Physico-chemical characteristics and microbial flora of sediments in Itagunmodi gold mining community in Atakumosa West Local Government Area of Osun State, Southwestern, Nigeria
In this study, the physical and chemical characteristics including the microbial flora of sediments in the waterbodies (rivers and reservoir) in Itagunmodi gold mining community of Atakumosa West Local Government Area of Osun State were investigated from June, 2014 to March, 2015. The aim of the study was to provide baseline information on aspects of the benthos limnology and assessing the impact of gold mining activities on the ecosystem functioning of the waterbodies. Three river stations and four reservoir stations were selected for investigation. Sediment samples were collected from these waterbodies for physical and chemical analysis and microbial analysis. Ambient air, water and sediment temperatures and location grid coordinates of the sampling stations were determined in situ. Particle size distribution of the sediment samples was measured using hydrometer method while exchangeable cations (Ca2+, Mg2+, Na+, K+) were determined using flame emission spectrophotometer (for Na+ and K+) and atomic absorption spectrophotometer (for Ca2+ and Mg2+). The sulphate, pH, electrolytic conductivity, nitrate, chloride and organic carbon content of the sediments were also determined. Microbial analysis was carried out using pour plate technique followed by microscopic examination and determination of morphological characteristics of the colonies (using Bergey’s Manual of Determinative Bacteriology). The data obtained were subjected to descriptive statistics and analysis of variance (ANOVA) using paleontological statistics software. The sediments were classified as acidic to alkaline over a pH range of 5.6 to 8.3 and generally sandy clay in texture. Mean values of calcium, ammonium, chloride, sulphate, phosphorus, organic carbon, manganese, iron, zinc and copper were significantly higher at the river stations than at the reservoir stations. The percentage base saturation was significantly higher (p<0.01) in dry season than in the rainy season. On the other hand, the mean values of organic carbon and calcium were significantly higher during the dry season than rainy season. A total of nine bacterial species and thirteen fungal species were recorded. The microbial flora were classified into taxonomic categories, abundance, distribution were evaluated with respect to river and reservoir stationsl species. Bacterial species were more abundant than the fungal species Seasonal variation in the benthic microbial flora showed more species collected in rainy season than in dry season. Some of the identified species of microbial flora (Corynebacterium, Micrococcus, Pseudomonas and Staphylococcus) are known to be pathogenic and capable of causing different types of diseases. However, most of the parameters fell within WHO guideline level. The study concluded that the residual effect of manual mining activities on sediments of waterbodies in Itagunmodi community of Atakumosa West Local Government Area of Osun State was insignificant.