Optical properties and spatial distribution of chromophoric dissolved organic matter (CDOM) in Poyang Lake, China

Chromophoric dissolved organic matter (CDOM) is a key component in aquatic ecosystem. CDOM plays a critical role in water optical attenuation and in biogeochemical processing. In this study the optical absorption properties and spatial distribution of CDOM were investigated during the wet season in Poyang Lake. Results showed that the absorption coefficients of CDOM varied significantly in four sections that contain different levels of turbidity. The absorption coefficients of CDOM in the section dominated by wetland water were higher than that in other sections. The study found that the absorption coefficients of CDOM were ranged from 1.59 to 4.71 m− 1 with an average value of 2.77 ± 0.76 m− 1 at 355 nm, and from 0.39 to 1.14 m− 1 with an average value of 0.70 ± 0.19 m− 1 at 440 nm, respectively. Spectral analysis with specific ultraviolet absorbance at 254 nm, absorption ratio between 250 and 365 nm and spectral slope indicated that CDOM in Poyang Lake was relatively high in molecule weight and aromaticity from terrestrial allochthonous inputs. Comparison of water samples revealed that CDOM in wetland contributed water had lower molecule weight and aromaticity influenced by autochthonous sources. Concentrations of dissolved organic carbon (DOC) and coefficients of CDOM absorption were significantly correlated at the range from 280 to 440 nm, especially at shorter wavelengths, which suggests that CDOM can be used as an effective DOC indicator in Poyang Lake. This study established a field-based knowledge for remote sensing measurements of CDOM in the largest fresh water lake in China.