Marine Radioecology in Bali and Lombok Waters: Present Status of 137 Cs and Natural Radionuclides in Lombok Strait Deddy Irawan Permana Putra 1,* and Heny Suseno 1 1) Marine Radioecology, Center for Technology of Radiation Safety and Metrology (BATAN), Jakarta, Indonesia *Corresponding author: deddyipp@batan.go.id Received 4 May 2017; Accepted 10 October 2017; Available online 28 November 2017 ABSTRACT The accident of Fukushima Dai-Ichi nuclear power plant in 2011, were released a large amount of 137 Cs into terrestrial and marine environment in Pasific Ocean. 137 Cs has a relatively long half-life and easily soluble in sea water can spread out by ocean currents. 137 Cs can entered to Indonesian waters from Pacific Ocean by Indonesian Through flow (ITF). This study aims to obtain baseline data of artificial radionuclide 137 Cs in Bali and Lombok Straits. The concentration of natural radionuclides was also measured to determine the dose rate and its impact to the ecosystem using Erica Tools. The sampling location were covered territorial waters of Bali and Lombok. The radionuclide samples were analyzed by co-precipitation process using K 4 Fe(CN) 6 and CuCl 2 at pH 8-9. Their concentration activities of natural radionuclides and 137 Cs were measured using Gamma HPGe spectrometer with 20 – 25 % efficiency. This study indicate the average concentration of 40 K 226 Ra 212 Pb 214 Bi 228 Ac 214 Pb and 137 Cs in the sediments of Strait Bali waters 165.16 Bq kg -1 , 25.11 Bq kg -1 , 8.36 Bq kg -1 , 7.51 Bq kg -1 , 7.05 Bq kg -1 , 6.68 Bq kg -1 and the lowest of 0.15 Bq kg -1 respectively. In the waters of Lombok concentration activity of radionuclides 40 K 226 Ra 212 Pb 214 Bi 228 Ac 214 Pb and 137 Cs in the sediments was 172.00 Bq kg -1 , 25.88 Bq kg -1 , 10.10 Bq kg -1 , 6.50 Bq kg -1 , 6.39 Bq kg -1 , 5.70 Bq kg -1 and 0,162 Bq kg -1 . The concentration activity of 137 Cs in seawater of Bali and Lombok was 0.113 Bq m -3 and 0.644 Bq m -3 respectively. Keywords : Natural Radionuclide, 137 Cs, Lombok Strait 1. Introduction Lombok Strait located in coordinates of 115 ° 37 'E - 116 ° 02' E and 8 ° 20 'S - 8 ° 50' S represents the marine waters between the islands of Bali and Lombok and connects western seas of Flores and the Indian Ocean. The Lombok Strait was route of water mass from Pacific Ocean into Indian Ocean via Indonesian Throughflow (ITF), which is influenced by differences of sea level, temperature and salinity (Brink and Robinson, 2005). The water mass from the Pacific Ocean enters to Indonesian Seas through two entrances i.e west channel and east channel. The western channel which is the main inflow water from the Pacific Ocean transports 11.8 Sv through the Makassar Strait and then exits the Lombok Strait and partially into the Banda Sea through the Flores Sea and Timor Sea into the Indian Ocean. The eastern channel of water mass enters through Halmahera and Maluku Seas and pass through the strait of Ombai and Timor Passage to Indian Ocean (Gordon et al, 2003, Gordon et al., 2010). In addition the large quantities of this water mass from ITF also contains 137 Cs radionuclide caused by nuclear activity in the Pacific Ocean. The main source of contamination 137 Cs radionuclide in marine waters comes from nuclear weapons tests proceeding within the period of 1945 - 1980 with a total release of 189 megatons from 543 nuclear weapons and mostly testing in northern hemisphere. The accident of Fukushima Nuclear Power Plant in March 2011 also give a contribution impact on radionuclide contamination in Pacific Ocean with an estimated released of 137 Cs about 12 to 41 PBq into the atmosphere (UNSCEAR, 2000; Hu et al. ; Baily du Bois et al., 2012). Until now data of radionuclides in Lombok Strait is limited, so it is difficult to estimate the radiological impacts in these marine waters. Previous research in monitoring radionuclide concentration has been conducted on some coastal areas of Indonesian Seas, the southern of Java Sea (Indian Ocean) and the eastern sea of Indonesia (Suseno and Prihatiningsih, 2014; Suseno et al., 2017). Furthermore monitoring of 137 Cs on previous research was only conducted on surface seawater. On the other hand, ITF from Pacific Omni-Akuatika, 13 (2): 180 – 189, 2017 ISSN: 1858-3873 print / 2476-9347 online Research Article