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

The radioactivity concentration of U-238, Th-232, Ra-226, K-40 and Cs-137 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 U-238, Th-232, Ra-226, K-40 and 137Cs, respectively. Statistical analyses suggested significant correlations between clay content and K-40 as well as Cs-137. 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 U-238, disequilibrium between U-238 and Ra-226, and change in material sources. (C) 2015 Elsevier Ltd. All rights reserved.