Investigation of Distribution and Origin of Polycyclic Aromatic Hydrocarbons (PAHs) in Chalous River Surface Sediments

Polycyclic aromatic hydrocarbons (PAHs) are among the important organic pollutants in the aquatic ecosystems generally generated by natural and human processes. The purpose of this study was to determine the concentration and distribution of PAHs and the origin of these compounds in the surface sediments of the Protected Chalous River in Mazandaran Province. Sampling of surface sediments of the riverbed was performed at four stations located along the river (Darkala, first ring bridge, Chalous fountain bridge and estuary). The extraction and analysis of PAHs was performed using standard Soxhlet method in two stages: column chromatography and gas chromatography-mass spectrometry. The highest and lowest total amount of these compounds (∑PAHs) was observed in the surface sediments of the riverbed at the estuary and Darkala stations (903.8±144.30 and 51.71±19.33 ng/g) respectively. The trend of accumulation of PAHs in the surface sediments showed that the ∑PAHs concentration increased from the upstream to downstream in the river. Determining the origin of PAHs in surface sediments of the riverbed using isomeric diagnostic ratios showed that the origin of PAHs in the river was a mixture of petrogenic and pyrogenic sources with petrogenic dominance. According to the NOAA sediment quality standard, the sediments samples were in the range of moderate pollution in the studied stations, except at Darkala station, located upstream of Chalous river and had low pollution. The influx of agricultural effluents from the surrounding farms, the increase in population and vehicles in the area has led to an increase in the composition of PAHs in river sediments.