Peter N. Eze - Academia.edu (original) (raw)

Papers by Peter N. Eze

A quarry in the Chobe Enclave, northern Botswana, exposes a prominent pedostratigraphic unit of a... more A quarry in the Chobe Enclave, northern Botswana, exposes a prominent pedostratigraphic unit of approximately 8 metres consisting of two pedostratigraphic levels (PL), older PL1 and younger PL2. In a region where proxies for palaeoenvironmental reconstruction are terribly lacking, this study assessed the potentials of paleosols (fossil soils) to answer fundamental questions about weathering, pedogenic intensity and environmental change using macromorphology, geochemistry and clay mineralogy. SiO2 is the dominant major oxide (40.6- 98.9 wt. %) followed by CaO (0.02-29.6 wt. %), Fe2O3 (0.48- 2.64 wt. %), MgO (0.14 – 1.81 wt. %) and Al2O3 (0.29 – 0.93 wt. %). The clay-sized minerals present in the paleosols are sepiolite, quartz, calcite and kaolinite. The carbonates had strong positive correlation with Sr (R2 = 0.935), while Fe2O3 had weak positive correlation with TiO2 (R2 = 0.0187). PL1 developed on materials of fluvial origin and is genetically immature with A/C horizons. In compar...

International Journal of Environmental Science and Technology, 2020

The bioavailability of trace elements is strongly influenced by the physical and chemical propert... more The bioavailability of trace elements is strongly influenced by the physical and chemical properties of the soil system. This study sought to establish the relationships between the trace elements (barium, strontium and rubidium), soil organic matter and soil separates in semiarid soils from Central Botswana in a bid to improve our understanding of trace elements biogeochemistry. Trace element contents were obtained using portable X-ray fluorescence spectroscopy, while routine soil analysis methods were used for soil organic matter analyses and particle size distribution. Both multivariate statistical analysis and structural equation model were applied to the data. Results for correlation matrix and principal component analysis showed trace elements affinity for silt, clay and soil organic matter: barium and silt ( r = 0.54, p < 0.01), rubidium with clay ( r = 0.69, p < 0.001) as well as strontium with stronger affinity for clay ( r = 0.83, p < 0.001) and soil organic matter ( r = 0.88, p < 0.001). Principal component analysis showed that trace elements interactions with silt, clay and soil organic matter were observed more in profiles 3 and 7. Three structural equation models were obtained and in two of them, soil organic matter showed statistically highly significant direct effect on strontium which is further supported by all the multivariate statistical analysis results. Further research may be necessary to understand detailed aspects (e.g., complexations) between strontium and soil organic matter in semiarid soils.

Quaternary International, 2015

ABSTRACT a b s t r a c t Neogene Langebaanweg (LBW) palaeosol-sediment-sequences at the West Coas... more ABSTRACT a b s t r a c t Neogene Langebaanweg (LBW) palaeosol-sediment-sequences at the West Coast of South Africa are well known for their well-preserved rich palaeontological heritage. The palaeosols developed on estuarine/ marine/coastal alluvial deposits stacked on each other, ranging in age from the Mid-Miocene to Qua-ternary. Elemental mobility and redistribution based on major and minor element geochemistry of 11 horizons of the w18 m sequences were studied to evaluate the degree of chemical weathering, a major process of soil formation; and to reveal important palaeoenvironments in which the palaeosols devel-oped. Elemental geochemistry was carried out on <2 mm samples by X-ray fluorescence spectropho-tometry. The carbonate horizons (Bk and 2Bkmb2) were dominated by CaO (mean wt.% ¼ 32.77), while the other horizons had preponderance of SiO 2 (>50% mean wt.). Two (WI-1 and WI-2) of the four weathering indices applied to evaluate weathering intensity proved unsuitable for use in an alluvial palaeosol-sediment sequences such as LBW. Chemical index of alteration (CIA) and chemical index of weathering (CIW) values were relatively more consistent in distribution pattern across the pedocomplex, but caution should be applied when using them in similar cases. The pedogenic carbonate horizons on average had the lowest values for both CIA and CIW (1.12e2.60) suggesting more advanced weathering. Plots of geochemical ratios (quantifying pedogenic processes) against depth show striking variations among and within the palaeosol and sediment sections. Soil formation was more advanced in the Mid-Miocene and Pliocene than in the Quaternary suggesting a more humid and warmer climate than pre-sent. We evaluated selected geochemical climofunctions and conclude that more data are obviously needed for a more robust calibration of the models in Langebaanweg palaeosols.

