**3.4. Nickel**

In soils around the Zobe dam catchment, the mean Ni concentration was 184.57 mg/kg in the wet season and 26.87 mg/kg in the dry season. Whereas mean concentrations of Ni of 46.31 mg/kg and 84.50. mg/kg were observed in dry and wet seasons respectively, in soils around the environs of the KTSRM (Table 2; Fig 4). The mean concentration of Ni in both sites were observed to be higher than the acceptable limits of WHO (80 mg/kg), USA (75 mg/kg), Canada, France and Germany (50 mg/kg), Austria (50 to 70 mg/kg), Luxembourg (30-75 mg/kg); and Netherlands, Sweden and the UK (Table 3).

In plant samples, *Senna siberiana* had the highest Ni concentrations of 3.69 mg/kg and 13.77 mg/kg in dry and wet seasons respectively in the environs of KSTRM. *Diospyros piscatoria* was observed to have the highest concentration of 2.20 mg/kg for Ni in the dry season while *Ipomoea ascarafolia* had the highest concentration of 3.63 mg/kg among plants collected in the wet season around the Zobe dam catchment (Fig 5). Normal concentration of Ni in plants has been described to be between 0.1 to 5 mg/kg, whereas concentrations between 10 to 100 mg/kg as excessive (Table 4).

### **3.5. Cadmium**

Soils around the Zobe dam catchment had a mean Cd concentration of 0.15 mg/kg in the dry season and 0.33 mg/kg in the wet season. In the environs of KTSRM, a mean concentration of 1.05 mg/kg was observed in the dry season. In the wet season Cd concentrations were below detectable limits in the wet season (Table 2; Fig 4). The above mean concentrations were found to be within the acceptable limits of the WHO and the Countries listed in Table 3.

*Ipomoeaascarafolia* had the highest concentration of cadmium in dry (3.90 mg/kg) and wet (1.03 mg/kg) seasons among plants sampled around the Zobe dam catchment. In the environs of KTSRM, *Ziziphus abyssinica* was observed to have the highest concentration of 4.5 mg/kg of Cd in the dry season, while in the wet season *Cadaba farinosa* was observed to have the highest concentration of 0.54 mg/kg (Fig 5).

Heavy Metal Deposition in Soils and Plants Impacted by Anthropogenic Modification of Two Sites in the Sudan… http://dx.doi.org/10.5772/57299 707

**NORMAL DEFICIENCY EXCESSIVE PHYTOTOXIC**

**Cd** NA NA NA 5 to 30

**Zn** 27-150 10 to20 100 to 400 70 to 400

**Cr** 0.1- 0.5 NA 5 to 30 75-100

**Cu** 5.1-30 2 to 5 20-100 60-125

**Ni** 0.1 -5 NA 10-100 100

In soils around the Zobe dam catchment, the mean Ni concentration was 184.57 mg/kg in the wet season and 26.87 mg/kg in the dry season. Whereas mean concentrations of Ni of 46.31 mg/kg and 84.50. mg/kg were observed in dry and wet seasons respectively, in soils around the environs of the KTSRM (Table 2; Fig 4). The mean concentration of Ni in both sites were observed to be higher than the acceptable limits of WHO (80 mg/kg), USA (75 mg/kg), Canada, France and Germany (50 mg/kg), Austria (50 to 70 mg/kg), Luxembourg (30-75 mg/kg); and

In plant samples, *Senna siberiana* had the highest Ni concentrations of 3.69 mg/kg and 13.77 mg/kg in dry and wet seasons respectively in the environs of KSTRM. *Diospyros piscatoria* was observed to have the highest concentration of 2.20 mg/kg for Ni in the dry season while *Ipomoea ascarafolia* had the highest concentration of 3.63 mg/kg among plants collected in the wet season around the Zobe dam catchment (Fig 5). Normal concentration of Ni in plants has been described to be between 0.1 to 5 mg/kg, whereas concentrations between 10 to 100 mg/kg as

Soils around the Zobe dam catchment had a mean Cd concentration of 0.15 mg/kg in the dry season and 0.33 mg/kg in the wet season. In the environs of KTSRM, a mean concentration of 1.05 mg/kg was observed in the dry season. In the wet season Cd concentrations were below detectable limits in the wet season (Table 2; Fig 4). The above mean concentrations were found

*Ipomoeaascarafolia* had the highest concentration of cadmium in dry (3.90 mg/kg) and wet (1.03 mg/kg) seasons among plants sampled around the Zobe dam catchment. In the environs of KTSRM, *Ziziphus abyssinica* was observed to have the highest concentration of 4.5 mg/kg of Cd in the dry season, while in the wet season *Cadaba farinosa* was observed to have the highest

to be within the acceptable limits of the WHO and the Countries listed in Table 3.

**Table 4.** Range Values of Heavy Metals in Vegetation (mg/kg)

706 Environmental Risk Assessment of Soil Contamination

Netherlands, Sweden and the UK (Table 3).

**3.4. Nickel**

excessive (Table 4).

concentration of 0.54 mg/kg (Fig 5).

**3.5. Cadmium**

**and Wet (b) Seasons**  Soil samples collected in the wet season were observed to have a higher concentration of Fe **Figure 5.** Concentration (mg/kg) of Cr, Cu, Ni and Cd in plants collected from Zobe Dam catchment and the environs of Katsina Steel Rolling Mill (KTSRM) during the Dry (a) and Wet (b) Seasons

(891.66 and 745.75 mg/kg in Zobe dam catchment and the environs of KTSRM, respectively) than the dry season (360.58 and 277.22 mg/kg in Zobe dam catchment and environs of

Plant species with the highest concentration of Fe in the wet season were *Ipomoea ascarafolia* (115.50 mg/kg) and *Guiera senegalensis* (264.10 mg/kg) for Zobe dam catchment and environs of KTSRM, respectively. In the dry season, *Coldenia procumbens* (184.00 mg/kg) and *Guiera senegalensis* (176.84 mg/kg) were observed to have the highest concentration of Fe Zobe dam catchment and the environs of KTSRM, respectively (Fig 6).

KTSRM, respectively (Table 2; Fig 4).

**Fig 5: Concentration (mg/kg) of Cr, Cu, Ni and Cd in plants collected from Zobe Dam catchment and the environs of Katsina Steel Rolling Mill (KSRM) during the Dry (a)** 

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