Assessment of heavy metal levels in an urban river in the Philippines using an unconstrained ordination- and GIS-based approach: evidence of the return of past pollution after the 2013 Typhoon Haiyan (Yolanda)

Assessment of urban river sediment quality is paramount to understanding the impacts of urbanization on aquatic ecosystems and public health. The study evaluated the health impacts and sources of heavy metal pollutants in the Mangonbangon river, Tacloban City. With the abundance of heavy metal contaminants in the river sediment (Fe>Mn>Zn>Cu>Cr>Ni>Co), Hazard indices (HIs) ranged from 0.04 to 0.10 for adults and 0.31 to 0.90 for children suggesting little or no non-carcinogenic effects to the population. Lifetime cancer risk (LCR) is below the tolerable threshold of 10⁻⁴, with Co contributing 61% of the cancer risk. Using unconstrained ordination and the GIS-based method (UOGM), we showed two non-multidimensional scaling groups of pollutants distributed based on dwelling density, presence of informal settlers, and types of activity at the sample sites. Given that sampling was performed three years after the city-wide destruction by Typhoon Haiyan (Yolanda), our analysis indicates the return of anthropogenic activities and pollution-related health problems in Tacloban. Our results reinforce the urgent need for proper river management and economic zoning to help curb the rapidly growing heavy metal pollution problem at its earliest stage. (author)