Concentrations of Total Petroleum Hydrocarbons N-Alkanes in Surface Seawater from The Red Sea Coast of Hodeidah City, Yemen

Introduction

The onset of significant oil pollution can be traced back to the adoption of oil as a primary fuel source for maritime transport. This pollution escalated as industrial demands necessitated the transportation of goods across seawater bodies [1]. With the global economy increasingly reliant on international trade, the volume of goods transported between nations has surged. This upsurge has given rise to two principal sources of oil pollution: deliberate discharges and accidental spills of crude oil and oil derivatives [2].

More than half of the world’s proven oil reserves are located in the Arabian region, where exploration, production, processing, and transportation are concentrated. The majority of oil extracted from both onshore and offshore wells is earmarked for export (with less than 10% allocated for local refining and consumption). Annually, over 100 million tons of oil traverse the Red Sea, with the Arabian Sea and Gulf of Aden handling sixty percent of global oil shipments [3]. This regional dependency on oil and petrochemical industries has made ports focal points of activity. Despite their pivotal role in the regional economy, the production and transport of oil have emerged as significant sources of marine and coastal pollution. Approximately half of the oil destined for export from the Red Sea arrives at the Yanbu Port in Saudi Arabia via the Yanbu Petroline from the Gulf. Other oil export terminals can be found in Yemen, namely Ras Isa on the Red Sea, Bir Ali and Shihr on the Gulf of Aden coast, and the Sumed pipeline and terminal at Ain Sukhna, which transports oil to the Mediterranean. The Red Sea sees between 25,000 to 30,000 ship transits each year, mainly involving the transport of petrochemical products between Yanbu, the Suez Canal, and the Sumed pipeline [3].

The Hodeidah coast, including one of Yemen’s primary harbors on the Red Sea, plays a vital role in marine activities, fisheries, tourism, and serves as the entry point for humanitarian aid and approximately 70% of commercial imports into Yemen (UNICEF). The nearby port of Ras Isa, north of Al Hodeida, is the terminus of the Marib - Ras Isa oil pipeline from inland Yemen and is equipped with a significant storage and offloading vessel named FSO Safer. Hodeida’s coastline receives substantial quantities of petroleum and its by-products. Predominantly, common pollutants in the coastal areas of Hodeida stem from the discharge of ballast seawater effluent from the SAFER oil terminal at Ras Isa. A comparable issue is observed in the Gulf of Aden with vessels deballasting at the Aden refinery. However, the primary cause of oil pollution in Yemeni seawaters, particularly in the Red Sea, appears to be vessels deballasting during their transit. There are two power stations, Ras Katheb and Al- Mocha, which receive heavy fuel oil through underseawater pipelines, and incidents involving pipeline and loading hose accidents are frequent [4]. Additionally, sewage and wasteseawater treatment plants, along with trace metal compounds, contribute to the pollution.

Oil pollution has posed a serious threat to the coastal ecosystem of the Red Sea, affecting several coastal cities [5]. Preliminary surveys along Yemen’s Red Sea coast have shown the concentration of oil-related pollutants in specific regions, especially around oil loading terminals and certain industrial areas. Tar deposits on Yemeni beaches are widespread [6, 7].

Consequently, the findings of these investigations in the locations can serve as a reference for future evaluations and studies.

Results

Total petroleum hydrocarbons n-alkanes (TPH) in the surface seawater of The Red Sea coast of Al-Hodeida city were evaluated in all the sampling points. The results covering two seasons (winter and summer) are summarized in Table 1 and spatial distribution of petroleum hydrocarbons in the seawater matrix is depicted in Figure 2.

