Ecological Risk Assessment of Heavy Metal Pollution in Surface Water and Sediment of Lahug River, Cebu, Philippines

The Lahug River, a significant urban waterway in Metro Cebu, was studied to assess its water quality and sediment characteristics. Physicochemical properties, such as pH and dissolved oxygen (DO), were measured in situ using a Multi-probe digital meter. At the same time, metal concentrations in both water and sediments were determined through Flame Atomic Absorption Spectroscopy (FAAS) with multiple standard addition techniques. In water, metal concentration showed a decreasing trend of Zn > Pb > Cu > Cr. Notably, copper (Cu) and chromium (Cr) exceeded the National Environmental Protection Agency (NEPA, 1989) threshold at the downstream station, while all stations exceeded the limit for zinc (Zn). In sediments, copper emerged as the most prevalent metal. Statistical analysis indicated significant correlations among Cu, Zn, Pb, and Cr, suggesting similar pollution sources or behaviors in the river environment. Ecological risk assessment revealed that the downstream area exhibited the highest risk, highlighting the urgency of rehabilitative measures to protect the river ecosystem. A comprehensive, large-scale environmental risk assessment is recommended to mitigate further degradation and ensure sustainable management of the Lahug River