Influence of sediment DOM on environmental factors in shallow eutrophic lakes in the middle reaches of the Yangtze River in China

Both three-dimensional excitation–emission matrix fluorescence spectroscopy and parallel factor analysis were utilized to identify dissolved organic matter (DOM) components in sediments of thirty eutrophic shallow lakes in the middle reaches of the Yangtze River in China. Four distinct DOM components were identified: two main components regarding terrestrial humic-like materials (C1 and C2), one about terrestrial fulvic/humic-like materials (C3), and one related to autochthonous tryptophan-like materials (C4). The dominance of terrestrial fluorescence materials in DOM indicated that terrestrial inputs have critical effects on the surveyed lakes. The Principal Component Analysis (PCA) and Canonical Corresponding Analysis (CCA) were applied to analyze DOM components and their relationship with the environmental variables. PCA graphs showed that there were spatial differences in DOM fluorophores among lakes with various environments. Components C1, C2, and C4 were correlated positively with PC1 axis (factor 1), while C3 was opposite. Component C1 and C3 showed positive correlations with PC2 axis (factor 2). The CCA and Pearson correlation analysis showed that sediment DOC was correlated significantly with sediment variables (TN, OM, and conductivity), water quality variables (TN, PO₄ ³⁻, and Chl a), and DOM components C1 and C3. All DOM components were related significantly to different environment variables, including water quality variables especially nutrient elements (NO₃ ⁻, TN, Chl a, and DOC) and sediment variables (OM, NH₄ ⁺, and HCl–P). The relationship between DOC and the lake comprehensive nutritive index TLI was marginally significant.