Chemical fractionation and mobility of nickel in soils in relation to parent materials

Abstract

Information on the various nickel (Ni) fractions and mobility in soils in relation to parent materials is critical in understanding the contribution of parent materials to nickel bioavailability and mobilization within the ecosystem. Sixty soil samples were collected from 0 to 20, 20 to 40 and 40 to 60 cm depths of five pedons dug in each of the parent material locations (Coastal plain sands (CPS), alluvium (ALV), false-bedded sandstones (FBS) and Imo clay shale (ICS)). Distribution of Ni fractions (water soluble (WS), exchangeable (EX), specifically sorbed/carbonate bound (SSC), Iron – Manganese oxides bound (Fe – Mn), organic matter bound (OMB) and residual bound (RE) fractions) was calculated using the modified sequential extraction procedure. The mobility factor (MF) was ascertained using the metal index of mobility (IM) equation. Findings indicated that nickel fractions differed significantly (p < 0.05) with parent materials and soil depths. The SSC Ni prevailed in the soils (40.4–60.4% of total Ni), being higher in ICS soil (4.06–4.34 mg kg−1) and lower in ALV soil (3.89–4.14 mg kg−1). Organic matter bound Ni was the least Ni fraction (0–4.6% of total Ni). High Ni MF was observed (66.5–89.1%).