Figure 1: XRF spectra for samples collected from Mombasa
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Gichumbi, JM1*, Maghanga JK2, Cheshari, E.C3, Ongulu, RO 4, Gichuki, JG5
Abstract— Geophagy is the deliberate consumption of soil and clay deposits by animals including man. The practice is wide- spread particularly in pregnant women in Africa. This study of geophagic soil from coast province in Kenya had its primary objectives in analyzing the geochemical and mineralogy of the geophagic material sold in open air markets in Taita and Momba- sa Districts. The elemental analysis and major oxides was carried out using AAS and Energy dispersive X-ray fluorescence. Ele- mental analysis showed that silica (SiO2) and alumina (Al2O3) were the main oxides present in the materials. The transition met- als Cd and Co were not detected, while the concentration of Cu, Zn, and Pb was low. The mineralogy studies using Fourier transform infrared spectroscopy showed that the samples were mainly siliceous with quartz being the dominant mineral and kaolin and calcite being present.
copy, Fourier transform infrared spectroscopy
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eophagy is a specific type of pica. Pica is the persistent eating of non nutritive substances or the tendency or craving to eat substances other than the normal foodstuffs [16]. Geophagy is defined as the craving and subsequent con- sumption of non-food substances [15].Geophagy is common in
both human cultures and animal kingdom [2]
Young and coworkers proposed three major hypotheses con- cerning the physiological courses of pica: hunger, micronutri- ent deficiency and protection from toxins and pathogens [2].
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1 Chuka University College, Kenya, P.O.Box 109-60400- Chuka. E-mail: jsmwangi2003@yahoo.co.uk
2 Pwani University College, P.O, Box 195-80108,
Kilifi,Kenya
3Laikipia University College, P.O.Box P.O,.Box 1100-
20300, Nyahururu
4Masinde Muliro University of Science and Technology, ,
P.O.Box 190-50100, Kakamega
The practice of Geophagy is widespread among pregnant and breast feeding women in sub-Saharan Africa. The practice cuts across social status, with pregnant women of low social status and affluent backgrounds consuming the materials [4]. South- ern Africa women and children in both urban and rural setting were found to engage in geophagia. The women surveyed by Woywodt and Kiss believed that the consumption of earthy materials including oils and clays enhance their beauty [17].
In some communities like the Chagga of Tanzania, geophagia is considered to be sacred to women [3]. Red soil is ingested in many communities to prevent and alleviate symptoms of iron deficiency anemia because of its inferred high Fe content [7].
The consumption of geophagic materials have been found to have drawbacks which impact negatively on human health and some of which include anemia, microbial infections, hel- minthiasis, intestinal obstruction, dental abrasion and heavy metal poisoning [4], [8], [11].The effects of ingesting geophagic soils on the consumer depends on the physico-chemistry, mineralogy and geochemistry of the ingested soils which to a large extent are influenced by the soils pedogenetic develop-
ment and the quantity of soil ingested.
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Research on Geophagy in Kenya by [6], [5], [15], have shown that the materials consist mainly of silica and alumina. The aim of this research was therefore to study the geochemistry and mineralogy of the geophagic materials from Taita and Mombasa in coastal Kenya. This was necessary in order to ascertain their elemental composition particularly the presence or absence of heavy metals.
Taita Taveta district is in Coast province of Kenya. The district
lies between 2˚46 ′ south and 4˚1′ South and longitudes
37˚36′East and 30 ˚ 14′ east. The samples from Taita were col- lected from Wundanyi, Taveta and Voi towns and were la- beled T1, T2 and T3 respectively.
Mombasa is in the South –Eastern part of coast province. The district lies between latitudes 3˚-80˚ and 4-10˚ South of the Equator and between longitudes 39-80 ˚ East of the Greenwich Meridian. The samples were collected from Kilifi, Malindi and Mombasa town open air markets. The samples were labeled M1, M2 and M3 respectively.
