The concentration of γ radionuclides in surface marine sediments from Yangjiang nuclear power plant and its adjacent sea area, South China Sea

Some radionuclides in surface marine sediments from Yangjiang nuclear power plant and its adjacent sea area were measured using HPGe γ spectrometer. The specific activities of ²³⁸U, ²²⁶Ra, ²¹⁰Pb, ²²⁸Th, ²²⁸Ra, ⁴⁰K and ¹³⁷Cs were 75.2~102.0, 32.6~38.6, 86.9~148, 54.3~71.3, 40.9~70.6, 580~660 and < 0.16~3.82 Bq/kg_DW, with the mean of 82.4±5.2, 35.5±2.0, 121.7±14, 60.2±3.1, 57.1±3.1, 621±29 and 2.21±0.31 Bq/kg_DW, respectively. The specific activities of ¹³⁴Cs, ^110mAg, ⁵⁸Co and ⁶⁰Co were below the limit of method. Ratio(²²⁶Ra/²³⁸U) and Ratio(²¹⁰Pb/²²⁶Ra) were 0.35~0.48 and 2.63~4.17, with the mean of 0.43 and 3.43, respectively. It was shown that the uranium decay series was in disequilibrium in the surface sediments, where ²¹⁰Pb relative of ²²⁶Ra were excess while ²²⁶Ra relative of ²³⁸U was deficient. The average value of Ratio(²²⁸Th/²²⁸Ra) was 1.06, ranging from 0.96 to 1.36. It was shown that ²²⁸Th and ²²⁸Ra was in equilibrium in the surface sediments. No obvious correlationship was found among the specific activities of radionuclides in sediments, the grain size characteristics and the offshore distance.