Background: Groundwater is the main and easily accessible source of water supply. Aside its over-exploitation problems, groundwater has undergone quality challenges-owing to its proximity to pollution sources. Methods and Materials: This study assessed the quality of hand-dug wells situated close to the pollution receiving streams in the Ondo City. Thirty water samples; from fifteen hand-dug wells and fifteen closely associated streams across the city were collected for the study. Physico-chemical, microbial and heavy metals parameters were comparatively analyzed in stream and groundwater samples to assess percolation impact on groundwater quality. Studies were carried out in wet and dry seasons. Results: The results obtained from the wells water show that beside temperature and PH, the mean values of other physicochemical parameters like turbidity (111.47 NTU & 68.77 NTU/), total dissolved solid (474.6 mg/l & 68.77mg/l), and electrical conductivity (822.31 µS/cm & 816.79 µS/cm) in both season respectively were above the World Health Organisation (WHO) highest desirable limits. The highest total coliform (T.col) recorded at 11,200 (cfu/100ml) and 11,300 (cfu/100ml) and Faecal coliform at 8,400 (cfu/100ml) and 12,100 (cfu/100ml) for dry and rainy seasons respectively. Highest level of aluminium, cadmium, lead, and chromium concentrations in well water at 1.632mg/l, 0.820mg/l, 0.079mg/l and 0.079mg/l recorded in the rainy season exceeded WHO’s recommendations. Pearson Correlation analysis between well and stream in the dry season shows positive correlation for all water parameters, with strong significance in PH, turbidity, faecal coliform and chromium concentration (0.544, 0.914, 0.414 &0.597) respectively. Similarly, in the rainy season, both well and stream had positive correlations for most parameter tested with significances in turbidity, electrical conductivity, total dissolved solid and cadmium concentration (0.708, 0.775, 0.766&0.655) respectively. Conclusion: The major outcome of this research revealed most water samples (well and stream) failed quality assessments. The positive correlations between wells and polluted stream parameters suggested that distance contributed significantly to well contaminations.

Rapid urbanization and industrialization in communities of Nigeria contribute significantly to environmental pollution. Amongst the diversity of these environmental contaminants are heavy metals, a rarely biodegradable and toxic class of metals. Heavy metals are known to be harmful to plants, aquatic species, and subsequently endanger human health through bioaccumulation or biomagnification. Even at low concentrations, heavy metals may affect key soil microbial processes; inhibit plant metabolism and growth. Toxic metals in groundwater affect water quality and potability, and their presence in aquatic systems also facilitate the production of reactive oxygen species that can damage physiological processes in fishes and other aquatic organisms. This chapter highlights the occurrence and impact of heavy metals in different environmental matrices and organisms sampled across some Southwestern states in Nigeria. Various studies including those of the authors found varying levels of heavy metals, especially in concentrations that can imperil ecosystem functions. While results of studies included in this chapter may suggest heavy metal introduction through anthropogenic-urbanization means, the lack of proper implementation of environmental monitoring laws in Nigeria also clearly exist. As such, the mitigation of heavy metals amongst other pollutants demands better home-grown decentralized technologies.