Effect of ultrasonic pretreatment on sludge dewaterability was determined and the fate of extracellular polymeric substances （EPS） matrix in mesophilic anaerobic digestion after ultrasonic pretreatment was studied. ...Effect of ultrasonic pretreatment on sludge dewaterability was determined and the fate of extracellular polymeric substances （EPS） matrix in mesophilic anaerobic digestion after ultrasonic pretreatment was studied. Characteristics of proteins （PN）, polysaccharides （PS）, excitation-emission matrix （EEM） fluorescence spectroscopy and molecular weight （MW） distribution of dissolved organic matters （DOM） in different EPS fractions were evaluated. The results showed that after ultrasonic pretreatment, the normalized capillary suction time （CST） decreased from 44.4 to 11.1 （sec·L）/g total suspended solids （TSS） during anaerobic digestion, indicating that sludge dewaterability was greatly improved. The normalized CST was significantly correlated with PN concentration （R2 = 0.92, p 〈 0.01） and the PN/PS ratio （R2 = 0.84, p 〈 0.01） in the loosely bound EPS （LB-EPS） fraction. Meanwhile, the average MW of DOM in the LB- EPS and tightly bound EPS （TB-EPS） fractions also had a good correlation with the normalized CST （R2 〉 0.66, p 〈 0.01）. According to EEM fluorescence spectroscopy, tryptophan-like substances intensities in the slime, LB-EPS and TB-EPS fractions were correlated with the normalized CST. The organic matters in the EPS matrix played an important role in influencing sludge dewaterability.展开更多
Unlike inorganic quantum dots,fluorescent graphene quantum dots(GQDs)display excitation-dependent multiple color emission.In this study,we report N-doped GQDs(N-GQDs)with tailored single color emission by tuning p-con...Unlike inorganic quantum dots,fluorescent graphene quantum dots(GQDs)display excitation-dependent multiple color emission.In this study,we report N-doped GQDs(N-GQDs)with tailored single color emission by tuning p-conjugation degree,which is comparable to the inorganic quantum dot.Starting from citric acid and diethylenetriamine,as prepared N-GQDs display blue,green,and yellow light emission by changing the reaction solvent from water,dimethylformamide(DMF),and solvent free.The X-ray photoelectron spectroscopy,ultraviolet-visible spectra results clearly show the N-GQDs with blue emission(N-GQDs-B)have relatively short effective conjugation length and more carboxyl group because H_(2)O is a polar protic solvent,which tends to donate proton to the reagent to depress the H_(2)O elimination reaction.On the other hand,the polar aprotic solvent(DMF)cannot donate hydrogen,the elimination of H_(2)O is promoted and more nitrogen units enter GQD framework.With the increase of effective p-conjugation length and N content,the emission band of N-GQDS red-shifts to green and yellow.We also demonstrate that N-GQDs could be a potential great biomarker for fluorescent bioimaging.展开更多
A sampling campaign was conducted monthly to investigate the occurrence of N-nitrosamines at a conventional water treatment plant in one city in North China.The yield of N-nitrosamines in the treated water indicated p...A sampling campaign was conducted monthly to investigate the occurrence of N-nitrosamines at a conventional water treatment plant in one city in North China.The yield of N-nitrosamines in the treated water indicated precursors changed greatly after the source water switching.Average concentrations of N-nitrosodimethylamine（NDMA）,N-nitrosomorpholine（NMOR）,and N-nitrosopyrrolidine（NPYR） in the finished water were6.9,3.3,and 3.1 ng/L,respectively,from June to October when the Luan River water was used as source water,while those of NDMA,N-nitrosomethylethylamine（NMEA）,and NPYR in the finished water were 10.1,4.9,and 4.7 ng/L,respectively,from November to next April when the Yellow River was used.NDMA concentration in the finished water was frequently over the 10 ng/L,i.e.,the notification level of California,USA,which indicated a considerable threat to public health.Weak correlations were observed between N-nitrosamine yield and typical water quality parameters except for the dissolved organic nitrogen.展开更多
AIM: To investigate the autofluorescence spectroscopic differences in normal and adenomatous coionic tissues and to determine the optimal excitation wavelengths for subsequent study and clinical application. METHODS: ...AIM: To investigate the autofluorescence spectroscopic differences in normal and adenomatous coionic tissues and to determine the optimal excitation wavelengths for subsequent study and clinical application. METHODS: Normal and adenomatous coionic tissues were obtained from patients during surgery. A FL/FS920 combined TCSPC spectrofluorimeter and a lifetime spectrometer system were used for fluorescence measurement. Fluorescence excitation wavelengths varying from 260 to 540 nm were used to induce the autofluorescence spectra, and the corresponding emission spectra were recorded from a range starting 20 nm above the excitation