College of Natural and Computational Sciences
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Item Comparative Evaluation of Digestion Methods for Heavy Metal Analysis in Soil, Water, and Plants from Tigray, Ethiopia(Mekelle University, 2025-08-25) Robel Dawit AregayHeavy metal contamination is a growing concern in Tigray, Ethiopia, due to mining activities, agricultural inputs, and potential risks to public health, yet no standardized local protocol exists for reliable, cost-effective, and accurate digestion methods essential for environmental monitoring. This study compared four wet digestion methods—Method A (HCl–HNO₃, 3:1), Method B (HCl–HNO₃–H₂SO₄), Method C (HCl–HNO₃–HClO₄), and Method D (HCl–HNO₃– HClO₄–HF)—for determining total concentrations of Cu, Zn, Pb, Co, Cr, Cd, Mn, Fe, and Ni in soil, plant, and water samples from Ezana Mining Development PLC, Mekelle, Ethiopia, using Flame Atomic Absorption Spectrophotometry (FAAS). Performance evaluation based on accuracy (Z-scores and spiking recovery), precision (relative standard deviation), and costeffectiveness, supported by one-way ANOVA (p < 0.05), revealed significant differences among methods, with overall recoveries ranging from 88% to 102% across matrices. Methods A and D showed superior accuracy and precision compared to Methods B and C, with Method A offering comparable performance to Method D while being simpler, safer, and more economical, making it suitable for routine monitoring. Although Method D achieved slightly higher extraction efficiencies for refractory metals, it demands specialized infrastructure, HFhandling safety, and advanced technical expertise. The findings suggest Method A is best suited for general environmental assessments in resource-limited laboratories, while Method D is recommended for targeted analyses requiring maximum recovery, thereby enhancing environmental data quality, strengthening heavy metal monitoring programs, and supporting evidence-based policy decisions in Tigray.Item Assessment of Heavy Metal Levels in Soil, Vegetables and Wastewater used for Irrigation in Wukro, Tigray, Ethiopia(Mekelle University, 2025-09-25) Nigisti GirumFresh vegetables and fruits are the most common foods of human diet all around humankind often used for balanced diet, prevention and treatment of various diseases. However, if these vegetables and fruits grow in a polluted environment they can be a major public concern due to their toxic property which leads to acute and chronic health effects. The aim of this study was to determine the level of manganese, chromium, copper, zinc and lead and to estimate their health risks associated with their daily intake in vegetables grown in Wukro town, Tigray. FAAS was used to determine concentrations of those heavy metals in selected vegetables (cabbage, onion, spinach, lettuce and tomato). 1 gm of each sample was digested by wet digestion method using a mixture of HNO3 (69%), HClO4 (70%) and H2O2 (30%) until a clear solution was prepared. After proper dilutions, the solutions were aspirated into the FAAS. The absorbance value of heavy metals was converted in to concentration using linear calibration curve equation. Finally, the concentration of each metal was expressed in mg/Kg of dry weight of each sample and health risk was estimated by using estimated daily intake (EDI), target hazard quotient (THQ), and hazard index (HI) for selected heavy metals. The validity of the method was checked by the analysis of spiked samples whose recovery was found in the range of 90.8-107.0% and %RSD value in the range of 0.03-7.7%. The average concentrations of Cr and Cu in all of the selected vegetables were lower than the maximum limit of normal values. However, concentrations (mg/kg) of Pb in cabbage (2.05), spinach (2.47), and lettuce (1.56) had exceeded the safe limit, 0.3 mg/Kg set by FAO/WHO. Hence, consuming plant products grown from contaminated water sources such as municipal wastes, industrial effluents, engine fuels, garages disposals, constructions and car washes are potentially toxic to plants, animals and humans. Therefore, people and concerned bodies should take care of the sources of water for irrigationItem EVALUATION OF AIR POLLUTION CONTROL TECHNIQUES IN MESSEBO CEMENT FACTORY, TIGRAY, ETHIOPIA(Mekelle University, 2025-09-25) Araya GebreyohannesCement production is one of the most emission-intensive industrial