Bottom sediments of the Arabian Gulf--III. Trace metal contents as indicators of pollution and implications for the effect and fate of the Kuwait oil slick.

The trace metal contents of 71 core samples collected in 1992 from the bottom sediments of the Arabian Gulf are used to determine the regional distribution of concentration and pollution levels of these substances in the region. Chronic contamination was recorded in seven locations: the northwestern area (Fe), the northeastern area (Fe, V and Ni), the north-central area (V and Ni), the central area (Fe, Pb, V and Ni), the south-central area (Cu), the eastern area (Cu) and the southeastern area (Fe, V and Ni). Present-day contamination was identified in three locations only: the north-central area (V), the central area (Pb, V and Ni) and the southeastern area (Fe, V and Ni). Diversified natural and anthropogenic inputs may have provided the sources of this contamination. The V/Ni ratios of recent marine sediments cannot be used in identifying oil spillages or in oil-sediment correlation studies. Positive correlations are found between increasing trace metal concentration and decreasing carbonate content and grain size, verifying that adsorption onto muds is the primary mechanism of trace metal concentration in marine sediments. Correlations with TOC (total organic carbon) contents indicate that organic matter is a significant concentrator only in the case of Pb and Cu. With the exception of the Fe contamination in the northwest area due to river transport, all chronic and present-day trace metal concentrations are within the permissible natural background levels in the western offshore areas, including the two areas thought to be polluted by the Kuwait oil slick, thereby supporting the idea that airborne fallout from oil fires was deposited in a limited coastal area between Kuwait and Bahrain, and verifying that the oil slick had minimal effect on the state of pollution by trace metals in the Arabian Gulf.