Physical Science International Journal

Assessment of Heavy-metal Pollution and Ecological Risk in Soils and Water of Oil-field Communities in Delta State, Nigeria, Using Integrated Pollution Indices

Mon, 12 Oct 2026 00:00:00 +0000

Petroleum exploration and production can alter the geochemical quality of surrounding soils and water through the introduction and redistribution of potentially toxic metals. This study assessed the degree of heavy-metal pollution and associated ecological risk in soils and water from the Apkai and Umusedege oil-field communities of Ndokwa East and Ndokwa West Local Government Areas, Delta State, Nigeria. Ten heavy metals, namely Ni, Cr, Cu, Co, Pb, Cd, Fe, Mn, As and Zn, were investigated in soil, while the detected subset was assessed similarly in water. Single-element pollution was evaluated using the contamination factor (CF), geo-accumulation index (I-geo), enrichment factor (EF) and potential ecological risk factor (Er); overall environmental quality was evaluated using the pollution load index (PLI), summed pollution index (PIsum), risk index (RI), average pollution index (PIave) and Nemerow pollution index. In soil, Cr, Co, Pb, Cd, As, Zn, Cu and Ni showed moderate contamination, while Fe and Mn showed considerable contamination; Ni, Cr, Cu, Pb and Zn were classified as low ecological risk, and Cd and As as moderate risk; most metals fell within the depletion-to-minimal-enrichment category, with As as the exception at moderate enrichment; and Cr, Fe, Mn and As showed light-to-moderate geo-accumulation, while the remaining metals were non-contaminated. In water, Cr, Cd and Ni showed moderate contamination, Fe and Mn showed considerable contamination, and Pb, Zn and Cu showed very high contamination; Pb showed considerable ecological risk, while Zn, Cu and Cd showed low-to-moderate risk. Mean PLI was 1.3 for soil and 1.7 for water, indicating pollution in both media under the adopted criterion; mean PIsum was 13.3 and 36.6, mean RI was 67.3 and 142.9, and mean PIave was 1.3 and 4.5 for soil and water, respectively, while the Nemerow index was almost identical between the media at 171.8 and 171.9. Collectively, the integrated indices point to measurable degradation of environmental quality in both compartments, with water showing consistently greater pollution pressure than soil, particularly through Pb, Zn and Cu. The results indicate that heavy-metal pollution in this oil-field environment warrants continued environmental monitoring and management, while also establishing an index-based baseline for the geochemical fractionation and human-health risk assessments that build on this dataset.

Signal Processing Approach for the Characterization and Modeling of Urban Noise: A Case Study of a City in Western Côte d'Ivoire

T. Guié Toa Bi, Bernard N’Zebaud, Sandjé Marcelin, Sié Ouattara, Alain Clement — Tue, 13 Oct 2026 00:00:00 +0000

Urban environmental noise is insufficiently characterized in many secondary cities in sub-Saharan Africa. This exploratory study characterizes short-duration urban sound recordings from five neighborhoods of Duékoué, Côte d’Ivoire (Kokoman, Antenne, Résidence, Belleville, and Guitrozon). Recordings were obtained with a Samsung Galaxy A13 smartphone at 09:00, 12:00, and 17:00 on Monday, Thursday, and Sunday and processed in MATLAB to derive A-weighted equivalent levels (LAeq), percentile levels (L10, L50, and L90), nuisance indices (LNP and TNI), loudness-related descriptors, spectral centroid, zero-crossing rate, and energy fractions in broad frequency bands. The processing chain emulated standard sound-level calculations; however, because the smartphone system was not traceably calibrated against a reference sound level meter and was not demonstrated to conform to IEC 61672, the reported sound-pressure levels are interpreted as approximate estimates rather than certified regulatory measurements. Across the tabulated sites, estimated LAeq ranged from 62.62 dB(A) in Antenne at 17:00 to 72.69 dB(A) in Résidence at 17:00. Temporal profiles differed among neighborhoods, while mid-frequency energy generally represented the largest share of the spectrum. The findings show that smartphone-based signal processing can provide useful comparative information on urban acoustic patterns when its metrological limitations are stated explicitly. Longer, traceably calibrated monitoring is required before formal compliance or population-exposure conclusions can be drawn.

