Assessment of Heavy Metal Distribution in Amaranthus hybridus L. and Zea mays L. Grown on an Undesignated Dumpsite Soil of Ibadan, Nigeria

Abstract

Heavy metal contamination from indiscriminate waste disposal poses significant environmental and health risks. This study assessed the levels, distribution, and effects of heavy metals on the growth and metal uptake of Amaranthus hybridus and Zea mays grown in an undesignated dumpsite soil in Ibadan, Nigeria. Soil and plant samples were analyzed for Fe, Zn, Cu, Pb, Ni, and Co concentrations using Atomic Absorption Spectrophotometry. Growth parameters, including plant height, stem diameter, leaf number, and leaf area, were recorded. The results showed that the heavy metal concentrations (mg kg⁻¹) were significantly higher (p < 0.05) in dumpsite soil, with Fe, Zn, Cu, Pb and Co exceeding at least one of FEPA, WHO and EU limits. While metal concentrations in plant tissues were mostly within normal ranges, Zn and Pb exceeded WHO permissible limits in A. hybridus. Growth analysis showed a significant increase (p < 0.05) in plant height, stem diameter, leaf number, and leaf area for A. hybridus in dumpsite soil, whereas Z. mays exhibited limited growth stimulation. Soil-plant metal analysis indicated that Z. mays is a poor accumulator of heavy metals (BF < 1), with limited translocation from roots to shoots (TF < 1). In contrast, A. hybridus demonstrated efficient Pb accumulation (BF = 3.84) and effective translocation of Zn, Pb, Ni, and Co from roots to leaves. Enrichment factor (EF) analysis further highlighted the phytoremediation potential of A. hybridus for Pb (EF = 8.22), compared to EF < 1 for all metals in Z. mays. This study concludes that the dumpsite soil is heavily contaminated with heavy metals, rendering crops grown on it unsafe for consumption. However, A. hybridus showed strong potential for consideration in the targeted remediation of Pb-contaminated soils. These findings highlight the urgent need for sustainable waste management and soil remediation strategies to mitigate pollution risks and ensure environmental and food safety.