5.4 Heavy mineral, provenance and distribution along the river
5.4.2 Mineralogical composition
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Table 5.21: Data of Heavy Minerals showing Z, T, R and ZTR index SAMPLE
LOCATIONS (Z) (T) (R) (S) (Si) (G) (A) (E) (Op) Non-opaque
ZTR index (%)
IGBOHO 7 4 5 10 1 2 0 2 94 31 51.61
SEPETERI 4 6 9 9 1 1 0 2 91 32 59.38
OJUBO SANGO 4 3 7 12 1 2 2 1 86 32 43.75
ODO-OGUN (OYO
WEST) 6 4 7 11 2 1 0 3 69 34 50.00
LASUPO 7 4 5 14 1 1 3 2 94 37 43.24
IDI-ATA 5 6 9 9 1 2 1 2 72 35 57.14
OLOPADE 6 6 12 10 1 1 3 2 88 41 58.54
OLOKEMEJI 6 9 8 9 1 2 1 2 89 38 60.53
EKERIN 6 9 8 11 2 2 3 2 79 43 53.49
OPEJI 6 4 6 10 1 2 1 1 88 31 51.61
LERIN 6 4 6 10 2 2 0 2 88 32 50.00
AGO-ODO 4 6 7 14 1 2 2 2 84 38 44.74
SOKORI 4 3 7 11 2 2 0 2 114 31 45.16
ADIGBE 7 4 5 10 1 2 1 1 114 31 51.61
MILE 8(OBA) 6 4 12 14 2 1 3 2 77 44 50.00
ABATA 4 6 9 8 0 2 0 1 84 30 63.33
OWERE 5 6 9 12 2 1 2 1 74 38 52.63
OGUNPA WASIMI 6 6 12 10 2 1 3 3 88 43 55.81
IRO 6 4 7 10 1 1 1 2 72 32 53.13
MAGBON 7 4 5 10 1 2 1 2 77 32 50.00
ILATE 6 4 12 12 2 1 0 1 88 38 57.89
OBA OSENI 4 3 7 11 1 2 0 2 76 30 46.67
IBARAGUN 5 6 9 10 1 1 1 1 74 34 58.82
ORUDU 6 4 12 12 1 1 0 1 93 37 59.46
MAIDAN 6 9 8 11 1 2 0 1 89 38 60.53
IGAUN 4 6 7 10 1 2
2 2 68 32 53.13
AKUTE 5 6 9 9 1 1 1 1 86 33 60.61
KARA 4 6 7 14 2 2 2 1 76 38 44.74
MILE 12-MAIDAN 6 4 7 10 1 2
2 3 69 33 51.52
TOWOLO 6 4 6 10 0 1 1 2 74 30 53.33
AGBARIWU 6 4 7 10 1 1 1 1 93 31 54.84
APA OSA 4 6 9 8 1 2 0 1 89 31 61.29
TOTAL 174 164 255 341 39 50 33 54 2697 1110 1708.52
*Note: (Z)-Zircon, (T)-Tourmaline, (R)-Rutile, (S)-Staurolite, (A)-Apatite, (G)-Garnet, (E)-Epidote, (Si)-Sillimanite and (Op)-Opaque.
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Table 5.22: Composition of Sediments based on visual estimates in percentage (Modal Analysis)
SAMPLE LOCATIONS
Quatrz Feldspar Rock fragment
Cement Matrix Mica
IGBOHO 60 15 5 2 3 5
SEPETERI 58 8 18 7 3 4
OJUBO SANGO 55 10 11 10 4 7
ODO-OGUN (OYO WEST)
45 10 20 10 8 8
LASUPO 60 15 5 2 3 5
IDI-ATA 60 11 14 5 2 5
OLOPADE 60 12 15 5 2 3
OLOKEMEJI 52 20 8 10 4 3
EKERIN 52 20 8 10 4 3
OPEJI 45 15 20 8 7 5
LERIN 45 15 20 8 7 5
AGO-ODO 60 15 10 5 2 5
SOKORI 55 10 11 10 4 7
ADIGBE 60 15 5 2 3 5
MILE 8(OBA) 60 12 15 5 3 5
ABATA 58 8 18 7 3 4
OWERE 60 11 14 5 2 5
OGUNPA WASIMI 60 12 15 5 2 3
IRO 45 10 20 10 8 8
MAGBON 60 15 5 2 3 5
ILATE 60 12 15 5 3 5
OBA OSENI 55 10 11 10 4 7
IBARAGUN 60 11 14 5 2 5
ORUDU 60 12 15 5 3 5
MAIDAN 52 20 8 10 4 3
IGAUN 60 15 10 5 2 5
AKUTE 60 11 14 5 2 5
KARA 60 15 10 5 2 5
MILE 12-MAIDAN 45 10 20 10 8 8
TOWOLO 45 15 20 8 7 5
AGBARIWU 45 10 20 10 8 8
APA OSA 58 8 18 7 3 4
Average 55.31 12.75 13.50 6.66 3.91 5.16
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Table 5.23 Calculated percentage composition of QFL in the sediments SAMPLE LOCATIONS
Quartz (Q)%
Feldspar (F)
%
Rock fragment (L) %
Mineral maturity index
= (Q/F+L)
IGBOHO 75 18.8 6.3 2.99
SEPETERI 69 9.5 21.4 2.23
OJUBO SANGO 72 13 14.5 2.62
ODO-OGUN (OYO WEST)
60 13.3 26.7 1.5
LASUPO 75 18.8 6.3 2.99
