Journal of Aquatic and Terrestrial Ecosystems

Effects of Adsorbent Dosage and Particle Size on Fluoride Removal Using Calcium-Spiked Moringa oleifera Seed Powder

Geoffrey Chavaregi , John Kituyi Lusweti, Pius Keronei Kipkemboi — Tue, 23 Sep 2025 00:00:00 +0000

Access to safe drinking water remains a major challenge in fluoride-endemic regions, where excessive fluoride concentrations can lead to dental and skeletal fluorosis. This study evaluated the effects of adsorbent dosage, particle size, and particle size classification (mesh size) on the fluoride removal performance of Moringa oleifera seed powder (MOSP) in both calcium-spiked and non-spiked forms. A three-factor factorial batch adsorption experiment was conducted using initial fluoride concentration of 1ppm, dosages of 0.25–2.0 g/100 mL, particle sizes of <250 µm, 250–500 µm, and >500 µm, and mesh classifications of 20 (850 μm), 40 (425 µm), and 60(250 μm). Response variables included fluoride removal efficiency, residual fluoride concentration, and adsorption capacity (qe), measured using a fluoride ion-selective electrode. ANOVA and linear regression were applied to evaluate the dose and size response relationships. Results showed that calcium-spiked MOSP consistently outperformed non-spiked MOSP across all parameters. Fluoride removal efficiency increased with dosage, reaching 88.95% for spiked and 70.34% for non-spiked MOSP at 2.0 g. Finer particle sizes and smaller mesh fractions significantly enhanced removal efficiency and reduced residual fluoride levels, with spiked MOSP at ≤250 µm achieving 89.80% removal and residual fluoride below WHO guidelines. Regression analysis confirmed strong inverse relationships between particle size/mesh size and fluoride removal performance, and positive correlations with dosage. The improved performance of calcium-spiked MOSP is attributed to increased surface-active Ca²⁺ sites enabling precipitation of CaF₂ and enhanced adsorption via electrostatic attraction and ion exchange. These findings indicate that calcium-spiked MOSP, optimally prepared at fine particle size and moderate dosage, is a viable, locally sourced defluoridation medium suitable for rural water treatment systems.

Influence of pH Variation on Lead Uptake and Accumulation in Raphanus raphanistrum and Brassica napus Grown in Spiked and Limed Agricultural Soils of Moiben Sub-County, Kenya

Faith J. Barno, Gelas M. Simiyu , Josephine M. Mulei — Tue, 21 Oct 2025 00:00:00 +0000

This study assessed Pb uptake and distribution in Raphanus raphanistrum (RR) and Brassica napus (BN) grown in agricultural soils from Moiben Sub-County, Kenya, under three soil treatments: Pb-spiked soil (to ≈1000 mg/kg), non-spiked soil, and spiked soil amended with lime (to achieve pH≈7.4). Pb concentrations were quantified using Atomic Absorption Spectrophotometry (AAS), and the Bioaccumulation Factor (BAF) was calculated for roots, stems, leaves and seeds. Data were analyzed using SPSS v25. Descriptive statistics (means, standard deviations) were computed for Pb concentrations in soil and plant tissues. One-way ANOVA tested differences among treatments (control, spiked, limed), with Tukey’s HSD applied for post hoc comparisons. Results showed that Raphanus raphanistrum accumulated mean Pb concentrations of 1043.80 ± 18.34 mg/kg in spiked soils, 25.49 ± 0.39 mg/kg in non-spiked soils, and 548.24 ± 17.75 mg/kg in spiked and limed soils. Brassica napus followed a similar trend, with significantly higher Pb accumulation in spiked compared to non-spiked soils, while liming reduced uptake by nearly 50%. In both species, roots exhibited the highest BAF across treatments, while stems consistently recorded the lowest. In spiked soils, the accumulation trend was roots > seeds > leaves > stem, whereas in limed soils it shifted to roots > leaves > seeds > stem, with overall BAF values reduced to <1. Although liming effectively reduced Pb uptake, both Raphanus raphanistrum and Brassica napus accumulated Pb levels in edible parts above FAO/WHO permissible limits (0.3 mg/kg for leafy vegetables, 0.1 mg/kg for root/tuber crops, and 0.2 mg/kg for cereals and oilseeds), raising concerns over food safety. The findings highlight the influence of soil amendments on metal bioavailability and underscore the phytoremediation potential of RR and BN, particularly in Pb-contaminated soils.

Assessment of Land Cover Changes in the Micro-Catchments of the Nyando River Basin within the Lake Victoria Basin, Kenya

John Ogembo Okungu, J. B. Okeyo-Owuor, Victor A. O. Odenyo — Sat, 27 Sep 2025 00:00:00 +0000

