Analysis of Trace Elements in Tomato Fruits from Ziway Lake Irrigated Farms

Abstract

Tomato is one of the most important edible and nutritional vegetable and can accumulate heavy metals when it is grown at polluted area. In this study, levels of selected heavy metals were determined in tomato, its farmland soil and water of Adami Tulu, Ethiopia. The samples were collected from four different localities of Adami Tulu. Tomato samples were collected from six sampling plots of each farm lands randomly. Composite soil samples were collected by digging up to the depth of 30 cm depth from where the tomato fruits collected. The irrigated water samples were collected in one liter polyethylene bottles after it has been diverted from Lake Ziway water in an open channel before entering into the farm plots of each four sampling site. The tomato, soil and water samples were digested following the protocol of microwave assisted digestion (wet digestion) method. The concentrations of the selected metals in tomato, soil and water samples were determined by flame atomic absorption spectroscopy. The results indicated that the concentration o f metals i n tomato samples were ranged from 5.56 to 10.37 mg/kg for Cu, 12.72 to 26.94 mg/kg for Zn, 3.16 to 8.64 mg/kg for Co, 0.13 to 0.27 mg/kg for Cd and 0.14 to 0.32 mg/kg for Pb. The concentrations of heavy metals in soil samples were ranged from 21.41 to 86.95 mg/kg for Cu, 52.76 to 66.21 mg/kg for Zn,11.52 to 13.91 mg/kg for Co, 0.38 to 0.67 mg/kg for Cd and 8.35 to10.34 mg/kg for Pb and in the water sample were ranged from 0.036 to 0.044 mg/L for Cu, 0.230 to 0.305 mg/L for Zn, 0.038 to 0.130 mg/L for Co, 0.011 to 0.021 mg/L for Cd and 0.019 mg/L to 0.041 mg/L for Pb. The content of Zn has the highest concentration in the tomato sample collected from all farm lands. The level of Cu, Co, Pb and Cd were higher in all sample sites and were below the permissible limit of WHO/FAO. The content of heavy metals such as Cd and Pb in tomato samples were slightly above the permissible value of WHO/FAO. Based on results obtained from this study we suggests concerned official body (ies) to take the necessary precaution measures for cleaning the source pollution.