1. ANALYSIS OF HEAVY METALS, MINERALS AND RADIONUCLIDES IN HEAVY SANDS FROM TIVA AND MWITA SYANO RIVERS, KITUI COUNTY By
Koech K. Nehemiah
Supervisors:
1. Mr. David M. Maina
2. Prof. Michael J. Gatari

2. 1.0 Introduction and Research Problems
Rivers are important as they provide water, sands, nutrients, recreation etc.
Kitui region’s rivers are rich in sands.
Sands contain minerals, heavy metals and radionuclides.
Assess the level of heavy metals pollution as well the presence of radionuclides and to quantify the mineral sands present.

3. 2.0 Objectives
To characterize sands from Tiva and Mwita Syano Rivers by:
Identifying and quantifying mineral sands using XRD technique and deduce their economic viability.
Finding the specific activities of radioactive elements and determining the associated gamma-radiation exposure.
Identifying the elemental composition of sands using EDXRF technique and determining the extend of heavy metals pollution.

4. 3.0 Methodology
3.1 map of the sampled area

5. 3.2 Sampling site layout (mineral sands)
About 200 m apart
Site A (mid-river position)
To Left
Site B (mid-river position)
To Right
Up the stream
5 samples collected from 5 sites
5 additional surface-deposit samples
1 km, distance covered
Sampled points

6. 3.3 Sampling site layout (Radionuclides)
50 cm deep
Surface collection (about 0 cm)
Sub-surface collection (about 50 cm deep)
About 200 m between the sampling sites
Left
Center
Right
Up the Stream
36 samples from 6 sampling sites.
1.2 km, distance covered

7. 3.4 Sampling site layout (heavy metals)
50 cm deep
Surface collection (about 0 cm)
Sub-surface collection (about 50 cm) deep
About 200 m between the sampling sites
Left
Center
Right
Up the Stream
100 cm deep
35 samples collected from 5 sites
Additional 4 surface-deposit samples
Deep-surface collection (about 100 cm deep)
100 cm deep
100 cm deep

8. Sample (air dried) Sieved thro’ 2 mm mesh Sieved thro’ 250 µm mesh
Sample (air dried)
Sieved thro’ 2 mm mesh
Sieved thro’ 250 µm mesh
Grounded and mixed
pulverized
Wet micro-milled (ethanol)
Packed ( 200 cc plastic containers)
Sieved thro’ 75 µm and mixed
Centrifuged (4000 rpm)
Stored (5 weeks)
Pelletized
Gamma radiation (HP Ge Detector)
Mixed (vortex mixer)
EDXRF analysis
Loaded, tamped on sample holder
Radionuclides identity
Elemental composition
XRD analysis
Mineral composition
Mineral sands analysis
Radionuclides analysis
Heavy metals analysis

9. 4.0 Results and Discussions
4.1. Mineral sands
Table 4.1. Summary statistics for minerals in surface- deposits sands. [] rep those from mid-river
Albite
Diopside
Hornblende
Microcline
Orthoclase
Quartz
Magnetite
Ilmenite
min
14.1[17.1]
0[4.1]
17.8[8.6]
[0]
32.6[51.6]
3.2[0]
max
27.3[27.9]
4.9[6.8]
21[13.9]
13.9
[5.3]
58.3[68.7]
10.9
11.6[2.5]
mean
20.4[21.9]
1.82[5.2]
19.4[10.3]
2.78
[1.06]
44.4[61]
3.86
7.3[0.5]
SE.mean.
2.2[1.9]
1.1[0.6]
0.5[0.9]
2.8
4.5[2.8]
2.0
1.5[0.5]

10. Figure 4.1. Mineral sands variation in heavy sand samples
Albite, diopside, quartz and hornblende are found in both set of samples in mineable amount.
Orthoclase and microcline missing because they appear once in either set of samples (feldspar origin).
Magnetite and ilmenite are accessory minerals in igneous rocks.