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Discussion

The concentration of Total Petroleum Hydrocarbons (TPH) in the study exhibited significant variation across the four locations, ranging from 9400.5 μg/l at Al-Hodeidah harbor to 2409.7 μg/l at Al-Hodeida Power Plant in winter, and from 4880.9 μg/l at Al-Hodeida Harbor to 1109.1 ug/l at Al-Hodeida Power Plant in summer (Table 1). It is a generally accepted criterion that seawater can be considered polluted when hydrocarbon concentrations exceed 2.0 μg/L [18]. Notably, the highest concentrations were consistently observed at Al-Hodeida harbor, followed by the Corniche of Al-Hodeida and the Fishing Port, as illustrated in Figure 2. These findings are indicative of TPH inputs resulting from direct discharges from boats with two-stroke engines and the deposition of fuel combustion residues from boats and vehicles, which were visibly observed during sampling activities. Boating activities, particularly instances of petroleum leakage and irresponsible disposal of engine oil from boats and ferries [19], are likely significant contributors to the recorded TPH levels in these areas. Additionally, frequent leaks from the reception of heavy fuel oil via pipelines at Al-Hodeidah harbor, as well as leaching processes, biological activity, and anchor disturbances in sediment, may reintroduce a minor quantity of TPH into the seawater column [20]. Despite the presence of oil basins beneath the harbors designed to contain oil leakage during crude oil and product unloading, human errors, negligence, and harbor traffic collectively contribute to petrogenic pollution. The higher values observed at Al-Hodeidah harbor and the Fishing Port can be attributed to the release of petroleum waste from ships and fuel handling operations. Among these sites, Al-Hodeidah Harbor, Corniche of Al- Hodeidah City, and the Fishing Port, which receive sewerage, stormseawater drains, and runoff from industrial (including the Fishing Port and Al-Hodeidah Harbor), residential, and commercial areas in Al-Hodeidah city, also contribute significantly to the TPH levels in these locations. The lowest concentrations of TPH were found at Hodeida power plant, which experiences fewer anthropogenic activities compared to the other locations in the study area. However, this power station is supplied by underseawater pipelines that receive heavy fuel oil, and frequent leaks and accidents occur in the pipelines and loading hoses. Additionally, a portion of TPH may originate from the cooling system seawater of the power plant, further contributing to the elevated TPH levels in this area [4].

Seasonal variation in Total Petroleum Hydrocarbons is evident, with concentrations being notably lower in summer compared to winter (Figure. 2). This discrepancy can be attributed to the greater discharge of total hydrocarbons during winter, primarily due to increased combustion processes and the heightened association of hydrocarbon compounds with atmospheric particles at lower ambient temperatures. Furthermore, hydrocarbon compounds deposited on land during the summer season do not reach the aquatic environment to the same extent as during winter when runoff from the land is more extensive, driven by rainstorms in the region [21]. Temperature is known to influence the activity of oil-degrading bacteria in seawater [22], with higher activity observed in summer. The photo- oxidation of oil components in a seawater environment is another contributing factor [23]. Intense solar radiation, coupled with relatively high-seawater temperatures and a higher rate of evaporation characteristic of subtropical climates, could account for the lower levels of hydrocarbon compounds in the seawater [24, 25, 26].

Conclusion

Petroleum hydrocarbons in the surface seawater on the Al-Hodeidah coast is caused by frequent inputs from localized sources such as sewerage, direct discharge of boats with two-stroke engine and the deposition of fuel combustion of boats and vehicles, frequently leakage from receiving heavy fuel oil via pipeline at Al-Hodeidah harbor. The distribution and concentrations of petroleum hydrocarbons depends on anthropogenic activities in locations, as well as the physic- chemical and biological factors.

Recommendations

These data are the first of their kind for this area and should furnish valuable information for future studies, both that they provide as the background values in the event of a major oil pollution incident. Continuous monitoring for petroleum hydrocarbons pollution in The Red Sea Coast of Al-Hodeidah is highly needed. Applying several technical and operational measures can reduce inputs from localized sources of pollution.

Acknowledgements

The authors wish to express their sincere gratitude and appreciation to Dr. Hagib, A. Al-Hagibi, Department of Environmental Science, Faculty of Petroleum and Natural Resources and anonymous reviewers for valuable comments and suggestions to improve the manuscript. Special thanks and gratitude are due to (The American Institute for Yemeni Studies for financial supported). Special thanks and gratitude also are due to (Yemen Standardization, Metrology and Quality Control Organization) for their help and supported.