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

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.

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.

3.0 Methodology 3.1 map of the sampled area

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

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

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

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

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]

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.

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

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

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]

Figure 4.3. Heavy metal concentrations variation in heavy sands.

 

 

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

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.

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.

Thank you