Abstract:
Heavy metals are introduced in the environment during natural weathering of bedrock. Currently,
environmental pollution by heavy metals is a global problem. Excessive level of heavy metal
pollution in the environment could cause harm. It is necessary to accurately determine heavy
metal concentrations in different environmental samples. This study investigated several
physicochemical parameters, and the levels of selected heavy metals (Cr, Cd and Pb) were
determined in selected cabbage, soil and Awetu River at Jimma town, southwestern Ethiopia. For
this purpose, seven samples (three from water, two from vegetable (cabbage) and two from soil)
were analyzed. The cabbage, soil and irrigation water samples were randomly collected from the
farmlands around Awetu River. The samples were digested using properly optimized digestion
procedures. The physicochemical parameters and heavy metal concentrations were determined
using Multimeter parameter probe and flame atomic absorption spectroscopy (FAAS). The results
of the physicochemical analysis were obtained in the following ranges: pH (6.8-7.02),
temperature (21-23 °C), conductivity (336-399 μS/cm), dissolved oxygen (6.17-6.705 mg/L) and
biological oxygen demand (2.345-2.88 mg/L),which were found to be below the maximum
permissible levels set by the WHO/FAO. In this study, the levels of selected heavy metals (Cr, Cd
and Pb) in cabbage, soil and irrigation water were investigated. Cd and Cr were not detected in
any of the samples. The mean concentration (mg/kg) of Pb in the soil downstream was 0.115 ±
0.035. However, Cr and Cd were not detected. For irrigation water, only lead was detected
downstream and its mean concentration (mg/L) was 0.033 ± 0.019. For vegetables (cabbage), the
levels of all heavy metals were found to be below the detection limit. The metal concentrations
determined on the farm were compared to the standards, and the Pb concentrations in the soil
and irrigation water were still below the permissible limits. This study concluded that the
concentration of lead detected in soil and downstream water is associated with the waste
discharged to the river as a sink.