IDI-ATA 70.6 12.9 16.5 2.4
OLOPADE 69 14 17 2.23
OLOKEMEJI 65 25 10 1.86
EKERIN 65 25 10 1.86
OPEJI 56.3 18.8 25 1.29
LERIN 56.3 18.8 25 1.29
AGO-ODO 70.6 17.6 11.8 2.4
SOKORI 72 13 14.5 2.62
ADIGBE 75 18.8 6.3 2.99
MILE 8(OBA) 69 13.8 17.2 2.23
ABATA 69 9.5 21.4 2.23
OWERE 75 18.8 6.3 2.99
OGUNPA WASIMI 69 14 17 2.23
IRO 60 13.3 26.7 1.5
MAGBON 75 18.8 6.3 2.99
ILATE 69 13.8 17.2 2.23
OBA OSENI 72 13 14.5 2.62
IBARAGUN 70.6 12.9 16.5 2.4
ORUDU 69 13.8 17.2 2.23
MAIDAN 65 25 10 1.86
IGAUN 70.6 17.6 11.8 2.4
AKUTE 70.6 12.9 16.5 2.4
KARA 70.6 17.6 11.8 2.4
MILE 12-MAIDAN 60 13.3 26.7 1.5
TOWOLO 56.3 18.8 25 1.29
AGBARIWU 60 13.3 26.7 1.5
APA OSA 69 9.5 21.4 2.23
Min 1.29
Max 2.99
Average (%) 2.203125
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CHAPTER SIX
DISCUSSIONS AND CONCLUSIONS
6.1 Activity Concentrations of 40K, 226R and 232Th for the Upper, Middle And Lower Regions of Ogun River.
Comparing the activity concentrations values of the radionuclides in the upper, middle and lower regions of the river, Figures 6.1 (a-c) (Tables 5.1-5.3), 40K was highest at the upper region of the river with the (regional) weighted mean activity concentration value of 519.3 ± 48.7 Bq/kg, followed by the value in the lower region 500.8 ± 58.2 Bq/kg and lastly the value in the middle region was 483.8 ± 68.8 Bq/kg. The values of the activity concentrations of 40 K in the three regions ranged from 186.6 16.55 Bq/kg to 732.2 63.6 Bq/kg in the upper region, ranged between 214.2 19.19 Bq/kg and 783.7 37.77 Bq/kg in the middle region and between 278.1 24.5 Bq/kg and 697.1 60.2 Bq/kg in the lower region of Ogun river.
The average concentrations of 40K in some locations had values greater than the world‘s average of 500Bq/kg (Ramasamy et al., 2009), but none of the location had its value of 232Th or 226Ra greater than the world‘s average of 50Bq/kg (Ramasamy et al., 2009).
Figure 6.2a showed the surface interpolations of 40K concentrations down the river. The activity concentrations of 226 Ra in the three regions of the river varied from 3.2 0.18 – 20.4 2.44 Bq/kg, BDL to 27.2 3.79 Bq/kg and BDL to 29.9 4.64 Bq/kg in the upper, middle and lower regions respectively. Figure 6.2b showed the surface interpolations of
226Ra concentrations down the river. The regional mean values of 226 Ra were 11.96 ± 1.7, 12.01 ± 4.5 and 13.2 ± 3.4 Bq/kg, for the upper, middle and lower regions respectively. The regional mean value of the middle region and that of the upper region were approximately the same. The activity concentrations of 232Th in the upper, middle and lower regions varied between 2.8 0.78 and 13.8 1.24, BDL and 31.5 6.04 and BDL and 31.4 1.33 Bq/kg respectively. The regional mean values of 232Th were 9.2 ± 0.6 Bq/kg, 10.4 ± 5.0 Bq/kg and 13.4 ± 5.6 Bq/kg, in the upper, middle and lower regions respectively. It was observed that the regional mean values for the concentration of 232Th was increasing down the river.
Figure 6.2c showed the surface interpolations of 232Th concentrations down the river.
