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6.3 Statistical test on concentrations of the radionuclides

6.3.3 Pearson correlation analysis between the concentrations

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have accumulated in ionic and particulate form from agricultural drains and also as the drifted pariculates from long shore currents and accredition processes.

6.3.3 Pearson Correlation Analysis between the Concentrations of Radionuclides,

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The indoor gamma dose rates significantly correated positively with 40K (0.89) at 0.05 level of significance, showed strong positive significant correlations with radium equivalence (1.00) at 0.01 level, strong positive significant correlations with representative gamma index (1.00) at 0.01 level of significance, had strong positive significant correlations with external hazard index (1.00) at 0.01 level of significance and had perfect positive significant correlations with indoor effective dose rates (1.00) at 0.01 level of significance.

The indoor effective gamma dose rate had the same relationship that the indoor gamma dose rate had as discussed above only that it correlated perfectly (1.00) at0.01 level of confidence with the indoor gamma dose rate.

The representative gamma index correlated with 40K (0.87) at0.05, radium equivalent (0.99) at 0.01, indoor gamma dose (1.00) at0.01, indoor effective dose (1.00) at0.01 amd external hazard index (0.99) at0.01 level of significant.

In the upper region of the river, excess lifetime cancer risk and the internal hazard index did not have any significant correlation with any of the parameters considered at the level of significance.

The external hazard index showed strong positive significant relationship with indoor gamma dose rate (1.00) at 0.01 confidence limit, showed strong positive significant correlation with indoor effective dose rates (1.00) at0.01significant level, strong positive correlation with representative gamma index (0.99) at 0.01 level and perfect positive correlation with the radium equivalent (1.00) at0.01 level of significance.

In the middle region, from Table 6.7, the Pearson correlation analysis to determine the inter – relation between the measured parameters showed that 40K did not correlate with any of the measured parameters considered at the levels of significance. 226Ra correlated positively (0.71) at 0.05 level of confidence with 232Th, 226Ra also showed positive significant correlation (0.80) at 0.05 with indoor hazard index . 232Th showed positive significant correlation with all the parameters considered except 40K.

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Table 6.6: Pearson Correlation Matrix of Measured Parameters In Upper Ogun River

40K 226Ra 232Th

Ra Equiv.

Indoor Gamma

In.

Effect.

Repr.

Gamma ELCR Ext.

Hazard Int.

Hazard

40K 1 -0.24 0.04 0.81 0.86* 0.86* 0.87* -0.14 0.81 -0.52

Ra226 -0.24 1 0.64 0.35 0.28 0.28 0.24 0.64 0.35 0.60

232Th 0.04 0.64 1 0.53 0.47 0.47 0.45 0.34 0.53 0.57

Ra Equiv. 0.81 0.35 0.53 1 1.00** 1.00** 0.99** 0.17 1.00** -0.09 Indoor

Gamma 0.86* 0.28 0.47 1.00** 1 1.00** 1.00** 0.14 1.00** -0.16 In. Effect. 0.86* 0.28 0.47 1.00** 1.00** 1 1.00** 0.14 1.00** -0.16 Repr.

Gamma 0.87* 0.24 0.45 0.99** 1.00** 1.00** 1 0.12 0.99** -0.18

ELCR -0.14 0.64 0.34 0.17 0.14 0.14 0.12 1 0.19 0.27

Ext. Hazard 0.81 0.35 0.53 1.00** 1.00** 1.00** 0.99** 0.19 1 -0.09 Int. Hazard -0.52 0.60 0.57 -0.09 -0.16 -0.16 -0.18 0.27 -0.09 1

*. Correlation is significant at the 0.05 level (2-tailed).

**. Correlation is significant at the 0.01 level (2-tailed).

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Table 6.7 Pearson Correlation matrix of Measured Parameters In middle Ogun River

40K 226Ra 232Th

Ra Equiv.

Indoor Gamma

In.

Effect.

Repr.

Gamma ELCR

Ext.

Hazard Int.

Hazard

40K 1 -0.55 -0.05 0.23 0.28 0.33 0.35 0.33 0.23 0.05

226Ra -0.55 1 0.71* 0.62 0.58 0.55 0.52 0.55 0.62 0.80*

232Th -0.05 0.71* 1 0.94** 0.92** 0.90** 0.90** 0.90** 0.94** 0.95**

Ra Equiv. 0.23 0.62 0.94** 1 0.99** 1.00** 0.99** 1.00** 1.00** 0.97**

Indoor

Gamma 0.28 0.58 0.92** 0.99** 1 0.99** 0.99** 0.99** 0.99** 0.95**

In. Effect. 0.33 0.55 0.90** 1.00** 0.99** 1 1.00** 1.00** 1.00** 0.94**

Repr.

