Assessment of Heavy Metal Residues in Soil and Vegetables along Urban-peri-urban gradient of Lagos State Nigeria

Abstract

Several studies have been carried out on leafy vegetables but many did not assess the heavy metals in soil and leafy vegetables along urban-peri-urban gradient of Lagos State. The study assessed the concentration of heavy metals in the soil and leaves of three commonly consumed vegetables (Amaranthus hybridus, Celosia argentea and Corchorus olitorius) in Lagos State. Sampling was conducted in 2019 and 2020. Fe, Pb, Cu and Cd residues in the soil and the leafy vegetables samples were digested and determined using Atomic Absorption Spectrophotometer. The collected data were analyzed using simple descriptive statistics and Analysis of Variance. The range of values of the mean concentrations of the heavy metals in soil showed that Fe =20.76±0.20mg/kg – 107.83±17.02mg/kg, Pb = 0.13±0.07mg/kg –2.47± 0.45mg /kg, Cd=0.08 ± 0.02mg/kg – 6.07 ± 2.90mg/kg and Cu = 0.24±0.11mg/kg–40.20±4.90mg/kg. The range of values of the mean concentrations of the heavy metals in the leafy vegetables showed that Fe = 113.10±14.05mg/kg – 1.51±0.02mg/kg, Pb=0.51±0.09mg/kg - 0.001±0.001 mg/kg, Cd=0.51±0.01mg/kg-0.001±0.01amg/ kg, Cu=7.54±0.97 mg/kg - 0.36±0.03mg/kg. The Level of heavy metals residues in soil and the three leafy vegetables were at safe levels set by WHO/FAO except for Pb and Cd found in vegetables in Ketu and Yaba study locations.