activities, contributing significantly to global air pollution and greenhouse gas emissions. This study assesses the effectiveness, limitations, and implementation status of air pollution control techniques and their associated occupational health impacts at Messebo Cement Factory PLC (MCF) in Northern Ethiopia. A mixed-method design was employed, integrating quantitative on-site pollutant measurements (CO₂, NOₓ, SO₂, CO, and particulate matter) with qualitative surveys and clinical health data. Field results indicated that pyroprocessing and raw material handling were the dominant emission sources. CO₂ emissions increased from approximately 78,884 tonnes in 2000/01 to 990,767 tonnes in 2015/16, primarily due to production expansion, while per-tonne emissions remained above international best practice benchmarks. Particulate matter concentrations at raw milling points reached 240 mg/Nm³, exceeding Ethiopia’s national limit of 150 mg/Nm³ and the WHO/IFC guideline of 50 mg/Nm³. Despite the presence of baghouse filters and other emission control systems, frequent exceedances revealed operational inefficiencies and maintenance deficiencies. Survey data from 1,235 respondents, including factory employees and nearby residents, showed that 65% observed visible dust emissions and 76% reported receiving no environmental or safety training. Analysis of clinical records from 2013–2017 further revealed high incidences of respiratory tract infections (up to 22.4%) and dermatitis linked to particulate exposure. The findings demonstrate that current air pollution control and occupational health practices at MCF are inadequate to meet regulatory and safety standards. The study recommends upgrading filtration systems, adopting cleaner fuels, improving occupational health and safety management, and aligning operations with ISO 14001 and IFC/World Bank environmental standards to promote sustainable industrial performanceItem GROUNDWATER POTENTIAL AND WELL YIELD DISCREPANCIES: HYDROGEOLOGICAL CONTROLS, DRILLING CHALLENGES, AND AQUIFER PARAMETER–RESISTIVITY RELATIONSHIPS IN UPPER BILATE RIVER BASIN, MAIN ETHIOPIAN RIFT VALLEY, SOUTHERN ETHIOPIA(Mekelle University, 2025-10-16) Fisseha Teka HailuDiscrepancies in well yields within the Upper Bilate River Basin (UBRB) of the Ethiopian Rift Valley Lake Basin highlight the intricate hydrogeology of its volcanic aquifers and Quaternary deposits. This study examines the influence of drilling-challenges such as partial penetration, well loss coefficient, wellbore storage on yield variations, which may surpass the effects of natural hydrogeological variability. By integrating data from meteorological, hydrological, remote sensing, vertical electrical sounding, and pumping tests with historical well records, key aquifer parameters like transmissivity and hydraulic conductivity are quantified, while empirical relationships between aquifer productivity and resistivity are established. This study's water balance analysis for the Upper Bilate River Basin reveals a semi-humid system with a 254.6 mm annual surplus. A significant wet-season surplus facilitates groundwater recharge, estimated at 58.9 mm/year (6% of rainfall), indicating moderate infiltration and strong surface water-groundwater interaction A hydrogeological framework and groundwater potential zone map, generated through weighted overlay analysis of ten thematic layers, categorized the basin into excellent (1.39%), very good (17.9%), good (79.17%), and low (1.54%) potential zones. Most wells align with high-potential zones, confirming predictive accuracy: 74% of Wells are in very good zones and 26% in good zones, with none in low-potential areas. Transmissivity (T) in the study area varies from 0.05 to 841.10 m²/day, indicating a heterogeneous aquifer system. Moderate to moderately high transmissivity zones (59.77–89.93 m²/day) dominate, covering nearly 60% of the area, mainly in the central and northern parts, suggesting good aquifer productivity. Geophysical investigations identify Layer 6 (highly weathered and fractured pyroclastic rocks) as the most promising aquifer, followed by Layers 5 and 4, while upper shallow layers function as aquitards. A strong correlation between transmissivity and transverse resistance (r = 0.83, p = 1.32×10⁻¹³) supports the integration of geophysical and pumping test data for aquifer assessment. Well yield discrepancies in the UBRB are influenced