Polycyclic aromatic hydrocarbons distribution, origin and risk assessment in Jeddah marine coastal zone sediments, Saudi Arabia

Polycyclic aromatic hydrocarbons (PAH) were determined in surface marine sediments collected from the Jeddah coastal zone (Saudi Arabia), in order to assess their levels, origin, and probable toxic effects on marine organisms. Two marine areas were selected (a) the Jeddah lagoon system, which is an area with shallow depth and restricted water circulation receiving wastewater and (b) Mena Jeddah, an extensive port facility within the Islamic Port of Jeddah, influenced by various activities associated with the port operations. Sediments were collected from 10 stations and PAHs were determined by gas chromatography – mass spectrometry. In total thirty-two parent and alkyl substituted compounds were quantified. High PAH concentrations, indicative of an enhanced pollutant burden, were recorded in the Jeddah Lagoon (mean value 5800 μg/kg for total polycyclic aromatic hydrocarbons (∑PAH)), whereas PAH levels in Mena Jeddah were lower (mean value for ∑PAH 615 μg/kg). PAH mixtures were mainly composed of methyl substituted compounds at all lagoon stations, suggesting a petroleum origin, whereas PAH from combustion sources accounted for only 8.5–28.8% of ∑PAH. In contrast, pyrolytic PAHs were found at higher concentrations in Mena Jeddah, where total PAH concentrations were lower, accounting for 39–61% of total PAHs. PAH sources and transport pathways were further examined by using various molecular diagnostic ratios/indices and applying Positive Matrix Factorization, which is a multivariate statistical method capable to calculate source profiles and contributions. Low temperature combustion was found to be the most significant source of PAHs with an average contribution of 41%, followed by high temperature combustion and petrogenic sources (21%) and low MW fossil inputs (17%). Petroleum related pollution seems to predominate in Jeddah lagoons, whereas pyrolytic PAHs produced from low temperature combustion processes were dominant in Mena Jedda. To evaluate probable toxicity risks to marine organisms, PAHs concentrations were compared to sediment quality guidelines, whereas Toxicity Equivalent Quotients (TEQs) of carcinogenic PAHs relative to benzo[a]pyrene were also calculated and used for ecological risk assessment. Based on these criteria it seems that, despite the high total values of PAHs, adverse biological effects are unlikely to occur, while a low to moderate ecological risk was found in the lagoon stations.

This study has been funded by the project “Marine and Coastal Assessment Protection Study for the Kingdom of Saudi Arabia Coastline” made between the Saudi National Center for Environmental Compliance (NCEC) and King Abdullah University of Science and Technology (KAUST) under the leadership of the Ministry of Environment, Water and Agriculture, as part of the Vision 2030 for economic growth and development in the Kingdom of Saudi Arabia.