Background: The interaction between continental and oceanic process is much intense in coastal region. The terrestrial freshwater mixes with seawater here which leads to the chemical constituents in water undergo rapid change. Purpose: The aim is to analyze and study the distribution characteristics of 224Ra and 226Ra and their influence factors in the water of Jiaozhou Bay area. Methods: The water samples of 224Ra and 226Ra were collected from groundwater

river water and seawater around the Jiaozhou Bay from April to May

2012. In the laboratory

the activities of 224Ra absorbed on the Mn-fiber were measured through the continuous emanation method. Finally

the Mn-fiber was sealed for more than 7 days

and the activities of 226Ra absorbed on the Mn-fiber were measured through the direct emanation method. Results: The results show that the activities of 224Ra and 226Ra in groundwater and river water are much higher in the granitic area which has higher concentration of 232Th and 238U. Because of mixing with seawater

the salinity of groundwater and river water in coastal region rises which leads to the increasing amounts of 224Ra and 226Ra desorbed from the particles

resulting in higher activities of 224Ra and 226Ra in coastal region. Affected by the input of river (dissolved and desorbed from suspended particles) and submarine groundwater discharge (SGD)

the activities of 224Ra and 226Ra are relatively higher in nearshore seawater

then with the decay of 224Ra and mixing dilution effect of the offshore seawater

the activities of 224Ra gradually decrease from nearshore region to the open ocean. The activities of 226Ra in the seawater of Jiaozhou Bay remain high-level values

and there are only a few zones of low 226Ra activities. The main reasons are that the activities of 226Ra from terrestrial freshwater are close to those from offshore seawater and the half-life of 226Ra is very long. Conclusion: The activities of 224Ra and 226Ra in groundwater relate to the rock around Jiaozhou Bay and the water salinity. In addition to rock and water salinity

the activities of 224Ra and 226Ra in river water are also concerned with human activities and the process of groundwater recharge. The activities of 224Ra and 226Ra in seawater depend on the sources and sinks of radium isotopes.Cited