Assessment of Heavy Metals’ Contamination of Soils and Vegetable from Farmlands on Selected Floodplains in Akure and Environs, Nigeria

Abstract

Aim: Among other absorption pathways, heavy metals affect human health via their introduction into the diet through the soil-food chain. This study was carried out to determine the concentration of heavy metals in soils and plant’s part of Amaranthus hybridus from five farmlands on floodplains in Akure and environs.
 Study Design: Soil and A. hybridus samples were obtained from five farmlands for the assessment of their heavy metals’ content and pollution levels.
 Place and Duration of Study: The study (six months’ duration) was conducted at the Department of Chemistry, The Federal University of Technology, Akure, Ondo State, Nigeria.
 Methodology: The assessment involved the use of standard methods of analyses and an atomic absorption spectrophotometer. Mathematical expressions were employed for estimating the bioconcentration factor, geoaccumulation index, contamination factor and pollution load index. Statistical difference of the results was evaluated using One-Way Analysis of Variance.
 Results: The experimental results revealed that the farmlands’ soils belong to four textural classes in which their heavy metals’ contents are all below the maximum allowable concentrations provided in the considered regulatory guidelines for soil. Evaluation of the geoaccumulation index showed that concentration of all heavy metals in the soils are not enriched above the baseline concentration as most of the soils belong to Class 0 (uncontaminated category). Pollution load index estimated from the contamination factors also indicated no overall pollution of the farmlands. Uptake of the studied heavy metals by A. hybridus was at varied levels while vegetable samples from Ogbese farmland had the highest bioconcentration factor for copper, nickel and chromium.
 Conclusion: Although most of the farmland soils have satisfactory physicochemical properties and present safe level of the studied heavy metals, the research revealed the need for cultivation of vegetables which are extremely poor bioaccumulators of heavy metals in these farmlands.