THE CHARACTERISTICS OF CDOM OPTICAL AND ITS INFLUENCE FACTORS IN ERHAI LAKE

Chromophoric dissolved organic matter (CDOM) is a chemical intermediary substance between terrestrial ecosystems and lake ecosystems, which has a profound impact on the structure and function of lakes. In order to understand the optical characteristics of CDOM and its influencing factors, 120 surface water samples from Erhai Lake were collected from November 2018 to October 2019. The composition and source of CDOM were analyzed by UV-Vis, and the correlation between optical properties and environmental factors was clarified by the principal component analysis (PCA). The result showed that CDOM absorption coefficient a(440) ranged from 0.22 to 0.90/m with significant difference in temporal distribution (P<0.01) but no difference in trophic state (P=0.97). There was a positive correlation between a(440) and dissolved organic carbon (DOC) (P<0.01), which was conducive to establish a remote sensing model for monitoring the spatial and temporal distribution characteristics of CDOM. Based on SUVA₂₅₄, S_R, M and S_275—295, it was found that optical characteristics of CDOM were significantly different with seasonal changes. All samples were mainly divided into the following two periods by the NMDS: November 2018 to July 2019 and August to October 2019. The latter SUVA₂₅₄ was lower than the former. The molecular weight of CDOM in Erhai Lake was relatively small, mainly due to endogenous production. In different periods, water temperature, pH and TP always have a greater impact on CDOM absorption characteristics. This paper clarified distribution characteristics of CDOM and its influencing factors, and provided a theoretical basis for the water management in Erhai Lake.