[Assessment of the Spatial-temporal Distribution Characteristics and Main Affecting Factors of Chromophoric Dissolved Organic Matter in Spring and Summer at the Changjiang Estuary and Adjacent Areas].

The composition and distribution characteristics of chromophoric dissolved organic matter(CDOM) of Changjiang Estuary and its adjacent waters in spring (March 2015) and summer (July 2015) were evaluated by excitation-emission matrix spectroscopy (EEMs) in combination with parallel factor(PARAFAC) analysis. Three humic-like components[C1(370/495 nm),C2(330/405 nm),C3(365/440 nm)] and one protein-like component[C4(295/345 nm)] were identified. The distribution patterns of the four components in spring and summer were almost the same, showing a decreasing trend from Changjiang Estuary to adjacent waters. In spring, the high value areas of three humic-like components were located inside of Changjiang Estuary, and the high value areas of the protein-like component were located in the South Passage of Changjiang Estuary. In the surface layer, the CDOM was mainly from terrestrial input and human activities; the influence of terrestrial weakened in the middle layer because of the lower fluorescence intensity values; and in the bottom layer the fluorescence values were higher than those in the middle layer, which was caused by sediment resuspension. There were high value areas in the Daishan Island, which were related to human activities. In summer, the high value areas of CDOM were almost the same as those in spring, and all layers had similar fluorescence intensity values, which indicated that they were mixed evenly. CDOM in spring and summer had high humification index (HIX) values in the Changjiang Estuary, whereas for biological index (BIX), its high values appeared in the adjacent waters. Four components (C1-C4), and DOC, TN, TP, DO, Chl-a, Salinity were evaluated by redundancy analysis (RDA), which indicated that C1-C4 and TN, TP were mainly affected by terrestrial input and human activities, and DOC was affected by terrestrial and marine source together. The use of EEMs-PARAFAC in combination with multivariate analysis to parse the composition of CDOM revealed the source of CDOM and main influencing factors in Changjiang Estuary and adjacent waters, and plays an important role in the biogeochemical research of biogenic elements in estuarine waters.