Humification Degree Of Dissolved Organic Matter Research Articles

Unveiling changes in the complexation of dissolved organic matter with Pb(II) by photochemical and microbial degradation using fluorescence EEMs-PARAFAC

Dissolved organic matter (DOM) is very important in determining the speciation, behaviors, and risk of metal pollutants in aquatic ecosystems. Photochemical and microbial degradation are key processes in the cycling of DOM, yet their effects on the DOM-Pb(II) interaction remain largely unknown. This was studied by examining the complexation of river DOM with Pb(II) after degradation, using fluorescence quenching titration and excitation-emission matrices-parallel factor analysis (EEMs-PARAFAC). Three humic-like and two protein-like components were identified, with strong removals of humic-like components and decreasing average molecular weight and humification degree of DOM by photo- and photo-microbial degradation. The changes in humic-like abundance and structure resulted in notable weakening of their interaction with Pb(II). The tryptophan-like C2 was also mainly removed by photo-degradation, while the tyrosine-like C3 could be either removed or accumulated. The Pb(II)-binding of protein-like components was generally weaker but was enhanced in some degradation groups, which might be related to the lowering competition from humic-like components. The binding parameters correlated significantly with the DOM indices, which were dominated by photo-degradation for humic-like components but by seasonal variations for the tyrosine-like component. These results have implications for understanding the key mechanisms underlying the variability of the DOM-metal interaction in aquatic environments.

Linking soil dissolved organic matter characteristics and the temperature sensitivity of soil organic carbon decomposition in the riparian zone of the Three Gorges Reservoir

Soil dissolved organic matter (DOM) is highly sensitive to external interference. However, little attention has been paid on how soil DOM characteristics in the dry period affect the warming response of soil organic carbon (SOC) decomposition in riparian ecosystems under flooding conditions. The temperature sensitivity (Q10) of SOC decomposition was determined by incubating 99 riparian soils under flooding across 11 transects of the Three Gorges Reservoir. Soil DOM characteristics in the dry period were measured by ultraviolet–visible spectroscopy (i.e., a254, a350, SUVA254 and SR) and 3D-fluorescence spectroscopy (such as FI, β:α, BIX, and HIX). The fluorescence components of C1, C3, and C4 were determined by parallel factor analysis. SOC decomposition was sensitive to warming with a higher Q10 value for CH4 (2.34 ± 1.30) and lower for CO2 (1.37 ± 0.23) under flooding. The soil DOM in dry period was mainly autochthonous with FI > 1.9 and 90% of BIX > 0.7. The humification of soil DOM was relatively weak at ∼ 95% of HIX < 0.8. The Q10 value of CO2 was positively correlated with Ln (SUVA254) and Ln (HIX) whereas negatively correlated with Ln (DOC), Ln (a254), and Ln (a350). The Q10 of CH4 was positively related to Ln (HIX), while on the contrary, negatively related to Ln (C4). These variations in Q10 were mainly driven by the aromaticity and humification degree of DOM. Out of all DOM characteristics, the lignin component was the key predictor of the Q10 variation. Overall, findings of this study indicate that soil DOM characteristics in dry period are closely linked with the response of SOC decomposition to warming during the reservoir impoundment.

Parallel Factor Analysis with 3DEEMS of Dissolved Organic Matter from Deep Porous Medium Reservoirs in the City of Kaifeng

