Radioactivity level of coastal sediments and water across the Sangihe Island as the outlying islands of Indonesia

Abstract

Indonesia as an archipelagic country is very concerned about maritime development, the outlying islands are the entrance for potential threats of radioactive distribution from global waters. Furthermore, the outlying islands have functions such as territorial defence, security, and sovereignty, economic and ecological. As environmental protection, level of natural and anthropogenic radioactivity was performed due to potential threats. The activity concentration of natural (226Ra, 232Th, and 40K) radionuclides inshore sediments samples are range from 3.44 ± 0.01 Bq kg-1, 5.13 ± 0.03 Bq kg-1 and 151.42 ± 0.04 Bq kg-1 respectively and average concentration level of anthropogenic of 137Cs in sediment and seawater obtained were 0.35 Bq kg-1 and 0.83 Bq m3 respectively. The concentrations value of NORM was lower compare to another region but the ratio sequence 226Ra<232Th<40K relatively have same pattern. The presence of fission product 137Cs in this region comes from global fallout since no nuclear activities in Indonesia and the level of 137Cs are almost same as the estimation the concentration 137Cs in the Pacific Ocean and comparable with other studies. Radioactivity levels in all samples are under the value of radiological hazard index (0.004-0.039, trace hold h-index=1) and annual effective dose rate are in save level (0.01 mSv/y, recommended limit AED=1mSv/year). The level of NORM radioactivity is locally and varied for each region meanwhile anthropogenic radioactivity are global and comparable since there are no nuclear activity in Indonesia.