Abstract

The present study investigated the level of toxic heavy metals such as Pb, Cd, Cr, and Cu in tomato and in support soil samples at the flower garden in Ziway horticulture and industrial area, Ethiopia. The obtained values of reagents volume, temperature, and time for optimal procedure are the mixture of 6mL of HNO3, and 2mL of H2O2, 210 ℃, 150min and 6mL of aquaregia (1HNO3:3HCl) and 2mL of H2O2, 270 ℃, 180min to mineralize powdered samples of tomato and its support soils during wet digestion, respectively. The concentrations of four selected metal in the tomato and its supporting soil samples were determined by flame atomic absorption spectrophotometer. The mean concentration of heavy metals in tomato sample near the flower garden exhibited decreased trend in the order of Pb (0.48±0.02ppm) > Cu (0.39±0.002ppm) > Cr (0.32±0.014ppm) > Cd (0.025±0.001ppm). While, the mean concentration of heavy metals in tomato sample far from the flower garden exhibited decreased trend in the order of Pb (0.399±0.009ppm > Cu (0.16±0.011ppm) > Cr (0.11±0.08ppm)> Cd (0.013±0.0007ppm). This indicates that the tomato vegetables grown near the industrial area contain the higher level of heavy metals than those grown far from it, which could be attributed to the addition of fertilizers, herbicides, pesticides, and other chemical repeatedly to the soils to enhance the agriculture crops. The similar trend was also observed for soil samples but with slightly higher concentrations of heavy metals. In the precision test, %RSD (relative standard deviation) for selected metals in tomato sample was in the range between 0.51% and 4.2% for tomato near the flower garden and between 2.26% and 6.9% for far from the flower garden. A significant difference was observed between the mean concentrations of all metals in tomato and its support soil samples.

Keywords: Heavy metals; Tomato soil; Horticulture; Fertilizers; FAAS