Influence of Agricultural and Agro-Industrial Activities on Nutrient Dynamics and Water Quality in River Keyian, Kenya
Main Article Content
Keywords
Dissolved inorganic nitrogen, soluble reactive phosphorus, sugar industry effluent, eutrophication, , River Keyian, Kenya
Abstract
Freshwater ecosystems adjacent to agro-industrial developments are increasingly threatened by nutrient enrichment, yet the effects on water quality remain uncharacterized. This study evaluated the spatial distribution of nitrate (NO₃⁻), nitrite (NO₂⁻), ammonium (NH₄⁺), soluble reactive phosphorus (SRP), and total phosphorus (TP) in River Keyian, Narok County, Kenya, and assessed nutrient stoichiometry and eutrophication potential downstream of a treated sugar industry effluent discharge point. A total of 112 Water samples were collected bi-monthly from seven river stations and one effluent outlet between January and April 2024 using standard methods. Spatial variation and nutrient relationships were evaluated using one-way analysis of variance (ANOVA), Tukey's Honestly Significant Difference (HSD) test, Pearson correlation analysis, and the dissolved inorganic nitrogen to soluble reactive phosphorus (DIN: SRP) ratio. Nitrate, ammonium, SRP, and TP varied significantly among sampling stations (p < 0.05), whereas nitrite showed no significant spatial variation (p = 0.115). Nitrate increased approximately 1.8-fold, from 9.345 ± 6.073 mg/L upstream to 17.020 ± 3.626 mg/L downstream, while SRP and TP increased approximately 4.1-fold (0.216–0.893 mg/L) and 4.5-fold (0.670–3.009 mg/L), respectively. Total phosphorus exhibited the strongest spatial response (η² = 0.582) and was positively correlated with nitrate and ammonium (p < 0.01), indicating common nutrient sources. The DIN:SRP ratio declined from 37.779 upstream to 8.788 downstream, demonstrating increasing phosphorus availability relative to dissolved inorganic nitrogen and an elevated potential for eutrophication in the lower reaches of the river. The findings indicate that nutrient enrichment in River Keyian is driven by the combined effects of treated sugar industry effluent and diffuse agricultural activities rather than industrial discharge alone. These results provide evidence to support integrated watershed management, improved nutrient removal technologies, and routine water quality monitoring to protect the ecological integrity of River Keyian.
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Rael Sankei , Department Of Environmental Science, School of Environmental Studies and Natural Resource Management, University of Eldoret, P.O. Box 1125-30100, Eldoret, Kenya
Department Of Environmental Science, School of Environmental Studies and Natural Resource Management, University of Eldoret, P.O. Box 1125-30100, Eldoret, Kenya
Judith Khanzenzi, Department Of Environmental Science, School of Environmental Studies and Natural Resource Management, University of Eldoret, P.O. Box 1125-30100, Eldoret, Kenya
Department Of Environmental Science, School of Environmental Studies and Natural Resource Management, University of Eldoret, P.O. Box 1125-30100, Eldoret, Kenya
Gelas Simiyu , Department Of Environmental Science, School of Environmental Studies and Natural Resource Management, University of Eldoret, P.O. Box 1125-30100, Eldoret, Kenya
Department Of Environmental Science, School of Environmental Studies and Natural Resource Management, University of Eldoret, P.O. Box 1125-30100, Eldoret, Kenya