more by drilling challenges than by aquifer natural heterogeneity. An analysis of 220 Wells indicates a partial penetration ratio (L/b) of 0.13 to 0.96, with a mean of 0.56, suggesting moderately penetrating wells. Wellbore storage shows that 49% of wells have high storage (Cw ≥ 0.9), while 27% have low storage (Cw < 0.1), reflecting variable aquifer connectivity. In a study of 25 wells, loss coefficients (C) range from 4.0×10⁻⁷ to 5.0×10⁻⁵ day²/m⁵, with 72% classified as severely clogged and none being properly developed. Well efficiency varies between 11.2% to 100% (mean 70.3%), with 18% rated Poor, 22% Fair, 30% Good, and 30% Excellent. This highlights the need for better well design, development, and maintenance practices. The correlation between transmissivity and well efficiency demonstrates that aquifer transmissivity primarily governs well performance, with high-transmissivity zones hosting the most efficient wells. In contrast, low efficiency in moderately transmissive areas mainly stems from technical issues—such as improper well design, partial penetration, or excessive wellbore storage rather than aquifer limitations. Enhancing well construction and maintenance practices is therefore crucial to fully realize groundwater potential in these zones.Item Evaluation Of Limestone as Coarse Aggregate in Concrete and Cobblestones: A Case study from Mekelle Area, Northern Ethiopia(Mekelle University, 2024-11-25) Muez AregawiEngineering geological investigation is essential for evaluating the quality of construction materials and ensuring the durability of engineering structures. This study assessed the physical and mechanical properties of limestone aggregates from selected quarries in the Mekelle area to determine their suitability for concrete and stone-paved road applications. A total of twelve representative samples and 50 kg of coarse aggregates were collected according to ASTM D75 from the Shugala, Kokolo, Mayalem, Mossobo, Chanadug, and Genha quarry sites and tested for gradation, specific gravity, unit weight, water absorption, moisture content, flakiness index (FI), aggregate crushing value (ACV), Los Angeles abrasion value (LAAV), and unconfined compressive strength (UCS), with results compared to ASTM and BS standards. The results indicate that the tested aggregates largely satisfy international specifications. Specific gravity values ranged between 2.43 and 2.83, while unit weight varied from 1.47 to 1.65 g/cm³. According to ASTM C33 classification, these unit weight values confirm that the aggregates are normal weight. Water absorption values (0.11%–0.78%) fall within the required range, indicating low porosity and good durability. Moisture content is very low (0.012–0.39%), significantly below the 4% limit, ensuring that the aggregates are dry. Mechanical tests revealed flakiness index values ranging from 12.11–20.30%, ACV values from 10.66–22.16%, LAAV values from 19.18– 25.40%, and UCS values from 105–117 MPa, indicating that all samples fall within the “highstrength” category (>55 MPa). Sieve analysis further revealed that aggregates from Chanadug, Genha, Mossobo, and Mayalem quarries exhibit favourable particle size distribution, making them highly suitable for construction, while those from Shugala and Kokolo did not meet gradation criteria.Item HYDROMETEOROLOGICAL STATIONS DISTRIBUTION AND PARAMETER TRENDS IN TIGRAY.(Mekelle University, 2025-09-25) MEBRAT AMAREThe effective management of water resources in Ethiopia's topographically complex Tigray Region is critically dependent on a robust hydro-meteorological observation distribution. However, the existing distribution suffers from severe deficiencies in spatial coverage and operational integrity, creating significant uncertainty for water resource planning. This thesis provides a systematic evaluation of the hydro-meteorological distribution in Tigray, analyzes long-term trends in key climatic and hydrological parameters, and proposes a data-driven framework for its optimization. The study employed a mixed-methods design, integrating Geographic Information Systems (GIS) to assess spatial adequacy against World Meteorological Organization (WMO) standards, non-parametric statistical tests (Mann-Kendall, Sen’s Slope) to analyze long-term (1960–2024) data, and field verification to assess operational status. Results reveal a network in critical failure. The conventional