Table 1. Average values of pH, conductivity & organic matter of soil samples
O. M.2 content%
|
EC1 (mS m-1)
|
PH
|
Areas
|
NO
|
11.58
|
0.38
|
7.28
|
A
|
1
|
8.59
|
0.25
|
7.24
|
E
|
2
|
9.77
|
2.18
|
7.55
|
S
|
3
|
9.43
|
0.33
|
7.17
|
H
|
4
|
Where, EC 1 = Electrical conductivity, O.M2= Organic Matter
A= Abroof
E= AL-Hetana
S= Shambat
H= AL-Halfia
Table 2. Average values of pH, conductivity & organic matter of sediment samples
O. M.2 content%
|
EC1 (mS m-1)
|
pH
|
Areas
|
NO
|
8.05
|
0.26
|
7.15
|
A
|
1
|
15.00
|
0.28
|
7.25
|
E
|
2
|
6.57
|
0.24
|
7.36
|
S
|
3
|
3.43
|
0.11
|
7.63
|
H
|
4
|
Where, EC 1 = Electrical conductivity, O.M2= Organic Matter
A= Abroof
E= AL-Hetana
S= Shambat
H= AL-Halfia
Soil and sediments samples were subjected to heavy metal analysis and also for physicochemical parameters measure including pH, organic matter and electrical conductivity.
(Tables 1and 2) showed the average values of physiochemical properties of the all soil and sediment samples, pH was recorded in the normal range while electrical conductivity of all soil samples was not far from the normal range. Mohamed (2007) [1] found that the WN was more alkaline than the BN, pH 8.2, and 7.5, respectively. At the point where the two rivers merge, there was a dilution of the H+ concentration compared to the Blue Nile. The pH observed in the water after passing Khartoum city was 7.9.
Organic matter in the sediment and soil played an important role in the adsorption of trace metals, it could be used as a simple pollution index of the sediment and soil. In soil (floodplains) the organic increase to wet season in order of RN > BN > WN, the values are 3.72, 2.99 and 1.90 % respectively [11]. The higher content in the soil in site A which near estuary and the higher content in sediment in site E. In 2013 areas around E is used sand and gravel as building materials, thus lead to change the bed sediment and soil, in 2015 new high way street was building.
Segarra et al. (2007) [12] showed that the mineralogical results reveal the riverine origin of the sediments of the Gda.sk Basin, with the coarser mineral grains deposited near the river mouth and the finest terrigenous particles transported further from the coast. This fine material is the best carrier for the external inputs of organic matter, which is then transported and accumulated in surface sediments far from the coast.
In all soil and sediments samples concentration of all heavy metals was recorded below the permissible limits worldwide table (3) and (4). Concentration of lead ranged between 0.078 to 0.141ppm, zinc ranged between 0.101 to 0.294 ppm and concentration of cadmium was recorded to range between 0.011 to 0.016 ppm.
Table 3. Concentration (ppm) of heavy metals (Pb, Zn & Cd) in soil samples
Mean Conc. Of Cd
|
Mean Conc. Of Zn
|
|
Mean Conc. Of Pb
|
Soil Sample
|
0.000
|
0.000
|
0.000
0.110
0.105
0.123
0.136
|
Blank
|
0.015
|
0.231
|
(A)
|
0.010
|
0.245
|
€
|
0.013
|
0.192
|
(H)
|
0.010
|
0.294
|
(S)
|
Where A= Abroof
E= AL-Hetana
S= Shambat
H= AL-Halfia
,
Table 4. Concentration (ppm) of heavy metals (Pb, Zn & Cd) in sediment samples.
Mean Conc of Cd
|
Mean Conc of Zn
|
Mean Conc of Pb
|
Soil Sample
|
0.000
|
0.000
|
0.000
|
Blank
|
0.014
|
0.181
|
0.078
|
(A)
|
0.016
|
0.101
|
0.127
|
(E)
|
0.011
|
0.134
|
0.141
|
(S)
|
0.011
|
0.171
|
0.135
|
(H)
|
Where, A= Abroof
E= AL-Hetana
S= Shambat
H= AL-Halfia
Heavy metal concentrations in sediment and soil are affected by particle size and composition of sediments and concentrations generally increased with decreasing particle size of sediments and concentrations generally increased with decreasing particle size of sediments [10].
Figures (1) and (2) show the comparison of elements concentration between soil and sediment samples for study, Cd was shown same distribution in all sites, but Zn and Pb were shown different, the presence of a point source of contamination may cause a sharp increase, for the sediment and soil samples and may be the source of Zn in soil from sediment deposition.
Mohamed (2007) [1] reported that exhausts from vehicles might contribute to increased concentration observed downstream the city Khartoum because exhausts are regarded as the major source of environmental contamination by lead and Ni.
Figure (3) showed the concentration of Pb in sediment and higher distribution in all sites compared to A, the presence of additional amounts of Pb is caused by human activity, including emission of furnace or coke dust or combustion of fluid fuel.
Muna I. Sh. Kamal K. T., et al, (2014) [13] reported that the River Nile had higher concentrations of Cd, Cr, Co, Zn and Mn than some the European and Asian ecosystems. All elements (Fe, Cu, Cd, Co, Cr, Ni, Zn, Mn, Al) have high mean concentration in BN, WN and RN at wet than dry season except (Ni, Cd and Pb) in WN and (Ni, Pb) in BN which these elements have high mean concentration at dry season this indicate that these two elements have anthropogenic source.
The concentration of Zn in soil was higher compared to sediment figure (4), the concentration of Zn difference between all sites in river, this indicate the difference of elements such sources and the concentration of Cd in E was higher compared to other sites figure (5), the strong association of Cd indicates common sources, and these metals may have been derived from anthropogenic sources, especially the paint industry, the application of phosphate fertilizers to the agricultural soil has led to increase.
Table 5. Comparison of lead (Pb), zinc (Zn) and cadmium (Cd) content in sediment samples and local study
Pb content
|
|
A
|
S
|
H
|
Study
|
0.0784
|
0.141
|
0.135
|
Local studies*
|
0.0128
|
0.0217
|
0.0031
|
Zn content
|
Study
|
0.181
|
0.134
|
0.171
|
Local studies*
|
0.254
|
0.078
|
0.052
|
Cd content
|
Study
|
0.014
|
0.011
|
0.011
|
Local studies*
|
0.00027
|
0.00003
|
0.00094
|
The figure (6) and (7) showed that the concentration of Pb and Cd elements in all study areas is greater than local study, the source of Pb element is automobile exhausts. Higher levels of Pb often occur in water bodies near highways and large cities due to high gasoline combustion. The concentration of Zn for all study areas is greater than local study except in site A (figure 8), the variation of heavy metal concentration in the study area was due to irrigation of land by industrial waste water and other agronomic practices.