Occurrence of Polycylic Aromatic Hydrocarbons (PAHS) in Iloilo River, Philippines
DONE in 2006 by Pamela Gerrez V. Tañeza and Paul Philp of the University of Oklahoma’s School of Geology and Geophysics, this study investigates the occurrence, distribution, concentration and potential sources of polycylic aromatic hydrocarbons (PAHs) at the Iloilo River using geochemical techniques. PAHs are ubiquitous environmental pollutants that have received special attention due to their highly mutagenic and carcinogenic properties.
Biomarkers, which include steranes and hopanes were also analyzed in order to determine the influence of petroleum. Six sampling stations were established along the 10-km long Iloilo River. In order to assess the influence of precipitation on the concentration of organic compounds in the river, sediment and water samples were collected during the wet and dry season, with a time difference of one month.
Concentration of PAHs was especially high when the sediment samples were taken during the dry season (1105.5 – 3134.3 µg/g) in comparison to the wet season (518.6 – 1304.8 µg/g). PAH concentration peaked at the middle reach of the river (Station 5) in both wet and dry seasons since the area is the confluence of Iloilo River and Dungon Creek thus receiving more organic material. Parameters including isomer ratios, the dominance of 4- to 6- ring parent PAH compounds particularly pyrene, and high parent/alkylated PAH ratios indicated a pyrogenic (combustion) source for the sediments in Iloilo River.
Motor vehicles from heavy duty diesel engines were a significant source of PAH emissions. A relatively smaller contribution from pyrogenic (petroleum – derived; most from the Middle East oil) was also evident, based on hopane and sterane biomarkers. Perylene, a high molecular weight PAH of biogenic/diagenetic origin, often associated with an anoxic marine environment, was also abundant except in the upstream portion of the river.
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