station network meets only 51% of the WMO minimum requirement, with precipitation stations achieving just 17% of the necessary coverage. This spatial gap is compounded by an operational collapse, with only 13% of the required stations currently functional, creating vast unmonitored areas. The streamflow gauging network is similarly sub-optimal, while the modern Automatic Weather Station (AWS) network is nascent. Trend analysis identified no significant long-term change in regional rainfall or streamflow. In conclusion, the existing monitoring infrastructure is structurally imbalanced, spatially biased, and operationally crippled, rendering it unfits to support reliable water resource assessment or climate-resilient development. This thesis culminates in a strategic roadmap with prioritized recommendations for the phased expansion and modernization of the network to build a scientifically robust observational foundation for the region.Item Landslide Susceptibility Mapping Using Frequency Ratio (FR) and Weight of Evidence (WoE) Methods, and Verification Using the Limit Equilibrium (LE) Method: A Case Study along the Bonga - Felegeselam Road.(Mekelle University, 2025-09-25) Hagos Kidanemariam GebregewergsLandslides are a critical geohazards in Ethiopia, particularly along mountainous and rift-margin road corridors, where they frequently disrupt transportation, damage infrastructure, and pose serious threats to human life. The study aims to generate landslide susceptibility mapping and slope stability analysis along the Bonga – Felegeselam road corridor. Initially, a total of 120 landslides were inventoried and mapped based on field visits and Google Earth image interpretation, and subsequently divided into two subsets: 70% for model training and 30% for validation. Eight landslide causative factors including slope angle, aspect, elevation, lithology, land use, distance to road, distance to stream and precipitation were selected based on geomorphological relevance and site verification. The relationship between landslide occurrence and causative factors was analyzed using frequency ratio (FR) and weight of evidence (WoE) models. Based on these models, landslide susceptibility maps were generated by integrating the weighted values of all factors and reclassified into five susceptibility zones: very low, low, moderate, high, and very high. The high and very high susceptibility zones accounted for 17.8% and 24.1% of the area in the FR and WoE models, respectively. The accuracy of the models was validated using the relative operating characteristic (ROC) curve and the area under the curve (AUC) values. The frequency ratio (FR) model achieved a prediction rate of 80.6%, while the WoE model yielded 79.1%, both indicating strong predictive capability. Geotechnical verification of eight road slope failures within moderate to very high susceptibility zones was performed using limit equilibrium method (LEM) based stability analyses. Secondary borehole and eight test pit data, supported by laboratory test results, were used to establish subsurface profiles and geotechnical parameters of the slope materials. Stability analyses using Bishop and Spencer methods under both dry and saturated conditions produced factors of safety ranging from 1.15 to 0.78 and 0.96 to 0.54, respectively. These results confirm the consistency of the susceptibility models by indicating strong agreement between mapped zones and stability analysis results. This approach provides a strong framework for landslide hazard management and informed infrastructure planning in Ethiopia and similar mountainous regions.Item Quantitative Analysis of Potentially Toxic Elements (Pb, Cd, Co, Cr, Fe, Mn, and Ni) in Lipstick Brands Available in Mekelle Markets, Tigray, Ethiopia(Mekelle University, 2025-09-25) Asfaw Mulugeta GebremedhinLipsticks, widely used cosmetic products, can be a significant source of potentially toxic elements exposure through unintentional ingestion. This poses potential long-term health risks due to the bioaccumulative nature of metals like Pb, Cd, and Cr. This study aimed to quantify the concentrations of seven potentially toxic elements (Pb, Cd, Co, Cr, Fe, Mn, and Ni) in three widely available and commonly sold lipstick brands from local markets in Mekelle, Ethiopia. Samples were prepared using a wet acid digestion method with a concentrated 5:1:1 mixture of HNO3, HCl, and