Effect of total solids content on anaerobic digestion of waste activated sludge enhanced by high-temperature thermal hydrolysis.

Total solids (TS) content may provide a regulatory strategy for optimizing anaerobic digestion enhanced by high-temperature thermal hydrolysis, but the role of TS content is not yet clear. In this study, the effect of TS content on the high-temperature thermal hydrolysis and anaerobic digestion of sludge and its mechanism were investigated. The results showed that increasing the TS content from 2% to 8% increased the sludge solubility and methane production potential, reaching peak values of 26.6% and 336 ± 6 mL/g volatile solids (VS), respectively. With a further increase in TS content to 12%, the strong Maillard reaction increased the aromaticity and structural stability of extracellular polymer substances, decreasing sludge solubility to 18.6%. Furthermore, the decrease in sludge biodegradability and the formation of inhibitory by-products resulted in a reduction in methane production to 272 ± 4 mL/g VS. This article provides a new perspective to understand the role of TS content in the thermal hydrolysis of sludge and a novel approach to regulate the Maillard reaction.

Response of dissolved carbon dioxide and methane concentration to warming in shallow lakes.

Shallow lake ecosystems are highly sensitive to temperature fluctuation because of their high water surface-to-volume ratios. Shallow lakes have been increasingly identified as a hotspot of CO2 and CH4 emissions, but their response to temperature variation remains unclear. Here, we report from a 5-month outdoor mesocosm experiment where we investigated the impacts of a projected 3.5 °C future warming and monthly temperature changes on lake CO2 and CH4, as well as the key drivers affecting the lake carbon cycling. Our results show that CO2 and CH4 concentrations had a significantly positive correlation with monthly temperatures. CH4 concentration was primarily regulated by monthly temperature, while nutrients effects on CO2 concentration overrode climate warming and temporal temperature changes. These findings imply the varied roles that temperature and nutrient levels can play on CO2 and CH4 dynamics in shallow lake systems. The relationship between temperature and CO2 concentration was nonlinear, showing a threshold of approximately 9 °C, at which CO2 concentration could be strongly modified by nutrient level in the lake systems. Understanding this complex relationship between temperature with CO2 and CH4 concentrations in shallow lakes is crucial for effective lake management and efficient control of greenhouse gases (GHGs) emissions.

RNA-Seq analysis of long non-coding RNA in human intestinal epithelial cells infected by Shiga toxin-producing Escherichia coli.

BACKGROUND: The Shiga toxin-producing Escherichia coli (STEC) infects animals and induces acute intestinal inflammation. Long non-coding RNAs (lncRNAs) are known to play crucial roles in modulating inflammation response. However, it is not clear whether lncRNAs are involved in STEC-induced inflammation. METHODS AND RESULTS: To understand the association of lncRNAs with STEC infection, we used RNA-seq technology to analyze the profiles of lncRNAs in Mock-infected and STEC-infected human intestinal epithelial cells (HIECs). We detected a total of 702 lncRNAs differentially expressed by STEC infection. 583 differentially expressed lncRNAs acted as competitive microRNAs (miRNAs) binding elements in regulating the gene expression involved in TNF signaling pathway, IL-17 signaling pathway, PI3K-Akt signaling pathway, and apoptosis pathways. We analyzed 3 targeted genes, TRADD, TRAF1 and TGFB2, which were differentially regulated by mRNA-miRNA-lncRNA interaction network, potentially involved in the inflammatory and apoptotic response to STEC infection. Functional analysis of up/downstream genes associated with differentially expressed lncRNAs revealed their role in adheres junction and endocytosis. We also used the qRT-PCR technique to validate 8 randomly selected differentially expressed lncRNAs and mRNAs in STEC-infected HIECs. CONCLUSION: Our results, for the first time, revealed differentially expressed lncRNAs induced by STEC infection of HIECs. The results will help investigate the molecular mechanisms for the inflammatory responses induced by STEC.

Study of 2,881 Nasal Bone Fractures using Multivariate Analysis.

