Environmental Engineering Reference
In-Depth Information
Fig. 5
Scores plot for the PCA of the rare earth elements and alkaline metals. C: control; SR L:
west roadside of the secondary road; SR R: east roadside of the secondary road; H 0.5, H 3, H 6
and H 9: highway soil samples at 0.5, 3, 6 and 9 m distance from highway
Table 2
Correlations
between trafic related metals
Hf
Zr
Cd
Cu
Mo
Nb
Ni
Pb
Sb
Sn
Sr
Zn
Hf
1.00
Zr
0.94
1.00
Cd
0.34
0.56
1.00
Cu
0.32
0.55
0.95
1.00
Mo
0.40
0.64
0.92
0.91
1.00
Nb
0.26
0.50
0.87
0.79
0.81
1.00
Ni
0.31
0.50
0.88
0.83
0.79
0.77
1.00
Pb
0.28
0.51
0.90
0.86
0.92
0.76
0.80
1.00
Sb
0.21
0.44
0.92
0.88
0.85
0.93
0.79
0.86
1.00
Sn
0.45
0.62
0.78
0.85
0.77
0.61
0.69
0.82
0.73
1.00
Sr
0.28
0.46
0.82
0.75
0.79
0.69
0.70
0.87
0.80
0.71
1.00
Zn
0.34
0.58
0.96
0.97
0.95
0.81
0.85
0.90
0.90
0.83
0.78
1.00
Following with the PCA of the soil samples, Fig.
5
represents the scores of the
two first principal components which explain 79% of the total variance (PC1, 65%;
PC2, 14%). In this case, concentrations of only rare earth elements and alkaline
metals have been taken into consideration. Samples from the west roadside of the
secondary road (SR L) and from the highway (H 0.5, H 3 and H 6) forms two
different groups. A third group is formed by samples from the east roadside of the
secondary road (SR R), further samples from the highway (H 9) and control soils.
Correlation analysis of the metal concentrations reveals two groups of metals
showing high correlations among them (Table
2
). A first group is formed by Hf and
Zr, meanwhile the rest of metals (Cd, Cu, Mo, Nb, Ni, Pb, Sb, Sn, Sr and Zn)
remains in another group.