Q- Q plot (Zn)
4.3 Multivariate Statistics
4.3.3 Cluster Analysis: Agglomerative Hierarchical Clustering
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This suggested high similarities between the locations, but due to locational, geological and concentration there were some differences too. There seem to be a consistent trend in the correlation between the metal elements concentrations in soil of waste disposal site.
Figure 4.8 and Figure 4.9 illustrated the correlation between the observation locations and the biplots, respectively, for the metal elements variables in rainy season. These plots showed positive correlations between the variables, observations and all areas with positive correlation (Olawoyin et al., 2012).
Based on the results of PCA for metal elements in dry season, it can be decided that the metal elements of Cu, Hg, Mn, Pb, and Zn derived from natural sources as they were closed to PC2, whereas, Al, As, Ba, Ca, Cd, Co, Fe, K, Na, Ni, Sb, Sc, Sr, Ti and V were also derived from anthropogenic activities because they were closed to PC1. Nevertheless, the metal element of Cr also derived from both natural soil parent materials and anthropogenic sources. In context of rainy season, the PCA results demonstrated that metal elements of As, Cr, Hg, K, Mn and Na were derived from different sources as the location of these metal elements were distinct from other metal elements of Al, Ba, Ca, Co, Cu, Fe, Ni, Sb, Sc, Sr, Ti and V. Moreover, it can be estimated as the metal elements of Al, Ba, Ca, Co, Cu, Fe, Ni, Sb, Sc, Sr, Ti and V were derived from anthropogenic activities and As, Cr, Hg, K, Na and Mn were derived from natural parent materials. Other metal elements of Cd, Pb and Zn were derived from both natural parent materials and anthropogenic sources.
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metal elements exhibited smallest distance indicated generation from both the natural and anthropogenic activities; whereas the largest maximum distance to centroid indicated the possible pollutant generation source is natural parent material, while comparative smaller value indicated pollutant due to anthropogenic activities.
(a)
(b)
Figure 4.10: Dendrogram for metal elements in soil during (a) dry and (b) rainy season.
Mn Pb Hg Cu Zn Cr Na Fe K Cd V Sb Sr Co Ca Ba Al Ti Sc Ni As
0 5 10 15 20 25 30 35
Dissimilarity
Dendrogram
Mn Hg As Cr Na K Cd Pb Zn Fe Co Ca Sc Al Sr Sb V Ti Ba Cu Ni
0 20 40 60 80 100 120
Dissimilarity
Dendrogram
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In case of dry season, cluster 1 comprises with metal elements of Al, As, Ba, Ca, Cd, Co, Fe, K, Na, Ni, Sb, Sc, Sr, Ti and V in soil which indicated these metal elements were generated from anthropogenic activities . In addition, cluster 2 comprises with Cu, Hg, Mn, Pb, and Zn, indicating origination from natural sources and Cluster 3 comprises with Cr which derived from both the natural parent materials and anthropogenic sources. Table 4.9 and Table 4.10 showed the results of cluster analysis by class for both the dry and rainy season, respectively.
Table 4.9: Results of cluster analysis for dry season
Class 1 2 3
Objects 15 5 1
Sum of weights 15 5 1
Within-class variance 4511.6859 18600.6792 0.0000
Minimum distance to centroid 24.7282 91.2381 0.0000
Average distance to centroid 58.8082 118.9985 0.0000
Maximum distance to centroid 122.5230 170.2796 0.0000
Fe, Ni, Cd, As, Co, Na, K, Ca, Al,Ti, Sb, Sc, Sr, V, Ba
Mn, Cu, Pb
Zn, Hg Cr
In this study, maximum distance to centroid was found for cluster 2 of 170.279 between three clusters, indicating generation of metal elements from natural sources (Table 4.9).
Moreover, maximum distance to centroid for cluster 1 was found comparatively smaller of 122.5230 than that of cluster 2, indicating generation of metal elements from anthropogenic or human activities. Cluster 3 showed maximum distance to centroid was zero, indicating it was closed to both the clusters, consequently generated from both natural sources and anthropogenic activities. In addition, for rainy season, cluster 1 comprises with metal elements of Al, Ba, Ca, Co, Cu, Fe, Ni, Sb, Sc, Sr, Ti and V which indicated these metal elements were generated from anthropogenic activities (Figure 4.10).
Cluster 2 comprises with As, Cr, Hg, Mn, K and Na indicating origination from natural sources and Cluster 3 comprises with Cd, Pb and Zn which derived from both natural parent materials and anthropogenic sources.
Maximum distance to centroid cluster 2 was found as 148.207 between three clusters, indicating generation of metal elements from natural sources. The maximum distance to centroid was found to be smaller for cluster 1 (89.064) than that of cluster 2 (148.2072), indicating generation of metal elements from anthropogenic activities. Cluster 3 showed
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maximum distances to centroid was smaller (64.249) than that of cluster 1 and 2, indicating it was closed to both classes, consequently generated from both natural and anthropogenic sources (Table 4.10).
Table 4.10: Results of cluster analysis for rainy season
Class 1 2 3
Objects 12 6 3
Sum of weights 12 6 3
Within-class variance 3042.8452 12931.7509 4559.6888
Minimum distance to centroid 25.5419 66.0451 41.0257
Average distance to centroid 48.7729 99.0971 54.2642
Maximum distance to centroid 89.0645 148.2072 64.2498
Fe, Cu, Ni, Co, Ca, Al, Ti, Sb, Sc, Sr, V, Ba
Mn, Cr, As,
Hg, Na, K Pb, Zn, Cd Based on AHC results for dry season, it can be decided that the metal elements of Cu, Hg, Mn, Pb, and Zn in soil derived from natural sources, whereas Al, As, Ba, Ca, Cd, Co, Fe, K, Na, Ni, Sb, Sc, Sr, Ti and V in soil were also derived from anthropogenic activities and Cr also derived from both natural soil parent materials and anthropogenic sources. In context of rainy season, the AHC results demonstrated that metal elements of As, Cr, Hg, K, Mn and Na in soil were derived from different sources as the location of these metal elements were distinct from other metal elements of Al, Ba, Ca, Co, Cu, Fe, Ni, Sb, Sc, Sr, Ti and V. Moreover, it can be estimated as the metal elements of Al, Ba, Ca, Co, Cu, Fe, Ni, Sb, Sc, Sr, Ti and V were derived from anthropogenic activities and As, Cr, Hg, K, Na and Mn were derived from natural soil parent materials. Other metal elements of Cd, Pb and Zn were derived from both natural parent materials and anthropogenic sources.