Extreme Rainfall Wet Events under Changing Climate and Impact on Future Flood Risk over Lake Tanganyika Basin (East Africa)

Célestin Manirakiza, Marc Niyongendako, Agnès Nakimana, Agnidé Emmanuel Lawin — Fri, 23 Oct 2026 00:00:00 +0000

Extreme rainfall events leading to floods are among the most severe threats facing communities today in the Lake Tanganyika Basin. This study analyses the spatial and temporal distribution of extreme wet events, detects their trends, and predicts the risk of rare wet conditions that could trigger floods. We used Climate Hazards group Infrared Precipitation with Stations (CHIRPS) data over the reference period 1991-2020 and simulations from ten selected Coupled Model Intercomparison Project Phase six (CMIP6) models over the period 1991-2050. Future projections under two Shared Socio-economic Pathway scenarios (SSP2-4.5 and SSP5-8.5) were analysed in quartiles for 2021-2050. The Standardized Precipitation Index (SPI) and the modified Mann-Kendall (TFPWMK) test were used to characterise extreme wet periods and trends, respectively, while extreme value theory was applied to estimate the probability of rare wet events and flood risk. The findings reveal flood-prone conditions in November, December, January, March, and April. Future changes in consecutive wet days (CWD), heavy precipitation days (R10mm), and very heavy precipitation days (R20mm) are projected to increase flood probability across the entire basin shared by Burundi, the Democratic Republic of the Congo (DRC), Rwanda, Tanzania, and Zambia. The flood risk ratio (FRR) for CWD is projected to reach 1.84 under SSP2-4.5 and 2.18 under SSP5-8.5 in Rwanda’s share, indicating the highest flood risk among the partner states. Flood risk due to maximum 1-day precipitation (Rx1day) shows no marked change (FRR 1.00 – 1.04) under either scenario by 2050. The findings can support efforts to minimise the loss of life, crop damage, and damage to infrastructure in the Lake Tanganyika Basin.

Thermal-Hydraulic Analysis of MHD Silver Nanofluid Flow over a Cylindrical Surface with Radiation and Chemical Reaction Effects

Ojo, Adetoye Solomon, Nwabuzor, Peter Onyelukachukwu — Fri, 30 Oct 2026 00:00:00 +0000

This study investigates the thermal-hydraulic characteristics of magnetohydrodynamic (MHD) silver nanofluid flow over a cylindrical surface under the combined effects of thermal radiation and chemical reaction. Effective thermophysical property correlations are incorporated to describe the influence of silver nanoparticle volume fraction on the nanofluid's thermal and momentum transport characteristics. The governing equations for mass, momentum, energy, and species concentration are formulated in cylindrical coordinates and reduced to dimensionless equations using appropriate transformations. The resulting equations are analysed using the Laplace transform technique, with Wolfram Mathematica employed for the associated symbolic and computational evaluations. The effects of the Reynolds, Prandtl, Schmidt, thermal and solutal Grashof, Hartmann, radiation, chemical reaction, electrical conductivity, and nanoparticle volume fraction parameters are examined through the velocity, temperature, and concentration distributions. The skin-friction coefficient, Nusselt number, and Sherwood number are also evaluated to assess the hydrodynamic, thermal, and mass-transfer characteristics. The analysis indicates that the magnetic field influences the velocity through the Lorentz force, while the Prandtl and Schmidt numbers govern the relative thermal and mass diffusion processes, respectively. Thermal radiation and chemical reaction modify the temperature and concentration fields, respectively, with corresponding effects on the surface heat- and mass-transfer rates. The results provide a theoretical basis for understanding the coupled momentum, heat, and species transport in MHD silver nanofluids over cylindrical surfaces.

Solar Energy Transition in a Pilgrimage City: A Document-Based Assessment of Renewable Energy Planning and Tourism Growth in Ayodhya, India

