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Implications of Dynamic Interactions between Meteorological Patterns and Surface Water Quality on Environmental Health—A Case Study of the Nairobi River

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Journal of Geoscience and Environment Protection 2024年第5期12卷 113-146页

作者： Haron Safari Hongbin Chen Edwin Kipkirui duncan mbuge College of Environmental Science and Engineering Tongji University Shanghai China National Engineering Research Center for Urban Pollution Control Shanghai China College of Environmental and Biosystems Engineering University of Nairobi Nairobi Kenya

Urban areas face significant challenges in maintaining water quality amidst increasing urbanization and changing climatic patterns. This study investigates the complex interplay between meteorological variables and water quality parameters in Nairobi City, focusing on the impacts of rainfall and temperature on surface water quality. Data from multiple sources, including the Water Resources Authority, Nairobi Water and Sewerage Company, and the World Bank’s Climate Change Knowledge Portal, were analyzed to assess the relationships between meteorological variables (rainfall and temperature) and water quality parameters (such as electroconductivity, biochemical oxygen demand, chloride, and pH). The analysis reveals varying impacts of rainfall and temperature on different water quality parameters. While parameters like iron and pH show strong relationships with both rainfall and temperature, others such as ammonia and nitrate exhibit moderate relationships. Additionally, the study highlights the influence of runoff, urbanization, and industrial activities on water quality, emphasizing the need for holistic management approaches. Recommendations encompass the establishment of annual publications on Nairobi River water quality, online accessibility of water quality data, development of hydrological models, spatial analysis, and fostering cross-disciplinary research collaborations. Implementing these recommendations can enhance water quality management practices, mitigate risks, and safeguard environmental integrity in Nairobi City.

关键词： Water Quality Meteorological Conditions Urban Environment Environmental Health Nairobi Water Quality Parameters

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Assessment of Super Absorbent Polymer (SAP) on Plant Available Water (PAW) in Dry Lands

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Engineering（科研） 2023年第2期15卷 90-105页

作者： Vincent Ng’eno Christian Omuto duncan mbuge Vitalis Too Department of Environmental and Biosystems Engineering University of Nairobi Nairobi Kenya

One of the ways of overcoming the cost of irrigation is through in-situ water harvesting at the plant roots. Super absorbent polymer (SAP) can facilitate water harvesting at the plant roots. This study attempted to assess the effect of SAP on plant available water (PAW) of different soils. In this study, SAP was sequentially added at the rate of 0.2%, 0.3% and 0.5% of the soil weight and its impact assessed in clay, sandy clay and sandy loam soils. The moisture retention characteristics of the original and SAP treated soils were studied using soil water retention curves (SWRC) and results modelled using Gardner model. PAW was estimated from SWRC as the difference between moisture content at 1.5 and 3 bar in all soils. The difference in PAW between original and treated soils was assessed at 5% level of significance. The WRC of all the samples was adequately found to be described by the Gardner model (Coefficient of determination R2 ≥ 98% and residual standard error (RSE) ≤ 0.04). SWRC changed with increase in SAP percentage in clay, sandy clay and sandy loam soils. Clay had a higher change in water retention then sandy clay and lastly sandy loam. Plant available water content (PAW) in all soils increased. In clay soil it increased with increase in SAP from 0.3291 at zero SAP to 0.6223 at 0.5% SAP. Sandy clay soil increased in PAW from 0.2721 at zero SAP to 0.5335 at 0.5% SAP and Sandy loam soils from 0.1691 at zero SAP to 0.3461 at 0.5% SAP. Hence, from the study SAP can be used to conserve irrigation water in the plant roots and therefore reducing the cost since PAW has been increased.

关键词： Plant Available Water (PAW) Soil Water Retention Curve (SWRC) Soil Super Absorbent Polymer (SAP)

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The Effect of the Operational Parameters on the Draft Requirement of Ripping in a Sandy Clay Soil

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Open Journal of Optimization 2016年第1期5卷 1-13页

作者： John Ndisya Ayub Gitau duncan mbuge Angela Hiuhu Department of Environmental & Biosystems Engineering University of Nairobi Nairobi Kenya

This study set out to investigate the effect of operational parameters (i.e. ripping depth and operational speed) during a ripping operation on the draft requirement during ripping in a sandy-clay soil. Field experiments, laboratory tests and numerical modelling techniques were utilised to observe how the draft force varied with changing values of the operational parameters. The discrete element method in the EDEM AcademicTM software platform was employed to model the soil en-masse to obtain a virtual experimentation platform on which different treatments combing different settings of the operational parameters were investigated. Statistical methods, including ANOVA, regression analysis and the student t-test were applied to establish the significance of the effect of the operational parameters on the draft requirement;statistical analysis revealed that the draft increased linearly with the ripping depth and operating speed suggesting that they are directly proportional. Lower values of the ripping depth and operating speed were found to give the minimum amount of the draft requirement.

关键词： Draft Requirement Discrete Element Method Numerical Simulation Specific Draft Ripping Depth Operational Speed

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Optimization of the Angle of Frog in Mouldboard Tillage Operations in Sandy Clay Soil

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Open Journal of Optimization 2015年第4期4卷 131-140页

作者： Angela Hiuhu Ayub Njoroge Gitau duncan Onyango mbuge John Ndisya Mulwa Department of Biosystems Engineering University of Nairobi Nairobi Kenya

This paper investigated the effect of three independent variables including: tillage speed (ranges of below 2.5 m/s and between 2.5 m/s and 5 m/s), tillage depth (range of 10 cm from 0 cm to 30 cm) and frog angle (30° 40°, and 50°) on draught forces. The experimental work was completed with determination of the draught forces using an analytical method (Saunders Equation). Numerical Simulation: Discrete Element Method (DEM) was used to verify the results obtained analytically. The results indicated that tillage depth has a stronger influence on the draught forces as compared to the tillage speed. Minimal draught forces can then be achieved through operating at shallow tillage depth and maintaining a frog angle of 30°. The results showed a variance of ±15.95% to the calculated values supporting DEM as a numerical method capable of predicting draft forces correctly, tillage power optimization and determination of optimal frog angle for the mouldboard plough.

关键词： DEM EDEM Soil-Cut Interactions Modelling Tillage Draught

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