Levels of Selected Heavy Metals in Soil, Tomatoes and Selected Vegetables from Lushoto District – Tanzania
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Date
2014
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Abstract
This study involved the determination of heavy metals of Cd, Cr, Cu, Pb and Zn in cauliflower (Brassica oleracea L.
var botrytis L.), carrot root (Daucus carota L.), tomato fruit (Lycopersicum esculentum Mill.), onion bulb (Allium cepa L.) and
leafy cabbage (Brassica oleracea L. var capitata L.) and the respective soils from Lushoto District, Tanzania. Samples were
collected from eight growing sites. The accumulated heavy metals were quantified and the levels compared to the FAO/WHO
CODEX-STAN 179:2003 and TZS 972:2007 contamination limits for such produce. The methodology involved random
sampling, extraction of the metals from the vegetable and soil and determination of heavy metals by using ICP-OES and GFAAS.
The levels of Cu in all vegetables were below the FAO/WHO limit while levels of Cr and Zn in all vegetables were found to be
above this limit therefore advocating a health risk for consumers. Pb was only found in carrots at 2 sites (Montisory and Resource
centre) and in onions at the market all at levels above the FAO/WHO limit while Cd was only found in onions and tomatoes at 2
sites (market and Montisory) at above the FAO/WHO limits. Vegetables especially onions from the Mlalo market advocate a
health risk to consumers. Levels of heavy metals in the soils were below the limits of the Tanzanian standard (TZS 972: 2007)
and were lower than levels found in vegetables. However, the bioconcentration factor for Cr, Pb, Cd and Zn in all vegetables and
tomatoes where they were detected except for cabbages at the Garage site were found to be above 1, an indication of high uptake
of heavy metals in the vegetables from the soil. Cu at 80% of the sites had a BCF lower than 1 indicating that Cu was more
abundant in the soil compared to the vegetables. These results suggest that these vegetables from Lushoto district are not safe for
consumption in their raw state.
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Keywords
Heavy metals, Vegetables, Tomatoes, Soil, Bioconcentration factor
Citation
Lugwisha, E.H., 2014. Levels of selected heavy metals in soil, tomatoes and selected vegetables from Lushoto district-Tanzania.