Evaluation and Ecological Risk Assessment of Selected Heavy Metal Pollution of Soils and Amaranthus cruentus and Telfairia occidentalis Grown Around Dump Site in Chanchaga Minna, Niger State, Nigeria

Abstract

The study investigate a series of selected heavy metal pollution of soil, the extent of their uptake by Telfairia occidentalis and Amaranthus cruentus as well as their ecological risk around dumpsite in Chanchaga Minna, Niger State, Nigeria. Soil samples were collected at 15 cm depth with the aid of soil auger and vegetable samples were collected from dumpsite and other samples with no activities served as control. The soil samples were collected at random and their physicochemical parameters such as pH, total nitrogen, total phosphorus, organic matter, total carbon and exchangeable cations (i.e., K+, Mg2+ and Na+) using a standard method and concentrations of the heavy metals in soils and vegetables, As, Cd, Cr, Cu, Hg and Pb were analyzed using flame Atomic Absorption Spectrometer (AAS). The ecological health risk assessment from the consumption of these vegetables was calculated using standard methods. The result showed a significant (p-value) increase of AC and TO in test soil samples relative to the control soils. The pH of the soil in dumpsite and control site was 5.93, and 7.35 respectively. Mean concentrations of As, Cd, Cr, Cu, Hg and Pb in the dump site were 6.35, 4.84, 6.67, 7.35, 5.72 and 4.96 mg/kg while the control site were 1.18, 0.28, 1.26, 6.83, 1.19 and 3.54 mg/kg respectively which was below the WHO/FAO limits of As (20), Cd (3.0), Cr (100), Cu (100), Hg (2.00) and Pb (50 mg/kg) for soil. The concentrations of As, Cd, Cr, Cu, Hg and Pb recorded in AC dump site were As (6.13), Cd (3.67), Cr (5.37), Cu (4.28), Hg (3.46), and Pb (4.52) and in TO As (5.67), Cd (3.13), Cr (4.67), Cu (3.65), Hg (3.19) and Pb (4.27 mg/kg) which were above the WHO/FAO permissible limits (0.5, 0.20, 0.3, 3.0, 0.1 and 0.3 mg/kg) respectively for edible vegetable. The concentrations of heavy metals in soils and vegetables from the dumpsite soil were significant (p < 0.05) from the controls. The bioaccumulation factor (BAF) for the vegetable showed that they exclude the element from soil. The Hazard Quotient (HQ) and Hazard index (HI) show that there is no harmful effect since the values obtain were not greater than >1. But continuous consumption can accumulate in the food chain especially for children. This study showed that the soils and vegetables within the vicinity of the dumpsites were polluted by heavy metals which can pose health risk. The study also calls for proper waste management practices and policy implementation.