Heavy Metal Contents of Some Common Tubers Sold in Benin Metropolis, Benin City, Nigeria

Abstract

This study was conducted to determine the concentration of heavy metal in tuber crops bought at two different markets in Benin metropolis. A total of 12 yam and potato tubers were bought at two markets in Benin City with 6 samples each from Ikpoba Hill market and Uselu market. Samples of tubers which include Hausa yam, native yam and yellow yam varieties, white potato, red potato and Irish potato varieties were obtained. The samples were washed, dried, digested and the concentration of iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), cadmium (Cd), chromium (Cr), lead (Pb), nickel (Ni) and Arsenic (As) were analysed using Atomic Absorption Spectroscopy (Bulk Scientific 210 VGP). It was observed that the peeled samples were having less concentration of metals than the unpeeled samples. Fe dominated all heavy metals analysed in both the yam and potato varieties. The concentrations of Zn, Cu, Cr and Pb showed significant difference in the unpeeled to peeled yam while Fe, Mn, Zn, Cr and Pb concentrations showed significant difference in the unpeeled to peeled potato. Processing (peeling) brought about reduction in the levels of the heavy metals. Cd and Pb concentrations in the unpeeled yam and potato varieties were above the international food standards (CODEX). The high  concentrations of heavy metals in this study can be linked to atmospheric deposition of exhaust fumes and other farming practices where these tubers were grown, transported and are been sold. However, further study is needed to determine the soil characteristics where food crops are grown.