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For the whole of Ogun river, the activity concentrations of 40K, ranged from 186.6 16.55 Bq/kg at Igboho to 783.7 37.77 Bq/kg at Olopade, for 226Ra, Ekerin and Maidan had the least values that were below detection limits and Ogunpa Wasimi had the highest value of 29.9 ± 4.64 Bq/kg, in this particular location, the activity concentration of 226Ra was relatively high compared to the values obtained from the remaining locations, which may be due to geochemical processes around the area ( Ricardo et al., 2009). The sediments in this area could be chemical sediments formed from dissolved materials derived from weathering which are precipitated from water streams, lakes or even river accumulations. For 232Th, Mile 12- Maidan,Magbon, Opeji, Ekerin and Olokemeji had the least values which are below detection limits of the machine while Sokori had the highest value of 31.5 ± 6.04Bq/kg. Sokori is in Abeokuta, Ogun state and perhaps that is one of the reasons for the little rise in value of 232Th and 226Ra, compared with other locations, as it had been reported that Abeokuta is one of the places with high natural radioactity in Nigeria (Farai and Jibiri, 2000). The overall mean of the activity concentrations of 40K for the sediments collected was 499.5 ± 59.2 Bq/kg, for 226Ra, the value was 12.7 ± 3.5 Bq/kg and for 232Th the value was 11.8 ± 5.1 Bq/kg. The value of 40K was about the world‘s average value of 500 Bq/kg, while the values of 226 Ra and 232Th were less than the world‘s average value of 50Bq/kg (Ramasamy et al., 2009). Granite rocks are commonly known to have high level of 40K concentrations. Looking at the trend of 40K especially in the upper region, the value was increasing from Idi- Ata upwards. The increasing trend of 40K in this region may be due to the presence of loamy and clay sediments (El-Gamal et al., 2007), or perhaps, the loamy and clay contents in the sediments in this region were decreasing down the region.
Comparing the results obtained from this study with the results from other studies in Nigeria, and areas in the world, Table 6.1, it was observed that the values of 226Ra and 232Th of Ogun river sediments were lower compared with the values obtained from the twenty dams and Ondo river sediments, but relatively fall within the same range with Osun river sediments in Nigeria. For the value of 40K, the value for Ogun river was higher than that of Osun river, lower than the sediments from the twenty dams and compared relatively well with the Ondo river sediments. Also from the Table, it could be seen that the activity concentrations of the three radionuclides were consistent with values from different parts of the world. Due to this fact, and from the ranges of activity concentrations of the
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Table 6.1: The range and (mean) of activity concentrations of the Radionuclides in Bq/kg estimated by different authors in comparison to the present study.
S/N COUNTRY 40K 226Ra 232Th REFERENCES
1 Turkey 155.7 -868.7 26.8 - 49.8 ** 17.06 - 35.62
Kam and Bozkurt, 2007
2 Egypt (Eastern Desert) 298.6 – 955.8 9.7 – 19.0 10.0 – 17.7 Harb, 2008 3 India (Jaduguda)
396.5 - 513.8
(464.21) 20.1 -120.0 (53.8)
23.8 - 69.9
(44.2) Maharana et al., 2010
4 Bengal 118 - 608 5.9 - 27.9 10.4 - 64.0 Alam et., 1997
5
Bangladeshi (Shango
River) 212- 292 (255)
21.6 - 28.3 (25.4)**
52.4 - 61.7 (57.5)
Chowdhurry et al., 2009
6 India (Kali river)
296.0 - 525.0 (394.7)
34.1 - 49.4
(40.1)** 4.6 - 12.2 (6.9)
Narayana et al., 2007,Isikaye,2009 7 Egypt, Wadi Nugrus, 306.7 -626.0
24.7 - 86.45 (43.91)**
20.3 - 48.72
(26.62) Abdel-Razek(2008)
8 India (Tamilnadu)
201.23 - 467.71
(384.113) BDL - 11.6 (7.31)
BDL - 106.11
(46.85) Ramasamy et al., 2009
9 Egypt, Nile river (351.9) (52) (76.20) Uosif, 2007
10 Kuwait (227) (36) (6)
Saad and Al-Azmi, 2002
11 Algeria (Algiers Bay) 56 - 607 (374)
