The aim of this study was to obtain a relationship that can estimate the emission pattern of 232Th in calm and low pressure aquatic environments such as Gorgan Bay. The 232Th emission pattern in sediments near the outlets of Gaz and Qarasu rivers using experimental data measured by gamma radiation spectrometry using high purity germanium (HPGe) detector and quasi-experimental model recommended by IAEA 2001 as well as the concentric circular diffusion model proposed by authors was investigated. The mean specific activity of 232Th in sediment samples for Gaz Block and Qarasu Block is 30.46 Bqkg− 1 and 28.80 Bqkg− 1 for, respectively. In Gaz Block, for model1: the average of CModel s 1 was 29.03 Bqkg− 1 and the mean relative error is 10.76%. For model2: the average of CModel s 2 was 30.34 Bqkg− 1 and the mean relative error is 7.58%. In Qarasu Block, for model1: the average of CModel s 1 was 27.48 Bqkg− 1 and the mean relative error is 12.08%. For model2: the average of CModel s 2 was 34.17 Bqkg− 1 and the mean relative error is 38.99%. The results of this research show that diffusion models 1 and 2 in the calm environment of Gorgan Bay can accurately predict 232Th diffusion. But as increase the amount of turbulence and interference effects in the environment, the accuracy of these two models decreases. These two models can be used in similar calm aquatic environments in other parts of the world.
