利用2007年8月31日采集于福建兴化湾西岸的潮间带沉积物岩心样品,用γ谱方法测量了其放射性核素含量,对岩心中核素的分布及其成因进行了讨论,估算了研究区沉积物的沉积速率,探讨了沉积物的物源,结果表明:(1)238u2、28TH2、28rA2、26rA2、10Pb1、37CS和40k的含量分别为35.0--60.6、52.6--69.3、49.0--66.5、22.7--36.2、26.3--84.8、0.5--1.3和775--831 bQ/kg;(2)用238u2、26rA1、37CS和40k作为示踪剂进行物源分析发现,兴化湾潮间带沉积物主要源于邻近的福州和莆田地区的土壤,所占比率分别为54%和46%;(3)用210PbEX和137CS方法估算得兴化湾西岸潮间带沉积物的平均沉积速率分别为0.38 CM/A和0.36 CM/A。岩心中210PbEX分布表明,自20世纪末,研究区潮间带沉积速率加快。One sediment core was collected from intertidal zone located west coast of Xinghuawan Bay,Fujian,China.The radionuclide contents in the cores were measured by γ spectrometry and the vertical distributions of the nuclides were discussed.The sources of sediment were evaluated using 238U,226Ra,137Cs and 40K as tracers.The sedimentary rate was estimated by 210Pbex and 137Cs methods.The detectable nuclides in this core are 238U,228Th,228Ra,226Ra,210Pb,137Cs and 40K.The contents of these nuclides are 35.0--60.6,52.6--69.3,49.0--66.5,22.7--36.2,26.3--84.8,0.5--1.3 and 775--831 Bq/kg,and with the averages of 45.4,61.2,61.2,31.4,45.6,0.9 and 804 Bq/kg respectively.The 238U activities in the 0--40 cm zone were comparable within the measuring error and high 238U contents were found in the depth of 50～60 cm and below which 238U activities fluctuate with no trend.With the similar trend,from surface to 22 cm depth the activities of 228Th and 228Ra are lower and increase slowly with increasing depth,and they are consistent within the error.Throughout the entire core length the 228Ra and 228Th is decay equilibrium.226Ra activities increase with increasing depth from surface to 22 cm depth,and the contents comparable from 22 cm to 72 cm,occurring fluctuation deeper than 72 cm.The 210Pb activities decrease exponentially both from surface to 12 cm and in the zone of 16～40 cm,but below the depth of 40 cm 210Pb is decay equilibrium with 26Ra.The distribution has a maximum activity at the depth of 16 cm,above which the 137Cs contents are consistent within measuring error but below which decrease with depth.40K is uniform distribution through entire length of the core.The sedimentation sources of Xinghuawan Bay are mainly from the surface soil of Fuzhou and Putian Prefectures surrounding it.Using 238U,226Ra,137Cs and 40K as tracer,by the content data of these four nuclides in the sediments measured in this study and in the land soil reported by literature,we calculated the contributions of the soils of Fuzhou and Putian Prefecture are 54% and 46% respectively.That means that natural radionuclides can be used as tracers to analyse material source of sediment.Sedimentation rate based on 210Pbex and 137Cs was estimated,that was 0.38 cm/a and 0.36 cm/a.From the 210Pbex distribution,we can deduce the sedimentation rate had changed at about 2000.The sedimentation rate was 0.27cm/a before 2000 and 1.07cm/a after that time,which was considered as abundant terrigenous material supplied by human activities after 2000.国家自然科学基金资助项目(40306018
