Abstract:
Heavy metals are potential environmental contaminants with the capability of causing
human health problems. This study aimed to determine the concentrations of heavy metals
(Pb, Cd, Zn, Cu, Mn, Fe, and Cr, ) in the soil and onion bulb (Allium cepa L.) samples from
Nono District , West Shoa Zone, Oromia regional state, Ethiopia. The air dried soil and
oven dried onion bulb were digested. Wet digestion method using a mixture of 5 mL of
concentrated 35.4% HNO3, 30% H2O2 and 70% HClO4 in ratio (5:1:1) was used for
digestion of the samples. The determination of heavy metals was done by flame atomic
absorption spectrometer (FAAS). The analysis of variations and connections between metal
levels in soil samples and those in onions was assessed using statistical software. The pattern
of heavy metal concentrations in the soil and Onion bulb at Biftu Jalala and Abdi gudina
were (Fe > Mn > Zn > Cu), and at Halo Dinki (Fe > Zn > Mn > Cu ) . Cr, Pb, and Cd
concentrations in onion bulbs and soil were not found. The results showed that mean
concentrations of heavy metals were higher in the soil sample than the onion bulb. In
general, the mean concentrations of heavy metals in the analyzed soil and onion bulb
samples were found below the FAO/WHO maximum permissible limit. Each of the heavy
metals had coefficients of determination (R2) values greater than 0.99, which suggests a
strong linear relationship between the analytical signal and the analyte concentration.
Heavy metals in soil and onion samples ranged in percentage RSD values from 1.20 to 11.93
and 3.14 to 8.61, respectively. The findings usually showed that there is no health risk
associated with eating onion bulbs from the research areas when compared to the harmful
heavy metals investigated
