Risk Assessment of Polycyclic Aromatic Hydrocarbons (PAHs) Pollution from Dezful City to the Persian Gulf (Khuzestan Province, Iran)

Polycyclic aromatic hydrocarbons (PAHs) are introduced into the environment by human activities and are deposited in the river bed. These compounds are among environmental pollutants and are extremely harmful to human health and other living things even in very small amounts. For this reason, determining the concentration of these pollutants is very important to evaluate the quality of river water. About a hundred compounds of PAHs that have been identified by the Environmental Protection Agency. They have 16 major harmful and pathogenic compounds, and for this reason, they have been introduced as pioneering pollutants. For this purpose, in the present study, the concentrations of PAHs were determined in the Karun River.

In this study, 19 samples of PAHs were collected along the Karun River from Cham Golak in the north of Khuzestan to Choibedeh in the south of Khuzestan in 2022. The collected samples were immediately stored in glass bags at a temperature of -10°C and transported to the laboratory. Until the time of extraction, the samples were dried in a freeze dryer and then kept in a freezer at -50°C. Before the extraction operation, all the samples were powdered and passed through a sieve with mesh less than 0.63. After determining the amounts of each of the desired PAHs, using Dionex™ ASE™ 3, it was determined whether the PAHs has fuel or petroleum origin. Finally, the concentrations of the obtained PAHs were compared with the American Sediment quality guidelines. In this standard, two risk categories, ERL and ERM, are considered for sediment pollution.

Based on the average concentration of studied PAHs, Benzo (b) fluoranthene and phenanthrene were the most polluted in proportion to concentration among all studied PAHs. The concentration of Benzo (k) fluoranthene, Fluorene, Pyrene and Indeno (1,2,3-c,d) pyrene was also more than 1 μg.kg-1 of sediment, which was high compared to the average concentration of other PAHs. Other PAHs had an average concentration of less than 0.80 μg.kg-1. The minimum concentration of hydrocarbons varied between 0.01-2.15 μg.kg-1 and their maximum concentration between 0.05-8.97 μg.kg-1 of sediment. The results of skewness (-0.75<SKW<3.0) showed that there were many spatial variations for all pollutants, but Anthracene with a skewness of 0.3 has the most spatial changes, with the highest concentration in the south of the Karun River, and Benzo (b) fluoranthene has the skewness equal to -0.75, then, the highest pollutant concentration was in the north of Karun River. Except for the four hydrocarbons Benzo (b) fluoranthene, Benzo (k) fluoranthene, Indeno (1,2,3-c,d) pyrene and Benzo (g,h,i) perylene, the concentration of the other pollutants in the Karun River is lower than the Sediment Management Standard (SQS) limits (

The origin of the pollutant’s evaluation showed that in the north of the Karun River, there was more fuel pollution, but in the center and south of this river, both fuel and oil sources were observed. These results showed that air pollution had a greater effect on increasing the concentration of hydrocarbons in the sediments of this river. In addition, the fuel of boats in the Ahvaz to Abadan area can be an important factor in increasing PAHs pollution with fuel origin. Therefore, although PAHs pollution was observed in this river, it was not at a critical level in terms of concentration.