210Po is a typical natural particle active radionuclide, which can be used as a tracer for the study of atmospheric aerosol deposition dynamics and particle dynamics in marine environment. In this study, the water quality parameters and the specific activities distributions and behavior of different phases for
210Po in six offshore sections of the north coastal Beibu Gulf were investigated. Results showed that the specific activities of dissolved, particulate and total
210Po were 0.16-2.78 mBq/L, 0.14-2.43 mBq/L and 0.51-3.94 mBq/L, respectively. There was no significant correlation between the specific activities of dissolved
210Po and the water quality parameters, but the specific activities of particulate
210Po showed significant correlation with water temperature, salinity and mass concentrations of TSM, respectively. At the same time, the specific activities of total
210Po were significantly correlated with water temperature and mass concentrations of TSM, respectively. The distribution trends of
210Po in different sections were not consistent, but in general, the particulate phase was the main existence form of
210Po in the nearshore water, and the offshore
210Po was confirmed mainly in the form of dissolved phase. Further analysis showed a negative correlation between the distribution coefficients of
210Po in the solid-liquid phase and the mass concentrations of total suspended particulate matter. Based on the one-dimensional steady-state irreversible removal model, a longer residence time of dissolved
210Po relative to particulate
210Po was obtained, indicating that the atmospheric deposition and riverine input of
210Po into the coastal Beibu Gulf would partially enter the dissolved phase after entering the seawater, so that its residence time in the water was prolonged.