Level of heavy metals in soil and some vegetables irrigated with industrial waste water around Sharada Industrial Area, Kano, Nigeria

The level of some heavy metals in soil and plant samples from Sharada Industrial Area was analyzed. Plants absorb contaminants through root systems and store them in the root biomass and/or transport them to the stem and/or leaves. The waste water generated by industries was used to irrigate plants; onion (Alium cepa), lettuce (Lactuca sativa), okra (Hibiscus esculentus), Drumstick (Moringa oleifera) and carrot (Daucus carota) which are consumed locally. The level of heavy metals in these plants differs with plant species. Level of lead (Pb) ranged from 10.21±0.20-17.14±0.10μg/g in okra and onion respectively, and the level in soil was found to be 28.00±2.00μg/g. The level of heavy metal was higher in soil than in plants studied. Accumulation of heavy metals varied from plant to plant. The soil levels of copper (Cu) was found to be 9.00±2.00 μg/g with onion having the highest value (8.00±0.10 μg/g) compared to other plants. The uptake of cobalt (Co) by plants varies with plant species. Moringa oleifera had highest concentration of cobalt (14.00±8.00μg/g) and onion had the least concentration of Co (5.00±2.00μg/g). The high values of these metals might be attributed to the use of untreated effluents from industries by farmers for the irrigation of these plants. Thus, the high values of these metals in the plant samples could put the consumers of these vegetables at health risk, since the levels of these metals in plants and soil samples are all above WHO permissible limits.Keywords: Accumulation, Heavy metals, Irrigation, Industrial effluents, Vegetable