Abstract/Summary

Monitoring water and sediment quality in freshwater ecosystems is essential for sustainable management and ecological protection. This study assessed heavy metal contamination in water and sediments from five sampling stations in Asejire Reservoir, Oyo State, Nigeria. A range of pollution indices was employed to quantify contamination levels. Principal Component Analysis (PCA) and Cluster Analysis (CA) were used to identify potential sources of pollution, while the Water Quality Index (WQI) provided an overall evaluation of water quality. The WQI score of 74.23 indicated generally good water quality, although localized contamination was observed. PCA results suggested that most heavy metals originated from anthropogenic activities, and CA grouped pollution sources into two main clusters. The geo-accumulation index showed low cadmium (Cd) levels at most stations, with slight to moderate pollution recorded at Station 5. Chromium (Cr), copper (Cu), and lead (Pb) exhibited moderate to strong pollution levels. Ecological risk assessment indicated no significant risk from Cr, low risk from Cu and Pb, and a very high ecological risk from Cd. The Heavy Metal Pollution Index (HPI), ranging from 290.35 to 294.75, further confirmed substantial human-related input. These findings highlight the need for routine monitoring and targeted remediation to prevent further degradation, safeguard aquatic ecosystems, and protect public health.