Natural uranium and thorium isotopes in sediment cores off Malaysian ports

Sediment cores collected from three Malaysian marine ports, namely, Kota Kinabalu, Labuan and Klang were analyzed to determine the radioactivities of U-234, U-238, Th-230, Th-232 and total organic carbon (TOC) content. The objectives of this study were to determine the factors that control the activity of uranium isotopes and identify the possible origin of uranium and thorium in these areas. The activities of U-234 and U-238 show high positive correlation with TOC at the middle of sediment core from Kota Kinabalu port. This result suggests that activity of uranium at Kota Kinabalu port was influenced by organic carbon. The U-234/U-238 value at the upper layer of Kota Kinabalu port was a parts per thousand yen1.14 while the ratio value at Labuan and Klang port was a parts per thousand currency sign 1.14. These results suggest a reduction process occurred at Kota Kinabalu port where mobile U(VI) was converted to immobile U(IV) by organic carbon. Therefore, it can be concluded that the major input of uranium at Kota Kinabalu port is by sorptive uptake of authigenic uranium from the water column whereas the major inputs of uranium to Labuan and Klang port are of detrital origin. The ratio of Th-230/Th-232 was used to estimate the origin of thorium. Low ratio value (lt; 1.5) at Labuan and Klang ports support the suggestion that thorium from both areas were come from detrital input while the high ratio (> 1.5) of Th-230/Th-232 at Kota Kinabalu port suggest the anthropogenic input of Th-230 to this area. The source of Th-230 is probably from phosphate fertilizers used in the oil-palm cultivation in Kota Kinabalu that is adjacent to the Kota Kinabalu port.