Georges-Ivo E. Ekosse

Influence of physico-chemistry and mineralogy on the occurrence of geohelminths in geophagic soils from selected communities in the Eastern Cape, South Africa, and their possible implication on human health

Geophagic soils from selected communities in Eastern Cape, South Africa were characterised to determine their properties and geohelminth content. The soils were coarse-textured with cation exchange capacity values ranging from 6.35 to 18.94 cmol (+)/kg. Quartz was the dominant mineral in the samples with SiO2, Al2O3, and Fe2O3(t) having the highest concentrations among major element oxides. The soil properties, mineralogical composition, and low amounts of particle binding substances may favour the survival of geohelminth ova in the soils. Seven of the samples contained at least one of the following geohelminths: Ascaris lumbricoides, Trichuris trichiura, Necator americanus, Ancylostoma duodenale and Strongyloides stercoralis. The presence of these geohelminths in the soils was attributed to agricultural and sanitary practices inherent in the communities and the soil properties. Communities need to be sensitised on the importance of safe sanitary and animal husbandry practices to reduce the prevalence of helminth infection among geophagists.

Mineral Constituents and Kaolinite Crystallinity of the <2 μm Fraction of Cretaceous-Paleogene/Neogene Kaolins from Eastern Dahomey and Niger Delta Basins, Nigeria

Abstract This study examines the mineral composition and kaolinite crystallinity of Cretaceous and Paleogene/Neogene kaolins from Nigeria based on X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy data of the <2 μm fraction. The purpose of this was to assess the minerals present, structural order, and possible industrial applications of the kaolins. A total of twenty-eight (28) samples comprising of fifteen (15) Cretaceous and thirteen (13) Paleogene/Neogene kaolins were analysed. The XRD results showed that both the Cretaceous and Paleogene/Neogene kaolins have kaolinite as the dominant phase followed by quartz with anatase, hematite, and goethite occurring in minor quantities. Based on the mineralogical composition, the Paleogene/Neogene deposits were classified as sandy kaolin and the Cretaceous deposits were classified as pure kaolin. The kaolinite structural order for the Cretaceous pure kaolin was higher than that obtained for the Paleogene/Neogene sandy kaolin with more quartz, iron, and titanium oxides. The economic consideration of the deposits showed that the sandy kaolin type can be used in pigment industrial applications whereas the pure kaolin type can be used in refractory, fiberglass, and ceramic industrial applications.

Fourier Transform Infrared Spectroscopy of Clay Size Fraction of Cretaceous-Tertiary Kaolins in the Douala Sub-Basin, Cameroon

Abstract The structural order of Cretaceous-Tertiary kaolins of the Douala Sub-Basin in Cameroon was determined in this study. This was achieved using Fourier Transform Infrared spectroscopy (FTIR) with attenuated total reflectance (ATR) on the Bomkoul, Dibamba, Ediki, Logbaba, Missole and Yatchika kaolins. Transmittance spectra of 20 samples were recorded in the mid-infrared regions (MIR). Results show that most of the kaolins had the four distinguishable bands in the hydroxyl (OH) stretching region, though the second transmittance band (3670 cm−1) had low intensities. The hydroxyl stretching of water bands (3457 and 3442 cm−1 for KGa-1b and KGa-2, respectively) were mainly observed in all Logbaba samples at 3443 cm−1 and 3445 cm−1. The two bands reflecting OH deformation of inner-surface hydroxyl and inner hydroxyl groups (937 and 915 cm−1) were quite visible in the Bomkoul, Dibamba, Logbaba and Missole II samples; slightly visible in all Yatchika and two of the Ediki; and not visible in Missole I and one of the Ediki samples. Therefore, based on the empirical classification of the degree of order of kaolinite, 10 of the studied samples had ordered structures. Three displayed partially ordered structures; four had poorly ordered structures, and three exhibited disordered structures. This study revealed that kaolins from Dibamba, Logbaba and Missole II in the Douala Sub-Basin had the best crystallinity, which is one of the important characteristics needed for industrial applications.

