The southern coast of the Caspian Sea, Iran, is frequently affected by tar balls deposition. Tar balls on the shores, as oil pollution warnings, attract a huge public concern and will have long-term impacts to the marine environment. The concentrations of seven metals (Ni, V, Co, Mn, Fe, Cr, and Cu) were studied in tar ball samples collected from five different locations and analyzed using ICP-OES. Co/Ni and V/Ni markers are fairly uniform in the tar balls, and it indicates that the tar balls are from an identical source. V/(V + Ni) ratios of the tar balls were compared with those of Kazakhstan and Azerbaijan crude oils. The results showed that the ratio measured in tar balls remained quite stable, at a value of approximately 0.57, which is comparable to the value of Kazakhstan crude oil, which was approximately 0.44. The data show that a remarkable difference exists in Azerbaijan crude oils, which varies between 0.03 and 0.18, and that of tar balls. It may be concluded that, based on the V/(V + Ni) ratios, the majority of the tar balls were probably formed from the Kazakhstan crude oil.
