The spectral resolution of DOM in urban rivers affected by different non-point source intensities using self-organizing maps

Abstract

UV–Vis, three-dimensional excitation–emission matrix fluorescence spectroscopy (EEMs) and a self-organizing map (SOM) were used to study changes in the composition and constituent concentrations of dissolved organic matter (DOM) in the water column of two urban rivers with different non-point source inputs during spring and summer. The level of humification and the relative molecular mass of DOM were remarkably higher in the summer than in the spring (P < 0.01) in both rivers. The SOM model showed that the fluorescence intensity of the spring component was lower than in summer in water bodies with higher levels of non-point source inputs, while the opposite was true for water bodies with lower levels of non-point source inputs. Principal component analysis (PCA) showed that nutrients like nitrogen and phosphorus promoted autogenous processes in these water bodies. Seasonal variations and differing intensities of non-point source inputs had remarkable effects on urban river waters (R2 = 0.775, P < 0.001). Non-point source inputs increased the concentrations of humus-like fractions and promoted autogenesis in the water bodies. HIGHLIGHTS Investigation of the variation of DOM spectral characteristics of urban rivers.; Application of unsupervised machine learning to spectral resolution.; Impact of seasonal variation on DOM in urban rivers.;

Keywords

• dissolved organic matter
• excitation–emission matrix spectroscopy
• self-organizing map
• urban rivers
• uv–vis