**Principal component analysis (PCA)**

PCA was applied in each region to assist in identifying sources of elements. 3-D plots of the PCA loadings are presented in Fig.3, where the relationships among the six trace elements are readily seen. As expected, four factors were obtained, accounting for 97.4, 98.0 and 99.4 % of the total variance in ESR, SSR and WSR, respectively. In ESR, Factor 1 is dominated by Co, Cu, Pb and Mn, while in SSR it was dominated by Co, Zn, As and Pb and in WSR by Co, Zn, As and Mn (accounting for 67.4, 69.9 and 90.7 % of the total variance, respectively). In each area, the loadings of certain minerals were lower than the others, which may, therefore, imply a quasi-independent behaviour within the group. These elements were Cu and Mn (0.42 and 0.4, respectively) for ESR, Co and Zn (0.5 and 0.4, respectively) in SSR and Zn and As (0.4 and 0.4, respectively) in WSR.

Factor 2 is dominated by Zn and As in ESR, by Mn in SSR and by Cu and Pb in WSR (accounting for 23.1, 15.3 and 6.0 % of the total variance, respectively). Factor 3 is dominated in ESR by As and Pb, by Zn As and Cu Pb in SSR and by Zn and As in WSR (accounting for 4.1, 7.7 and 1.4 % of the total variance, respectively). Zn is negatively correlated with Cu in SSR, and with As in WSR. In each region, certain elements (As and Zn in ESR, Mn in SSR and Cu in WSR) were separated from the others by a large distance in the 3-D PCA loading plot, suggesting that these elements are poorly correlated and may have different sources (Fig.3). Factor 4 is dominated by Cu, As and Mn (accounting for 2.7 % of the total variance; Mn is negatively correlated with Cu and As) in ESR, Zn, As and Pb (accounting for 5.4 % of the total variance; Zn and Mn are negatively correlated with As and Pb) in SSR and Pb and Mn (accounting for 1.3 % of the total variance; Mn is negatively correlated with Pb) in WSR.

### **Pearson's correlation matrix for the trace element concentrations in agricultural soils from Libya.**

The correlations between trace element concentrations in agricultural soils showed a high, positive, linear relationship (Table 2). To determine whether geochemical associations exist between the different trace elements analysed in this study, the datasets for agricultural soils from each region and soils from ESR, WSR and SSR were subjected to simple correlation analysis. A scatter plot for the trace element correlations that were found to be significant (*P*<0.05) in some of the soils studied are presented in Fig.4. The correlation analysis was also performed on the composite data sets of all agricultural soils for this study. The Pearson correlation coefficients and *P*-values for Co, Zn, Cu, As, and Pb were significant and all the analyses are shown in Table 2.

#### **Manganese**

A summary of trace element Pearson correlation coefficients of soils from different regions of Libya are shown in Table 2, Fig.4 and Appendices 3.11, 3.12 and 3.13.Mn concentration showed

Conducted and Investigate Arsenic (As), Cobalt (Co) Copper (Cu), Manganese (Mn), Lead (Pb), and Zinc (Zn)... http://dx.doi.org/10.5772/57429 857

Figure 3. PCA loading plots for the three rotated components for a) SSR, b)WSR and c) ESR. **Figure 3.** PCA loading plots for the three rotated components for a) SSR, b)WSR and c) ESR.

a significant correlation with Co, Zn, Cu and Pb in WSR and ESR. However, Mn is not correlated with As and Pb in ESR or SSR, respectively, or with the other metals (Co, Zn and Cu) in SSR, reflecting different sources for Mn and the other elements. Moreover, Mn is not correlated with As and not significant in ESR and SSR, which may suggest a common origin (Table 2 and Fig.4). **Pearson's correlation matrix for the trace element concentrations in agricultural soils from Libya.**  The correlations between trace element concentrations in agricultural soils showed a high, positive, linear relationship (Table 2). To determine whether geochemical associations exist between the different trace elements analysed in this study, the datasets for agricultural soils from each region and soils from ESR, WSR and SSR were subjected to simple correlation analysis. A scatter plot for the trace element correlations that were found to be significant (*P*<0.05) in some of the soils studied are presented in Fig.

