Heavy Metal Pollution in Soil and Surface Sediments of Meycauayan River, Philippines and Their Relationship to Environmental Indicators

The City of Meycauayan is an industrial powerhouse in the Philippines. It is considered as one of the most polluted cities in the developing world on the account of industrial discharges of toxic materials to the environment. This work investigated the sources of the heavy metal pollution in Meycauayan by analyzing soil and sediment samples for heavy metals like Chromium (Cr), Mercury (Hg), Nickel (Ni), and Lead (Pb) together with selected environmental indicators such as Total Nitrogen (TN), Total Organic Matter (TOM), and Total Phosphorus (TP) located along the Meycauayan River. Hierarchical cluster analysis (HCA), principal components analysis (PCA), and Pearson correlation analysis (CA) were used to identify the sources of the metals. Our results show delineated locations of severe levels of heavy metal pollution downstream of the river because of the concentration of industrial activities. Cr is due to proliferation of tanneries discharging untreated wastewaters to the river. Significant input of Pb and Hg from Pb-acid battery recycling and gold smelting industries were also found. The risk assessments also indicate severe levels of heavy metal pollution in locations where industrial activities are concentrated. Our findings indicate that the heavy metals have similar impacts to K, TN, TOM, and TP in the soil and sediments. Our study shows the serious need to address heavy metal pollution in Meycauayan aside from the ongoing cleanup of solid wastes as part of rehabilitation efforts by the local government.