Objective: This retrospective cohort study is aimed to provide a certain reference for the clinical prevention and treatment of nasal bone fracture, and further formulated a more perfect diagnosis and treatment plan. Methods: In detailed cases, 2881 patients with nasal bone fracture were recorded. Its general clinical data, cause of injury, fracture site, and fracture typing were collected through the database. All hospitalized patients admitted to the Ninth People's Hospital Affiliated to the School of Medicine of Shanghai Jiao Tong University with integrated medical records could be retrospectively included from June 2013 to July 2018 and comprehensively analyzed for their gender, age, fracture type and cause of injury. Results: The sex ratio of nasal bone fracture was 2.44:1. The most patients with nasal bone fracture were 19-29 years old (35.6%). The injury rate of traffic accidents was the highest, 33.8%, followed by violent strikes, 24.1%. Statistical analysis showed that the number of patients with nasal bone combined with maxillary frontal bone fracture and type II nasal bone fracture was significantly higher than other fracture types. Logistic multiple regression analysis showed that the relative risk of nasal bone fracture in men was lower (odds ratio, OR = 0.807, P < .05), and the risk of nasal bone fracture decreased with age (OR = 0.978, P < .001). Compared with car accident injury, the relative risk of simple nasal bone fracture comes from violence, exercise or collision [OR = 1.244, P < .05; OR = 1.410, P < .05; OR = 1.453, P < .05]). Conclusion: Given these findings, it's evident that nasal bone fractures exhibit distinct patterns based on individual characteristics, causes of trauma, and injury site, and relevant strategy research should be conducted.

Changes in CO2 concentration and degassing of eutrophic urban lakes associated with algal growth and decline.

Urban lakes are numerous in the world, but their role in carbon storage and emission is not well understood. This study aimed to answer the critical questions: How does algal growing season influence carbon dioxide concentration (cCO2) and exchange flux (FCO2) in eutrophic urban lakes? We investigated trophic state, seasonality of algal productivity, and their association with CO2 dynamics in four urban lakes in Central China. We found that these lightly-to moderately-eutrophic urban lakes showed a shifting pattern of CO2 source-sink dynamics. In the non-algal bloom phase, the moderately-eutrophic lakes outgassed on average of 12.18 ± 24.37 mmol m-2 d-1 CO2; but, during the algal bloom phase, the lakes sequestered an average 1.07 ± 6.22 mmol m-2 d-1 CO2. The lightly-eutrophic lakes exhibited lower CO2 emission in the algal bloom (0.60 ± 10.24 mmol m-2 d-1) compared to the non-algal bloom (3.84 ± 12.38 mmol m-2 d-1). Biological factors such as Chl-a (chlorophyll a) and AOU (apparent oxygen utilization), were found to be important factors to potentially affect the shifting pattern of lake CO2 source-sink dynamics in moderately-eutrophic lakes, explaining 48% and 34% of the CO2 variation in the non-algal and algal bloom phases, respectively. Moreover, CO2 showed positive correlations with AOU, and negative correlations with Chl-a in both phases. In the lightly-eutrophic lakes, biological factors explained a higher proportion of CO2 variations (29%) in the non-algal bloom phase, with AOU accounting for 19%. Our results indicate that algal growth and decline phases largely affect dissolved CO2 level and exchange flux by regulating in-lake respiration and photosynthesis. Based on the findings, we conclude that shallow urban lakes can act as both sources and sinks of CO2, with algal growth seasonality and trophic state playing pivotal roles in controlling their carbon dynamics.

Intense methane diffusive emissions in eutrophic urban lakes, Central China.

