Chemical Fractionation of Copper, Manganese and Zinc in Dumpsite Soil Samples in Kaduna Metropolis, Nigeria

Aims: In this research, sequential chemical extractions were performed to fractionate copper, manganese and zinc in dumpsite soil samples into six geochemical fractions with varying mobility and bioavailability.

Study Design: Determination of chemical forms of metals in soils and evaluation of their mobility and bioavailability.

Place and Duration of Study: This study was conducted between March, 2011 and June, 2013 in the Department of Chemistry, Ahmadu Bello University, Zaria, Nigeria.

Methodology: Collection of soil samples from Kawo (KW), Rafin Guza (RG), Angwan Dosa (AD), Badarawa (BD), Malali (ML), Angwan Shanu (AS), Kurmi Mashi (KM), Tudun Wada (TW), Kakuri (KK) and Trikania (TK) dumpsites; sequentially extraction of samples into six fractions and determination of metal concentrations in extracts.

Results: Copper had high mobility factor values in the rainy season at TK (43.76%), TW (13.51%), AS (13.48%) and ML (0.14%); and in the dry season at TK (44.79%), KW (14.65%), AS (14.18%), ML (13.43%) and TW (13.31%). Manganese in the rainy season recorded relatively high mobility values at KK (2.18%), AD (2.07%), and TW (1.67%) and in the dry season at ML (2.57%), BD (2.23%), KK (2.06%) and TW (1.51%) while Zinc had high mobility values in the rainy season at BD (54.14%), AS (26.62%), KM (18.08%), TK (16.11%), ML (5.88%) and KK (3.54%) and in the dry season at RG (145.79%), BD (44.59%), AS (31.08%), KM (21.65%) and TK (18.19%). Copper and zinc were distributed evenly across the non-residual and residual fractions, while manganese was predominantly retained by residual fractions. The mobility and potential bioavailability of the metals in decreasing order is: zinc > Copper > Manganese.

Conclusions: The amount of metals bound to each fraction differed significantly according to metal type, dumpsites and seasons. The study indicates the tendency for bioavailability of the metals studied for plant uptake from soil.