Changes in perturbation-correlation moving-window two-dimensional correlation spectroscopy of dissolved organic matter induced by dam regulation in a river-type reservoir.

Dam regulation, a hydraulic engineering measure, has a significant impact on dissolved organic matter (DOM) which works as the carbon pool; however, no exact relationship has been established between alterations in water level, caused by the long-time regulation of dams, on the distribution of DOM fluorescence components in the upstream reservoir. Here, four sampling campaigns were conducted under both high- and low-water levels in Shuikou Reservoir, and parameters of water quality and hydrology were comprehensively determined and statistically analyzed. Utilizing perturbation-correlation moving-window two-dimensional (PCMW2D) correlation spectroscopy technology and Mantel tests, we have found a significant correlation between DOM fluorescence components and both basic water quality parameters and indicators of inorganic pollutants, particularly during low-water level periods. High water velocity increased dissolved oxygen (DO) concentration to quench DOM fluorescence during low-water level periods, while low DO levels were correlated with increased fluorescence during high-water level periods. Turbidity showed a positive relation to certain DOM components and significantly influenced the composition of DOM. The main components of DOM (fulvic-like, humic-like and tryptophan-like fluorophores) increased to varying degrees under high-water levels, while decreased under low-water levels. Hence, the increment of DOM component in high-water level periods was more considerable than that in low-water level periods. Furthermore, DOM in urban river reaches mainly came from terrestrial organic matters introduced by human activities, while DOM in certain river sections originated from endogenous sources, such as the accumulation of humic substances in aquaculture systems. This study provided supporting data and optimization ideas for predicting the migration and transformation of pollutants in rivers and managing dam gates scientifically.