Prem Kumar, Rajesh Kumar Verma — Wed, 04 Nov 2026 00:00:00 +0000

Pilgrimage destinations can experience concentrated and variable visitor flows that complicate urban electricity planning. Ayodhya, Uttar Pradesh, provides a pertinent setting because rapid growth in reported visits has coincided with its development as a model solar city. This document-based, single-case study examines whether publicly described solar interventions explicitly address six analytically defined pilgrimage-related demand clusters: temple and institutional buildings, hospitality, mobility, public spaces, municipal and food-supply services, and residential communities. Government information, corporate disclosures, news reporting and relevant research literature were examined; reported installations and targets were distinguished from independently documented commissioning. State-reported visits increased from approximately 5.76 crore in 2023 to 16.44 crore in 2024. The reviewed intervention catalogue includes a 40 MW grid-connected solar plant with documented commercial operation, alongside distributed measures reported at different implementation stages. The catalogue contains no intervention specified exclusively for hospitality, although broader commercial rooftop targets may encompass hospitality properties. This is a gap in available documentation rather than evidence that the sector received no investment. The Uttar Pradesh Solar Energy Policy 2022 defines its solar-city criterion as a reduction of at least 10% in projected conventional-energy demand over five years through renewable-energy systems and efficiency measures; compliance with this criterion cannot be assessed from the available data. A four-stage Tourism–Solar Alignment Framework and explicitly defined candidate indicators are proposed for subsequent field validation. No measured hourly load, solar dispatch or programme-wide coverage outcomes are inferred.

Intercity Comparison of Aerosol Optical Depth and Modelled Surface Dust Concentrations across Seven West African Cities (2019–2025)

Fri, 06 Nov 2026 00:00:00 +0000

Satellite aerosol optical depth (AOD) is widely used as a proxy for surface particulate pollution where ground monitoring is scarce, including in West Africa. This study tests whether this substitution holds for mineral dust by comparing MODIS MAIAC AOD (550 nm) with MERRA-2 modelled surface dust concentrations in seven cities (Dakar, Bamako, Niamey, Korhogo, Bouaké, Cotonou and Abidjan) over 2019–2025, on days matched by city and date, in November–March and April–October, using stationary-bootstrap 95 % confidence intervals. City rankings differ between the two quantities: Niamey has the highest surface dust in both windows, whereas the highest AOD occurs in Cotonou in November–March and in Dakar in April–October. Surface dust is higher in November–March in all seven cities, but AOD follows this seasonality only in Cotonou and Abidjan; it is opposite in Dakar and Bamako, and no clear contrast is detected elsewhere. The daily AOD–dust correlation is positive everywhere in November–March but becomes indistinguishable from zero in Abidjan in April–October. These dissociations persist even though MERRA-2 assimilates MODIS AOD. In April–October, AOD is less often available in the southern and central cities, where observed days are dustier than average. In practice, AOD captures part of the day-to-day dust variability within each city in November–March, but it should not be used to rank cities by surface dust concentration, to infer the seasonal cycle of surface dust, or as a proxy for surface dust on the Gulf of Guinea coast during the monsoon.

Hybrid Modeling of Solar Drying of Peppers: Integration of Classical Thermodynamics and a Predictive Random Forest Model

Mon, 09 Nov 2026 00:00:00 +0000

This study investigated the drying behaviour of green, red and yellow peppers in an indirect forced-convection solar dryer by combining conventional drying-kinetics analysis with Random Forest prediction. Solar irradiance, dryer-air temperature, product temperature and changes in product moisture content were monitored during drying. Irradiance reached 872 W/m², while dryer-air and product temperatures reached 54.6 °C and 56.6 °C, respectively. The air temperature exceeded ambient temperature by more than 21 °C during the reported period. All varieties showed a decrease in moisture content with time, with a higher initial evaporation rate and faster dehydration observed for green peppers. Red and yellow peppers showed broadly similar moisture-content profiles. Six semi-empirical models were fitted to the experimental moisture-ratio data. The two-term model provided the best fit for green peppers (R² = 0.9947), whereas the Midilli model performed best for red and yellow peppers (R² = 0.9908 and 0.9903, respectively). Effective diffusivity, estimated using a simplified solution of Fick's second law, was highest for green peppers (4.943 × 10⁻¹⁰ m²/s), followed by yellow (3.125 × 10⁻¹⁰ m²/s) and red peppers (2.768 × 10⁻¹⁰ m²/s). Random Forest feature importance identified elapsed time (approximately 35%) and product temperature (approximately 28.7%) as the leading predictors of residual moisture ratio. The findings describe varietal differences in solar-drying kinetics and show the potential value of combining semi-empirical drying models with data-driven prediction.