#### **Lead**

**Results of analysis of variance (ANOVA)**

856 Environmental Risk Assessment of Soil Contamination

**Multivariate analysis results**

0.4, respectively) in WSR.

analyses are shown in Table 2.

**Libya.**

**Manganese**

**Principal component analysis (PCA)**

A one-way analysis of variance (ANOVA) was performed on each of the three regions studied. For SSR, the ANOVA showed that that the mean As levels between sites were not significantly

PCA was applied in each region to assist in identifying sources of elements. 3-D plots of the PCA loadings are presented in Fig.3, where the relationships among the six trace elements are readily seen. As expected, four factors were obtained, accounting for 97.4, 98.0 and 99.4 % of the total variance in ESR, SSR and WSR, respectively. In ESR, Factor 1 is dominated by Co, Cu, Pb and Mn, while in SSR it was dominated by Co, Zn, As and Pb and in WSR by Co, Zn, As and Mn (accounting for 67.4, 69.9 and 90.7 % of the total variance, respectively). In each area, the loadings of certain minerals were lower than the others, which may, therefore, imply a quasi-independent behaviour within the group. These elements were Cu and Mn (0.42 and 0.4, respectively) for ESR, Co and Zn (0.5 and 0.4, respectively) in SSR and Zn and As (0.4 and

Factor 2 is dominated by Zn and As in ESR, by Mn in SSR and by Cu and Pb in WSR (accounting for 23.1, 15.3 and 6.0 % of the total variance, respectively). Factor 3 is dominated in ESR by As and Pb, by Zn As and Cu Pb in SSR and by Zn and As in WSR (accounting for 4.1, 7.7 and 1.4 % of the total variance, respectively). Zn is negatively correlated with Cu in SSR, and with As in WSR. In each region, certain elements (As and Zn in ESR, Mn in SSR and Cu in WSR) were separated from the others by a large distance in the 3-D PCA loading plot, suggesting that these elements are poorly correlated and may have different sources (Fig.3). Factor 4 is dominated by Cu, As and Mn (accounting for 2.7 % of the total variance; Mn is negatively correlated with Cu and As) in ESR, Zn, As and Pb (accounting for 5.4 % of the total variance; Zn and Mn are negatively correlated with As and Pb) in SSR and Pb and Mn (accounting for

**Pearson's correlation matrix for the trace element concentrations in agricultural soils from**

The correlations between trace element concentrations in agricultural soils showed a high, positive, linear relationship (Table 2). To determine whether geochemical associations exist between the different trace elements analysed in this study, the datasets for agricultural soils from each region and soils from ESR, WSR and SSR were subjected to simple correlation analysis. A scatter plot for the trace element correlations that were found to be significant (*P*<0.05) in some of the soils studied are presented in Fig.4. The correlation analysis was also performed on the composite data sets of all agricultural soils for this study. The Pearson correlation coefficients and *P*-values for Co, Zn, Cu, As, and Pb were significant and all the

A summary of trace element Pearson correlation coefficients of soils from different regions of Libya are shown in Table 2, Fig.4 and Appendices 3.11, 3.12 and 3.13.Mn concentration showed

1.3 % of the total variance; Mn is negatively correlated with Pb) in WSR.

different (SSR: *P*=0.398), but were for ESR and WSR (*P*<0.0016, *P*<0.015, respectively).

The Pb concentration showed a significant correlation with Co, Zn, Cu and As concentrations in all three of the agricultural soil regions (Fig.5a, b & c and Table 2). and all the analyses are shown in Table 2. **Manganese** 

.4. The correlation analysis was also performed on the composite data sets of all agricultural soils for this study. The Pearson correlation coefficients and *P*-values for Co, Zn, Cu, As, and Pb were significant

#### **Arsenic**

As is not correlated with Co and Cu in ESR; however, As concentration showed a significant correlation with Zn concentrations in all three of the soil regions. Trace element correlations with As were slightly varied across regions. As is also positively correlated with Co, Cu and Zn in SSR and WSR (Table 2 and Fig.6a, b & c).