The deep geothermal water found within Kaifeng City, Henan province, China, is mainly contained within a loose-pore geothermal reservoir in the Minghuazhen Formation (Neogene Period). To understand the role and composition of Dissolved Organic Matter (DOM) in geothermal water, water samples collected from 13 geothermal wells at different depths were studied using three-dimensional (3D) excitation-emission matrix-parallel factor (EEM-PARAFAC) analysis. Fluorescent components were analyzed according to depth, and DOM in geothermal water between 800 m and 1600 m was classified. The results show that the fluorescence index (FI), biological index (BIX), and humification index (HIX) of DOM differ among geothermal water from different thermal reservoirs. Based on these three indices, the humification degree of DOM in deep geothermal water in Kaifeng City is low and is mainly derived from an endogenous source, which is closely related to microbial activities in thermal reservoirs. The fluorescent components of DOM in geothermal water from depths less than 1200 m are mainly tryptophan, tyrosine, and fulvic acid-like. The fluorescent components of DOM in geothermal water from depths greater than 1200 m are more complex, with tryptophan, tyrosine, humic acid, and fulvic acid-like components. Therefore, the characteristics of DOM composition in the geothermal water from different reservoirs in Kaifeng can also be used to infer and explain that the quality of deep geothermal water has not been affected by human activities, and there is no obvious hydraulic connection between the geothermal water of each thermal reservoir.

Unveiling the role of dissolved organic matter on phosphorus sorption and availability in a 5-year manure amended paddy soil.

Dissolved organic matter (DOM) is an active component of organic manure that is widely used in agroecosystems to increase nutrient availability and consequently enhance crop yields. However, the ways in which soil DOM characteristics are influenced by organic manure and how it contributes to crop yield and soil P availability remains unclear. Here, we conducted a 5-year field experiment and demonstrated that partial replacement of chemical P fertilizer with swine manure could maintain high rice yield and soil available P levels and increase P fertilizer use efficiency (PUE) in comparison to chemical fertilization, even when the total P input was reduced. This suggests that organic manure application can significantly mobilize soil P and increase P availability. Structural equation modeling analysis indicated that the soil pH and humification degree of DOM, rather than DOM content, directly decreased maximum P adsorption capacity. The combined results of the optical spectroscopy and ultrahigh-resolution mass spectroscopy obtained from the laboratory validation experiment based on the DOM-removed soil demonstrated that manure-derived DOM competing with P for adsorption was one of the main reasons for the increase in soil P availability and that the effective DOM components were N-containing lignins, tannins, and condensed polycyclic aromatics with higher O/C and lower H/C ratios. Overall, our results provide solid evidence that soil DOM characteristics are influenced by manure application and facilitate soil P availability, which could help guide the sustainable P management and manure application in agroecosystems.

Abundance and Fluorescent Components of Dissolved Organic Matter Affected by Land Use in a Drinking Water Source

Regional concentrations, fluorescent components, and sources of dissolved organic matter (DOM) in a drinking water source in Chaobai River across seasons were investigated here using fluorescence excitation-emission matrices, parallel factor analysis, and fluorescence indexes. Five fluorescent-DOM components were identified, including two microbial humic-like components and one autochthonous tyrosine-like, one reduced quinone-like, and one terrestrial humic-like component. DOM was mainly derived from microorganisms. The farmland-dominated region showed the highest DOM concentration and significantly lower maximum fluorescence intensities (Fmax) of almost all fluorescent components than those in the forest-dominated region. The region dominated by urban lands exhibited obviously lower DOM concentrations than those in the farmland-dominated region and lower Fmax values of fluorescent components than those in the forest-dominated region. No interaction was found between land use and season when considering their effects on DOM. Season had a significant influence on the humification degree of DOM. This study shows that agricultural land use had a greater impact on DOM than that of forests and urban areas, and the increased riverine DOM resulting from farmland was mainly non-fluorescent parts.

Spectral Characteristics of Dissolved Organic Matter in Sediments from Poyang Lake