Maximum Power Point Tracking for Bifacial Solar Cells: An Adaptive Approach Based on Grain Size

Wed, 11 Nov 2026 00:00:00 +0000

Maximum power point tracking (MPPT) methods based on a constant fraction of open-circuit voltage (FOCV) or short-circuit current (FSCC) offer relatively simple means of estimating the operating point of photovoltaic cells. This study examines their applicability to bifacial polycrystalline silicon solar cells and assesses how silicon grain size affects the factors used in these methods. A three-dimensional columnar-grain model of an n–p–p+ bifacial cell was used, with an empirical relationship connecting minority-carrier diffusion length and grain size. Photocurrent, photovoltage and electrical power were obtained for front-side and simultaneous double-sided illumination. Current–voltage and power–voltage characteristics were used to locate maximum power points, and the fractions relating maximum-power-point voltage and current to their open-circuit and short-circuit counterparts were evaluated across grain sizes from 10 to 300 µm. The simulations indicated that, for a given grain size, the fractions varied little between the two illumination modes. However, both fractions changed with grain size, indicating that fixed coefficients may be unsuitable across different grain structures. Using the simulated data, correlation equations were developed to estimate grain size from open-circuit photovoltage and then determine a grain-size-dependent voltage fraction. These equations were incorporated into a proposed adaptive FOCV tracking procedure represented by a flowchart. The results support using the constant-fraction principle for the two illumination modes within the model, while highlighting the potential value of grain-size adaptation.

Seasonal and Solar-Cycle-Phase Distributions of Solar Flares, Solar Proton Events, Intense Geomagnetic Storms, and Ground-Level Enhancements, 1996–2024

Gyebre Aristide Marie, Kabore Salfo, Segda Abdoul Kader, Ouattara Frédéric — Thu, 12 Nov 2026 00:00:00 +0000

Background: Solar eruptions and their near-Earth consequences vary across the solar cycle, but the apparent distribution of disparate event classes requires comparable event definitions and observation windows.

Objective: To describe seasonal and solar-cycle-phase frequencies of C-, M-, and X-class solar flares, solar proton events, intense geomagnetic storms, and ground-level enhancements during 1996–2024.

Methods: Publicly catalogued observations were tabulated by event onset year and calendar-month season. Phase comparisons were divided by the number of years assigned to each phase, whereas seasonal comparisons used event shares and calendar-day exposures.

Results: The catalogued totals were 33,636 C–X flares (29,704 C, 3,683 M, and 249 X), 187 solar proton events, 127 intense geomagnetic storms, and 22 ground-level enhancements. Autumn accounted for 27.3%, 29.9%, 43.3%, and 36.4% of these four event classes, respectively. For all four classes, the largest events-per-year frequency was observed in the years designated as solar maximum. No ground-level enhancement was assigned to the minimum-phase years.

Conclusions: The descriptive patterns are compatible with solar-cycle modulation and, for geomagnetic disturbances, a possible equinoctial contribution. The distributions alone do not establish terrestrial-season causation of solar eruptions, nor do they quantify catalog completeness or cross-event causal relationships.

Simulation and Machine Learning Prediction of the Dielectric Properties of Pure ZnO: Real ε₁(E,T) and Imaginary ε₂(E,T) Parts Using the Tauc–Lorentz–Kramers–Kronig Formalism

Fri, 13 Nov 2026 00:00:00 +0000

Aims: This study presents the theoretical modelling and machine-learning-based prediction of the dielectric properties of pure zinc oxide (ZnO) as a function of photon energy and temperature.

Study Design: Theoretical modelling and machine-learning-based prediction.

Place and Duration of Study: Solar Energy Materials and Systems Laboratory (LASES), Faculty of Science and Technology, Université Cheikh Anta Diop – Dakar, Senegal.

Methodology: The complex dielectric function is described using the Tauc–Lorentz model, in which the real part, ε₁(E,T), is obtained through the Kramers–Kronig transformation, while the temperature dependence of the optical band gap is incorporated using the empirical Varshni law. The simulated data constitute a reference dataset of 4,500 samples (inputs: photon energy E and temperature T; outputs: ε₁ and ε₂), randomly split into a training set (80%, 3,600 samples) and an independent test set (20%, 900 samples). This dataset is used to train and evaluate two machine learning models: Random Forest (RF) and Multi-Layer Perceptron (MLP). Model validation is based on the coefficient of determination (R²), the root mean square error (RMSE), residual analysis, parity plots, and energy-dependent spectral comparison at T = 300 K.

