崇明东滩不同高程潮间带沉积物中210Po和210Pb的时空特征

210Po和210Pb在海洋环境过程和放射生态学研究中有重要的意义。基于2010年每月采集崇明东滩潮间带表层沉积物,分析其210Po和210Pb活度,结合大气沉降和长江河流输入的210Po和210Pb通量,研究了210Po和210Pb的时、空变化规律及其影响因素。结果表明:表层沉积物平均粒径春夏季接近,且明显低于秋冬季;由北到南,由陆向海,平均粒径均逐渐增大。崇明东滩表层沉积物中210Po和210Pb的比活度介于20.9~124 Bq/kg和26.1~101 Bq/kg,均高于同期徐六泾(长江河流入海节点)悬浮颗粒物中210Po和210Pb相应的值。北、中、南三个断面210Po/210Pb比值的平均值分别为:1.05,1.06和0.97,崇明东滩表层沉积物的主要来源为陆源的河流输送。从空间分布来看,210Po和210Pb的比活度随潮滩高程的降低而逐渐减小的特征,季节特征为在夏季最高,而冬季相对较低。

The temporal and spatial distributions of 210Po and 210Pb in the surface sediment of eastern tidal flat,Chongming,China

210Po and 210Pb are one pair of the most important radionuclides used in the study of marine environment and radioecology.Based on the analysis of activities of 210Po and 210Pb in surface sediments collected monthly (2010) eastern tidal flat of Chongming Island,the fluxes of 210Po and 210Pb in the atmospheric deposition and the discharge of the Changjiang River,the temporal and spatial distributions of 210Po and 210Pb and their impact factors were discussed.The results showed that the mean grain size of the surface sediments were similar in spring and summer,which were significantly lower than those in autumn and winter,and it exhibited decreasing trend with a landward and a northward all the year round.The activities of 210Po and 210Pb in the surface sediments ranged from 20.9 to 124 Bq/kg and 26.1 to 101 Bq/kg,respectively,which were higher than those of suspended particles in Xuliujing(the end number of fresh water input of Changjiang River).The average activity ratios of 210Po/210Pb in northern section,middle section and southern section in East Chongming tidal flat were 1.05,1.06 and 0.97,respectively.The sediments of the Chongming tidal flat were mainly controlled by the supply of the Changjiang River input.The activities of 210Po and 210Pb of surface sediment in East Chongming tidal flat decreased with the decreasing of tidal flat elevation.For the seasonal change,the activities of 210Po and 210Pb surface sediment in the East Chongming tidal flat showed high in summer and low in winter.