Optical absorption properties of CDOM and tracing implication of DOC in the Changjiang Estuary

The spectral absorption properties of chromophoric dissolved organic matter(CDOM) and the concentration of dissolved organic carbon(DOC) in the Changjiang Estuary from Luchaogang Dock to Shengsi Islands was studied during winter of 2009.The distribution of absorption coefficient α(355) and spectral slope of CDOM were analyzed and the source character and relationship between CDOM and DOC were discussed.Over a salinity range of 18.96~28.00,α(355) ranged from 0.2689~1.183 1 m-1,while the average value was 0.824 9 m-1,lower than values in the wet season,also the other estuaries of China and abroad,which may be attributed to the low degree of vegetative cover in the Changjiang drainage basin and low river flow in winter.The river discharge has significantly influenced on the CDOM distribution in the estuary.The spectral slopes varied from 0.011 3 to 0.017 4 nm-1,and the average value was 0.015 3 nm-1,a little lower comparing with that in the wet season.The inverse relationship between DOC and salinity(R2=0.882) showed the dissolved organic matter(DOM) were primarily terrestrial.And the relationship between CDOM and DOC(CDOMα(355)=0.371DOC+1.012(R2=0.48)) showed that CDOM was a promising tracer for the land source DOC,but the stable inverse model need further study.