Gamma 0.35 0.52 0.90** 0.99** 0.99** 1.00** 1 1.00** 0.99** 0.93**

ELCR 0.33 0.55 0.90** 1.00** 0.99** 1.00* 1.00** 1 1.00** 0.94**

Ext.

Hazard 0.23 0.62 0.94** 1.00** 0.99** 1.00** 0.99** 1.00** 1 0.97**

Int. Hazard 0.05 0.80* 0.95** 0.97** 0.95** 0.94** 0.93** 0.94** 0.97** 1

*. Correlation is significant at the 0.05 level (2-tailed).

**. Correlation is significant at the 0.01 level (2-tailed).

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Radium equivalent activity showed strong positve significant correlations (0.94) with

232Th, strong positve significant correlations (0.94) with indoor gamma dose rates, strong positve significant correlations (0.99) with representatative gamma index, positve significant correlations (1.00) with ELCR, perfect positve significant correlations (1.00) with the external hazard index, all at the 0.01significant level, but did not correlate significantly with40K and 226Ra. The indoor gamma dose rates showed positive significant correlations with all the parameters considered except with 40Kand 226 Ra. The correlation coefficients were between (0.82) and (1.00), all at 0.01 level of significance. The indoor effective dose rates showed positive significant correlations with all the parameters considered except with

40Kand 226 Ra. The correlation coefficients were between (0.09) and (1.00) ELCR, all at 0.01 level of significance. The representative gamma index showed positive significant correlations with all the parameters considered except with 40Kand 226 Ra. The correlation coefficients were between (0.99) and (1.00) ELCR, all at 0.01 level of significance. ELCR strong positve significant correlations (0.90) with 232Th, strong positve significant correlations (0.995) with radium equivalent, strong positve significant correlations (0.99) with indoor gamma dose rates, perfect positve significant correlations (1.00) with indoor effective gamma dose rates, perfect positve significant correlations (1.00) with representative gamma index, strong positve significant correlations (1.00) with external hazard index and showed strong positve significant correlations (0.94) with internal hazard index. All at 0.01 level of significance. ELCR did not correlate with 40K and 226Ra, at the level of significance considered.

For the inter relation between external hazard index and other parameters, it was observed that there was strong positve significant correlations (1.00) with 232Th, perfect positve significant correlations (1.00) with radium equivalent activity, strong positve significant correlations (0.99) with indoor gamma dose rates, strong positve significant correlations (1.00) with indoor effective dose rates, strong positve significant correlations (0.99) with representative gamma index, strong positve significant correlations (1.00) with ELCR and strong positve significant correlations (0.97) with internal hazard index, all at 0.01 level of significant level. There was no significant correlations between 40K and 226Ra.

Implying that where there were high concentration values of 40K might not necessary imply high concentration value of 226Ra.

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For the correlations between internal hazard index and other parameters. It was observed that there was positive significant correlation between internal hazard index and

226Ra (0.80) strong positve significant correlations (0.95) with 232Th, strong positve significant correlations (0.97) with radium equivalent activity, strong positve significant correlations (0.95) with indoor gamma dose rates, strong positve significant correlations (0.94) with indoor effective dose rates, strong positve significant correlations (0.93) with representative gamma index, strong positve significant correlations (0.94) with ELCR and strong positve significant correlations (0.97) with external hazard index, all at 0.01 level of significant level. There was no significant correlations between 40K and 226Ra. Only 40 K did not correlate with any of the parameters considered.

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Table 6.8: Pearson Correlation Matrix of Measured Parameters In lower Ogun River

40-K Ra-226 Th-232 Ra Equiv.

Indoor Gamma

In.

Effect.

Repr.

Gamma ELCR

Ext.

Hazard Int.