Quaternary International, 2014

ABSTRACT Palaeosols are common along the coastline of southern South Africa as stacked aeolian du... more ABSTRACT Palaeosols are common along the coastline of southern South Africa as stacked aeolian dune deposits but have rarely been studied. We selected two late Quaternary palaeosols exposed in a marine cliff-face at Koeberg and coastal barrier dune at Goukamma, South Africa in order to improve our understanding of their pedogenesis and palaeoclimate dynamics. Palaeosol-based proxies explored include: elemental geochemistry by X-ray fluorescence spectrophotometry, δ13C and δ18O isotopes, micromorphology and clay mineralogy by x-ray diffraction. Selected physico-chemical soil properties were analyzed by routine laboratory procedures. The palaeosols comprise predominantly loamy sand to sandy clay loam textures, have a high pH (>6.5), and very low electrical conductivity (<0.89 mS cm−1). SiO2 and CaO are the most abundant of all the elements in the cambic and calcic horizons respectively. The low levels of Al in the parent materials most likely invalidated the applicability of chemical weathering indices (CIA) to assess weathering intensity. In the case of chemical index of weathering (CIW), the age and sedimentary settings of the palaeosols overruled the possibility for K metasomatism and illitization by metamorphism. The indices WI-1 and W1-2 developed by Darmody et al. (2005) appear more consistent with depth. The palaeo MAT computed from palaeosol carbonate oxygen isotope is 14 and 11 °C for Koeberg and Goukamma respectively, while the maximum MAP obtained from the cambic horizon (Bw) of the Goukamma coastal barrier is 653 mm y−1. The layering seen in the thin section of the calcic layer at Goukamma indicates deposition, possibly by sedimentary differentiation across a palaeo-slope. Clastic calcite and muscovite mica are the dominant minerals in these palaeosols indicating impeded chemical weathering. Similar to many other parts of the world, the coastlines of South Africa has experienced environmental and climate oscillations in the Quaternary. We conclude that along the southern South Africa coasts, a palaeosol based approach to palaeoenvironmental and palaeoclimate reconstruction in combination with other proxies such as pollen and marine based isotopes can provide insights into the environmental oscillations of the late Quaternary.

Scientific African, 2019

In this paper, we consider the use of prior knowledge within neural networks. In particular, we i... more In this paper, we consider the use of prior knowledge within neural networks. In particular, we investigate the effect of a known transform within the mapping from input data space to the output domain. We demonstrate that use of known transforms is able to change maximal error bounds. In order to explore the effect further, we consider the problem of X-ray material decomposition as an example to incorporate additional prior knowledge. We demonstrate that inclusion of a non-linear function known from the physical properties of the system is able to reduce prediction errors therewith improving prediction quality from SSIM values of 0.54 to 0.88. This approach is applicable to a wide set of applications in physics and signal processing that provide prior knowledge on such transforms. Also maximal error estimation and network understanding could be facilitated within the context of precision learning.

Humic substances are extremely important attributes of soil quality but the impacts of long-term ... more Humic substances are extremely important attributes of soil quality but the impacts of long-term fertilization on their composition and structure remain controversial and are still not fully understood. A study, employing various methods was conducted to elucidate the influence of long-term fertilization practices on the composition and structure of humic substances. Soil samples were collected from eight treatments at the Red Soil Experimental Station of the Chinese Academy of Agricultural Sciences. Data were subjected to analysis of variance (ANOVA), using the MSTAT-C software package. In general, the Fourier transform-infrared (FT-IR) spectra discriminated bands between humic fractions. The humic acid (HA) from the NPK plus manure (NPKM) and manure alone (M) treatments showed higher values of the O/R ratios (1.24 and 1.18, respectively) as compared to that from the 1.5 NPKM and fallow (H) treatments, which decreased these ratios (0.66 and 0.85, respectively). Except for NPKM plus wheatsoybean-sweet potato between the lines (NPKMR), the O/R ratios of the fulvic acid (FA) did not differ among the treatments. However, the humin (HM) from H and the control (CK) displayed the highest value of O/R ratios (about 3.23 for both). Humic substances from organic treatments showed more aliphatic nature, whereas more condensed-alkali soluble humic substances were formed in the unfertilized and mineral treatments. Among fractions, the HA formed more phenolic or aromatic structures than did the FA or HM. In addition, the C, H, N and S contents of humic substances increased significantly, whereas their oxygen content decreased.

