Global Journal of Geological Sciences

Comparative Study Of Nitrate Evaluation And Bacteriological Characterisation Of Shallow Groundwater In Adjoining Towns Around Oyo Area, Sw Nigeria

Akanbi O A, Joseph G D, Olayiwoola J O — Fri, 14 Mar 2025 00:00:00 +0000

The study aimed at assessing the quality of groundwater from forty-five shallow hand-dug wells (HDs) in adjoining towns of Awe, Akinmorin, Ilora and Oyo within the southwestern Nigeria. The amounts of nitrate and bacterial counts and species identification were carried out in water samples in these communities where groundwater is the major reliable water source using spectrophotometric, multiple tube and plate counts techniques.

From the results, nitrate concentration was between 1.48 and 191.8 mg/L in sampled wells and its occurrence in water exceeded the recommended level of 50 mg/L in about 38% of sampled wells across all the towns. Oyo town has the highest nitrate level in water with a range of 5.11 - 191.8 mg/L and average of 71.24 mg/L, compared to 29.87 mg/L in Awe, 41.33 mg/L in Akinmorin, 45.09 mg/L in Ilora. The minimum total bacteria count (TBC) was 26 cfu/100 mL while the total coliform count (TCC) ranged from 14 to 46 cfu/100ml. The presence of coliform bacteria depicts fecal contamination of groundwater in the study area. From the morphological studies, four bacteria species were identified; namely, Bacillus cereus (which is the most abundant), Bacillus species, Pseudomonas aeroginosa and the Klebsiella species. The deepest hand-dug well was 20.8 m in the area and the correlation between the depths of the HDs and nitrate concentrations is negative-indicating that nitrate concentration moderately decreases with increasing well depth. Likewise for bacteria counts, the relationship was indirect in most towns, which depicts that bacterial occurrence will likely fade out as well depth increases in most cases. Also, the cross-plots of nitrate against bacterial counts in groundwater were positive that confirms that high nitrate level in water will favour bacterial activities. From these deductions, deeper wells are recommended and remedial decontamination of functioning wells should be in place in these communities to guarantee safety of human lives.

Geospatial assessment of landslide vulnerability mapping using remote sensing and fuzzy-ahp in urban and rural regions of orumba north, southeastern nigeria.

Wed, 07 May 2025 00:00:00 +0000

Landslides present a significant geohazard in Orumba North, southeastern Nigeria, with varying impacts on urban and rural regions. This study aims to assess and compare the vulnerability of both regions to landslides using a combination of remote sensing, (GIS), and the fuzzy analytical hierarchy process (Fuzzy AHP). The integration of these methodologies allows for a precise spatial delineation of landslide-prone zones based on the factors contributing to the differential susceptibility of urban and rural landscape. These conditioning factors include; slope, rainfall, elevation, curvature, land use and land cover, normalized difference vegetation index, and proximity to streams and roads, which were used for the assessment. Through fuzzy-AHP, these factors were assigned weighted importance based on expert judgement and environmental conditions, the defuzzification process converted the fuzzy weights into crisp value for precise evaluation these crisp values was used to rank the factors based on their relative importance. Using the defuzzified weights, a landslide vulnerable map was generated, classifying the study area into four susceptibility levels; low, moderate, high, very high. The result highlight that the urban areas such as Oko, Nanka, and Ajalli exhibit higher vulnerability to landslide due to intense human activities, including construction, deforestation, and poor drainage management that exacerbate slope instability. In contrast rural area like Ufuma and Omogho are largely affected by natural factors including steep slope, agricultural practices, leading to significant but less human induced susceptibility. Statistically, the affected urban area covers about 78% of the study area, while the rural area cover about 22%. This geospatial assessment offers valuable knowledge for local planner and decision markers, as the generated susceptibility map can serve as a guide for hazard mitigation strategies, By identifying high risk area, particularly those in urban centres with higher development pressure, targeted efforted can be made to improve land use planning, drainage system and slope stabilization. The study findings are crucial for formulating policies that address both human and natural factors contributing to landslides, ultimately aiding in disaster risk reduction in the urban and rural area of Orumba North region.

Quality Of Construction Materials And Their Effects On The Sustainability Of Highway Pavements In Parts Of Anambra State, Southeastern Nigeria

Wed, 07 May 2025 00:00:00 +0000

Construction of any sustainable road requires the determination of engineering properties of the materials to be used in the project. In this work, the impact of the construction materials used in some parts on Anambra State (southeastern Nigeria) with significant road pavement failure rate is investigated. Soil and aggregate samples were collected in situ on some failed spots on major roads in the state and were subjected to standard laboratory analyses. The results indicated that the roads were constructed on sandy subgrades with gravel-sized particles that ranged from 0 – 43 %, sand 25 – 77 %, and fines 14 – 63 %. The liquid limit of the subgrade materials ranged from 27 – 44 %, plasticity index 10 – 24 %, while the linear shrinkage ranges from 8 – 11 %. These Atterberg limit results denote low to moderate expandable soils. Maximum dry density ranged between 1.93 - 2.20 Mg/m³, while optimum moisture content ranged from 6.78 to 15.9%. The California bearing ratio (CBR), on the other hand, ranged between 60 – 161 %, for unsoaked condition, and 17.8 %, for soaked condition, indicating fairly stable materials. Based on the American Association of State Highway and Transportation Officials (AASHTO) classification system, the subgrade samples classify mainly as A-2-6 soil or as CL according to the Unified Soil Classification System (USCS). The particle density value ranges from 2.35 - 2.71 Mg/m³, while the field relative compaction density ranges between 89 – 108 %. Analysis on the sub base and base course aggregates indicated bulk density of fine aggregate (sand) that ranged from 0.16 - 1.68 Mg/m³. Comparison of the results with an engineering standard revealed that the materials did not meet standard limits(FMW&H), hence, the failure recorded on the paved roads. Water inflow would result in subgrade material expansion, hence, stability and bearing capacity reduction. ANOVA test result indicates significant variable from the data source while principal component and correlation analyses suggests that moisture content, liquid limit and plasticity index have direct statistical relationships. This research therefore advocates proper drainage design and stabilization of the subgrade materials in the area during road construction.