Quantification and Risk Assessment of Some Trace Metals in Vegetables Obtained in Sand Mining Environment of Ukat Nsit, Nigeria

Quantification and risks of Cd, Cu, Pb, Zn, Ni, Fe, As and Cr were assayed in two vegetables (Lasianthera africana and Telfairia occidentalis) obtained from the sand mining environment of Ukat Nsit. Vegetable and soil samples were collected from four farms. Samples were also collected from a farm out of Ukat Nsit where there are no sand mining activities to serve as controls. The results revealed variable levels of the trace metals in the samples. In the soil, the metals levels ranged from 3.67 mg/kg Pb to 19.10 mg/kg Cu. In the vegetables, the trace metals levels ranged from 0.150 mg/kg Ni to 17.3 mg/kg Cu in L. africana and from 0.00 mg/kg Ni to 10.16 mg/kg Fe in T. occidentalis, respectively. Cd in the soil and vegetables exceeded the safe limits set by USEPA and WHO. The metal levels in the vegetables and soil from the control site were lower than those of the study area. This could be attributed to the negative impact of sand mining activities. Positive correlation at p < 0.01 was seen between Cd and Pb, Cd and Fe, Pb and Zn, As and Fe as well as Fe and Zn, indicating that Cr, Pb, Fe, Cu and Zn originated from the same anthropogenic sources. The target hazard quotient (THQ) for all the measured trace metals for the vegetables were lower than 1 (except Cd), indicating that the vegetables are relatively safe for consumption, except that their Cd levels could have adverse health effects.