G.T. Oyerinde, K.O. Oluwasemire, S.O. Oshunsanya
Abstract: The cultivation of valley bottoms has been one of the means of coping with recent unpredictable rainfall pattern and climate change. These valleys are often prone to pollution from adjacent plains due to their lower elevation which might have significant impacts on soil physical and hydrological properties. The effects of water pollution on soil physical and hydrological properties of a valley bottom was evaluated during 2010 dry season at a site within the University of Ibadan, Nigeria. Geo-referenced ground and surface water samples were collected from the field and analyzed for their physical and chemical properties. Bulk soil and plant samples were collected for analysis. River soil sediment samples were collected and analyzed for their relative distribution of Sand, Silt and Clay fractions. All soil, water and vegetable plants collected from the field were also analyzed for their metal contents. Collected data were compared with WHO and FEPA standards to assess the level of pollution in the valley bottom. Pollution to surface water comes from drainage and sewage channels alongside remnants from adjacent recently constructed roads. The physical and chemical properties of the surface water shows a high concentration of sodium ion, and sodium adsorption ratio (SAR) with values ranging from 29mg/l to 3400 mg/l and SAR values of 5.2 meq/l to 439.8meq/l. However, ground water samples have a lower sodium ion concentration of 38.2mg/l to 605mg/l and a mean SAR value of 6.9meq/l. A BOD value range of 105mg/l to 279.2mg/l was recorded alongside with TSS of 357.6mg/l to 978.5mg/l. The turbidity, total dissolved solids trend is in the same direction with BOD and TSS. The soil expressed a high total porosity that shows no correlation with volumetric moisture content. Recommendations for the prevention of pollution of surface water to ensure sustainable agricultural land resources management of the valley bottom were suggested.
Keywords: Water pollution, Valley bottom, Soil physical, Hydrological properties