Hazard

40-K 1 0.08 0.05 0.44 0.52* 0.52* 0.51* 0.45 0.44 0.15

Ra-226 0.08 1 0.66** 0.77** 0.76** 0.76** 0.74** 0.74** 0.77** 0.78**

Th-232 0.05 0.66** 1 0.89** 0.85** 0.85** 0.86** 0.85** 0.89** 0.80**

Ra Equiv. 0.44 0.77** 0.89** 1 1.00** 1.00** 1.00** 0.96** 1.00** 0.83**

Indoor

Gamma 0.52* 0.76** 0.85** 1.00** 1 1.00** 1.00* 0.96** 1.00** 0.81**

In. Effect. 0.52* 0.76** 0.85** 1.00** 1.00** 1 1.00** 0.96** 1.00** 0.81**

Repr.

Gamma 0.51* 0.74** 0.86** 1.00** 1.00** 1.00** 1 0.96** 1.00** 0.80**

ELCR 0.45 0.74** 0.85** 0.96** 0.96** 0.96** 0.96** 1 0.96** 0.79**

Ext. Hazard 0.44 0.77** 0.89** 1.00** 1.00** 1.00** 1.00** 0.96** 1 0.83**

Int. Hazard 0.15 0.78** 0.80** 0.83** 0.81** 0.81** 0.80** 0.79** 0.83** 1

*. Correlation is significant at the 0.05 level (2-tailed).

**. Correlation is significant at the 0.01 level (2-tailed).

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For the inter relationship in the lower region of the river, it was observed from Table 6.8 that

40K positively correlated significantly although weakly (0.52) with indoor gamma dose rate, weakly (0.52) with indoor effective dose rates and also weakly(0.51) with representative gamma index at the 0.05 level of significance. 226Ra showed fair positve significant correlations with all the parameters considered, except with 40K, all at 0.01 level of significance. Their correlation coefficience ranged between 0.66 (232Th) and 0.78 (internal hazard).

232Th showed positve significant correlations with all the parameters considered, except with

40K, all at 0.01 level of significance. Their correlation coefficience ranged between 0.66 (226 Ra) and 0.89 (Radium equivalent and external hazard index).

Radium equivalent showed positve significant correlations with all the parameters considered, except with 40K, all at 0.01 level of significance. Indoor gamma dose rates, indoor effective dose rates ELCR and representative gamma index showed strong positive significant correlations.The correlation coefficience ranged between 0.77 (226Ra) and1.000 (external hazard index). For the inter relation between indoor gamma dose rates and other parameters It was observed that there was inter- relationships between it and all the parameters. strong positve significant correlations (1.00) with radium equivalent, strong positve significant correlations (1.00) with representative gamma index, strong positve significant correlations (0.96) with ELCR, strong positve significant correlations (1.00) with external hazard index, positve significant correlations (0.85) with 232Th, positve significant correlations (0.81) with internal hazard index, positve significant correlations (0.76) with

226Ra, weak but positive significant correlation (0.52) with 40K and perfect positve significant correlations with indoor hazards index, all at 0.01 level of significance.

Indoor effective dose rates showed positve significant correlations with all the parameters considered, all at 0.01 level of significance. Their correlation coefficience ranged between 0.52 (40K) and 1.00 (indoor gamma dose rates). Representative gamma index showed positve significant correlations with all the parameters considered, all at 0.01 level of significance. Their correlation coefficience ranged between 0.510 (40K) and1.00 (indoor gamma dose and indoor effective dose). ELCR showed positve significant correlations with all the parameters considered, except with 40K, all at 0.01 level of significance. Their correlation coefficience ranged between 0.74 (226Ra) and 0.96 (radium equivalent and

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external hazard index). All at 0.01 level of significance. External hazards index showed positve significant correlations with all the parameters considered, except with 40K, all at 0.01 level of significance. Their correlation coefficience ranged between 0.77 (226Ra) and 1.000 (radium equivalent). All at 0.01 level of significance. Indoor gamma dose rates, indoor effective dose rates, representative gamma index and ELCR, all had strong correlation with external hazards index in the lower region.

Indoor hazards index showed positve significant correlations with all the parameters considered, except with 40K, all at 0.01 level of significance. Their correlation coefficience ranged between 0.78 (226Ra) and 0.83 (radium equivalent and external hazard index). All at 0.01 level of significance. Buttressing the location effect result, looking specifically at the inter-relationship of the natural radionuclides‘ concentration with one another, using Pearson correlation analysis, it could be seen that, in the middle and lower regions 232Th most especially correlated well with 226Ra, but 40K did not correlate with any of the two. Showing that 232Th had most significant effect and 226Ra also had weak effect in the regions. In the upper region, the relationship between the concentrations of the three radionuclides falls within linear correlations (r < 0.3) and moderate (r between 0.5 and 0.7), which did not give a strong inter- relationship. For the middle region, the relationship between the concentrations of the three radionuclides falls within linear correlations (r < 0.3) and moderate as well, but 232Th and 226Ra related significantly although not too obvious. This implies that the presence of one may enhance the other in an area and also enhances any parameter that depends on either of them. Lastly, the lower region has same relationship as the middle.

