SOIL – PLANT TRANSFER FACTOR OF Pb, Cd, Cu and Zn IN SPINACH, JUTE MALLOW AND TOMATO OF KADUNA METROPOLITAN FARMS

Abstract

 This study assesses the soil-plant Transfer Factor (TF) of Pb, Cd, Cu and Zn in some common vegetables; spinach, jute mallow and tomato in vegetable farms and gardens located within the city of Kaduna, Nigeria, in order to quantify the relative differences in bioavailability of metals to plants, vis-à-vis the soil properties and vegetable type. The city was divided into 20 zones of approximately equal areas and composite samples of soil and vegetables were collected from farms and gardens from each zone. Soil samples were digested using HNO3 followed by 3:1 mixture of HNO3 and HClO4 acids while the vegetable samples were digested directly using 3:1 mixture of HNO3 and HClO4 acids. The digests were analysed for the metals using Flame Atomic Absorption Spectrophotometer. Recovery test on method of digestion gave % recoveries > 95% while in the analysis of certified reference materials of soil and plant, t-test results (at 95% confidence limit) show that statistically, there existsno significant difference between certified and sample values.The general trend of TF for heavy metals in the vegetables is in the order Cd > Zn > Cu >Pb.Spinach generally have the highest TF followed by jute mallow and tomato. Pearson correlation coefficient of the soil properties and Transfer Factor ranged from weak negative to strong positive correlations. Results revealed that the ability of vegetable to uptake metals from the soil is related to the soil physicochemical properties and differs from one metal to another as well asfrom one plant species to another.