Abstract:
This study was carried out to investigate the accumulative levels of Pb, Cr, Cd, Ni
and Cu in roadside topsoil of three major streets in Khartoum State and the relation
between the concentration of these metals and soil chemical properties. The
collected roadsides topsoil samples were prepared with an improved closed wet
digestion system and the heavy metals concentrations in the extracts were
determined using flame atomic absorption spectrometry. The mean concentration
ranges of metals (μg /g) were (17.74-536.65) for Pb, (less than 0.10-0.63) for Cd,
(43.82-283.6) for Cr, (4.54-33.72) for Ni, and (7.42-23.03) for Cu. The method of
determination used was evaluated using a certified reference material (IAEA soil-
7). The recovery values were found to be (106.20, 118.64, 102.31, 91.80 and
93.54) % for Pb, Cd, Cr, Ni and Cu respectively. The accuracy was within 95%
confidence interval levels for all the heavy metals determinations and the
calibration curves correlation coefficients of linearity were better than 0.999.
Significant correlations were found between the metals contents and soil chemical
properties specifically organic matter contents and to some extent total dissolved
solids and roadside soils texture as all soils samples showed moderately alkaline
nature that ranged between 7.58 and 8.2 pH unit. The percentage of total organic
matter and total dissolved solids in (ppm) were determined, determinations were
within 0.0-9.40 % of RSD % of the mean values. The extend of heavy metals
contamination was assessed, and the results inference was that there is a
considerable level of contamination with Pb and Cr while low to no contamination
with Cd, Cu and Ni on these roadside soils