At present, there are few studies on the spectral characteristics of dissolved organic matter (DOM) in the sediments of the Poyang Lake basin. Therefore, excitation-emission matrix spectroscopy (EEMs) technology and ultraviolet-visible spectra combined with the parallel factor analysis (PARAFAC) were applied to investigate the fluorescent components and sources of DOM in sediments from Poyang Lake. The results showed that the DOM in sediments originated from both terrestrial and autochthonous sources with a high humification. Compared with the sub-lakes, the DOM from the main lake was characterized with a higher concentration of colored DOM, larger particle size, and higher aromaticity and humification degree. In addition, four fluorescence components of DOM in sediments were identified by the PARAFAC model, including three humic-like components (C1, C2, and C4) and one protein-like component (C3). The fluorescence intensity of the humic substances in the sub-lakes was higher than those in the main lake. Furthermore, the percentage of fluorescence abundance of C1 was the highest both in the sub-lakes (42%) and main lake (46%). The spatial distribution of the fluorescence intensity of the four components gradually increased from west to east, and the peak values were observed in the Duchang and Nanji Wetland. This may be related to the death of a large number of plants due to the rise in the water level during the wet season and human activities. Principal component analysis showed that although there were no significant differences in the four fluorescent components between the sub-lakes and the main lake, the humification degree of DOM in the sub-lakes was slightly higher than that in the main lake.

Investigation on depth-dependent properties and benthic effluxes of dissolved organic matter (DOM) in pore water from plateau lake sediments

Dissolved organic matter (DOM) in sediment pore water plays a key role in lake water quality, complexation of the contaminants, biogeochemical cycles, and even climate. To better understand the vertical dynamics and characteristics of DOM among pore water profiles, we investigated concentrations, chemical structures, and benthic fluxes of DOM in plateau lake sediments via stoichiometric analysis, ultraviolet–visible (UV–vis) absorption, three-dimensional fluorescence matrix spectroscopy (EEMs), and parallel factor model (PARAFAC). The results revealed that dissolved organic carbon (DOC), concurrent with chromophoric DOM (CDOM) and fluorescent DOM (FDOM), tended to accumulate in the anaerobic deeper layers. These trends also demonstrated a good agreement with the ammonium nitrogen (NH4+-N) concentration, implying that the pathway of DOM dynamics was closely related to the redox state. The EEMs-PARAFAC model revealed that DOM in pore water mostly consisted of two terrestrial humic-like components (average contribution:> 60%) followed by microbial and tryptophan-like components, respectively. Terrestrial humic-like components were relatively stable, and their abundance was positively correlated with the FDOM level (p < 0.05). The changes of aromatic, molecular weight, and humification degree of DOM were possibly driven by microbial activities at different depths. Moreover, benthic flux estimations indicated that DOM and the total dissolved nitrogen (TDN) in inland sediments were potential sources for the overlying water and possibly affected the quality and ecological safety of lake water bodies.

Applying synchronous fluorescence and UV-vis spectra combined with two-dimensional correlation to characterize structural composition of DOM from urban black and stinky rivers.

UV-visible spectroscopy and synchronous fluorescence spectroscopy (SFS) combined with two-dimensional correlation spectroscopy (2D-COS) were applied for extracting fluorescence components, tracing organic functional groups, and revealing variations of dissolved organic matter (DOM) in Puhe River. Water samples were collected from the mainstream and two tributaries (Nanxiaohe River and Huangnihe River). DOM in three rivers was composed of protein-like fluorescent (PLF), microbial humus-like fluorescent (MHLF), fulvic-like fluorescent (FLF), and humic-like fluorescent components, which were relative to aromatic groups, phenolic groups, carboxylic groups, and microbial products. The PLF and MHLF were dominated in DOM fractions in the rivers, and the average content of the PLF was the highest in Nanxiaohe River. Humification degree of DOM was the highest in Puhe River, followed by Huangnihe River and Nanxiaohe River. However, molecular mass of DOM in Puhe River was the lowest, followed by Huangnihe River and Nanxiaohe River. Based on the 2D-COS of the SFS and UV-visible spectra, the variation order of DOM fractions in Puhe River was PLF → MHLF → FLF, and the PLF was consistent with the phenolic groups, aromatic groups, and carboxylic groups, but the adverse trend with the microbial products. The variation order in Nanxiaohe River was MHLF → PLF → FLF, and the MHLF was consistent with the aromatic groups, phenolic groups, carboxylic groups, and microbial products. The variation order in Huangnihe River was MHLF → PLF → FLF too, and the PLF was consistent with the carboxylic groups and aromatic groups. The results of the present study demonstrate that UV-visible spectroscopy and SFS combined with 2D-COS are useful methods to characterize structural composition of DOM from urban black and stinky rivers so as to investigate their pollution status.

