Assessment of Pollution Status of Soils and Vegetables Irrigated by Awash River and its Selected Tributaries

Abstract

Abstract This assessment was done to determine the concentrations of Cadmium (Cd), Chromium (Cr), Copper (Cu), Lead (Pb) and Manganese (Mn) in soil and vegetable (Spinach) samples collected in some farmlands irrigated with Awash River. Graphite Furnace Atomic Absorption Spectrometer was used for analyzing heavy metal concentrations. The test results showed that in the soil samples, from five heavy (Cd, Cr, Cu, Mn, and Pb) metals Cr and Mn were detected in all the soil samples collected from farmlands in the Lower, Middle, and Upper Awash River Basin. However, Cu was detected only in soil samples collected from farmlands in the lower Awash River Basin. The order of heavy metals concentrations (mg/kg) in soil from Lower, Middle, and Upper Awash River basin, respectively, was: Mn (1027, 1118, 89.8), Cr (82.2, 67.2, 57.2), Cu (27.4, ND, ND), Cd and Pb (ND, ND, ND). The concentrations of Cr, Mn and Cu analyzed in some of the soil sampling sites were below maximum permissible limits set for agricultural soils by (FAO/WHO: 2001). The vegetable (spinach) samples collected from same sites as the soil samples result showed that Cr and Mn were detected in all sites and Cu was detected only lower Awash River basin. The order of heavy metals concentrations (mg/kg) in soil from Lower, Middle, and Upper Awash River basin, respectively, were: Cr (89.8, 82.4, 125.6) Mn (535.8, 5.8, 67, Cu (6.4, ND, ND), Cd (Not Detected, ND, ND) and Pb (ND, ND, ND). The soil-to-plant transfer factor (Kd) order was found to be Cr (1.094, 1.23, 2.2) > Mn (0.52, 0.01, 0.73) > Cu (0.23). The concentrations of the metals analyzed in some of the vegetable sampling sites were above maximum permissible limit set for vegetables by (FAO/WHO; 2001). Therefore, the consumption of Spinach from the farmlands irrigated by Awash River could pause a health risk to consumers. Therefore, it is advised that consumers become cautious of their vegetable consumption. It is recommended that this kind of assessment is continued to monitor changes in the future. Keywords: Awash River; Contamination; Trace elements; Vegetables; Soil Introduction