Comparative Study of Some Heavy and Trace Metals in Selected Vegetables from Four Local Government Areas of Plateau State, Nigeria

Abstract

This study was conducted to analyze some heavy and trace metal contents of selected edible vegetables commonly sold in four local government areas (LGAs) of Plateau State, Nigeria, with a view to unearth their toxicological implications on the populace. The vegetables sampled are Spinacia oleracea (spinach), Lactuca sati (lettuce), Cucumis sativus (cucumber), Daucus car (carrot) and Brassica oleracea (cabbage), while the metals analysed are Cd, Pb, Fe, Cr and Mn. Atomic absorption spectrophotometer was used to determine the concentration of the various metals and Tukey-Kramer multiple comparison tests in a one-way analysis of variance was used to compare variations in metal concentrations. Cd and Pb were not detected in all the vegetables sampled from Bassa LGA, but were detected in vegetables of Jos-North, Jos-South and Barkin Ladi LGAs. Cd and Pb concentrations in most samples from Jos-North, Jos-South and Barkin Ladi LGAs were above the WHO maximum permissible limits for vegetables. Cr concentrations in all the vegetables from all the LGAs were far above the WHO maximum permissible limit in the order: Jos-South > Jos-North > Barkin Ladi > Bassa. Fe concentration in most vegetables from all the LGAs is above the WHO maximum permissible limit in the orders: Jos-North – Lettuce > Spinach > cucumber > carrot > cabbage; Jos-South – Lettuce > Spinach > cabbage > carrot > cucumber; Barkin Ladi – Lettuce > cucumber > Spinach > carrot > cabbage; Bassa – Letuce > carrot > spinach > cabbage > cucumber. Mn order of concentrations in the vegetables is: Jos-north – spinach > Lettuce > carrot > cucumber > cabbage; Jos-South – spinach > lettuce > cabbage > carrot > cucumber; Barkin Ladi – Lettuce > cucumber > Spinach > carrot > cabbage; Bassa – Lettuce > spinach > cabbage > carrot > cucumber. The order of lead concentrations in the vegetables are: Jos-North – cabbage > spinach > carrot > lettuce > cucumber; Jos-South – Lettuce > cucumber > carrot > cabbage > spinach; Barkin Ladi – Lettuce > spinach > cucumber > carrot > cabbage. The results indicate that vegetables from Jos-North, Jos-South and Barkin Ladi are contaminated with the metals sampled, while lettuce and spinach are very good bioaccumulators of these metals.