Urban lakes are hotspots of methane (CH4) emissions. Yet, actual field measurements of CH4 in these lakes are rather limited and our understanding of CH4 response to urban lake eutrophication is still incomplete. In this study, we measured dissolved CH4 concentrations and quantified CH4 diffusion from four urban lakes in subtropical China during wet and dry seasons. We found that these lakes were constantly CH4-saturated, contributing the greenhouse gas (GHG) to the atmosphere. Nutrient enrichment significantly increased CH4 concentrations and diffusive fluxes. Average CH4 flux rate in the highly-eutrophic lake zones (4.18 ± 7.68 mmol m-2 d-1) was significantly higher than those in the mesotrophic (0.19 ± 0.18 mmol m-2 d-1) and lightly/moderately-eutrophic zones (0.72 ± 2.22 mmol m-2 d-1). Seasonally, CH4 concentrations and fluxes were significantly higher in the wet season than in the dry season in the mesotrophic and the lightly/moderately-eutrophic lake zones, but an inverse pattern existed in the highly-eutrophic lake zones. CH4 concentrations and fluxes increased with elevated levels of nitrogen, phosphorus and dissolved organic carbon (DOC). The accumulation of nutrients provided autochthonous substrate for methanogenesis, indicated by a negative correlation between CH4 and the C:N ratio. Ammonium-nitrogen (NH4+-N) was the best predictor for spatial fluctuation of CH4 concentrations and diffusive fluxes in the mesotrophic and the lightly/moderately-eutrophic lake zones, while total nitrogen (TN) and total phosphorus (TP) levels showed the highest predictability in the highly-eutrophic lake zones. Based on the findings, we conclude that nutrient enrichment in urban lakes can largely increase CH4 diffusion, and that urban sewage inflow is a key concern for eutrophication boosting CH4 production and diffusive emission. Furthermore, our study reveals that small urban lakes may be an important missing source of GHG emissions in the global C accounting, and that the ratio of littoral-to-pelagic zones can be important for predicting lake-scale estimation of CH4 emission.

Acetylation of K188 and K192 inhibits the DNA-binding ability of NarL to regulate Salmonella virulence.

Salmonella infection significantly increases nitrate levels in the intestine, immune cells, and immune organs of the host, and it can exploit nitrate as an electron acceptor to enhance its growth. In the presence of nitrate or nitrite, NarL, a regulatory protein of the Nar two-component system, is activated and regulates a number of genes involved in nitrate metabolism. However, research on NarL at the post-translational level is limited. In this study, we demonstrate that the DNA-binding sites K188 and 192 of NarL can be acetylated by bacterial metabolite acetyl phosphate and that the degree of acetylation has a considerable influence on the regulatory function of NarL. Specifically, acetylation of NarL negatively regulates the transcription of narG, narK, and napF, which affects the utilization of nitrate in Salmonella. Besides, both cell and mouse models show that acetylated K188 and K192 result in attenuated replication in RAW 264.7 cells, as well as impaired virulence in mouse model. Together, this research identifies a novel NarL acetylation mechanism that regulates Salmonella virulence, providing a new insight and target for salmonellosis treatment.IMPORTANCESalmonella is an important intracellular pathogen that can cause limited gastroenteritis and self-limiting gastroenteritis in immunocompetent humans. Nitrate, the highest oxidation state form of nitrogen, is critical in the formation of systemic infection in Salmonella. It functions as a signaling molecule that influences Salmonella chemotaxis, in addition to acting as a reduced external electron acceptor for Salmonella anaerobic respiration. NarL is an essential regulatory protein involved in nitrate metabolism in Salmonella, and comprehending its regulatory mechanism is necessary. Previous research has linked NarL phosphorylation to the formation of its dimer, which is required for NarL to perform its regulatory functions. Our research demonstrated that acetylation also affects the regulatory function of NarL. We found that acetylation affects Salmonella pathogenicity by weakening the ability of NarL to bind to the target sequence, further refining the mechanism of the anaerobic nitrate respiration pathway.

Establishment of a Finite Element Model of Normal Nasal Bone and Analysis of Its Biomechanical Characteristics.