The Nyando and Awach river catchments serve as vital headwaters draining into the Winam Gulf of Lake Victoria, an ecosystem increasingly threatened by sediment and nutrient loading. Despite its crucial role in regional hydrological stability, this region has undergone immense, largely unregulated anthropogenic pressure, leading to suspected widespread environmental degradation. The lack of long-term spatial data on the nature and level of land cover conversion constitutes a major barrier to formulating effective conservation strategies. To address this gap, this study quantified the extent, magnitude, and spatial dynamics of Land Cover Change (LCC) to assess the actual scale of environmental degradation. LCC was quantified through a time-series analysis of LANDSAT TM/ETM satellite imagery (1995, 2000, 2006, and 2012). A comparative micro-catchment classification (Uninterfered, Interfered, and Intervened sites) provided the environmental sampling framework. Images were processed using a Hybrid Supervised Classification approach to delineate four key thematic classes: Vegetation, Built-up Land, Water, and Open Land. Change detection matrices were then generated to calculate the absolute change, rate of change and conversion pathways. The results revealed significant vegetation decline in the Nyando catchment, characterized by a net loss of 54.2% of vegetative cover over the 17-year period. This loss corresponded with a marked increase in Open Land (≈41.5%) and Built-up Area (≈14.3%). The dominant conversion pathway, accounting for approximately 40.9% of all change, was the direct transformation of Vegetation to Open Land, signifying widespread, non-conservative agricultural expansion in the highlands. However, the Awach catchments registered comparatively lower net change, largely due to the replacement of indigenous forests with commercial plantations, which concealed ongoing ecological degradation. The significant expansion of exposed Open Land critically increases the risk of soil erosion and intensifies runoff, posing a serious threat to the hydrological stability of the basin and contributing to sediment loading in Lake Victoria. Urgent policy interventions focused on mandating soil conservation practices, regulating settlement expansion and immediate rehabilitation of riparian zones are necessary to reverse these detrimental trends and ensure the sustainable use of basin resources.

Water Availability, Demand and Distribution in Kimng’oror Water Project in Nandi County

Leley Kipyego Bitok , Fatuma Daudi , Eudiah J. Arusei — Tue, 02 Sep 2025 00:00:00 +0000

Access to adequate and reliable water remains a challenge in many rural areas of Kenya, limiting household use and agricultural productivity. In Kimng’oror Water Project, Nandi County, households experience inconsistent supply despite the existence of piped water systems, raising concerns about water availability, demand and equitable distribution. The objective of this study was to assess the status of water availability, analyze household demand, and examine distribution mechanisms within the project area. The study employed a cross-sectional quantitative research design. Data were collected from 240 households selected through cluster and simple random sampling across four sub-areas: Kimng’oror, Kapter, Koiban, and Kapkoimur. Structured questionnaires were used to gather data, while descriptive and correlation analysis were performed using SPSS version 26. The findings revealed that while 67.5% of residents considered the water supplied by the project sufficient for daily use, 62.8% expressed doubt about the system’s ability to meet future domestic and agricultural needs. Only 24.2% of respondents viewed existing infrastructure as adequate for storage and distribution. Water availability was strongly related to demand (r = 0.684, p < 0.01) and moderately linked to distribution (r = 0.592, p < 0.01), while the strongest relationship emerged between demand and distribution (r = 0.721, p < 0.01). This indicates that as availability improves, demand rises, and growing demand directly pressures the distribution system to expand and adapt, influencing the overall sustainability of the project. The study concludes that although the Kimng’oror Water Project has improved access to piped water, supply remains insufficient and unevenly distributed. It recommends strengthening storage and distribution infrastructure, promoting sustainable catchment practices, enhancing community participation in planning and governance and adopting long-term strategies to align water supply with rising demand.

Modification of Solution pH as a Mechanism of Tolerance to Acidity and Aluminium Stress in Selected Cowpea (Vigna unguiculata L. Walp) Cultivars

Janeth Sang, Emily J. Too. , Beatrice A. Were — Thu, 09 Oct 2025 00:00:00 +0000

Aluminium toxicity is a major constraint to crop production in soils with a pH below 5.5. However, plant species exhibit varied tolerance mechanisms. Nine (9) cowpea cultivars that were coded; UOE-COWPEA-1, UOE-COWPEA-2, UOE-COWPEA-3, UOE-COWPEA-4, UOE-COWPEA-5, KEN-KUNDE-1, K-80, M-66 and KVU-27-1 were assessed for modification of solution pH and tolerance to acidity and aluminium stress in solution culture. Cowpea seeds were sterilized and pre-germinated in paper-lined trays and the seedlings were transferred to constantly aerated growth trays containing 1/5 X Hoagland Nutrient solution with a starting pH of 4.3, supplemented with 0 µM and 185 µM Al. The seedlings’ initial root and shoot lengths per cultivar were measured and recorded. pH measurements of the nutrient solutions were recorded daily for seven (7) days without adjusting. The final root and shoot lengths and number of lateral root branches per cultivar and treatment were assessed and recorded. Fresh root and shoot biomass were also measured and recorded. The data collected were subjected to analysis of variance (ANOVA), and the means were compared at significant level of P≤ 0.05 and separation of means was done using Tukey’s test. All the nine (9) cowpea cultivars progressively increased the pH of the solution culture. The growth of cowpea cultivars at 0 µM Al induced a higher change in pH compared to when grown in 185 µM Al concentration. UOE-COWPEA-4 caused the highest increase in pH from 4.3 to 5.13 while K-80 cultivar induced the least change in pH from 4.21 to 4.58 at 0 µM Al. UOE-COWPEA-5 induced the highest increase in pH when compared to others from 4.03 to 5.06 while K-80 cultivar induced the least increase in pH change from 4.32 to 4.53 when grown in solution culture supplied with 185 µM Al. UOE-COWPEA-4, KVU 27-1, KEN-KUNDE-1 and UOE-COWPEA-2 had higher relative net root length. UOE-COWPEA-3 produced significantly higher number of lateral root branches in low pH without Al compared to the other cultivars. UOE-COWPEA-3 produced a significantly higher number of lateral branches at 185 µM Al. The findings of this study show that cowpea exhibits genotypic variation in tolerance to acidity and aluminium stress. Furthermore, differences in modification of pH varied among the tested cowpea cultivars. It was concluded that acidity and aluminum tolerance were associated with alteration of pH of the solution, suggesting that cowpea adapts to acidity and Al stress by raising the solution pH.