11. 4.2. Radionuclides 238U_s 238U_sb 232Th_s 232Th_sb 40K_s 40K_sb min
Table 4.2. Summary statistics for radionuclides activities in sands (s=surface, sb=sub-surface)
238U_s
238U_sb
232Th_s
232Th_sb
40K_s
40K_sb
min
5.4
6.15
6.12
56.4
155
124
max
14.03
11.72
411
484
649
535
mean
9.15
8.45
205
193
292
365
SE.mean
0.84
0.58 31 25 35 32

12. Figure 4.2. Surface and subsurface activities for radionuclides in heavy sands

13. 4.3 Heavy metals
Table 4.3. Summary statistics of heavy metal concentrations in µg/g. []for deposit samples Fe Ti V Mn Cr Cu Zn Co Sr Zr Pb Ni As
min
16125
[36203]
1550
[3963]
54.9
[66]
409
[1425]
179
[288] 33
[62] 23
[42]
102
[277]
265
[348]
100
[223]
0.8
[4.9] 2
[4]
[2.1]
max
76000
[342083]
20438
[77417]
988
[5500]
1638
[4621]
396
[536] 82
[243] 95
[417]
553
[4329]
547
[577]
785
[4204] 10
[55] 18
[31]
4.2
[9.3]
mean
36203
[192385]
6037
[47740]
275
[3264]
846
[3254]
260
[424] 50
[155] 51
[240]
253
[2190]
358
[440]
264
[2145]
3.8
[24]
6.7
[19]
1.7
[5.5]
SE.mean
2553
[71844]
751
[17488] 36
[1322]
[771]
[53]
[47] 3
[92] 22
[950] 11
[49] 30
[848]
0.5
[10]
[6]
0.2
[2]

14. Figure 4.3. Heavy metal concentrations variation in heavy sands.

17. Table 4.4. Heavy metals’ EF and Igeo values and their implications summary
EF implications
Igeo Implications
river sands
Surface-deposits Fe
[1]Def. - Min.
[-0.97]Unpolluted
[1.44]Moderate Ti
[1.71]Def. - Min.
[2.55]Moderate
[-0.19]Unpol. – Mod.
[2.79]Mod-strongly V
[2.76]Moderate
[6.16]Significant
[0.50]Unpol. – Mod.
[4.07]Strong –very Str. Cr
[3.77]Moderate
[1.16]Def. - Min.
[0.95]Unpol. – Mod.
[1.65]Moderate Zr
[2.25]Moderate
[3.29]Moderate
[0.14]Unpol. – Mod.
[3.16]Strongly Mn
[1.30]Def. - Min.
[0.94]Def. - Min.
[-0.59]Unpolluted
[1.35]Moderate Co
[17.4]Significant
[28.3]Very high
[3.15]Strongly
[6.26]Very strongly Sr
[2.75]Moderate
[0.63]Def. - Min.
[0.49]Unpol. – Mod.
[0.79]Unpol. – Mod. Cu
[1.48]Def. - Min.
[0.85]Def. - Min.
[-0.40]Unpolluted
[1.20]Moderate Zn
[0.70]Def. - Min.
[0.62]Def. - Min.
[-1.48]Unpolluted
[0.75]Unpol. – Mod. Pb
[0.24]Def. - Min.
[0.30]Def. - Min.
[-3.0]Unpolluted
[-0.29]Unpolluted Ni
[0.17]Def. - Min.
[0.09]Def. - Min.
[-3.49]Unpolluted
[-1.97]Unpolluted As
[0.10]Def. - Min.
[-3.51]Unpolluted
[-1.82]Unpolluted

18. 5.0 Conclusions and recommendations
Eight minerals sands were positively identified. Magnetite and Ilmenite are viable if extraction cost is less than output benefits.
Estimated absorbed dose was 150 nGy h-1, translating to an annual effective dose of 0.18 mSv yr-1. Radioactivity pose no danger general population.
Generally, the mean concentrations of heavy metals exceeds the recommended CBSQG values. Sands were deficiency to moderately enriched and unpolluted to moderately polluted.

19. 5.2 Recommendations
Research on the volume of the heavy mineral deposits is required as well as the cost of mineral separation and transportation.
Radiological study on water from these rivers should be done so as to gauge the ingested radiation by either through drinking or food.
The concentration anomalies of heavy metals could be indication of mineral deposits hence geochemical study is required.

20. Thank you