Heavy metals concentrations and uptake by carrot (Daucus carota var. Sativa) cultivated in a savanna alfisol irrigated with industrial effluent contaminated water

Heavy metal contamination is a major environmental problem especially in industrial areas adjacent to city centers, where industrial effluent laden with heavy metals are channeled to rivers and streams used for domestic and agricultural purposes. This study was conducted to evaluate the heavy metals concentration of soil (Alfisols) irrigated with effluent discharged from industries in Kaduna state, Nigeria. The uptake of heavy metals by carrot (Daucau carotar var. sativa) grown on this soil was also evaluated. Research plots were established along effluent discharged points of three (3) manufacturing industries and on a control site not receiving effluent. Soil samples were collected from two depths (0-15 and 15 – 30 cm) before crop establishment and at harvest to compare the concentrations of Iron (Fe), lead (Pb), copper (Cu), zinc (Zn), chromium (Cr), nickel (Ni) and cadmium(Cd). Results showed that the concentrations of all the extractable heavy metals were higher before crop establishment than at harvest at both soil depths. Irrespective of location, sampling depth and period, the concentration of heavy metal followed the sequence: Fe>Cr>Zn>Cu>Cd>Ni. In most cases, heavy metals in plant and soil were negatively correlated with each other, though these correlations were not significant (p = 0.05). Heavy metal concentrations in carrot, soil and effluent were below the standard safe limit recommended by the world health organization (WHO) across the various sites and therefore posed no threat to human health at the time of this finding.