Effects of Biochar on Distribution of Pb and Cd Species in Contaminated Alfisols of Nigerian Northern Guinea Savanna and Sudan Savanna Agro-Ecologies

Authors: Onokebhagbe VO, Abdu N, Oyinlola E

DOI Info: N/A

ABSTRACT

Heavy metal species’ distribution in soils provide information which is used to evaluate the movement and bioavailability of such metals in the soils. The effects of biochar on specie distribution of lead (Pb) and cadmium (Cd) was investigated in contaminated Alfisols of Nigerian Sudan Savanna and Northern Guinea Savanna agro-ecologies. Biochar was derived from wood shavings (plant char (PC)) and bones (bone char (BC)). A sequential extraction procedure was established with six treatments replicated three times in a completely randomized design: B (Barkalau); B+PC (Barkalau + plant char); B+BC (Barkalau + bone char); BG (Bagega); BG+PC (Bagega + plant char); BG+BC (Bagega + bone char). Concentrations of total Pb in the surface soils (0-20 cm) ranged from 1.28-29.31 mgkg^-1 for Barkalau and 1.34-31.25 mgkg^-1 for Bagega while Cd concentration ranged from 0.015-0.085 mgkg^-1 for Barkalau and 0.021-0.092 mgkg^-1 for Bagega. The results indicated that Pb and Cd in Fe-Mn bound fractions dominated in the soils before and after the use of amendments. The average distribution of the fractions in magnitude of the metals obtained from both soils was as follows: Pb in treatments without biochar: bound to oxides > bound to organics > residual > bound to carbonate > exchangeable. Lead in treatments with biochar: bound to oxides > bound to organics > bound to carbonate > residual > exchangeable. Cadmium in treatments was distributed as follows: bound to oxides > bound to carbonates > bound to organics > exchangeable > residual. The addition of biochar modified the partitioning of Pb but showed no effect on Cd distribution in the soils.

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