黄茅海-广海湾及其邻近海域表层沉积物中γ放射性核素含量水平

摘要

用HPGe-γ谱分析方法测定了黄茅海—广海湾及邻近海域表层沉积物中238U、226Ra、210Pb、228Th、228Ra、40K和137Cs 核素,其放射性比活度范围分别为66.5~98.8、32.0~48.7、96.2~174.7、57.7~101.0、49.7~64.8、505~644和0.72~2.15Bq·kgDW–1,平均值为77.4、36.6、123.8、64.5、58.1、571和1.52Bq·kgDW–1。沉积物中226Ra/238U、210Pb/226Ra和228Th/228Ra比值的范围分别为0.42~0.50、2.80~4.09和1.06~1.66,平均值为0.47、3.38和1.20。结果显示,该海域表层沉积物中天然210Pb相对于226Ra过剩,228Th相对于228Ra过剩,226Ra相对于238U缺损；γ放射性核素含量与沉积物的粒度分布、离岸距离无明显相关性。%Radionuclides in the surface sediments from Huangmaohai Esturary-Guanghai Bay and its adjacent sea area of the South China Sea were measured using HPGe-γspectroscopy. The specific activities of 238U, 226Ra, 210Pb, 228Th, 228Ra, 40K, and 137Cs were 66.50~98.80, 32~48.70, 96.20~174.70, 57.70~101.00, 49.70~64.80, 505~644, and 0.72~2.15 Bq·kgDW–1, with the mean values of 77.40, 36.60, 123.80, 64.50, 58.10, 571, and 1.52 Bq·kgDW–1, respectively. The ratios of 226Ra/238U, 210Pb/226Ra and 228Th/228Ra were 0.42~0.50, 2.80~4.09 and 1.06~1.66, with the average values of 0.47, 3.38 and 1.20, respectively. It was shown that the uranium and thorium decay series were in disequilibrium in the surface sediments, where 210Pb relative of 226Ra and 228Ra relative of 228Ra were excess while 226Ra relative of 238U was deficient. The distances from the sampling site to the coast were not interrelated with γ radionuclides contents and grain-size characteristics of the surface sediments.