Evaluation of trace metals in vegetables sampled from farm and market sites of Accra Metropolis, Ghana

Abstract

This is the first reported study of long term monitoring of heavy metal contamination of vegetables from Ghana. This study monitored heavy metals namely Arsenic (As), Cadmium (Cd), Cobalt (Co), Chromium (Cr), Copper (Cu), Iron (Fe), Manganese (Mn), Nickel (Ni), Lead (Pb) and Zinc (Zn) in consumable vegetables during 2013–2014. A total of 479 vegetables including cabbage (Brassica oleracea), carrot (Daucus carota), cucumber (Cucumis sativus), green pepper (Capsicum annuum) and lettuce (Lactuca sativa) were purchased from both farm and market sites within Accra Metropolis, Ghana. Samples were subjected to acid digestion and then analysed with Atomic Absorption Spectrometer (AAS). All the vegetables studied contained at least two or more metals; 18.99% of the samples had metal detections below the European Union (EU) guideline values, whereas 81% were above the limits. Vegetables from Mallam Attah market and the Ghana Broadcasting Corporation (GBC) sites registered the highest percentage exceedances (100%) with the largest value occurring in lettuce (97.41%). The data from Principal Component Analysis (PCA) revealed higher metal contaminations in leafy and fleshy vegetables than root vegetables. The results demonstrate the need for continuous monitoring of heavy metals in vegetables at various farm and market sites in Accra Metropolis, Ghana.

Keywords:

• Metals
• vegetables
• contamination
• farms
• markets
• Ghana

Acknowledgements

The authors are grateful to the Department of Chemistry, University of Ghana, for technical support. They thank Dr V.R. Manoj, Department of Chemistry, Velammal Engineering College, Chennai, for his careful advice, and the Editor for his help.