Optical Characteristics of Chromophoric Dissolved Organic Matter (CDOM) in Upstream and Downstream Lakes of Taihu Lake Basin: New Insights for Water Environmental Management

Chromophoric dissolved organic matter (CDOM) is a key component of organic matter that contributes to the ecological functioning of lakes. The lakes in Taihu Lake Basin play an important role in maintaining regional ecological stabilities; however, the optical characteristics of the CDOM in the upstream and downstream lakes in this basin have not yet been systematically studied. Here, the optical characteristics of CDOM in ten lakes of upstream and downstream of the Taihu Lake Basin were studied using UV-Visible and excitation-emission matrix spectroscopies. Three different fluorophores consisting of two humic-like components (C1, C2) and one protein-like component (C3) were identified by parallel factor analysis. Soil or surface erosion was responsible for the higher abundance of C1 in the upstream lakes, and increased biological activities accounted for the higher abundance of C3 in the downstream lakes. Rainfall erosion in the wet season led to an increase in CDOM. We also found that the photodegradation and flocculation degree, which played a significant role in reducing CDOM, were higher in downstream lakes than in upstream lakes. Optical analysis of CDOM provides a promising method for monitoring water qualities (e.g., total phosphorus and potassium permanganate index) in each lake. Reductions in soil or surface erosion in the upstream are needed to improve water quality.

Automated summary

Chromophoric dissolved organic matter (CDOM) is a key component that affects the ecological functioning of lakes. The optical characteristics of CDOM in the upstream and downstream lakes of the Taihu Lake Basin were systematically studied, revealing differences in CDOM composition. Soil or surface erosion was identified as the main factor contributing to higher abundance of C1 in the upstream lakes, while increased biological activities accounted for higher abundance of C3 in the downstream lakes. Rainfall erosion during the wet season led to an increase in CDOM. Photodegradation and flocculation degree played a significant role in reducing CDOM, with downstream lakes exhibiting higher levels. Optical analysis of CDOM provides a promising method for monitoring water quality in lakes.