Bacteriological quality of soil and surface water around the Ika-Ogboyaga coal mining site, Ankpa, Kogi state, Nigeria

Abstract

Coal mining alters the physicochemical character of soils and water, and with it the microbial communities responsible for nutrient cycling and self purification, yet little is known about the bacteriology of Nigerian mining areas. This study determined the occurrence, diversity and habitat distribution of culturable bacteria in soils and stream water around the Ika-Ogboyaga coal mining area of Ankpa, Kogi State, comparing a mining impacted zone with an adjacent non mining reference zone over four months from August to November 2024. Water was sampled at three stations along the stream, upstream, midstream and downstream, and surface soil was sampled at a depth of 0 to 15 cm at three points in each zone, giving twelve samples per medium per zone. Bacteria were isolated by the serial dilution pour plate method on nutrient agar and identified presumptively by colonial and cellular morphology, Gram reaction and conventional biochemical tests, without serological or molecular confirmation. Occurrence was scored as presence or absence per sample, and richness and frequency of occurrence served as the measures of diversity. Thirteen bacterial taxa were recovered overall. Richness was consistently lower in the mining zone than in the reference zone in both media: four taxa against eight in stream water, a reduction of 50 percent, and eight against eleven in soil, a reduction of 27 percent. Mining zone assemblages were largely nested within reference zone assemblages, with Jaccard similarity of 0.333 for water and 0.727 for soil, and only Shigella spp. in water was exclusive to the mining zone. Occurrence in the mining zone was concentrated in a few resilient taxa: Salmonella spp. and Shigella spp. were recovered from every water sample, and Bacillus spp., Enterococcus spp. and Salmonella spp. from every soil sample. The persistence of enteric taxa alongside reduced overall richness indicates a community that is both biologically simplified and of public health concern. The study concludes that mining pressure at Ika-Ogboyaga has narrowed the culturable bacterial community to a stress tolerant subset while leaving enteric contamination undiminished, and recommends protection of the stream from both mine drainage and faecal input.