Abstract
Problem section: Effluents from the surrounding industries such as tannery and textile are used by vegetable farmers for the irrigation of their crops. These effluents may contain some toxic metals which bioaccumulate along the food chain. Moreover the uptake of such toxic metals by crops is governed by their availability and concentration in the soil. Therefore such crops may accumulate heavy metals in excessive amount in their various parts. This may ultimately, adversely affect humans and other species that depend on such crops for food, hence the need to evaluate the pollutant levels in vegetables samples in these areas. Approach: Six vegetable samples of various organs were freshly harvested from ten farms within the vicinity of Challawa industrial areas. The concentration of heavy metals which include, Cu, Zn, Co, Mn, Mg, Fe, Cr, Cd As, Ni and Pb, were determined using Perkin-Elmer analyst 300 Atomic Absorption Spectroscopy (AAS). Levels of some anions (nitrate, nitrite, sulphate and phosphate were determined using Hach direct reading 2000 Spectrophotometer. Results: The results obtained from this analysis revealed that Cr and Fe shows the highest concentrations, while As shows the lowest levels in the whole vegetable organs studied. The concentrations of the anions ranged between 40.00-1300.00 µg g−1 nitrite, 65-1500 µg g−1 nitrate, 122.00-765.00µg g−1 and 12.00-60.00 µg g−1. The leaves contained much higher concentrations of heavy metals and anions than roots and stems. Conclusions: The concentrations of the above parameters were higher than the FAO, WHO/EU and FAO/WHO allowed limit. The high values might be attributed to the used of untreated effluents from textile and tanneries industries by farmers for the irrigation of these vegetables. Thus, the high values of these trace metals and anions in the vegetable samples could put the consumers of these vegetables at health risk. Further works should be carried out in the soil samples were the vegetables are grown.
Highlights
The consumption of vegetables and fruits as food offer rapid and least means of providing adequate vitamins supplies, minerals and fibre
The concentrations of heavy metals in different parts of vegetable samples are presented in Fig. 1a and b
The concentrations of heavy metals in different parts of carrot ranged from 3.66-9.23 μg g−1 Cr, 0.54-2.33 μg g−1 Mn, .00-4.22 μg g−1 Mg, 4.00-14.00 μg g−1 Fe, 0.322.00 μg g−1 Cu, 0.23-01.25 μg g−1 Co, 0.11-0.34 μg g−1 As, 2.00-7.44 μg g−1 Ni, 0.32-2.00 μg g−1 Pb, 2.00-4.00 μg g−1 Zn, 0.11-1.66 μg g−1 Cd for spinach. 1.00-5.00 μg g−1 Cr, 0.61-3.00 μg g−1 Mn, 0.22-3.12 μg g−1 Mg, 2.00-5.00 μg g−1 Fe, 0.02-2.00 μg g−1 Cu, 0.11-0.43 μg g−1 Co, 0.33-4.00 μg g−1 As, 1.00-4.06 μg g−1 Ni, 0.031.00 μg g−1 Pb, 2.00-o 4.00 μg g−1 Zn, 0.11-2.00 μg g−1 and the least were observed in cabbage (1.00-2.44 μg g−1)
Summary
The consumption of vegetables and fruits as food offer rapid and least means of providing adequate vitamins supplies, minerals and fibre. The excessive application of nitrogen and other inorganic fertilizers and organic manures to these vegetables can accumulate high levels of nitrate and other anions as well as heavy metals. Their consumption by humans and animals can pose serious health hazards. Some heavy metals such as Cu, Zn, Mn and Fe are essential in plant nutrition, many of them do not play any significant role in the plant physiology The uptake of these heavy metals by plants especially leafy vegetables is an avenue of their entry into the human food chain with harmful effects on health[1]
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