#### **Zinc**

Zn concentration correlated well with Co and Cu in soils from WSR and SSR sites but not with those from ESR (Table 2). The Cu-Zn and Zn-Co correlations, however, remained significant (*P*<0.01) when the analysis was performed on the composite data sets (Figs 3.7 and 3.8, respectively). [6]Reported that in Libya, depending on the crop and soil, farmers use an average of 100 kg/hectare of phosphate fertilizer annually.


**+**: positive correlation (significant at *P*< 0.05)

**–**: negative correlation (significant at *P*< 0.05)

**NS**: not significant at *P*< 0.05

\*:significant at *P*< 0.05

**0**: no correlation

**C**: correlation (*r*> 0.50)

**Table 2.** Summary of trace element correlation in soils from different regions of Libyan soils (see for correlation coefficients and *P*-values).

Conducted and Investigate Arsenic (As), Cobalt (Co) Copper (Cu), Manganese (Mn), Lead (Pb), and Zinc (Zn)... http://dx.doi.org/10.5772/57429 859

**Arsenic**

**Zinc**

Zn in SSR and WSR (Table 2 and Fig.6a, b & c).

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of 100 kg/hectare of phosphate fertilizer annually.

**+**: positive correlation (significant at *P*< 0.05) **–**: negative correlation (significant at *P*< 0.05)

**NS**: not significant at *P*< 0.05 \*:significant at *P*< 0.05 **0**: no correlation **C**: correlation (*r*> 0.50)

coefficients and *P*-values).

As is not correlated with Co and Cu in ESR; however, As concentration showed a significant correlation with Zn concentrations in all three of the soil regions. Trace element correlations with As were slightly varied across regions. As is also positively correlated with Co, Cu and

Zn concentration correlated well with Co and Cu in soils from WSR and SSR sites but not with those from ESR (Table 2). The Cu-Zn and Zn-Co correlations, however, remained significant (*P*<0.01) when the analysis was performed on the composite data sets (Figs 3.7 and 3.8, respectively). [6]Reported that in Libya, depending on the crop and soil, farmers use an average

Mn-Co (+ C \* ) (+ C \* ) (+ 0 NS) Mn-Zn (+ C \* ) (+ C \* ) (+ 0 NS ) Mn-Cu (+ C \* ) (+ C \* ) (+ 0 NS ) Mn-As (+ 0 NS ) (+ C \* ) (+ C NS ) Mn-Pb (+ C \* ) (+ C \* ) (+ 0 NS ) Pb-Co (+ C \* ) (+ C \* ) (+ C \* ) Pb-Zn (+ C \* ) (+ C \* ) (+ C \* ) Pb-Cu (+ C \* ) (+ C \* ) (+ C \* ) Pb-As (+ C \* ) (+ C \* ) (+ C \* ) As-Co (+ 0 \* ) (+ C \* ) (+ C \* ) As-Zn (+ C \* ) (+ C \* ) (+ C \* ) As-Cu (+ 0 \* ) (+ C \* ) (+ C \* ) Cu-Co (+ C \* ) (+ C \* ) (+ C \* ) Cu-Zn (+ 0 \* ) (+ C \* ) (+ C \* ) Zn-Co (+ 0 \* ) (+ C \* ) (+ C \* )

**Table 2.** Summary of trace element correlation in soils from different regions of Libyan soils (see for correlation

**ESR WSR SSR**

**Figure 4.** Mn correlations against other trace elements in agricultural soils from ESR, SSR and WSR sites.

**Figure 5.** Pb correlations against other trace elements in agricultural soils from ESR, SSR and WSR sites.

Conducted and Investigate Arsenic (As), Cobalt (Co) Copper (Cu), Manganese (Mn), Lead (Pb), and Zinc (Zn)... http://dx.doi.org/10.5772/57429 861

