Contamination Assessment of Mangrove Ecosystems in the Red Sea Coast by Polycyclic Aromatic Hydrocarbons

Mangroves are known as a naturally based solution for climate mitigation and adaptation. Mangroves are at a potential risk of degradation by contaminants such as polycyclic aromatic hydrocarbons (PAHs). In this study, sixteen priority PAHs were analyzed and characterized in forty samples of mangrove seawater and mangrove sediments collected from two coastal areas (i.e., Sharm and Khor Rabigh) along the Red Sea Coast of Rabigh city in August 2013. We found that the average concentration of total PAH in mangrove sediments in the Sharam area (22.09 ng/kg) was higher than that in the Alkhor area (6.51 ng/kg). However, the average concentration of the total PAH in the mangrove seawater in the Alkhor area (9.19 ng/L) was double that in the Sharam area (4.33 ng/L). Phenanthrene and pyrene were the major components in both the mangrove seawater and sediment in all the investigated areas. We observed that the abundance of PAHs with 2-3 aromatic rings was dominant in sediment samples collected from both study areas. This abundance was also observed in seawater from the Sharam area. However, seawater samples from the Alkhor area had abundant PAHs with four aromatic rings. The majority of PAHs in sediment samples of both study areas originated from petrogenic sources, whereas the majority of PAHs in seawater samples originated from pyrogenic sources.