distributions of the total concentrations and the chemical fractions of the metals were then analyzed to study the metal migration in the soils. The chemical fractionation was performed by using an eight-step sequential extraction technique. Most of the added metals were retained in the uppermost (0 to 2 cm with filter) soil layers, but small portions were moved to the sublayers. Major chemical fractions ((greater than010% in proportion) of the added metals were residual, H2O2 extractable organic-bound (H2O2Org), and metal-organic complex-bound (Me-Org) fractions for Ag, Me-Org, residual, carbonate-bound, and H2O2-Org fractions for In, residual, Me-Org, amorphous metal oxides-bound (am-MeOx), and crystalline Fe oxides-bound fractions for Sn, Me-Org, residual, amMeOx, and H2O2-Org fractions for Sb, and H2O2-Org, am-MeOx, and Me-Org fractions for Bi. Metal migration in soils was mainly associated with the exchangeable, carbonate-bound, and Me-Org fractions. The capacity of soils to retain the metals was in the order Andosol (greater than) Fluvisol (greater than) Regosol [approximately equal to] Cambisol. The mobility of metals was in the order In [approximately equal to] Bi (greater than) Sb (greater than) Ag [approximately equal to] Sn.