[Optical Characteristics and Source Analysis of Dissolved Organic Matter in Hypersaline Lakes in Cold and Arid Regions]

The composition and source information of the aquatic dissolved organic matter （DOM） in the Daihai Lake, a typical saline lake at the ecologically fragile agro-pastoral area, were explored with three-dimensional excitation and emission matrix fluorescence （3DEEM）, parallel factor analysis （PARAFAC）, and fluorescence peaks （B, T, A, M, C, D, and N）. Further, the relationship between aquatic DOM fluorescence characteristics and environmental factors were analyzed using correlation analysis in the Daihai Lake. The results showed that the water of Daihai was weakly alkaline, with high nutrient salt concentration and serious organic pollution. Two protein-like substances （C1 and C3） and one humic-like substance （C2） were identified using PARAFAC. The sum of C1 + C2 accounted for 80% of DOM. The results of fluorescence peaks showed that the total percentage of protein-like fluorescence absorption peaks （B, T, and N） was 49.67%. Aquatic DOM of Daihai demonstrated both terrigenous and endogenous characteristics. Terrestrial inputs were mainly from intensive agricultural activities and rapid ecological degradation of the watershed leading to large amounts of organic matter entering the lake. The environmental behavior of DOM was highly correlated with the metabolic activity of organisms and nutrient status of lakes. NH₄⁺-N, DOP, TP, DO, and permanganate index characterized the effect of the lake trophic state on DOM composition. DO, SAL, and Chla were mainly related to microbial metabolic processes （P<0.05）. This study provides basic data and insights for the improvement of inland lake environments in saline lakes.