A GEOCHEMICAL STUDY OF INTERTIDAL BOTTOM SEDIMENTS IN SULAIBIKHAT BAY, KUWAIT: WITNESS THE ANTHROPOGENIC IMPACT

Sulaibikhat Bay is a shallow embayment located in the west of Kuwait City with several man-made activities around its 12 km margin. It is bounded by Doha Port to the northwest with Power and Desalination Plants and Shuwaikh Port with the Industrial area on its east. There are, in addition, 10-12 storm water outfalls which usually used as "emergency outlets" for sewage. The tide range reaches about 4 m creating a broad intertidal zone extending several kilometers offshore. Mud flats that dominate along the shoreline, make this area less attractive for beach recreation but highly attractive to birds and other wildlife that forage on tidal flats. However, parts of the flat area have been degraded by construction debris and they are currently undergoing large-scale development. Sediments of short cores from six sites (SB1, SB3, SB4, SB5, SB7, and SB8) within the intertidal zone of the Bay were analyzed for major and trace elements in attempt to trace the secular variation of chemical elements and assess the anthropogenic impact on heavy metal abundance. Sedimentation rates for the bottom sediments were estimated with the Pb²¹⁰and Cs¹³⁷ methods, which yield the sedimentation ratio of 0.5 to 0.9 cm/year. “Enrichment factor” is used to evaluate anthropogenic impact on the studied sediments. The Cr levels are 2 and 4 times higher than the background level at the core SB3 and SB4, respectively. These sites are considered as point source of Cr. The V and Ni levels in all studied cores do not show any significant anthropogenic flux, suggesting that these metals are at the background level of the sediments. Evidence of sewage discharge is shown by the higher Zn concentrations at the upper parts of most studied cores. E.F was 2 to 3 times higher than the background level.

All studied cores exhibit intensive anthropogenic flux of Hg. From 1940s up to recent, the Hg level exhibits bumpy fluctuation. This is an indication of multiple sources of Hg or broken Hg pollution source which likely to be from sewage or industrial discharge. The core SB1 exhibits the highest Hg level (E.F=12) at 10 cm depth. This immense contamination at that time could be a result from the consequences of Kuwait Invasion and Gulf War. Cu has higher concentrations at lower depths compared with the upper parts in all studied cores. This would be due to the mobilization of Cu under high acidity conditions.