INVESTIGATION OF ESSENTIAL AND POTENTIALLY TOXIC HEAVY METALS IN SOILS AND KHAT LEAVES BY USING ATOMIC ABSORBATION SPECTROSCOPY (AAS) TECHNIQUE.

Abstract This study was conducted to assess the concentration of heavy metals ( Cd, Zn, Pb, Cu, Fe, Cr)in soil and khat leaves by using Atomic Absorbation Spectroscopy(AAS). A1-g of powdered soil sample was accurately weighed Using Zeta citizon. A 10-mL of 1:3mixture of concentrated HNO3 and HCl were added to the flask and digested on Kjeldahil digestion block for an optimized period of 2:30 hour at the optimized temperature of 150°C.A 0.5-g of powdered khat leaves sample was accurately weighed by using zeta citizon.A4-mL of 1:1 mixture of concentrated HNO3 and HCl were added to the reaction vessel. Digested by using Kjeldahil digestion block for an optimized period of 2:00 hours at the optimized temperature of 150°C.The percentage recovery for the soil and khat leaves samples are found in the range of 90.9 to 97.17%.The pH value of the soils ranged from 5.6±0.03 to 6.08±0.13 then,soil samples collected from khat growing area were moderately acidic. The transfer factor (TF) value of essential heavy metals were found to be for: Fe (0.54), Cu (0.33), for Zn (0.29) and the potentially toxic heavy (Cd, Pb and Cr) were excluded in the khat leaves tissue. The average concentration for the analyte heavy metal in the research sample is higher than the average concentration for the control sample for both the soil and khat leaves, this shows that the area is contaminated. However, it have not reached the pollution stage at 95% confidence level. The average concentration of heavy metals in the research and control sample for both soil and khat leaves are lower than the maximum allowable limit (MAL) set by WHO/FAO standard at 95% confidence level.