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Hierarchical cluster analysis (CA) grouped the 12 sampling sites into two clusters (Eastern Chaohu Lake and Western Chaohu Lake). Temporal CA classified the 12 months into four periods (March-May; June-August; September-November; January, February and December) with a distinct regular seasonal cycle in Eastern Chaohu Lake and four periods (January-April and December; May, July and November; June, September and October; August) with an irregular seasonal cycle in Western Chaohu Lake. Trophic state index analysis showed that Eastern Chaohu Lake was in mesotrophic levels, while Western Chaohu Lake was in eutrophic and hypereutrophic levels. Based on pollutant source statistics data, the dominant pollution sources were identified as domestic sewage and non-point pollution in Eastern Chaohu Lake. Domestic sewage, industrial and non-point sources were contributed to eutrophication in Western Chaohu Lake.

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Two defined peaks, at wavelengths of 260∼300 nm (peak I) and 300∼350 nm (peak II), could be identified for soil DOM at a Δλ value of 30 nm. In sediment DOM extracts, a third peak (III) was observed near 364 nm. The results show that there is a significant difference in the structure of DOM because of different sources. The humification degree is significantly higher for soil samples than those of sediment samples. The FT-IR spectra of DOM show that structure in sediment DOM is more functional groups than those in soil DOM. DOM has a stronger Cu binding affinity in soils than in sediment in the Hetao region, which may lead to potentially significant influence on the migration and transformation of Cu (II).

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The elemental composition and the UV–visible spectroscopic properties of dissolved fulvic acids (FA) extracted from salined fluvo-aquic soils in the Hetao Irrigation District were examined to evaluate the humification degree of FA and salinisation processes of soils. Composite soil samples of different depths (0–20, 20–40, 40–60, 60–80 cm) were collected from four native halophyte soils [communities Salicornia europaea (CSE), Suaeda glauca (CSG), Kalidium foliatum (CKF), Sophora alopecuroides (CSA)] and two furrow-irrigated fields [corn (CFD), wheat (WFD)] along a saline impact gradient. Seven humification indices (HIXs: C/N, SUVA, E2/E3, E2/E4, S275–295, S350–400, and S250–400), deduced from elemental analysis and UV–visible spectroscopy of FAs, were used to evaluate the humification degree. The humification degree of FA from the WFD soil was the highest, followed by CFD, CSA, CKF, CSG, and CSE. There were significant relationships between the seven HIXs (P < 0.05). The exchangeable sodium percentage (ESP) exhibited close correlations with the seven HIXs, and the humification degree increased with decreasing ESP. The HIX can not only indicate the humification degree of soil organic matter but also characterise the salinisation processes of soils.

Dissolved organic matter (DOM) collected from different sampling sites in Lake Wuliangsuhai (Inner Mongolia Autonomous Region of China) was investigated using UV–Vis absorption and fluorescence spectroscopy. The three indices, SUVA280 and two spectral slopes (S275–295 and S350–400), were used to detect the change in the aromatic structure of DOM. DOM aromaticity was lower at sites W1 and W3, where industrial wastewater and domestic sewage, and agricultural drainage, contributed respectively. The humification index also indicated a low humification degree at sites W1 and W3, and high humification degree in other sites with relatively better water quality. Fluorescence regional integration (FRI) analysis has been used to quantitatively analyse fluorescence excitation–emission matrix spectra. The results showed that external contaminants can influence the distribution of Pi,n values from the FRI analysis. Serious pollution area obtained a relatively high Pp value. A significant negative correlation between Ph/Pp and f450/500 indicated the terrestrial or autochthonous sources of DOM. Therefore, the spectroscopic techniques combined with regional integration analysis can be used as a useful tool for investigating and assessing the lake ecological environment.