Transfer of heavy metals from soil to lettuce (Lactuca sativa) grown in irrigated farmlands of Kaduna Metropolis, Nigeria

Abstract

This studied was carried out to investigate the amount of heavy metals (Fe, Cd, Zn,Cu and Pd) transferred from soil to lettuce so as to know the extent of  contamination from Soil and lettuce samples collected from different irrigated  farmlands of Kaduna metropolis and Rigachikun as control site. These heavy metals were determined from soil and lettuce with the use of atomic absorption  spectrophotometer. The result obtained revealed that Zinc from Kabala and Iron from Kabala had the highest concentrations of 18.45 ± 28.39 μgg^-1 and 18.20 ± 20.19μgg^-1 respectively being the highest elements absorbed by the lettuce  samples from the irrigated farmland of the Kaduna metropolis. This is because with soil being acidic, the solubility of Zn and Fe play a principal role in the retention of these metals in the soil thereby increasing their absorption by the plants especially in lettuce sample. All the transfer factor obtained are below 1 with the exception of samples from Rigasa (2.66 μgg^-1for Cd), Malali (1.01 μgg^-1for Cd, 1.03 μgg^-1 for Fe and 1.17 μgg^-1 for Cu),Kawo (1.48 μgg^-1 for Cd) , Tudunwada(1.00 μgg^-1 for Cd ),Doka (1.09 μgg^-1 for Cd) and Rigachikun (control) 1.18 μgg^-1 for Cu.Result of this analysis also showed the transfer factor of soil to lettuce is in this order, Cadmium > Copper > Lead > Iron > Zinc. This because of atmospheric deposition of such heavy metal from their sources of contamination such as fertilizers, pesticides, sewage sludge and organic waste.

Keywords: Soil,lettuce, transfer factor, heavy metals, atomic absorption  spectrophotometer, Kaduna Metropolis, Nigeria.