Environmental pollution by potentially toxic element (PTE) and the associated health risks in hum... more Environmental pollution by potentially toxic element (PTE) and the associated health risks in humans are increasingly becoming a global challenge. The current study is an in-depth assessment of PTEs including the often studied lead (Pb), manganese (Mn), zinc (Zn), arsenic (As) and the less-studied titanium (Ti), rubidium (Rb), strontium (Sr), zirconium (Zr), barium (Ba) and thorium (Th) in highly polluted floodplain topsoil samples from the Litavka River, Czech Republic. Soil chemical properties including carbon (Cox) and reaction (pH_H2O) together with iron (Fe) were assessed in the same soils. A portable X-ray fluorescence spectrometer (p-XRFS) (Delta Premium) was used to measure the PTEs and Fe contents of the soils. Soil organic carbon and reaction pH were determined following routine laboratory procedures. The concentration level of each PTE was compared against world average and crustal values, with the majority of elements exceeding the aforementioned geochemical background l...

Modeling Earth Systems and Environment

Given that soil properties including micronutrient contents vary in space and time, geospatial ma... more Given that soil properties including micronutrient contents vary in space and time, geospatial mapping is necessary for robust site-specific management planning. Kriging interpolation is often used in GIS environments for mapping, but it has inherent limitation of having a smooth effects. In this study, sequential Gaussian simulation (SGS) was used to map the spatial distribution of Cu concentration in and model the spatial uncertainties for an arable dryland in central Botswana. The field was divided into 30 parallel lines in an NE–SW orientation. Soil samples were collected at intervals of 25 m on each line; and 35 sampling points were obtained. A total of 1050 soils sampled at a depth of about 20 cm were air dried and analyzed using an Olympus Delta Sigma® portable X-ray fluorescence analyser. The average concentration of Cu (146 mg kg−1) in the Maibele Airstrip of Botswana is higher than the global average copper concentration (30 mg kg−1). Low copper contents were found dotted around the northern and southern edges of the study area, while high content zone is found in the interior. In comparison to kriging interpolation, SGS technique shows better performance. Kriging generally overestimated where lower values are probable and underestimated where higher values are probable. A large portion of the area has Cu content above the critical threshold of 125 mg kg−1. Since total and not plant available Cu were the measured parameter, we recommend that further study in this location should focus on confirming the plant available Cu in the high-risk areas.

Environmental Monitoring and Assessment

The suitability of a reference element or normalizer used in assessing soil contamination levels ... more The suitability of a reference element or normalizer used in assessing soil contamination levels using enrichment factor (EF) is important for soil quality assessment and monitoring. This study evaluated the results of using three reference elements Ti, Fe, and Zr for EF determination of Rb and Sr in soils within treated wastewater discharge vicinity, Central Botswana. The upper continental crust (UCC), world average values (WAV), and the local background values (LBV) were used in EF assessment of eight pedons. The elemental concentrations of the soils were determined with portable X-ray fluorescence (pXRF) analyzer. Relationships between the elements were strongly significant between Rb and Ti (r = 0.600, p < 0.01), Rb and Fe (r = 0.735, p < 0.01), Sr and Ti (r = 0.545, p < 0.01), and Sr and Fe (r = 0.841, p < 0.01). Second-level correlation analysis between contamination factor (CF) and EF levels showed Zr as the best reference element for Rb and Sr in the soils. Results from this study provide baseline knowledge necessary for contamination assessment and monitoring of soils with similar environmental conditions.

Archives of Agronomy and Soil Science, 2016

ABSTRACT This study examined zinc (Zn) fixation pattern and kinetics in three semiarid alkaline s... more ABSTRACT This study examined zinc (Zn) fixation pattern and kinetics in three semiarid alkaline soils of the Southern High Plains, USA. Soil chemical data obtained from Zn-extraction experiments conducted at different depths were fitted to various kinetic models to examine Zn fixation patterns. Within the experimental period of 90 days, approximately 57% of the total plant-available Zn fixed occurred in the first 14 days when averaged across all soils and depths. Zinc fixation over the experimental period (90 days) was better described by the power function (pfxn) model (R2 = 0.87–0.92, standard error [SE] = 0.130–0.154), but poorly described by the zero-, first- and second-order models (R2 = 0.55–0.76, SE = 0.038–0.267). Average reaction rate constant (from the pfxn model) was higher in the subsurface soils (0.323), suggesting a more rapid Zn fixation, compared to the surface soils (0.293). Zinc fixation within the first 35 days was also more rapid and better described by both the second-order (R2 = 0.91, SE = 0.018) and pfxn (R2 = 0.92, SE = 0.119) models. Findings are applicable to field settings and kinetic parameters obtained will help to advance Zn studies and management in these semiarid soils.

