Assessment of heavy metal concentration in Ipomoea batatas (L.) and spinach consumed in Zanzibar by Energy Dispersive X-ray Fluorescence (EDXRF)

This work aimed to assess the levels of heavy metal concentrations in Ipomoea batatas (L.) and spinach associated with uncontrolled municipal waste, motor vehicles fumes, pesticides and fertilizer in the Urban West Region Zanzibar. Twenty samples of Ipomoea batatas (L.) and spinach were randomly collected; 15 were from farm sites, and five were from the local markets. The samples were analyzed using energy dispersive X-ray fluorescence method at Tanzania Atomic Energy Commission in Arusha. Essential and non-essential elements, namely, Mn, Cu, Fe, As, Zn, Pb and Ni, were detected and discussed. The samples of spinach collected from farms and local markets had significant higher (P < 0.05) concentrations of As, Pb, Fe, Zn and Cu than Ipomoea batatas (L.), whilst Ipomoea batatas (L.) from farms had significantly higher (P < 0.05) concentrations than spinach. The mean concentration of As in samples of Ipomoea batatas (L.) from local markets was below minimum detection limit value of 0.02 μg/g of the EDXRF machine used in the current study. Although the mean concentration of Mn was within the range reported in the literature, the concentrations of Zn, Ni, Cu, Fe, As and Pb in Ipomoea batatas (L.) and spinach were recorded above the acceptable tolerance limit set by FAO/WHO for human consumption. These results suggest that both Ipomoea batatas (L.) and spinach collected from local markets and grown within the study region might expose consumers to hazardous elements. (author)