A large excess of 210Po in the overlying water of the Zhubi Coral Reef flat, in the South China Sea

► Large excess of 210Po was observed in the overlying water of the Coral Reef flat. ► Different mechanisms control the input of 210Po and removal of 210Pb. ► Diffusion of 210Po contributes more than 60% of the total 210Po. ► Preferential recycling of 210Po is related to interaction between 210Po and POM.