Nasal bone is a long, paired series of small bones, which is narrow at the top and broad at the bottom, that forms the base of the nasal dorsum. Together with the nasal part of the frontal bone, the frontal process of the maxilla and the middle plate of the ethmoid bone constitute the bone scaffold of the external nose. In this paper, the DICOM image data file was imported into the Mimics software for 3D reconstruction. At the same time, the Geomagic software was used for relevant image processing, and the finite element software ANSYS was used to establish a finite element model to analyze the stress characteristics of the nasomaxillary complex. Results. The maximum principal stress and maximum strain force at the lower segment of nasal bone and the junction of nasal bone and maxilla were relatively large. When the same external force acts on the lower segment of the nasal bone and the angle is 0° (sagittal force), the maximum principal stress and maximum strain force are the smallest. When the angle continues to increase, the maximum principal stress and maximum strain force continue to increase.

Source and quality of dissolved organic matter in streams are reflective to land use/land cover, climate seasonality and pCO2.

Sources and quality of dissolved organic matter (DOM) in streams may be largely controlled by the landscape and season. In this study, we attempted to answer three critical questions: 1) Do land use/land cover (LULC) types affect DOM characteristics? 2) Is there a seasonal fluctuation in DOM components? 3) How do DOM quality and LULC types influence aqueous carbon dioxide partial pressure (pCO2). To achieve this, we investigated the fluorescence characteristics of DOM and its implication for pCO2 in three streams draining land with different urban intensities under distinctive dry and wet seasons. Four fluorescence components were identified, including two terrestrial humic-like components, one protein-like component and one microbial humic-like component. We found a significant positive relationship of the maximum fluorescence intensity (Fmax) of the four components and fluorescence index (FI370) with urbanization intensity in both the dry and wet seasons. The mean Fmax, biological index (BIX) and FI370 all exhibited an increasing trend from upstream to downstream in the stream with highest proportions of urban and cropland. The fluorescence characteristics were negatively related to proportion of forested land in the both seasons. The terrestrial humic-like DOM was dominating in the studied streams. Moreover, the seasonality altered the DOM composition, with protein-like component emerging only in stream waters during the dry season, while microbial humic-like component exclusively occurred during the wet season. pCO2 values were positively related to terrestrial humic-like and biological protein-like components, and urban land. The dry season had much higher pCO2 than the wet season. Results from the Partial Least Squares Path (PLS-PM) models further indicated that LULC types were important in mediating fluorescence DOM whilst pCO2 was more sensitive to the direct effect from FDOM dynamics. We conclude that DOM source and quality in streams are reflective to LULC and climate seasonality, and are good indicators of pCO2 via source tracer and quality of fluorescence components.

Acetylation of NarL K188 and K192 is involved in regulating Escherichia coli anaerobic nitrate respiration.

As a facultative anaerobe, Escherichia coli can activate various respiratory chains during anaerobic growth, among which the mode of anaerobic respiration with nitrate allows good energy conservation. NarL is one of the regulatory proteins in the Nar two-component system that regulates anaerobic respiration in E. coli. Previous studies have shown that NarL activates downstream gene regulation through phosphorylation. However, there are few studies on other protein translational modifications that influence the regulatory function of NarL. Herein, we demonstrate that acetylation modification exists on K188 and K192, the two lysine residues involved in contacting to DNA, and the degree of acetylation has significant effects on DNA-binding abilities, thus affecting the anaerobic growth of E. coli. In addition, NarL is mainly regulated by acetyl phosphate, but not by peptidyl-lysine N-acetyltransferase. These results indicate that non-enzymatic acetylation of NarL by AcP is one of the important mechanisms for the nitrate anaerobic respiratory pathway in response to environmental changes, which extends the idea of the mechanism underlying the response of intestinal flora to changes in the intestinal environment. KEY POINTS: • Acetylation was found in NarL, which was mainly mediated by AcP. • Non-enzymatic acetylation at K188 and K192 affects NarL binding ability. • Acetylation of NarL K188 and K192 regulates anaerobic nitrate growth of E. coli.

Efficient biodegradation of di-(2-ethylhexyl) phthalate by a novel strain Nocardia asteroides LMB-7 isolated from electronic waste soil.

