Organic Pollution in Sediments along the Coastal zone of Saudi Arabia, Red Sea, During Field Survey in Summer 2021

As part of the Vision 2030 for economic growth and development in the Kingdom of Saudi Arabia, the Marine and Coastal Environment Protection (MCEP) Initiative for Saudi Arabia was established (https://mcep.kaust.edu.sa/). In the frame of this project, we traced the discrete sources of pollution in critical hotspot areas including: wastewater treatment plants (WWTP), desalination plants, ports, industries, petroleum platforms, aquaculture facilities and urban development.

In this work, we present measurements of organic pollutants in sediments obtained during a surveillance cruise conducted in June 2021 with the HCMR  R/V AEGAEO, over a north - south coastal transect in the Red Sea. The hot spots areas surveyed, from north to south, were: the area near the Saudi-Jordanian border (Phosphate Terminal in Aqaba Port in Jordan; cross-border pollution) and Haql (desalination, power and WWTP, port activities), Magna (maritime traffic), Tabuk Fisheries (aquaculture activities), Duba (desalination plant), Al Wajh (port facilities; desalination plant), Red Sea Project Lagoon (north and west channels), Yanbu Cement Company (industrial discharges), Yanbu King Fahd Port (industrial and shipping center- the largest in Saudi Arabia), Jeddah Lagoon System (wastewater inputs), Jeddah Mena (port operations), Al Khurma (Jeddah WWTP), Al Lith (shrimp and fish farms), Al-Shuqaiq (desalination plant) and Jizan Economic City (expanding industrial facility).

This is the first broad coverage study in a one-off sampling campaign in Saudi Arabian coastal zone, constituting the first multidisciplinary and geographically comprehensive survey of contaminants. Aliphatic (C₁₀-C₄₀) and polycyclic aromatic (32 substances including both parent and methylated compounds) hydrocarbons (AHC and PAH) and polychlorinated biphenyls (PCB), which constitute important classes of organic contaminants that may cause degradation and pose a risk of serious damage in the marine environment, were determined in surface sediments collected from the coastal zone of the Red Sea. In general, north-south increasing gradients were evident for all pollutants, revealing a link between the hydrographic conditions and biogeochemical properties. AHC concentrations did not exceed 44 μg/g with the exception of Jeddah Mena, Al Khumra and Lagoons, where values almost 200 times higher were detected. Very increased PAH levels (>1000 ng/g) were measured only in the lagoons, whereas moderate pollution was found in Jeddah Mena and Al Khumra. PCBs concentrations were low in all the samples studied. The examination of various molecular indices and ratios revealed a chronic petroleum-associated anthropogenic pressure in Jeddah Lagoons, Jeddah Sea Port and Al Khumrah, whereas some petroleum residues were also found at King Fahd Yanbu Port, shrimp and fish farms near Al Lith and to a lesser extent at Magna. The domestic and industrial activities probably enrich the coastal zone of the Red Sea with organic pollutants. Hydrocarbons were linked with different sources, e.g domestic sewages (detergents) in Jeddah Lagoons and weathered petroleum in Jeddah Mena, whereas in Al Shuqaic hydrocarbons were mostly of biogenic origin. Pyrolytic PAHs predominated only in Jeddah Mena, indicating that limited combustion processes occur in the Red Sea which do not  affect the marine environment. Regarding sediment quality guidelines PAHs concentrations were, in general,  lower than ERL values.