Accumulation pattern of trace metals in Spinacia oleracea harvested from soil treated with urine in comparison with other soil amendments in Pretoria, South Africa

Purpose The study assessed trace metal levels in theleaves, stalks and roots of Spinacia oleracea harvestedfrom soil treated with urine in comparison to chemicalfertilizers and biosolids.Methods Spinacia oleracea seedlings were planted on soilspretreated with urine, chemical fertilizers and biosolids.Results The soil treated with chemical fertilizers resultedin an increase of Cr, Pb, Cd, Cu, Ni and Sb while there wasan increase in the concentrations of Zn and Hg in the soiltreated with urine. The soil with no amendments recordedhigher mean values of As and Mn, whereas the biosolidstreatment did not show any increases of the trace metals inthe soil. The concentration of Mn, Pb and Ni in the leavesand stalks of S. oleracea harvested from soil treated withurine were below the recommended limits for trace metalsin edible plants as set by WHO even though the urinetreatment recorded the highest concentration of Cd in theroots, stalks and leaves. The S. oleracea harvested from thesoil treated with chemical fertilizers showed an accumulationCu and Mn in the stalks and leaves while thoseharvested from soil treated with biosolids showed anaccumulation of Cr, As, Zn and Ni in the stalks and Cr, Pband Sb in the leaves and all trace metals in the roots exceptCd and As. S. oleracea harvested from the soil with noamendments showed an accumulation of Cr, As, Zn and Niin the stalks and Cr, Pb, Zn and Sb in the leaves. Thetransfer factor showed that Cd, Zn, Mn and Sn weretranslocated from the soil to the leaves even though theconcentrations were below acceptable limits for humanconsumption.Conclusions The study demonstrated that the use of urineas a soil amendment may not facilitate or increase thebioavailability of trace metals in the plant tissues.