6.3.4 Cluster Analysis of the Radionuclides Distribution in Ogun River

Cluster analysis is one of the multivariate techniques used to identify and classify groups with similar radiometric character in a new group of observations (Nasr et al., 2006:

IAEA, 2003). Each observation in a cluster is mostly like others in the same cluster. Cluster analysis, (single linkage, using the method of Euclidean distances- nearest neighbour was applied to the sample activity concentrations (40K, 226Ra and 232Th), using Windows 16.0 software in the light of identifying locations with similar characters. Figure 6.9a-c showed

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40 –K Dendrogram using Single Linkage

Rescaled Distance Cluster Combine

C A S E 0 5 10 15 20 25 Label Num +---+---+---+---+---+

OPEJI 10 ─┐

TOWOLO 30 ─┤

IDI ATA 6 ─┼─────┐

KARA 28 ─┤ │

SOKORI 13 ─┤ ├───────┐

AGBARIWU 31 ─┘ │ │ OLOKEMEJI 8 ─┐ │ │ ADIGBE 14 ─┼─────┘ │ ABATA 16 ─┘ │

LASUPO 5 ─┐ ├───────┐

MAGBON 20 ─┤ │ │ ODO OGUN (OYO W 4 ─┤ │ │ MAIDAN 25 ─┤ │ │ OJUBO SANGO 3 ─┤ │ │ ILATE 21 ─┼─────────────┘ │ IBARAGUN 23 ─┤ │

ORUDU 24 ─┤ ├─────────────────────────┐

EKERIN 9 ─┤ │ │ MILE 12- 29 ─┤ │ │ OBA OSEN 22 ─┘ │ │ AGO ODO 12 ─┬─┐ │ │ IRO 19 ─┘ │ │ │ SEPETERI 2 ─┐ ├─────┐ │ │ LERIN 11 ─┼─┤ │ │ │ AKUTE 27 ─┘ │ ├─────────────┘ │ OGUNPA W 18 ───┘ │ │ OWERE 17 ─┬─────┐ │ │ APA OSA 32 ─┘ ├─┘ │ IGBOHO 1 ─┬─────┘ │ MILE (8) OBA 15 ─┘ │ OLOPADE 7 ─────────────────┬───────────────────────────────┘

IGAUN 26 ─────────────────┘

Fig. 6.9a: Dendrogram for classifying sample locations as groups according to the concentrations of 40 K in the sediments from Ogun river.

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Th-232

C A S E 0 5 10 15 20 25

Label Num +---+---+---+---+---+

MILE (8) OBA 15 ─┐

IGAUN 26 ─┼───┐

IBARAGUN 23 ─┘ │ ADIGBE 14 ───┬─┤

OWERE 17 ───┘ │ OJUBO SANGO 3 ─┐ │ LASUPO 5 ─┤ ├─┐

APA OSA 32 ─┤ │ │ ODO OGUN (OYO W 4 ─┤ │ │ OLOPADE 7 ─┤ │ │ MAIDAN 25 ─┤ │ │ EKERIN 9 ─┼───┘ │ ORUDU 24 ─┤ │

LERIN 11 ─┤ ├─────────────────────────────────────────┐

MAGBON 20 ─┤ │ │ IGBOHO 1 ─┤ │ │ SEPETERI 2 ─┤ │ │ AGO ODO 12 ─┤ │ │ IDI ATA 6 ─┤ │ │ OLOKEMEJI 8 ─┘ │ │ KARA 28 ─┬─────┤ │ MILE 12- 29 ─┘ │ │ OPEJI 10 ───────┘ │ TOWOLO 30 ─┬─────┐ │ AGBARIWU 31 ─┘ ├─────────┐ │ ILATE 21 ─┬─────┘ │ │ AKUTE 27 ─┘ ├─────────┐ │ SOKORI 13 ───┬───────────┐ │ │ │ OBA OSEN 22 ───┘ ├─┘ ├─────────────────────┘

ABATA 16 ───────┬───────┘ │ OGUNPA W 18 ───────┘ │ IRO 19 ───────────────────────────┘

Figure 6.9b: Dendrogram for classifying sample locations as groups according to the concentrations of 232Th in the sediments from Ogun river.

