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

Sanda Yusuf Sadau — 2026-10-12

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 — 2026-10-13

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 — 2026-10-23

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.