Determination of some heavy metals in selected edible vegetables grown along River Yedzaram in Uba area Adamawa State, Nigeria

The levels of some heavy metals were investigated in selected edible potions of the vegetables; Amarathus caudatus (Spinach) and Hibiscus sabdariffa (Rosella) are grown in Uba area along the Yedzaram River in North Eastern Adamawa State, Nigeria. All samples were randomly collected from two different gardens. The levels of the heavy metals, (Cu, Fe, Cd, Cr and Zn) were analyzed using Atomic Absorption Spectrophotometer (AAS) (BUK 210 model). In all the samples analyzed, Cd and Cr were not detected. The levels of heavy metals in Farm A for H. sabdariffa leaves ranges from Cu (30.00 ± 0.15 mg/kg to 31.00 ± 0.18 mg/kg), Fe (37.39 ± 0.02 mg/kg to 48.47 ± 0.10 mg/kg), Zn (13.00 ± 0.01 mg/kg to 25.50 ± 0.48 mg/kg), respectively. In Spinach, the results ranged from Cu (34.33 ± 0.42 mg/kg to 34.50 ± 0.05 mg/kg), Fe (31.72 ± 0.71 mg/kg to 43.33 ± 0.02 mg/kg), Zn (21.17 ± 0.14 mg/kg to 10.83 ± 0.17 mg/kg), respectively. The data were analyzed with t-test and analysis of variance (ANOVA). There were significant differences (p Cu > Zn in Farm A and Cu> Fe> Zn in Farm B. The elevated levels of metals in vegetables in the two gardens could be attributed to excessive usage of fertilizers and other agro - chemicals and of course the environmental factors of the areas. The results were however lower than the published threshold values considered toxic for mature plant tissue, except Fe which has higher values. The consumption of these vegetables as food may not pose possible health hazards to human at the time of the study. Key words: Heavy metals, Amarathus caudatus, Hibiscus sabdariffa, Uba area, fertilizers.