Polluted Alamuyo River: Impacts on surrounding wells, microbial attributes and toxic effects on <i>Allium cepa</i> root cells

Abstract

The physicochemical analysis and microbial load of polluted Alamuyo River in Ibadan, Nigeria and selected wells along its course were evaluated. Toxic effects of water samples obtained from upstream
(A) and down stream (F) of the river were also evaluated using Allium cepa root assay. The result of the analysis revealed that the water sample contained toxic substances. However, almost all parameters
evaluated were within the allowable limit of treated wastewater. High microbial load was observed in river water samples compared to the well water samples throughout the sampling periods with overall highest value observed at Late Rainy Season upstream water sample (LRS-A). MPN of faecal coliform showed that LDS-A, ERS-F and LRS from A – F were significantly different. Echerichia coli, Bacillus substillis, Staphylococcus aureus, Pseudomonas fragii were among the microbes observed in the samples. T-test analysis on A. cepa root length showed that only 50% of LDS-A, LDS-F and LRS-A were significantly different from control (P < 0.05) though there were reduction in root length in all
concentrations tested through out the sampling period except 5% ERSA, 10% ERSF and 10% LRSF. Microscopic evaluation of A. cepa cells showed decreasing number of dividing cells and mitotic indices
were not dose dependent in most cases. Chromosome fragments, bridge, lag and disturbed spindle were the aberrations observed in this study. Our result showed that water samples from the river
contained toxic substances and high microbial load, which have effects on the surrounding wells due to infiltration.