8. Distribution and Sources of Hydrocarbon Compounds in Sediments from Obhur Lagoon: Red Sea Coast of Saudi Arabia

Surface sediment samples from Obhur Lagoon on the Red Sea coast of Saudi Arabia were collected and analyzed to determine the levels, distribution and sources of hydrocarbon compounds. The sediments were collected using a Van Veen grab sampler, dried, extracted with a mixture of dichloromethane/methanol, and analyzed by gas chromatography-mass spectrometry. The major hydrocarbons of these lipid extracts included n-alkanes (6–645 ng g⁻¹), methyl n-alkanoates (1–311 ng g⁻¹), hopanes (3–219 ng g⁻¹), steranes (5–258 ng g⁻¹), phthalates (4–201 ng g⁻¹), and an unresolved complex mixture (UCM) (0–4571 μg g⁻¹). Anthropogenic petroleum products and plasticizers were the main sources of these hydrocarbons, with lesser amounts from biogenic sources, including natural waxes of terrestrial higher plants and marine microbial detritus. The estimated anthropogenic inputs of the total lipid hydrocarbons for all sediments ranged from 14 to 98% for petroleum products and from 2 to 18% for plasticizers, whereas biogenic inputs ranged from 0 to 10.7% for terrestrial higher plant waxes and from 0 to 68.5% for marine microbial detritus. The presence and inputs of petroleum residues and plasticizers to the coastal sediments of the lagoon likely affect the marine ecosystems and associated species groups that use the lagoon as a coastal nursery and spawning area.