Assessment of Common Heavy Metal Pollution in Topsoils Along Major Roadside Areas due to Traffic Activity in Khartoum State -Sudan

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