The di-2-ethylhexyl phthalate (DEHP) degrading strain LMB-7 was isolated from electronic waste soil. According to its biophysical/biochemical characteristics and 16S rRNA gene analysis, the strain was identified as Nocardia asteroides. Optimal pH and temperature for DEHP degradation were 8.0 and 30 °C, respectively, and DEHP removal reached 97.11% after cultivation for 24 h at an initial concentration of 400 mg/L. As degradation intermediates, di-butyl phthalates, mono-2-ethylhexyl phthalate and 2-ethylhexanol could be identified, and it could be confirmed that DEHP was completely degraded by strain LMB-7. To our knowledge, this is a new report of DEHP degradation by a strain of Nocardia asteroides, at rates higher than those reported to date. This finding provides a new way for DEHP elimination from environment.

Riverine dissolved organic matter (DOM) as affected by urbanization gradient.

Rapid urbanization has considerably altered carbon biogeochemical cycle and river hydrology. However, the influences of urban land use and urban-induced nutrient increase on dissolved organic matter (DOM) characteristics are poorly understood. Here we hypothesize that the alterations significantly change sources and levels of DOM in river systems that drain the urban areas. To test the hypothesis, we investigated DOM in headwater rivers with varied urban intensities in the Three Gorges Reservoir Area (TGRA), China, through field sampling conducted in the dry and wet seasons. We found positive relationships of urban land (%Urban) with DOC concentration and chromophoric DOM (CDOM) absorption coefficients a254, a280 and a350, as well as fluorescence index (FI370), indicating the significantly increased levels of DOM and autochthonous sources along an urbanization gradient. A stepwise regression analysis demonstrated that occurrences of DOC and CDOM can be predicted by %Urban, while increasing autochthonous source is predictable by the increase in riverine nitrogen. Moreover, a254, a280 and FI370 values showed distinct seasonal variations, with significantly higher CDOM concentration in the wet season and with much higher autochthonous signal in the dry season with high nitrogen loading. Based on the findings, we conclude that urbanization influences occurrences and sources of DOM, with increasing urbanization making an important and direct contribution to DOM, and an indirect effect of urban induced nutrient enrichment, i.e., enhanced nutrient loadings increase autochthonous DOM production in rivers.

Long Noncoding RNA CRNDE Functions as an Oncogene to Facilitate Aggressive Behaviors of Nasopharyngeal Carcinoma Cells by Modulating miR-3163/TWIST1 Axis.

Long noncoding RNA (lncRNA) CRNDE has been broadly implicated in many malignancies. The aim of this study was to explore the function and potential mechanisms of CRNDE in nasopharyngeal carcinoma (NPC). Here, we discovered that CRNDE level was increased in NPC tissues and cell lines. Additionally, elevated CRNDE positively correlated with large tumor size, advanced TNM stage, distant metastasis, EBV infection and worse prognosis. Furthermore, depletion of CRNDE significantly impaired the capacity of proliferation, migration and invasion in NPC cells. Mechanically, CRNDE could serve as a molecular sponge of miR-3163 to regulate the expression of TWIST1. Importantly, the inhibitory effects of CRNDE knockdown on cell proliferation and metastasis were blocked by silence of miR-3163 or restoration of TWIST1 expression. Overall, our data highlighted that CRNDE could promote NPC progression via altering miR-3163/TWIST1 axis, suggesting CRNDE as a potential prognostic biomarker and therapeutic target for NPC treatment.

Hydrological seasonality and nutrient stoichiometry control dissolved organic matter characterization in a headwater stream.

