Accumulation of soil-borne aluminium, iron, manganese and zinc in plants cultivated in the region of Moan da (Gabon) and nutritional characteristics of the edible parts harvested

BACKGROUND: In central Africa, studies on the transfer of metals from soil to food crops, the composition of foods and the dietary intake of cultivated vegetables are scarce. In this study, aluminium (Al), iron (Fe), manganese (Mn) and zinc (Zn) transfer from naturally (pedogeochemically) contaminated soils into ten edible plants and human exposure to these metals via edible parts of the plants were investigated. RESULTS: The fertility of the soils studied was still satisfactory. Soil Al (33 029-40 031 mg kg super(-1)), Fe (20 869 plus or minus 1124 mg kg super(-1)) and Zn (248.3 plus or minus 37.9 mg kg super(-1)) concentrations were consistent with those found in agricultural soils, but Mn concentrations were above those normally encountered in arable fields (10 000 mg kg super(-1)). The results indicated a substantial accumulation of Fe in red roselle leaves and of Al, Mn and Zn in some leafy plants and okra (fruits). The present study highlights that adults consuming vegetables grown on naturally Mn-rich soils ingest significant amounts of Al, Mn and Zn. However, Zn amounts were below the recommended maximum tolerable levels for hazard risk. CONCLUSION: The study indicated that Al and Mn accumulation in food crops cultivated in the Moanda area of Gabon may represent a health hazard. However, the high levels of Zn in vegetables could be a pathway for Zn supplementation in human nutrition to reduce Zn deficiency in developing countries.