Polycyclic Aromatic Hydrocarbons (PAHs) in Urban Runoff Sediments (Case Study: Tehran City)

Polycyclic aromatic hydrocarbons (PAHs) attract great attention because of their toxicity, stability, lipophilicity, bioaccumulation, carcinogenesis and mutagenic characteristics. Urban runoff contains significant amounts of PAHs, which transfer to receiving environments and cause significant environmental and health risks. Because of their hydrophobicity characteristic, transport of these compounds in aquatic environment, mainly coupled to suspended particles and sediments. Therefore, assessment of sediments is considered as a medium that affect fate and transport of PAHs. Present study evaluates the concentrations and sources of PAHs in sediments of Tehran runoff. The samples were taken from three main subcatchments of Tehran city in April 2017 and concentration of 16 PAHs and organic carbon were measured and their probable sources were determined using five diagnostic ratios. The total PAHs concentration ranged from 57 to 978.2 ng/g dry weight. Also, the concentrations in the sub- catchment 2(57-976.6 ng/g) was higher than the sub-catchment 1(84.4 -773.2 ng/g) and sub-catchment 3(76.3 – 978.2) due to its location in the center of the city and the diversity of pollutant sources. Moreover, a significant and strong correlation is observed between total organic carbon and PAHs, while its coefficient varied in each sub-catchments. At all stations except station C1S27, 3 and 4 rings compounds had significant dominance. Four indexes show the origin of compounds is pyrogenic while LMW/HMW index indicates that the source of contamination in 30% of the stations is petrogenic. Generally, the portion of pyrogenic sources is significantly higher due to high population density, traffic and human activities.