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±2.9Bqkg^-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 1m 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.