Environmental radionuclides in a coastal wetland of the Southern Laizhou Bay, China

The radioactivity concentration of 238U, 232Th, 226Ra, 40K, and 137Cs in soil samples collected in a coastal wetland of the Southern Laizhou Bay, China were measured. Mean activity concentrations were 54.4 ± 11.7, 57.9 ± 9.7, 28.6 ± 4.3, 542 ± 21, and 10.2 ± 2.9 Bq kg−1 dry weight for 238U, 232Th, 226Ra, 40K and 137Cs, respectively. Statistical analyses suggested significant correlations between clay content and 40K as well as 137Cs. The radium equivalent activity, the absorbed dose rate in the air at 1 m above the ground surface, and the external hazard index were calculated. The result showed that the radioactivity level in the wetland was in normal range. But sites along the river tended to have higher radiological hazard indexes. The vertical distributions of radionuclides in profiles illustrated some phenomena, such as vertical transport of 238U, disequilibrium between 238U and 226Ra, and change in material sources.