A cruise from Luchaogang Dock to Shengsi Island was carried out on 15th August 2008 for acquiring 16 surface water samples in the Changjiang River estuary, China. Sea surface salinity (SSS) and CDOM absorption and fluorescence spectroscopy measurements were obtained. Over a salinity range of 8.4-26.5o/oo, CDOM absorption coefficient at 355nm ranged from 0.42-1.44m-1, and the mean value for a355nm was 0.86 m-1, showing relatively variable optical properties of the waters in the Changjiang River estuary region at the same scale and range as that in other Chinese estuaries and coastal waters. The values for S ranged from 14.9 to 20.1μm-1, with the average value of 17.1μm-1. Three distinct principal fluorophore types including tryptophan-like (T), UV humic-like (A) and visible-terrestrial humic-like (C) fluorophores were observed here, but marine fluorophore (visible-marine humic fluorophore (M) was absent in all sampling stations, suggesting its dominant controlling role for the diluted water masses in the Changjiang River. Both
the aCDOM and the S value as well as the normalized concentration of FCDOM tend to decrease from the inner to the outer estuary; their strong opposite relationship with salinity imply a conservative behavior of terrestrial source matters in the Changjiang River estuary during the mixture of the Changjiang diluted waters and marine waters, suggesting that it is appropriate to adopt CDOM optical properties as a tracer of the diluted water masses in the Changjiang River and its terrestrial source matters.