Resource aromaticity affects bacterial community successions in response to different sources of dissolved organic matter

Microbe-mediated transformation of dissolved organic matter (DOM) contributes substantially to the carbon dynamics and energy flow of aquatic ecosystems; yet, the temporal dynamics of bacterial communities in response to diverse DOM sources are scarcely known. Here, we supplied four distinct sources of DOM (algae-derived, macrophyte-derived, sewage-derived, and soil-derived) to the same bacterial community to track the effects of these DOM sources on the carbon processing and successional dynamics of bacterial communities. Although by the end of the incubation the proportion of bio-degraded DOM was significantly lower in the soil-derived DOM treatment than for the other sources, rapid initial metabolism of protein-like and aliphatic compounds and increasing aromaticity and humification degree of DOM during the incubation period were observed for all sources. The role of stochastic processes in governing the community assembly decreased substantially from 61.4% on the first day to 16.7% at the end of the incubation. Moreover, stronger deterministic selection and lower temporal turnover rate were observed for the soil-derived than the other DOM sources, indicating stronger environmental filtering by the more aromatic DOM. Significant correlations were also observed between the humification index (HIX) of DOM and bacterial community diversities, co-occurrence patterns, habitat niche breadths, and the contribution of deterministic ecological processes. In addition, we demonstrated that taxa with different abundance patterns all play crucial but different roles in the response to DOM variation. Our results indicate the importance of DOM aromaticity as a predictor of the outcome of different DOM sources on bacterial community dynamics.

Ecological indication based on source, content, and structure characteristics of dissolved organic matter in surface sediment from Dagu River estuary, China.

Dissolved organic matter (DOM) controls the fate of a variety of nutrients and trace metals in river estuary systems. The aim of our study is to explore the sources, structure characteristics of sediment DOM, and potential ecological release risk (heavy metal, N and P) under the environmental conditions of Dagu River estuary. The relative contribution of DOM source was calculated by carbon stable isotope (combining δ13CDOM and C/N ratios). The structural characteristics of sediment DOM in Dagu River estuary were determined by ultraviolet-visible spectroscopy (UV-vis) absorbance and fluorescence spectroscopy. The potential ecological risks of heavy metals and N and P release were also assessed. Results show that the relative contributions of rural area and aquaculture are high in Dagu River estuary. The humification degree of DOM in downstream river is higher than that in the estuary, and the sediment DOM in Dagu River estuary is influenced by both terrestrial input and biological metabolism. The potential risk of eutrophication in the estuary is high. Moreover, under the effect of aquaculture and rural area, there is higher potential ecological release risk of heavy metal in the estuary. And samples in the middle transect have the highest potential ecological risks of heavy metal. Therefore, a framework has been proposed to predict the ecological status of the estuary by analyzing the sources, content, and structural characteristics of sediment DOM. These results provide a new insight on ecological indication of DOM in Dagu River estuary.

Application of UV-visible absorption spectroscopy combined with two-dimensional correlation for insight into DOM fractions from native halophyte soils in a larger estuarine delta.

