Distribution of mercury in molluscs, seawaters and coastal sediments of Tarut Island, Arabian Gulf, Saudi Arabia

• Evaluate levels of Mercury along Tarut coast.
• Assess the impact of environmental changes along the coast.
• Document the difference between gastropods and bivalves in Mercury uptake.
• Comparison between rate of pollution in Tarut coast and others coasts.

In order to assess the distribution of mercury along the Tarut coast, Arabian Gulf, Thirty eight (38) sediment samples, twenty six (26) seawater samples, and forty (40) Mollusca specimens were collected from the Tarut coast. The concentrations of Mercury in the sediments of the studied area (average = 0.55 μg/g) are generally high comparing to the reported values from the Gulf of Oman, Red Sea, and the Gulf of Finland. The concentrations of Hg exceeded the wet threshold safety values (median effect concentration (MEC), and probable effect concentration (PEC) indicating possible Hg contamination. According to the Swedish Environmental Protection Agency (SEPA), thirty four (34) samples occur in class 4 and four (4) samples occur in class 5, which means that the sediments of the Tarut Island are largely contaminated with Hg. Enrichment factor (EF) results (average = 1.76) suggested that, the coastal sediments of the Tarut Island are considered to entirely originate from the crustal materials or natural processes. The studied sediments show lower values (Igeo<0) indicating that the sediments are unpolluted. These sediments according to contamination factor (Cf) are considered contaminated with Hg (1 < CF < 3). The Hg concentration in water samples (average = 30 μg/g) considered high. Comparison with Hg contents in coastal sediments, seawaters and molluscs in the Red Sea, the Arabian Gulf suggested that the studied samples have higher concentrations of Hg. The suggested natural sources of Hg in the study area are the weathering and decomposition of neighboring deserts. The anthropogenic sources are the land reclamation, petrochemical industries, boat exhaust emissions, oil leakage, desalination plants and sewage effluents exceeded in the study area and in Al Jubail industrial city to the north.