H2O2 and analyzed through Flame Atomic Absorption Spectrophotometer (FAAS). Cd was not detected in any sample. The concentration ranges across all samples in ppm were: Pb (0.0400–0.1000), Co (3.740–5.570), Cr (10.62–18.05), Fe (75.00–1838), Mn (0.1500–0.1600), and Ni (12.83–51.41). The levels of Pb were well below the 10 ppm guidance limit set by international bodies like Health Canada, U.S. Food and Drug Administration (FDA), their consistent presence is a concern. However, concentrations of Cr and Ni, known sensitizers, were notable. As an intentionally added pigment, Fe showed the highest and most variable concentrations. Although the detected levels of toxic metals were within international permissible limits, their consistent presence is a public health concern. Given the direct ingestion route and frequency of application, daily use may contribute to the cumulative body burden of these metals over time. This study, though limited by a small sample size, highlights the urgent need for healthy regulatory oversight and routine quality control of cosmetics in Ethiopia. Further research is essential to assess a wider range of products and evaluate the associated health risks for consumers.Item The steady-state squeezing and entanglement properties of the cavity radiation from parametric oscillation(Mekelle University, 2025-01-29) Shambel AligazIn this thesis, we study the quantum properties of the light generated by a para metric oscillation with the cavity mode driven by coherent light beams coupled to a two-mode squeezed vacuum reservoir. Applying the master equation describing the interaction of the cavity modes with the driving coherent light beams and with the two-mode squeezed vacuum reservoir, we obtain the quantum Langevin equations. The solutions of the resulting equations are then used to calculate the mean and vari ance of the photon number, the quadrature variance, global quadrature squeezing and local quadrature squeezing of two-mode cavity light. It is found that the squeezing occurs in the plus quadrature and the driving coherent light beams have no effect on the squeezing properties of the two-mode cavity light. We have found that, at steady state and at threshold, there is a maximum squeezing of the two-mode cavity light when the cavity is coupled to squeezed vacuum reservoir. In general, the degree of squeezing increases with the squeezed parameter whereas the driving coherent light beams and the squeezing parameter have the effect of increasing the mean photon number of the two-mode cavity light.ContentsItem Muon Pair Production from Electron-Positron and Positronium Annihilation in Polarized Laser Field(Mekelle University, 2025-08-22) Seid Yimer AhmedThis thesis investigates muon pair production resulting from electron-positron annihilation and positronium interactions within polarized laser fields. The study systematically examines how various parameters of the laser field; specifically polarization, intensity, and photon energy affect the production rates and energy distributions of muon pairs. Through a series of computational simulations and sensitivity analyses, we established that increased laser intensity significantly enhances muon pair production rates, corroborating theoretical predictions from Quantum Electrodynamics (QED). Furthermore, the analysis reveals that circularly polarized light is more effective than linearly polarized light in facilitating muon pair production, underscoring the critical role of polarization in the interaction dynamics. Sensitivity analyses indicate that muon production rates are particularly responsive to changes in laser intensity and polarization, while variations in the initial energies of electron-positron pairs exert a comparatively minor influence. To validate these findings, future work is proposed, which includes experimental studies employing high-intensity laser systems to observe muon pair production under controlled conditions. The exploration of additional parameters, such as the energy distribution of the electron-positron pairs and varying laser wavelengths, is recommended to gain further insights into optimizing muon production. This thesis contributes to the growing body of research in high-energy particle physics, offering valuable insights for future experimental designs and the development of advanced laser systems aimed at enhancing muon production efficiencies.