Sr-Nd isotope stratification along water depth:An example from Datong hydrological station of Yangtze River  

作　　者：LUO Chao ZHENG HongBo WU WeiHua WANG Ping CHEN YuLiang WEI XiaoChun 

机构地区：[1]Key Laboratory of Surficial Geochemistry,School of Earth Sciences and Engineering,Nanjing University,Nanjing 210093,China [2]School of Geography,Nanjing Normal University,Nanjing 210000,China

出　　处：《Chinese Science Bulletin》2012年第34期4482-4490,共9页

基　　金：supported by the State Key Program of National Natural Science of China (40830107);the Key Program for International S&T Cooperation Projects of China (2010DFA24480);the Geological Survey Program of China (water (2010) mineral assessment 03-07-08)

摘　　要：This study examines the effects of hydrologic sorting and mixing of sources on the Sr-Nd isotopic compositions of suspended sediments at different water depths. The samples were collected from three layers (surface, middle and bottom) at Datong hydrological station of Yangtze River during the flood season of 2010. Our results show that, 87 Sr/ 86 Sr values decrease from surface to bottom, ranging from 0.730332 to 0.720857. ε Nd (0) values range from 14.75 to 10.09, with surface sediments being the most negative. The isotope composition at the middle layer can best represent the mean isotopic composition of the total suspended sediments transported by a river. It is believed that the stratification of Sr-Nd isotope is attributable to mixing of sediments from different sources due to hydrological sorting. Sediments from the upper stream are found to be coarser, and tend to contribute more to the lower water column. Although Sr-Nd isotope is a well acknowledged tool to trace sediment provenance, the current study suggests that the grain size of the samples and the sampling locations should be taken into consideration when applying this method to provenance study.This study examines the effects of hydrologic sorting and mixing of sources on the Sr-Nd isotopic compositions of suspended sediments at different water depths. The samples were collected from three layers （surface, middle and bottom） at Datong hydro- logical station of Yangtze River during the flood season of 2010. Our results show that, 878r]86Sr values decrease from surface to bottom, ranging from 0.730332 to 0.720857. eNd（0） values range from -14.75 to -10.09, with surface sediments being the most negative. The isotope composition at the middle layer can best represent the mean isotopic composition of the total suspended sediments transported by a river. It is believed that the stratification of Sr-Nd isotope is attributable to mixing of sediments from different sources due to hydrological sorting. Sediments from the upper stream are found to be coarser, and tend to contribute more to the lower water column. Although Sr-Nd isotope is a well acknowledged tool to trace sediment provenance, the current study suggests that the grain size of the samples and the sampling locations should be taken into consideration when applying this method to provenance study.

关 键 词：SR-ND同位素 水文站 长江 水深 悬浮沉积物 同位素组成 个例 大通 

分 类 号：P333[天文地球—水文科学]