Speciation of metals in soils and mobilization by acid‐base treatment

To estimate the behaviour of metals in soils during pH change, polluted soil from an industrial area was subjected to sulphuric acid and calcium hydroxide additions. The behaviour of metals was studied by speciation techniques with separation into five fractions, namely: exchangeable, linked to carbonates, organic matter + sulphides or Fe‐Mn oxides and rest (associated to primary materials). As extractants, ammonium acetate, acetic acid, hydrogen peroxide and hydoxylamine were successively used. Determined metals include macro‐ (Na, K, Ca, Mg, Fe) and microconstituents (Cu, Pb, Mn, Zn) measured by AAS directly from extractant solutions and after HNO3—FH—HCIO4 digestion for total content. Analytical data are discussed as percentages of each metal in the different fractions at different soil pH values. The following results were obtained: (i) some macroconstituents (Mg, K, Na) are not influenced by acid‐base treatments of soil, (ii) calcium is probably retained as gypsum by soil treated with sulphuric acid,...