Strontium isotopic geochemistry of the Changjiang estuarine waters: Implications for water-sediment interaction

The Sr concentrations and Sr-87/Sr-86 ratios have been measured for the Cha ngjiang estuarine waters with a main purpose to understand physical and che mical processes at the estuary. The result shows that the Changjiang River water has higher Sr concentration (150 ng/g) and lower Sr-87/Sr-86 ratio (0 .7105) when compared with the average values (0.7119 for Sr-87/Sr-86 and 78 ppb for Sr, respectively) of large world rivers. In the mixing process, no simple mixing of two end-members has been found according to the variations of Sr concentration and isotope ratios. There is an abrupt rise of Sr isot ope ratios at the salinity about 1 mg/g during river-sea water mixing at th e estuary. This abrupt rise of Sr isotope ratios is mostly ascribed to the strong water-sediment interaction, because there exists the same rise of su spended particulate materials due to energetic resuspension of bottom sedim ents.