Dissolved organic matter (DOM) is a diverse and highly complex mixture of organic macromolecules, and thus plays a central role in aquatic ecosystems. However, responses of components and sources of DOM to hydrological processes and trophic levels (nutrient stoichiometric ratios) are poorly understood, particularly in monsoonal headwater streams of Asia that are vulnerable to catchment physical characteristics. In this study, the excitation - emission matrix florescence spectroscopy coupled with parallel factor analysis (EEM-PARAFAC) was used to explore the DOM characters in a headwater stream, where seasonal rainfalls and nutrient levels vary largely. The EEM-PARAFAC modelling identified one autochthonous protein-like fluorescence substance (C1) and two allochthonous fulvic- and humic-like fluorescence compounds (C2 and C3). The allochthonous compounds dominated the overall DOM signal in the headwaters. The hydrological seasonality coupled with nutrients was key in modulating headwater DOM sources and components. Seasonal rainfall events contributed more allochthonous terrestrial-derived DOM flushing into river waters, resulting in higher fulvic- and humic-like organic matter (C2 + C3) in the wet season. In the dry season, longer water residence time accompanying with higher C:P stoichiometric ratio was responsible for higher autochthonous microbial- and plant-derived DOM (tryptophan and tyrosine fractions), also reflected by higher C1, biological index (BIX) and freshness index (ß:α). In-stream microbial metabolism of labile DOM fractions largely contributed to autochthonous DOM and partial pressure CO2 increase in the headwater stream. Our findings indicate that quality and quantity of DOM in headwater streams play a crucial role in downstream carbon cycle. Furthermore, the evidence combined from PARAFAC components, pCO2 and spectral slope clearly highlights the importance of microbial metabolism of carbon in lotic systems, especially during a dry season with increased residence time.

Chromophoric dissolved organic matter in inland waters: Present knowledge and future challenges.

Chromophoric dissolved organic matter (CDOM) plays an important role in the biogeochemical cycle and energy flow of aquatic ecosystems. Thus, systematic and comprehensive understanding of CDOM dynamics is critically important for aquatic ecosystem management. CDOM spans multiple study fields, including analytical chemistry, biogeochemistry, water color remote sensing, and global environmental change. Here, we thoroughly summarize the progresses of recent studies focusing on the characterization, distribution, sources, composition, and fate of CDOM in inland waters. Characterization methods, remote sensing estimation, and biogeochemistry cycle processes were the hotspots of CDOM studies. Specifically, optical, isotope, and mass spectrometric techniques have been widely used to characterize CDOM abundance, composition, and sources. Remote sensing is an effective tool to map CDOM distribution with high temporal and spatial resolutions. CDOM dynamics are mainly determined by watershed-related processes, including rainfall discharge, groundwater, wastewater discharges/effluents, and biogeochemical cycling occurring in soil and water bodies. We highlight the underlying mechanisms of the photochemical degradation and microbial decomposition of CDOM, and emphasize that photochemical and microbial processes of CDOM in inland waters accelerate nutrient cycling and regeneration in the water column and also exacerbate global warming by releasing greenhouse gases. Future study directions to improve the understanding of CDOM dynamics in inland waters are proposed. This review provides an interdisciplinary view and new insights on CDOM dynamics in inland waters.

Determination of aldehydes in water samples by coupling magnetism-reinforced molecular imprinting monolith microextraction and non-aqueous capillary electrophoresis.

Excess 2, 4-dinitrophenylhydrazine (2, 4-DNPH) is often applied for the derivatization of aldehyde prior to the chromatographic analysis. However, the residual 2, 4-DNPH may cause background interference and limit the enrichment efficiency of trace aldehydes. To overcome the above bottle-neck problems, improve the extraction efficiency and omit the manipulation for changing the polarity of solvent for the hydrophobic analytes separation, a new method combining magnetism-reinforced in-tube solid phase microextraction (IT-SPME) technique with non-aqueous capillary electrophoresis (NACE) was developed. The monolithic extraction cartridge was prepared in situ inside a capillary and doped with magnetic molecular imprinting polymers (mMIPs). The selective and efficient extraction of the derived analytes with simultaneous removal of the superfluous derivatization agent was achieved owing to the combined effect of molecular imprinting and magnetism reinforcement. By coupling with NACE, the highly hydrophobic effluent can be analyzed directly. The LODs of the method are between 0.0032~0.0049 mg L-1 and the recoveries are between 87.3~99.8% for the tested aldehydes. The developed approach is sensitive enough for detection of surface (drinking) water. The aldehydes in real water samples have been detected by this method, showing results that are in good agreement with the standard SPE-HPLC method.