UV-visible absorption spectroscopy combined with principal component analysis (PCA) and two-dimensional correlation (2D correlation) is used to trace components of dissolved organic matter (DOM) extracted from soils in a larger estuarine delta and to investigate spatial variations of DOM fractions. Soil samples of different depths were collected from native halophyte soils along a saline gradient, i.e., Suaeda salsa Comm. (SSC), Chenopodium album Comm. (CAC), Phragmites australis Comm. (PAC), and Artemisia selengensis Comm. (ASC). Molecular weights of DOM within the SSC soil profile were the lowest, followed by the CAC, PAC, and ASC soil profiles. Humification degree of DOM within the ASC soil profile was the highest, followed by the PAC, SSC, and CAC soil profiles. DOM within the soil profiles mainly contained phenolic, carboxylic, microbial products, and aromatic and alkyl groups through the PCA, which presented the significant differentiation among the four native halophyte soil profiles. The 2D UV correlation spectra of DOM within the SSC soil profile indicated that the variations of the phenolic groups were the largest, followed by the carboxylic groups, microbial products, and humified organic materials according to the band changing order of 285 → 365 → 425 → 520nm. The 2D UV correlation spectra of DOM within the CAC soil profiles determined that the decreasing order of the variations was phenolic groups > carboxylic groups > microbial products according the band changing order of 285 → 365 → 425nm. The 2D UV correlation spectra of DOM within the PAC soil profile proved that the variations of the phenolic groups were larger than those of the carboxylic groups according to the band changing order of 285 → 365nm. The 2D UV correlation spectra of DOM within the ASC soil profile demonstrated that the variations of the phenolic groups were larger than those of the other DOM fractions according to the broad cross-peak at 285/365-700nm.

Assessing the environmental impact of phenanthrene in different types of land use based on the binding characteristics with dissolved organic matter

The binding characteristics of phenanthrene with dissolved organic matter (DOM) were studied by the excitation emission matrix fluorescence spectroscopy with parallel factor analysis in four types of land use which derived from forest (F), meadow (M), cropland (C), and greenhouse (G). The results showed that the humification degree and binding characteristics of phenanthrene with DOM were distinct differences in the four soils. The binding capacities of humic-like components with phenanthrene were stronger than those of protein-like components. The log K derived from the Stern-Volmer equation significantly correlated with the humification degree of DOM (p < 0.05) in different types of land use. Besides, correlation analysis demonstrated that the potential binding index (Fk) obtained from the modified Stern-Volmer model was a more accurate parameter to describe the combination degree of DOM with phenanthrene than log K, which presented a decrease order of C > F > M > G. Therefore, the environmental impact of phenanthrene in different types of land use could be assessed deeply based on the Fk and DOM concentration.

Investigating the spectral characteristic and humification degree of dissolved organic matter in saline-alkali soil using spectroscopic techniques

Soil samples were collected from the areas surrounding Wuliangsuhai Lake in China. Dissolved organic matter (DOM) was extracted from the samples and characterized by fluorescence and UV-Vis spectra. Spectral properties and humification degree of DOM were studied. The results indicated that both humic- and protein-like fluorophores were present in the DOM spectra, and the former was the dominant component. The analysis of humification (HIX) and r (A, C) indices revealed that the maximum humification degree in three agricultural soils (AAF, ASC, and ASW) was presented in the second soil layer (20‒40 cm). However, the humification degree of the two Halophytes soils (SSE and GKF) decreased with increasing depth. One index, I344/270, showed that humification degree increased gradually with an increasing proportion of humic-like acid. There was a significant positive correlation between humification degree (HIX) and aromaticity (SUVA254), indicating that a higher aromaticity corresponded to a higher humification degree. Land use was an important factor responsible for the major difference of cation exchange capacity (CEC) in different soils, which led to a higher CEC value in the second soil layer for the three agricultural soils. CEC values and humification degree had the same trend for all five soils. The correlation analysis showed that there was a significant positive correlation between HIX and CEC, and a negative correlation between the r (A, C) index and CEC, indicating that humification degree increases gradually with increasing CEC values.

Composition, structural characteristics and indication of water quality of dissolved organic matter in Dongting Lake sediments

