Heavy Metal Contamination in Taft River Sediments Affected by Bagacay Mine Post-Operation in Hinabangan, Samar, Philippines

Abstract

The purpose of this study was to assess the level of heavy metal contamination in the sediments of the Taft River Basin in Taft Eastern Samar, Philippines. The concentrations and levels of heavy metal contamination in sediments were assessed using the Pollution Load index (PLi), the Contamination Factor (Cfi), and the Geoaccumulation Index (Igeo). Our findings revealed moderate to high levels of potentially toxic elements (PTEs) such as Ti, Cr, Mn, Ni, Cu, Zn, As, Mo, Cd, and Pb. The CF and Igeo values indicated significant pollution, with Igeo values ranging from class 2 to class 6. The CFi indicated moderate to high contamination in river bank sediments following the order of Pb>As>Zn>Mo>Mn>Cu>Ni>Cr>Ti>Cd, and Pb>Cu>Zn>As>Mn>Cr>Ni>Mo> Ti>Cd in river bottom sediments. The PLi values exceeded the critical threshold of 1, confirming severe contamination, especially in the upper reaches of the river near the Bagacay mining site. The contamination showed a consistent presence of heavy metals, with Pb, As, Zn, and Mo being dominant in river bank sediments, and Cu, Pb, Zn, and As in river bottom sediments. Downstream attenuation of PTE levels was observed and is attributed to dilution and sedimentation processes. Overall, the study confirmed the contamination of these heavy metals in the sediments and underscored the need for rehabilitating the Bagacay mine to prevent the buildup of these contaminated sediments in the basin. It is recommended to expand monitoring to include groundwater and biotic components to better assess long-term ecological risks. Regular sediment quality assessments, and multi-stakeholder watershed management are essential for the sustainable health of the Taft River and its surrounding communities.