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Dendrogram using Single Linkage

Rescaled Distance Cluster Combine

C A S E 0 5 10 15 20 25 Label Num +---+---+---+---+---+

IGBOHO 1 ─┐

LERIN 11 ─┤

OJUBO SANGO 3 ─┤

AGO ODO 12 ─┤

IBARAGUN 23 ─┼─┐

MAIDAN 25 ─┤ │ IDI ATA 6 ─┤ │ ORUDU 24 ─┤ │ OWERE 17 ─┘ │ SEPETERI 2 ───┤

OLOKEMEJI 8 ─┬─┼───────┐

AGBARIWU 31 ─┘ │ │ MILE (8) OBA 15 ─┬─┤ │ KARA 28 ─┘ │ ├─────┐

MILE 12- 29 ───┘ │ │ OPEJI 10 ─┬───┐ │ │ APA OSA 32 ─┘ │ │ │ ABATA 16 ─┬─┐ ├─────┘ │ IGAUN 26 ─┘ │ │ │ LASUPO 5 ─┐ ├─┘ │ OBA OSEN 22 ─┼─┤ │

ODO OGUN (OYO W 4 ─┘ │ ├─────────────────────┐

OLOPADE 7 ─┐ │ │ │ MAGBON 20 ─┼─┤ │ │ ILATE 21 ─┤ │ │ │

TOWOLO 30 ─┤ │ │ ├─────────┐

ADIGBE 14 ─┤ │ │ │ │ AKUTE 27 ─┘ │ │ │ │ IRO 19 ───┘ │ │ │ OGUNPA W 18 ─────────────────┘ │ │ SOKORI 13 ───────────────────────────────────────┘ │ EKERIN 9 ─────────────────────────────────────────────────┘

Figure 6.9c: Dendrogram for classifying sample locations as groups according to the concentrations of 226Ra in the sediments from Ogun river

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dendrogram of classifying sample locations as groups according to the radionuclides concentrations in the sediments from ogun river.

The Cluster analysis was carried out on the concentrations of the radionuclides to identify and classify groups with similar characters in a new group of observations.

The dendrogram was used to give a pictorial representation of the groups having similar characters just like what a contour map will do, connecting parameters of similar values.

Igaun, Iro and Ekerin were observed to exist as unique locations considering the concentrations of 40K, 232Th and 226Ra respectively. From Figure 6.9a, Olopade was classified as a unique location looking at the figure below, this can be, deduced from the relatively high distance at which its cluster was joined perhaps it was due to the fact that Olopade had the least value of 40K in the whole region (370.97 ± 19.26). Igaun too was classified as a unique location on its own, the location was also the second least location with

40K concentration value (393.19± 19.83), although its group was relatively at the forth highest distance and its cluster was not joined to any group.

The closest locations in their characters were Opeji, Towolo, Idi – Ata, Kara, Sokori and Agbariwu in one group. From figure 6.9b, for 232Th, the closest locations in their characters were Mile (8) Oba, Igaun and Ibaragun. Pair of combinations had been identified in the groups, Kara, Mile -12 Maidan, Towolo, Agbariwu, Ilate and Akute. Adigbe, Owere and Sokori, Oba Oseni, also formed Pair of combinations but in a higher order.

Iro exists as a unique location on its own, perhaps because it was the only location having

232Th concentration value of 15.0 ±3.9Bq/kg. From figure 6.9c for 226Ra, the closest locations in their characters were Igboho, Lerin, Ojubo Sango, Ago Odo, Ibaragun, Maidan, Idi – Ata, Orudu and Owere.

Ogunpa Wasimi and Sokori were classified as unique locations, this can be deduced from the relatively high distances at which these clusters were joined. Ekerin was observed to exist as a unique location on its own, perhaps because it had the least value of 226Ra. Olokemeji , Agbariwu, Mile (8) Oba, Kara, Opeji, Apa Osa, Abata, Igaun, all had Pair of combinations and were connected in a higher group. The cluster analysis had been able to show ways of seeing pictorially, relationship within the radionuclides concentrations along the course of Ogun river.