Journal of Geochemical Exploration

Agriculture, Ecosystems & Environment

Applied and Environmental Soil Science

Termite mounds are replete with natural nanoparticles, and they vary in physicochemical, geochemi... more Termite mounds are replete with natural nanoparticles, and they vary in physicochemical, geochemical, mineralogical, and biological properties from the adjoining soils. Although termite mounds have wide ecological and environmental roles including soil formation, faunal and vegetation growth and diversity, organic matter decomposition, geochemical exploration, water survey, treatment of underground contamination, thermoregulation, gas exchange, and global climate change, their nanoscale structures made by the associated organomineral complexes are still poorly understood because of technical limitations. In this review, we highlight the ecological and environmental significance of termite mounds and the documented techniques that have been successfully used to study nanostructure of termite mounds, namely, midinfrared spectroscopy (MIRS), photogrammetry and cross-sectional image analysis, a combination of transmission electron microscopy (TEM) and pyrolysis field ionization mass spe...

Physics and Chemistry of the Earth, Parts A/B/C

Fluvial geomorphology affects river character, behaviour, evolution, trajectory of change and rec... more Fluvial geomorphology affects river character, behaviour, evolution, trajectory of change and recovery potential, and as such affects biophysical interactions within a catchment. Water bodies in South Africa, in common with many other water-stressed parts of the world, are generally under threat due to increasing natural and anthropogenic influences including aridity, siltation and pollution, as well as climate and environmental change. This study reports on a case study to characterise the geomorphology of different river systems in South Africa, with the aim of better understanding their properties, controls, and implications for biophysical interactions including water quality, biodiversity (aquatic and riparian), and human activity within the catchment. The approach adopted is based on the River Styles® framework (RSF), a geomorphology-based approach developed for rivers in New Zealand and Australia, but applied here for the first time to South Africa. Based on analysis of remote sensing imagery, SRTM-2 digital topographic data and field observations on sites through the entire river system, six geomorphic elements were identified along the Sabie River, northeast South Africa (gorge, bedrock-forced meander, low-moderate sinuosity planform controlled sand bed, meandering sand bed, low sinuosity fine grained sand bed, and floodouts), using the RSF classification scheme and based on the RSF procedural tree of Brierley and Fryirs (2005). Previous geomorphological studies along the Sabie River have shown that different reaches respond differently to episodic floods; we use these data to link river geomorphological character (as defined by the RSF) to the hydrodynamic conditions and processes giving rise to such character. This RSF approach can be used to develop a new management approach for river systems that considers their functional biophysical behaviour within individual reaches, rather than considering them as homogeneous and uniform systems.

Natural Resources Research

With a mining-driven economy, Botswana has experienced increased geochemical exploration of miner... more With a mining-driven economy, Botswana has experienced increased geochemical exploration of minerals around existing mining towns. The mining and smelting of copper and nickel around Selibe-Phikwe in the Central Province are capable of releasing heavy metals including Pb, Fe, Mn, Co, Ni and Cu into the soil environments, thereby exposing humans, plants and animals to health risks. In this study, turning bands co-simulation, a multivariate geostatistical algorithm, was presented as a tool for spatial uncertainty quantification and probability mapping of cross-correlated heavy metals (Co, Mn, Fe and Pb) risk assessment in a semiarid Cu-Ni exploration field of Botswana. A total of 1050 soil samples were collected across the field at a depth of $ 10 cm in a grid sampling design. Rapid elemental concentration analysis was done using an Olympus Delta Sigma portable X-ray fluorescence device. Enrichment factor, geoaccumulation index and pollution load index were used to assess the potential risk of heavy metals contamination in soils. The partially heterotopic nature of the dataset and strong correlations among the heavy metals favors the use of co-simulation instead of independent simulation in the probability mapping of heavy metal risks in the study area. The strong correlation of Co and Mn to iron infers they are of lithogenic origin, unlike Pb which had weak correlation pointing to its source in the area being of anthropogenic source. Manganese, Co and Fe show low enrichment, whereas Pb had high enrichment suggesting possible lead pollution. We, however, recommend that speciation of Pb in the soils rather than total concentration should be ascertained to infer chances of possible bioaccumulation, and subsequent health risk to human by chronic exposure.