Determination of some Major and Trace Metals Levels in Onion (Allium Cepa L.) and Irrigation Water Around Meki Town and Lake Ziway, Ethiopia
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Date
2009-07
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Addis Ababa Universty
Abstract
The levels of major (Ca and Mg) and trace (Cu, Co, Cr, Mn, Zn, Cd and Pb) metals were
determined in onion (Allium Cepa L.) bulbS and well water and Lake Ziway water employed for
irrigation were determined by flame atomic absorption spectroscopy(FAAS). Sample dissolution of
onion was carried out by wet digestion with a total volume of 2 mL HNO3 (69-72 %) and 2 mL
HClO4 (70 %) mixture in flask fitted with reflux condenser on Kjeldahl heating apparatus.
Higher levels of Ca (599 and 550 μg/g) than Mg (516 and 407 μg/g) in onion irrigated with
well and Lake Ziway water, respectively were detected. Among trace metals, the highest level
was that of Zn (18 and 14.1 μg/g) followed by Mn (8.8 and 13 μg/g) Cr (4.9 and 6.6), Cu (3.2
and 3.6 μg/g), Co (1.2 and 0.8 μg/g) and Cd (0.64 and 0.53 μg/g) in onion irrigated with well
and Lake Ziway water, respectively all in dry weight basis. Lead was below detection limit of the
analytical procedure in this study.
The levels of Ca and Mg detected in well water and the Lake Ziway water used for irrigation
were (22.7, 9.9) and (30.2, 8.6 mg/L), respectively. Higher levels of Zn (0.08 mg/L) and Co
(0.06 mg/L) were found in the lake water while higher Mn (1.1 mg/L) and Cr (0.44 mg/L) were
determined in well water. Cu, Cd and Pb were below the method detection limit in both well and
Lake Ziway water samples of the study area. Mn in well water and Cr in both water exceeded
the FAO limit of maximum recommended level in irrigation water.
Key words: Onion (Allium Cepa L.), irrigation water, Lake Ziway, FAAS and wet digestion
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Keywords
Onion (Allium Cepa L.); irrigation water; Lake Ziway; FAAS and wet digestion