长江口及其邻近海域CDOM光谱吸收特性分析

Optical characteristics of Colored Dissolved Organic Matter(CDOM) in Changjiang River Estuary and its adjacent sea areas

研究了长江口及其邻近海域有色可溶性有机物(CDOM)的光吸收特性,分析了CDOM浓度(吸收系数a(440))、光谱斜率(Sg)与盐度的关系。结果表明:长江口及其邻近海域CDOM的a(440)变化范围为0.21～0.85m-1,平均值为0.44m-1;Sg值的范围为0.013 3～0.016 7nm-1,平均值为0.014nm-1;a(440)的水平分布表现为长江口海区比外海区高,Sg的水平分布表现为长江口海区比外海区低,反映了长江口海区CDOM中的腐殖酸成分比外海区大。研究区内a(440)与盐度、Sg与盐度明显线性相关,表明CDOM在河口混合行为中呈保守行为,CDOM具有良好的保守性质。

Optical properties of Chromophoric Dissolved Organic Matter （CDOM） have played an important role in quantitative water-color remote sensing retrieval. The optical properties of CDOM in coastal waters of Changjiang River Estuary were investigated in June of 2011. This area is affected by terrigenous factor strongly with different hydro-dynamic characteristics. CDOM absorption coefficient and spectral slope were got through sampling, laboratory measurements and subsequent data processing. Then, CDOM absorption cofficient and spectral slope were discussed. CDOM absorption coefficients at 440 nm [-a （440）] varied between 0.21 and 0.85 m-1, with an average value of 0.44 m-1. In addition, the spectral slope, Sg varied between 0. 013 3~0. 016 7 nm 1, with an average value of 0. 014 nm-1. Significant spatial difference in absorption cofficient and spectral slope was observed varied tremendously in the estuary and the offshore area. The higher absorption coefficients of the cruise appeared in the estuary area while the lower spectral slope of the cruise appeared in the area which is greatly influenced by the terrestrial sources; the lower absorption coefficients appeared in the offshore area while the higher spectral slope of the cruise appeared in the area which is greatly influenced by the mixing of terrestrial humic sources and seawater. A significant positive relationship between salinity and a （440） was found in the whole area showing conservative behavior of CDOM. There was a good correlative relationship between the spectral slope Sg and salinity in the whole area, which also reflected conservative behavior of CDOM.