4.45 - 25.04
(15.8)** 6.5 - 31.7 (19.5)
Benemar et al., 1997, Isikaye, 2009 12 China (Wei River)
514.8 - 1175.5
(833.3) 10.4 - 39.9 (21.8)
15.3 - 54.8
(33.1) Xinwei et al., 2008
13 Pakistan (647.4) (32.9) (53.6) Matiullah et al., 2004
14
Nigeria, Southwest (Twenty Dams)
191.1 - 1025.9
(549.3) 17.1 -51.9 (27.9)**
26.2 - 130.1
(62.0) Isinkaye, 2009 15
Nigeria, Southwest
(Osun River) 175.6 - 188.5 13.1 -28.4 ** 11.4 - 16.3 Oyebanjo, 2010 16
Nigeria, Akoko river,
Ondo 142.57 -839.28 9.40 -52.71 24.87 - 301.14 Ajayi, 2008
17
Nigeria, Southwest (Ogun River)
186.6 - 783.7
(499.5) BDL - 29.9 (12.7)
BDL - 31.5
(11.8) Present Study
*- 228Ra, **238U ( ), = mean concentration
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Fig 6.1a Chart of the average values of the three radionuclides in each location from Upper region of the river
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Fig 6.1b Chart of the average values of the three radionuclides in each location from middle region of the river
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Fig 6.1c Chart of the average values of the three radionuclides in each location from lower region of the river
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IRO
KARA ABATA
OWERE
ILATE
IGAUN AKUTE ORUDU
OPEJI
SOKORI ADIGBE
MAGBON
MAIDAN TOWOLO
EKERIN LASUPO
MILE 12 OLOPADE
IBARAGUN
AGBARIWU AGO -ODO
IDI -ATA (IGBOHO)
OLOKEMEJI ODO -OGUN
AGO FULANI
OBA - OSENI
OJUBO SANGO
(MILE 8) OBA LERIN-MAWUKO
ODO-OGUN O-W
OGUNPA WASIMI
SEPETERI (SE)
MAIDAN-AGILITI APA (OSA)
Th 232 4.98 - 6.98 6.98 - 8.99 8.99 - 11 11 - 13.01 13.01 - 15.01 15.01 - 17.02 17.02 - 19.03 19.03 - 21.04 21.04 - 23.04
N
E W
S
IRO
KARA ABATA
OWERE
ILATE
IGAUN AKUTE ORUDU
OPEJI
SOKORI ADIGBE
MAGBON
MAIDAN TOWOLO
EKERIN LASUPO
MILE 12 OLOPADE
IBARAGUN
AGBARIWU AGO -ODO
IDI -ATA (IGBOHO)
OLOKEMEJI ODO -OGUN
AGO FULANI
OBA - OSENI
OJUBO SANGO
(MILE 8) OBA LERIN-MAWUKO
ODO-OGUN O-W
OGUNPA WASIMI SEPETERI (SE)
MAIDAN-AGILITI APA (OSA)
K-40 352.03 - 380.43 380.43 - 408.82 408.82 - 437.21 437.21 - 465.6 465.6 - 493.99 493.99 - 522.39 522.39 - 550.78 550.78 - 579.17 579.17 - 607.56
N
E W
S
IRO
KARA ABATA
OWERE
ILATE
IGAUN AKUTE ORUDU
OPEJI
SOKORI ADIGBE
MAGBON
MAIDAN TOWOLO
EKERIN LASUPO
MILE 12 OLOPADE
IBARAGUN
AGBARIWU AGO -ODO
IDI -ATA (IGBOHO)
OLOKEMEJI ODO -OGUN
AGO FULANI
OBA - OSENI
OJUBO SANGO
(MILE 8) OBA LERIN-MAWUKO
ODO-OGUN O-W
OGUNPA WASIMI
SEPETERI (SE)
MAIDAN-AGILITI APA (OSA)
U-238 5.56 - 7.22 7.22 - 8.87 8.87 - 10.53 10.53 - 12.19 12.19 - 13.85 13.85 - 15.5 15.5 - 17.16 17.16 - 18.82 18.82 - 20.47
N
E W
S
Fig. 6.2(a) Fig. 6.2(b) Fig. 6.2 (c)
Fig 6.2(a-c) Surface interpolation plots of the concentrations of each radionuclides
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radionuclides obtained in this study, the activity concentrations of the sediments from Ogun river can be classified under the area with normal background radiation (Isikaye, 2009; Farai and Jibiri, 2000). The along the river ranges observed in this study are within the range of values for crustal concentrations of 140-820 Bq/kg for 40K, 16-110 Bq/kg for 238U and 11-64 Bq/kg for 232Th reported in UNSCEAR (2000) for areas with normal background radiation levels around the world (Isikaye, 2009).
The activity concentrations of natural radionuclides in the study area were in agreement with the global trend on the distribution of natural radionuclides in sediments. The variations observed in the different location could be attributed partly to drainage pattern of the study area. The foliation and joints on these rocks control the course of the rivers, causing them to form a trellis drainage pattern, particularly to the north of the area. Apart from these natural processes, human activities such as agricultural practices in which fertilizers are applied to improve crop yield had been known to contribute to the variations of activity concentrations of natural radionuclides.