This study aims to establish the relationship between the composition, structure of sediment dissolved organic matter (DOM) and water quality based on changes of environmental conditions in Dongting Lake. Hence, UV–vis absorbance and fluorescence spectroscopy were combined to characterize the components and structure of DOM in surface sediments of Dongting Lake. The relationship of the structural characteristics of DOM with N, P contents and water quality was also explored. The results showed that the DOC contents of Dongting Lake sediments were between 60.004 and 368.286mgkg−1, with the general trend of Eastern>Southern>Western for the Dongting Lake regions. The DOM in the sediments mainly comprised humic-like substances, which were greater in the Eastern than in the Southern and Western Dongting Lake regions by 4.1% and 6.43%, respectively. The humification degree of DOM in the sediments was high, and the substitution groups in the aromatic rings mainly contained carbonyl, carboxyl, hydroxyl, and esters. The source of DOM in the Dongting Lake sediments was significantly influenced by terrestrial input and biological metabolism. Furthermore, the composition and structural characteristics of DOM in the Dongting Lake sediments were found to be closely related to the contents of N and P in the sediments, as well as the water quality. Especially, the ratio of humic-like substances to protein-like substances (P(III+V,n)/P(I+II,n)) can be indirectly taken as an indicator of water quality. Thus, the changes of composition and structure of sediment DOM can establish a relationship with the water quality, and will have an indicative effect on lake trophic status.

UV-Visible Spectra Properties of DOM from Taizi River in Benxi City Section by Multivariable Analysis

This study investigated the ability of ultra violet-visible (UV-Visible) spectroscopy to analyze the origin,compositions,structure and humification level of dissolved organic matter(DOM). Seven surface water samples were collected from the Benxi City section of mainstream in Taizi River. Nine indices (SUVA254, E2/E3, E2/E4, E4/E6, S275-295, S350-400, A2/A1, A3/A1 and A3/A2), deduced from elemental analysis and UV visible spectroscopy of DOM, were used to assess the humification degree. The results showed that the characteristics of DOM were distributed along urban river and industrial wastewater discharge, and the DOM of waste water from Benxi steel plant contained a low degree of condensation of small organic molecules. E2/E3 showed positive correlation with E2/E4, and negative correlations with S275-295, S350-400, A2/A1,indicating that humification degree of DOM was not only concerned with the degree of condensation of organic molecules, but also closely associated with the ratio between humic acid and fulvic acid. Composition structure of DOM showed significant positive correlations with A2/A1, SUVA254 and S275-295, and significant negative correlations with E2/E3 and E2/E4. Based on the loadings of DOM component and scores plot of sampling sites in Taizi River (Benxi City section),the characteristics of DOM were distinctly distributed along urban river and industrial wastewater discharge, proving that the river was deeply influenced by human activity.

Characterization of bulk and chromophoric dissolved organic matter in the Laurentian Great Lakes during summer 2013

The Laurentian Great Lakes contain ~ 21% of the Earth's surface freshwater and are experiencing dramatic decadal-scale changes to their water quality, biogeochemistry and ecosystem functions.We report here the first data set of dissolved organic carbon (DOC) and chromophoric dissolved organic matter (DOM), including UV–visible absorbance and derived optical properties and fluorescence excitation–emission matrices (EEMs), for open-lakesurface waters from each of the Great Lakes. Concentrations of DOC ranged from 86 to 240 μmol/L and the absorption coefficient at 254 nm (a254) varied from 2.67 to 10.47 m− 1 in Great Lakes waters.UV–visible and fluorescence characterization indicated that the DOM in open-lake waters in all the Great Lakes was primarily autochthonous. Both DOC and a254 increased from Lake Superior to Lakes Erie and Ontario where aromaticity, molecular weight and humification degree of DOM were also higher.These variations are consistent with both the water transport pathway and the trend of increasing human population and relative watershed drainage area along the Great Lakes. Parallel factor analysis on fluorescence-EEM data revealed three terrestrial humic-likeDOM components (C1, C2 and C4) and one protein-likeDOM component (C3). Open Lake Huron had the highest protein-like/humic-like DOM ratio (C3/C1), while sites in Lakes Erie and Ontario had lower C3/C1 ratios, indicating a greater proportional influence of terrestrial DOM. Changes in DOM composition along the water transport pathway in the Great Lakes indicate varying impacts from terrestrial inputs and human activities in the different lake systems.

