Spatial Distribution of Uranium and Radium in the Sedirnents, Musels (Mytilus sp.) and Sea Water in Port of Sibenik

The purpose of this study is to assess the response of theaquatic environment (sediment, sea water and mussels Mytilussp.) on uranium and radium activity and concentration followingthe decrease of phosphate discharges from a technologicallyimproved transhipment terminal, situated at the CroatianAdriaticcoast in the port of Sibenik. The highest 238U activities(485±16 Bq kg" 1 dry weight) and 226Ra activities(662±6 Bq kg" 1 dry weight) were found in the sediment samplecollected from the sampling site closest to the terminal.The maximum concentrations in the sediment samples areabove the natural ranges and are clearly indicative of technologicaI influence.Mussel samples from the port of Sibenik showed levels of238U activities in the range from 12.1 ±2.9 to 19.4±7.2 Bq kg"1dry weight and 226 Ra activities from 1. 9 ± 0. 5 to 5. 9 ± 1.1 Bqkg"1 dry weight, which is somewhat higher than in consumemussels.Only the sea water sample at the sampling site, taken justabove the bottom sediment, shows higher uranium concentration(3.1±0.2 f.Lg L 1) comparing to the samples taken in uppersea water layers (2.1 ±0.2 f.Lg L 1). Higher concentration is in therange of the concentration level of uranium in natural seawater.Since the transhipment terminal in the port of Sibenik wasmodernised in the eighties, the discharge of the phosphate oreinto the seawater was drastically reduced and, consequently,uranium concentration levels in the seawater decreased. Theenhanced uranium and radium activity levels are found only inthe sediment near operational docks, and in the mussels whichlive on this docks