Effect of different pH levels on adsorption and desorption of Pb in contrasting parent materials of south eastern agro climatic zone of Nigeria

Abstract

Lead adsorption and desorption at different pH levels in acid soils of diverse parent materials were evaluated. The soil samples were collected from soils underlain by olivine basalt (Ikom), coastal plain sands (Ihiagwa) and false bedded sandstone (Ishiagu). The collected samples were air -dried, crushed, sieved with a 2 mm sieve and analyzed in the laboratory. The adsorption of lead (Pb) increased with increasing solution pH. At pH 3, 4 and 6, the adsorption of Pb was higher in false bedded sandstone than the other soils. At pH 5, adsorption of Pb was higher in olivine basalt than the other soils. Except at pH 3, desorption of Pb was higher in coastal plain sands than the other soils. At the same time it was lower in false bedded sand stone than the other soils at all pH. At pH 5, adsorption of Pb had a significant positive correlation with organic matter (r =0.774481, p≤ 0.05), while at pH 6, it had a significant positive correlation with soil pH (r =0.738401, p ≤ 0.05). Organic matter and soil pH are the most critical soil properties affecting adsorption-desorption of Pb on these soils.