[Epidemiological analysis of 2 881 patients with nasal bone fracture].

Objective:This thesis studies on epidemiological characteristics of patients with nasal bone fractures. Method:This thesis retrospectively studies on 2 881 patients with nasal bone fractures. The characteristics, causes, and fracture types are collected and reviewed retrospectively. The type of nasal bone fracture is classified according to Fred's classification, and SPSS 25.0 software is used in statistical analysis. Result:The sex ratio of nasal bone fracture between males and females is 2.44：1, male cases are obviously more than female cases. The group aged 19-29 years occupies the largest proportion, accounted for 35.54%. Traffic accident was the leading cause of the nasal bone fracture, accounting for 33.84%. The second cause was violent assault, 24.12% totally. The number of patients suffering nasal bone fractures combined with maxilla frontal process fractures is higher than that of simple nasal bone fractures. Type Ⅱ fracture is significantly more common in patients with other types nasal bone fractures. Logistic regression analysis for simple nasal bone fracture showed that the relative risk of simple nasal bone fracture is lower in men than in women, and the risk of simple nasal fractures decreased with age increasing. Compared with traffic accident, the relative risk of simple nasal bone fracture is higher in violence injury, sports injury and collision injury. Conclusion:The distribution of the nasal fractures of the inpatients has certain characteristics in terms of individual characteristics, injury cause and fracture types, which is worthy of further strategic study on prevention and treatment of the nasal fractures.

[Bioavailability Characteristics of Chromophoric Dissolved Organic Matter in Lake Gaoyou, Lake Nansi, and Lake Dongping Under Different Hydrological Scenarios].

The bio-lability of chromophoric dissolved organic matter (CDOM) directly reflects its biodegradability potential, and also affects the migration and conversion of pollutants and impacts water quality. This study combines excitation-emission matrices and parallel factor analysis (EEMs-PARAFAC) with laboratory 28 days of bio-incubation experiments, and analyzed the bioavailability characteristics of CDOM samples collected from Lake Gaoyou, Lake Nansi and Lake Dongping in flood season and dry season. Our results showed that:① four fluorescent components were obtained using EEMs-PARAFAC, including a microbial humic-like C1, a terrestrial humic-like C4, a tryptophan-like C2, and a tyrosine-like C3. ② The differences of CDOM absorption pre-and post-incubation, i.e. Δa(254) of the three lakes were positive in the three lakes in the flood season, while partially negative in the dry season, indicating a quite different response of CDOM bioavailability to hydrological seasons. ③ Under different hydrological scenarios, the two humic-like components C1 and C4 increased post-bio-incubation compared with that pre-incubation for the samples collected from Lake Nansi and Lake Dongping, and the two protein-like components in Lake Nansi in both the flood and dry seasons and in Lake Dongping in the flood season (t-test, P<0.001, P=0.005) were lower in the post-than those pre-incubation. In Lake Gaoyou, C1-C3 post-incubation were significantly lower than pre-incubation (t-test, P=0.008, P=0.005). In the dry season, in comparison, C1-C4 except for C2 increased post-incubation than pre-incubation for Lake Gaoyou. This indicated that the protein-like components are unstable and more easily uptaken by microorganisms and may be potentially converted into more stable humic-like components. HIX and IC:IT of the three lakes increased post-incubation while the spectral slope S275-295 decreased, which further confirmed the aforementioned conclusion. ④ During both the flood and dry seasons, the bioavailability of the protein-like components C2-C3 and the fluorescence intensity of C1 and C4 in the inflowing river mouths of the three lakes were higher than in the remaining lake regions. It is therefore necessary to strengthen the water quality management in the inflowing river mouths of the three lakes to maintain the water quality of the lakes.