The geophagic samples were randomly selected and were
purchased from vendors who were selling them in open air markets. The purchased samples were in the state in which they were consumed.
.
The samples were dried in an oven at 105˚ C and then placed in a dessicator to cool and then weighed until a constant weight is obtained. The dried samples for mineralogical and chemical analyses were ground in a pulverizer prior to anal- yses.
Preliminary Elemental analysis was performed by Energy Dispersive X-ray fluorescence (XRF) using PANanalytical Minipal QC model and Atomic Absorption Spectrometry
(AAS) using A Varian Spectra AA-10 Model.
XRF was performed on pressed disks and involves no pre- treatment other than simple crushing and milling procedures. The mineralogy of the geophagic samples was determined by Fourier transform infrared (FT-IR) spectroscopy using Shi- madzu 800 instrument.
Fourier transform infrared spectrometry was done using a modified procedure employed by [3], [14]. The sample was dried in an oven at 105˚C for 12 hours. The mineral sample of about 2 mg was then mixed with 40 mg of spectroscopic KBr in the ratio 1:20 using a clean mortar and pestle to prepare a sample pellet. The ratio of sample to KBr was varied in the ratio 1:100 and 1:200 to avoid overlap of the peaks. Before mix- ing of the sample with KBr, the KBr was dried at 120˚ C for six hours in an oven to avoid the broad spectral peak due to free OH which would seriously affect the interpretation of the bound hydroxyls associated with the minerals. A pellet of about 1 mm thickness and 12 mm in diameter was prepared by pressing. The prepared pellet was placed in a suitable sam- ple holder immediately after preparation and introduced in the infrared beam for analysis. Peaks were reported based on percentage transmittance to given wavelength, recorded in the range 4000-200 cm-1.
Elemental analysis was performed using atomic absorption spectrometry (AAS). Standard procedures for digestion of the samples were followed and standard solutions of the elements were used in calibrating the AAS. The elements determined were chosen because of their possible association with this materials and their toxicity potential.
The results for major oxides (full assay) from Mombasa and Taita district are shown in Table 1.0 and 1.1.The samples from Mombasa had SiO2values ranging from 61.45 to 53.16 with an average of 57.31. The samples from Taita also had SiO2 having
the highest values as compared with the other oxides,with
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values ranging from 58.23 and 60.48% and an average value of
59.59%.This shows that silica is the main oxide in all the stud- ied geophagic samples and this is in agreement with values reported by [6], [12], [2].
The levels of Al2O3 oxide were the second highest with values ranging from 30.8% to 33.60% for Mombasa with an average of
31.76%.The Al2O3 values of samples from Taita had an average of 31.16% with values ranging from 30.0% to 31.9%.
The values for the alkali and alkaline earth elemental oxides CaO, MgO, Na2O and K2O were generally low. The transition metal oxides were lowest for MnO with an average value of
0.01% for both Mombasa and Taita. Titanium ranged between
3.46% to 4.63% and 3.50% to 4.06 % for Mombasa and Taita respectively.
The values for transition metal oxide Fe2O3 had an average of
3.49% and 2.59% for Mombasa and Taita respectively which were low compared to those reported by [6]
Sample | SiO2 | Al2O3 | CaO | MgO | Na2O |
M 1 | 53.16 | 33.60 | 0.08 | 0.15 | 0.07 |
M 2 | 60.45 | 30.90 | 0.07 | 0.21 | 0.40 |
M 3 | 57.32 | 30.80 | 0.08 | 0.19 | 0.39 |
T 1 | 60.48 | 30.00 | 0.08 | 0.31 | 0.19 |
T2 | 58.23 | 31.60 | 0.04 | 0.30 | 0.71 |
Taita 3 | 60.08 | 31.90 | 0.07 | 0.37 | 0.53 |
The trace elements analyzed were; Cu, Zn, Cr, Pb, Sb, Co, Cd. Sr, B, V and Mo. The results were obtained from both AAS and XRF data and are represented in figure 2-5. The Energy dispersive XRF was used for preliminary investigations while quantitative analysis was carried out using AAS. The levels of Cu ranged from 4.0 to 9 ppm while Zn levels ranged from 27.5 ppm to 58.0 ppm. These values were lower as compared to those reported by [2] for geophagic clay samples from Came- roon and Nigeria.