Physicochemical, Geochemical and Mineralogical Aspects of Agricultural Soils in Limpopo Province, South Africa

ABSTRACT Soil samples were collected from three selected sites (uncultivated, cultivated and grazing land) at University of Limpopo Experimental Farm (Syferkuil) in Mankweng area to characterise their physicochemical, geochemical and mineralogical properties and their influence on soil fertility for agriculture. Soil textural triangle using Texture Auto Lookup Software (TAL 4.2) Package was used to determine particle sizes of samples which were all dominated by a loamy texture. Chemical characterisation carried out included determination of exchangeable cations, major elemental oxides and trace elements. Silica was the dominant oxide with the highest weight percentage values ranging from 75.99 to 83.45. Chemical index of alteration values of 66 to 75 depicted moderate silica weathering with depletion of soil nutrients due to leaching. Seven minerals were identified i n soil samples which were dominated by kaolinite. The presence of mica and smectites in the soils displayed properties typical of soils rich in exchangeable cations compared to those with mineral assemblage dominated by kaolinite and quartz. The overall findings indicated moderate concentrations of nutrient elements and favorable plant growing conditions, where addition of adequate nutrient fertilizers would potentially optimize crop yield.

Geochemistry of Selected Kaolins from Cameroon and Nigeria

Abstract The geochemical characteristics of selected kaolins from Cameroon and Nigeria are presented, with an attempt to elucidate on their possible industrial applications by comparing them to world-known kaolin deposits. Major oxides concentrations were subjected to factor analyses in interpreting their relationships. Geochemical indices, including chemical index of alteration (CIA), chemical index of weathering (CIW) and the index of compositional variability (ICV) were computed and plotted on binary and ternary diagrams to determine the intensity of weathering of the kaolins and discriminate their different source rock types. Kaolinite was the major phase, followed by quartz, illite and goethite as minor phases. Minerals in trace phases included smectite, anatase, muscovite, gibbsite, microcline, palygorskite and calcite. Mean abundances of major oxides in wt% were: SiO2 (56.96)>Al2O3 (24.09)>Fe2O3 (3.78)>TiO2 (1.53)> K2O (1.26)> MgO (0.27)>CaO (0.20)>Na2O (0.17)>P2O5 (0.05)>MnO (0.04). The CIW versus CIA and ICV versus CIA plots showed that most of the kaolins clearly depicted extreme silicate weathering. The current applications of kaolins from Cameroon and Nigeria include ceramics and manufacturing of bricks and tiles. Low MgO, CaO, Na2O, K2O and TiO2 further position the kaolins for pharmaceutics, cosmetics, rubber and plastic applications. Thus, the studied kaolins have the potential to contribute to improved economic development of these countries.

Environmental Geochemistry of Geophagic Materials from Free State Province in South Africa

Abstract Nine geophagic material samples were analysed in order to characterise their mineralogical and elemental constituents, and infer on their health threats. Most abundant mineral in the samples was quartz, followed by smectite, kaolinite and muscovite in minor; and microcline, plagioclase, and goethite in trace quantities. Dominant major oxides were SiO2 (43 - 74 wt%) and Al2O3(15 - 19 wt%). Chemical Indices of Alteration (79.37-99.34) and Weathering (94.38-99.92) values suggest moderate to extreme silicate weathering, and alkali and alkaline earth metals depletion. Based on molar proportions of Al2O3, CaO + Na2O, and K2O, weathering trend and mineralogical compositions of the soils showed more advanced argillic alteration with rare earth elements being more concentrated compared to Upper Continental Crust. Excessive amounts of quartz and heavy metals in the geophagic soils represent significant health threats to geophagic individuals, though heavy metals had low biaccessibility values. There is need for soils beneficiation before ingestion.

Minerals in Human Geophagic Soils from Selected Rural Communities in Gauteng and Limpopo Provinces in South Africa

Abstract Twelve representative human geophagic soil samples collected from selected rural communities in Gauteng and Limpopo Provinces, South Africa, were analyzed using X-ray diffractometry to identify, quantify and characterize their minerals constituents. Kaolinite, smectite, talc, muscovite, quartz, calcite, dolomite, microcline, goethite and hematite were the clay and non-clay minerals identified. Two most dominant minerals in the geophagic soil samples were quartz (35-52 wt%) and kaolinite (31-53 wt%). Abundances for the other minerals were 8-27wt%. Based on the results, the clay minerals and mineral oxides could serve as elemental sources for supplementation of Al, Na, K, Ca, Mg, and Fe in the bodies of the geophagic individuals. There could however be influential factors such as the soil matrix itself, soil type, chemical form of the element, stomach and intestinal pH, and the soil to solution ratio, which could affect the elemental bio-accessibilities.