Results: Over the temperature range of 0–400 K, the band-gap energy decreases from 3.441 to 3.373 eV, corresponding to a redshift of 68 meV. The maximum of ε₁ increases from 6.931 to 7.666 (+10.6%), while the maximum of ε₂ increases from 2.939 to 3.805 (+29.5%) and shifts from 3.961 to 3.905 eV. For ε₁, the MLP model gives the best performance (R² = 0.999330, RMSE = 0.016569), compared with the RF model (R² = 0.998770, RMSE = 0.022444). For ε₂, the trend is reversed: the RF model outperforms the MLP model (R² = 0.999526, RMSE = 0.016334 versus R² = 0.999347, RMSE = 0.019173).

Conclusion: Both models reproduce the TL+KK+Varshni reference model with very high accuracy and provide a fast surrogate for numerical Kramers–Kronig calculations. This agreement is a validation against the theoretical reference model, not an experimental validation. The main limitation is the assumption of a temperature-independent broadening parameter C, which will be addressed in future work by introducing a Bose–Einstein-type temperature-dependent function C(T) and by comparison with experimental ellipsometric data.

Latitudinal Variability of the VTEC Response to the 10 May 2024 Geomagnetic Superstorm in the 20°E-40°E Sector

Sat, 14 Nov 2026 00:00:00 +0000

The geomagnetic superstorm of 10 May 2024 produced pronounced ionospheric disturbances whose magnitude and temporal evolution differed across latitudes. This study examined the vertical total electron content (VTEC) response in the 20°E–40°E Europe–Africa sector using observations from seven Global Navigation Satellite System (GNSS) stations spanning northern high latitudes, the equatorial region and southern high latitudes. VTEC and its percentage deviation from a quiet-time reference were analysed over 8–15 May 2024, together with interplanetary and geomagnetic parameters, equatorial electric fields estimated using the Prompt Penetration Equatorial Electric Field Model (PPEFM), and thermospheric O/N₂ maps derived from GUVI observations aboard TIMED. The response varied markedly with latitude, hemisphere and storm phase. Positive VTEC disturbances during the main phase reached approximately +180% at SUTH and exceeded +400% at SYOG. In contrast, negative disturbances reached −63% at VARS, −84% at GLSV and −66% at RAMO, with depletion extending into the recovery phase. At ADIS and MAL2, alternating positive and negative disturbances occurred alongside fluctuations in the interplanetary magnetic field Bz component and PPEFM-estimated equatorial electric fields. Changes in the thermospheric O/N₂ distribution were also observed during the event. Overall, these observations indicate interhemispheric asymmetry and suggest possible contributions from electrodynamic forcing, changes in thermospheric composition and seasonal background circulation. The findings characterise the latitudinal variability of VTEC within the sampled longitude sector.

Comparative Analysis of the Chemical Reactivity and Physicochemical Properties of Selective and Non-selective Herbicides

Sat, 14 Nov 2026 00:00:00 +0000

This study compared electronic reactivity and selected physicochemical properties of eight herbicides classified as selective or non-selective: glyphosate, butachlor, clethodim, fluazifop, fosamine, glufosinate, paraquat and propanil. Molecular geometries were optimised using density functional theory at the CAM-B3LYP/6-31G level. Frontier molecular orbitals, global reactivity descriptors and condensed Fukui indices were examined, while EPI Suite provided structure-based estimates of lipophilicity, water solubility, bioconcentration, bioaccumulation and persistence. The reported HOMO–LUMO energy gaps ranged from 2.933 to 9.081 eV. Clethodim exhibited the smallest gap and highest tabulated electrophilicity index, whereas glyphosate had the largest gap and greatest chemical hardness. The local reactivity indices suggested variation in preferred atomic sites across the molecular structures, with carbon atoms predominating in the reported assignments. Estimated lipophilicity, solubility and bioaccumulation-related descriptors also differed among the compounds. However, these results describe molecular and model-based properties rather than experimentally measured herbicidal activity, crop selectivity or environmental risk. Interpretation is constrained by the assumptions of the DFT approach and the applicability of the EPI Suite prediction models, particularly for ionisable structures. Furthermore, the software inputs and derivation of persistence values were incompletely specified, and some reported physicochemical results require reconciliation with the original outputs. The analysis therefore provides a comparative theoretical framework for the selected herbicides and identifies the need for computational verification and experimental assessment before broader biological or environmental conclusions are drawn.