Characterization of the composition of water DOM in a surface flow constructed wetland using fluorescence spectroscopy coupled with derivative and PARAFAC

This study was conducted to discuss fluorescence spectroscopic properties of water dissolved organic matter (DOM) in a large-scale constructed wetland and to reveal the composition and humification degree. Four humification indices (HIXs) deduced from emission spectra (A 4/A 1), excitation spectra (I 426/I 366), synchronous fluorescence spectra (I 370/I 330) and derivative (I 360/I 320) were used for the description of composition and humification degree of DOM. Three components (C1–C3) were derived from excitation-emission matrices with parallel factor analysis (PARAFAC). The results showed that dissolved organic carbon (DOC), total nitrogen (TN) and total phosphorus (TP) concentrations in tributaries water decreased when they flowed through the constructed wetland. The values of A 4/A 1, I 426/I 366, I 370/I 330 and I 360/I 320 suggested that the DOM consisted of organic components with low molecular weight and low aromatic contents in the tributary. I 360/I 320 could differentiate humification degree more clearly than the other three HIXs. The fluorescence index indicated a more microbially derived composition of DOM in the constructed wetland. The DOM fluorescence was dominated by the tryptophan-like fluorescence material (C3, more than 40 %), followed by humic-like substance (C1, about 30 %). Non-humic component (C2, about 20 %) was the least component. The percentage of C1 declined from upstream to downstream along the wetland, while C3 showed inverse tendency. The proportion of C2 remained relatively constant in all sampling points. Principal component analysis suggested that the humification degree of the DOM in the slowly flowing region was the highest among the wetlands, followed by those from the regions disturbed by tributaries, the sampling sites in mainstream and the outlet zone of wetland. The humification degree also showed a good correlation mainly with TN, TP and Chlorophyll a. Therefore, fluorescence spectroscopy technique coupled with derivative and PARAFAC might be a useful method to investigate composition and to evaluate the humification degree of DOM in aquatic environment.

Composition, source characteristic and indication of eutrophication of dissolved organic matter in the sediments of Erhai Lake

Composition and source characteristics of dissolved organic matter (DOM) in the surface sediments of Erhai Lake were studied by using fluorescence spectroscopy and UV–Vis absorbance. Moreover, the influence factors and the indication significance for eutrophication are also discussed. The results are as follows: (1) The DOC content of Erhai Lake sediments ranges from 0.17 to 0.77 g kg−1, which is higher in dry season than that in wet season. Its DOC content of the sediment from the northern part is higher than that from the southern, and that is the smallest in the central. Moreover, DOM in Erhai Lake sediments comprise of protein- and humic-like substances. The average contents of protein-, fulvic acid-like substances and soluble microbial byproduct-like materials in the wet season are higher than those in the dry season by 25.92, 11.82 and 2.96 %, respectively; while the content of humic-like substance in the wet season is lower than that in the dry season by 6.94 %. As to the spatial distribution, the contents of protein- and fulvic acid-like substances are the highest in the central of Erhai Lake sediments, and that of the humic-like substance is the highest in the southern part. In addition, the humification degree of DOM in the dry season is higher than that in the wet season. (2) The DOM in Erhai Lake sediments mainly originated from terrestrial sources, of which the terrestrial pollutant has a main impact in the dry season, and the terrestrial pollutant input and biogenetic derivation play an equally important part in the wet season. Terrestrial pollutant and aquatic plants are the important factors that influence the DOM composition of Erhai Lake sediments. (3) The characteristic parameter (P(III+V,n)/P(I+II,n)) (the content ratio of humic-like substance to protein-like substances) of the DOM composition of Erhai Lake sediments is positively correlated with the contents of the different nitrogen (N) forms in the sediments (R2 = 0.68–0.83, P < 0.01). The contents of N forms in sediments and its source characteristic can be reflected by the P(III+V,n)/P(I+II,n) value. So the P(III+V,n)/P(I+II,n) value can be taken as the indirect indicator of the contents of N forms in sediments. Moreover, the composition characteristic of DOM in sediments can reflect the contents of N forms to some extent, that is, the risk of N release from Erhai Lake sediments can be indicated to some extent.