**a**

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Co

**c**

Cu

Mn

0

200

400

600

800

1000

0

**e**

5

10

15

20

25

30

Pb 0 5 10 15 20 25 30

Pb 0 5 10 15 20 25 30

Pb 0 5 10 15 20 25 30

**Figure 5.** Pb correlations against other trace elements in agricultural soils from ESR, SSR and WSR sites.

**b**

Zn

d

As

0

ESR SSR WSR

5

10

15

20

Pb 0 5 10 15 20 25 30

Pb 0 5 10 15 20 25 30

**Figure 6.** As correlations against other trace elements in agricultural soils from ESR, SSR and WSR sites.

**Figure 7.** Cu correlations against other trace elements in agricultural soils from ESR, SSR and WSR sites.

Conducted and Investigate Arsenic (As), Cobalt (Co) Copper (Cu), Manganese (Mn), Lead (Pb), and Zinc (Zn)... http://dx.doi.org/10.5772/57429 863

**a**

862 Environmental Risk Assessment of Soil Contamination

Co

**c**

**e**

Mn

0

200

400

600

800

1000

0

5

10

15

20

As

Cu 0 5 10 15 20 25 30

Cu 0 5 10 15 20 25 30

**Figure 7.** Cu correlations against other trace elements in agricultural soils from ESR, SSR and WSR sites.

Cu 0 5 10 15 20 25 30 **b**

Zn

Pb

**d**

ESR SSR WSR

Cu 0 5 10 15 20 25 30

Cu 0 5 10 15 20 25 30

**Figure 8.** Zn correlations against other trace elements in agricultural soils from ESR, SSR and WSR sites.

#### **Overview of total shoot, soil and grain As for ESR, SSR and WSR**

A one-way analysis of variance (ANOVA) was performed on each of the three regions studied. The ANOVA showed that that the mean As levels for grain between sites were not significantly different (*P*=0.662 ), but that those for soil and shoot were (soil: *P*<0.001; shoot: *P*<0.002). Fig.9 shows a comparison of the distribution of As concentrations in the shoot, soil and grain from ESR, WSR and SSR.

**Figure 8 Cumulative ranked distribution of As concentrations in Libyan agricultural soil, shoot and grain from ESR (solid), WSR (dash) and SSR (square dot). Figure 9.** Cumulative ranked distribution of As concentrations in Libyan agricultural soil, shoot and grain from ESR (solid), WSR (dash) and SSR (square dot).

13

The mean shootAs contentfor SSR(range 0.07–0.35 mg/kg; mean: 0.19 ± 0.02 mg/kg) was higher than for ESR (range 0.04–0.34 mg/kg; mean: 0.13 ± < 0.01 mg/kg) and WSR (range 0.01–0.19 mg/ kg; mean: 0.12 ± < 0.01mg/kg). At the 50th percentile, shoot As content for SSR (0.17 mg/kg) was more than 1.5 times that recorded for ESR (0.12 mg/kg) and WSR (0.11 mg/kg; Fig.9).

ESR recorded the highest mean As level in Libyan soil (8.10 ± 0.48 mg/kg, range 0.01–18.94 mg/ kg), followed by WSR (1.97± 0.41 mg/kg, range 1.19–2.48 mg/kg) and SSR (1.70 ± 0.58 mg/kg, range 0.73–2.92 mg/kg), i.e. mean As concentrations in ESR are nearly 4.8 and 4.1 times higher than in SSR and WSR, respectively.

The mean grain As content for SSR (range 0.02–0.2 mg/kg; mean: 0.07±0.01 mg/kg) was also significantly higher (*P*< 0.01) than for ESR (range 0.02–1.1 mg/kg; mean: 0.05 ± 0.02 mg/kg) and WSR (range 0.02–0.04 mg/kg; mean: 0.02 ± < 0.01mg/kg). At the 50th percentile, grain As content for SSR (0.05 mg/kg) was over twice that recorded for ESR (0.02 mg/kg) and WSR (0.02 mg/kg; Fig.9).

The ranges of total grain, shoot and soil As concentrations over the three regions studied were relatively wide; however, the distribution was markedly skewed, with 65 % in ESR having grain, shoot and soil As concentrations of < 0.03, 0.17 and 9.9 µg, respectively, 21 % in SSR < 0.09, 0.28 and 1.8, respectively and 12 % in WSR < 0.02, 0.16 and 2.4, respectively (Fig.9).
