Abstract:
Speciation and mobility of selected heavy metals including Cd, Pb and Fe were
investigated in Kofe dumpsite soils of Jimma Town, Jimma, Ethiopia. To study vertical
mobility of the metals, soil samples were collected at three depth profiles comprising
surface soil (0-10 cm), subsoil (20-30 cm), and bottom soil (40-50 cm) using soil auger.
Similarly, for horizontal mobility assessment, soil samples were collected from 5 m, 10 m
and 15 m distances starting from the edge of the dumpsite in east, west, north and south
directions. Control soil samples were also collected at the same depth profiles, from 200 m
away from the dumpsite. The collected samples were air dried, sieved as well as ground
before processing utilizing a Community Bureau of Reference (BCR) sequential extraction
procedure. The fraction of the target metals in the extracted samples were then
determined by flame atomic absorption spectroscopy (FAAS). The mobility factor (%MF) of
the target metals was investigated in both vertical and horizontal variations and the
obtained results showed that the target metals have exhibited both vertical and horizontal
mobility. The texture, organic matter and pH of the soil samples were also analyzed for
correlation study. Variation among obtained results, i.e., %MF and concentration of
analytes, were evaluated using one way ANOVA at (P<0.05). It was observed that Cd and
Pb exhibited vertical mobility and thus could lead to pollution of the underground water.
Similarly, the highest amount of Pb in the bioavailable fraction may also indicate its
horizontal mobility and its high tendency to pollute surface water, sediment as well as
agricultural products.
