Characterization of CDOM absorption of reservoirs with its linkage of regions and ages across China.

The absorption of chromophoric dissolved organic matter (CDOM) is an important part of light absorptions in aquatic systems. The increasing eutrophication of reservoirs and regional characteristics would affect the CDOM properties sensitively which would be important for the application of remote sensing monitoring. The highest (4.07 ± 2.31 m-1) and lowest (0.79 ± 0.67 m-1) CDOM concentrations of reservoirs were observed in the northeastern lake region (NER) and Tibetan Plateau lake region (TPR), respectively. The differences between S275-295 among the five lake regions were significant (p < 0.05) in which the steepest S275-295 (0.0173 ± 0.0026 nm-1) was observed in TPR and the shallowest (0.0326 ± 0.0152 nm-1) in Yungui Plateau lake region (YGR). The strong relationships between aCDOM(355) and DOC appeared in the NER (R2 = 0.43), eastern lake region (EAR) (R2 = 0.69), Mengxin lake region (MXR) (R2 = 0.61), and YGR (R2 = 0.79) which would be a good proxy for DOC in regional reservoirs. Most of all, the correlation between reservoir's establishing time and CDOM absorption under oligotrophic states was relatively strong in the EAR and MXR regions. It indicated that the establishing time of reservoirs affected the CDOM absorption to some extent under the oligotrophic states without much human disturbance. Our results indicate CDOM absorption varies with regions, and the relationships between CDOM and DOC are variable for different regions. Therefore, DOC estimation in reservoirs through CDOM absorption needs to be considered according to lake regions and trophic states.