The levels of Cr, Pb and Co were low ranging from 0.5 ppm to
9.0 ppm, 0.68 ppm to 1.54 ppm and 1.5 ppm to 5.5 ppm respec- tively. Molybdenum ranged from 30 ppm to 52.0 ppm. Cad-
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mium, boron and vanadium were not detected in all the sam- ples. A representative XRF spectra for samples collected from Mombasa is shown in Figure 1.
Figure 1: XRF spectra for samples collected from Mombasa
Figure 3: Pb, Zn and Cu concentrations in p
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of Kaolinite [10].The presence of Calcite (calcium carbonate ) is confirmed by the presence of the absorption peaks at 875-870 cm-1.This is in agreement to other workers [14].
A representative FT-IR spectra for a sample from Taita is shown in Figure 6
Figure 4: Mo, Sr and B concentrations in ppm
Concentartion of Co,Sb and Cd
1
0.8
0.6
0.4
0.2
0
T1 T2 T3 M1 M2 M3
Sample number
Concentartion of
Co,Sb and Cd
Figure 6: FTIR spectrum of geophagic material from Taita 1 sample.
Figure 5: Cobalt, Sb and Cd concentrations in ppm
The FT-IR peaks showed an indication of –OH Stretching bands at 3621,3624,3648,3649,3650,3692,3694 and 3695 cm-1 and OH deformation bands at 907,908 and 909 cm-1[1].
Bands associated with SiO stretching were 692,994 and 695 cm-
1,753 and 754 cm-1, 791,795 and 796 cm-1. SiO deformation bands were 1007, 1032 and 1033 cm-1.The appearance of Si-O bands supports the presence of quartz. The interlayer hydro- gen bonding is assigned by the characteristics band at 3622.1 cm -1 [12], [14].
Most of the bands such as 3695.4, 3693.4, 3622.5, 3440.8,
1016.1, 916.1, 788.8, 686.6, 547.7, 466.7 cm-1 shows the presence
The high level of quartz in all the geophagic samples studied could have a negative effect on human health. Quartz particles are coarse, hard and angular with strong potential of damag- ing the dental enamel, the main inorganic component of tooth. This damage can occur through grinding, cracking, splitting and breakage during the process of consumption of geophagic materials[12].The ability of quartz to resist chemical alteration would lead to scratching and eventual perforation of the intes- tines and would also cause soil peritonitis due to perforation of the sigmoid colon [17].
The concentration of transition elements was generally low for the entire samples studied. The concentration of Pb, Zn, Cu and molybdenum were relatively low (< 30 ppm) while the
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levels of chromium and vanadium were relatively high in all samples (> 50 ppm). However, levels of chromium were high- er than those reported in geophagic samples from Nigeria and Cameroon [2].The metals Co, Sb and Cd were not detected in all the samples.
The mineralogy shows that the materials were mainly sili- ceous with quartz and kaolinite being the dominant phases. The presence of kaolin in the samples agrees with the protec- tion hypothesis advanced by [15].
Geophagic materials from Mombasa and Taita have been studied and were found to contain high levels of silica and alumina. The levels of heavy metals found were generally low. Their consumption should be discouraged due to the high level of quartz which may damage the enamel and cause per- foration in the large and small intestines.
The health effects on the consumers should be investigated
futher,particularly the bioavailability studies of the elements in the geophagic materials consumed.
Acknowledgment
The authors would like to aknowledge the Mines and Geology
Department for providing the Equipments and Apparatus needed for this study.
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