wavelength and extending to 800 nm. Emission spectra were assembled into a three-dimensional fluorescence spectroscopy and an excitation-emission matrix (EEM) to exploit endogenous fluorophores and diagnostic information. Then emission spectra of normal and adenomatous coionic tissues at certain excitation wavelengths were compared to determine the optimal excitation wavelengths for diagnosis of coionic cancer. RESULTS: When compared to normal tissues, low NAD (P)H and FAD, but high amino acids and endogenous phorphyrins of protoporphyrin IX characterized the high-grade malignant coionic tissues. The optimal excitation wavelengths for diagnosis of coionic cancer were about 340, 380, 460, and 540 nm. CONCLUSION: Significant differences in autofluorescence peaks and its intensities can be observed in normal and adenomatous coionic tissues. Autofluorescence EEMs are able to identify coionic tissues.展开更多
The membrane bioreactor(MBR)technology is a rising star for wastewater treatment.The pollutant elimination and membrane fouling performances of MBRs are essentially related to the dissolved organic matter(DOM)in the s...The membrane bioreactor(MBR)technology is a rising star for wastewater treatment.The pollutant elimination and membrane fouling performances of MBRs are essentially related to the dissolved organic matter(DOM)in the system.Three-dimensional excitation-emission matrix(3D-EEM)fluorescence spectroscopy,a powerful tool for the rapid and sensitive characterization of DOM,has been extensively applied in MBR studies;however,only a limited portion of the EEM fingerprinting information was utilized.This paper revisits the principles and methods of fluorescence EEM,and reviews the recent progress in applying EEM to characterize DOM in MBR studies.We systematically introduced the information extracted from EEM by considering the fluorescence peak location/intensity,wavelength regional distribution,and spectral deconvolution(giving fluorescent component loadings/scores),and discussed how to use the information to interpret the chemical compositions,physiochemical properties,biological activities,membrane retention/fouling behaviors,and migration/transformation fates of DOM in MBR systems.In addition to conventional EEM indicators,novel fluorescent parameters are summarized for potential use,including quantum yield,Stokes shift,excited energy state,and fluorescence lifetime.The current limitations of EEM-based DOM characterization are also discussed,with possible measures proposed to improve applications in MBR monitoring.展开更多
Dissolved organic matter(DOM)plays a crucial role in both the carbon cycle and geochemical cycles of other nutrient elements,which is of importance to the management and protection of the aquatic environments.To achie...Dissolved organic matter(DOM)plays a crucial role in both the carbon cycle and geochemical cycles of other nutrient elements,which is of importance to the management and protection of the aquatic environments.To achieve a more comprehensive understanding the characteristics of DOM in the Changjiang(Yangtze)River basin,water samples from four natural lakes(Xiandao,Baoan,Daye,and Qingshan)in southeastern Hubei Province in China with different eutrophication levels were collected and analyzed.The optical characteristics were analyzed using ultraviolet-visible spectrophotometry and excitation-emission matrix spectroscopy coupled with parallel factor analysis.The results show that:(1)two humic-like components(C1 and C2)and two protein-like substances(C3 and C4)of DOM were identified in all waterbodies;(2)C3 originated primarily from the degradation of microalgae and contributed substantially to humic-like components during transformation.C4 was widely present in the Changjiang River basin and its formation was related to microbial activity,rather than algal blooms or seasons.Influenced by the water mixing,the protein-like components were more likely to be transformed by microorganism,whereas humic-like components were more easily to be photobleached;(3)the concentration of DOM and the fluorescence intensity of humic-like components gradually increased with rising lake eutrophication levels.With respect to protein-like components,only C3 showed changes along the eutrophication gradients;(4)DOM showed a high affinity with permanganate index(COD Mn)and chlorophyll a(chl a)while the relationship was variable with phosphorus.This study helps us systematically understand the DOM characteristics,microbial activities,and pollutant transformation in the Changjiang River basin and provides reference to the ecological restoration of aquatic environments.展开更多
基金supported by the National Natural Science Foundation of China (No. 20977066)the National Key Project for Water Pollution Control (No.2008ZX07316-002, 2008ZX07317-003)the Specialized Research Found for Doctoral Program of Higher Education of China (No. 200802470029)
文摘Effect of ultrasonic pretreatment on sludge dewaterability was determined and the fate of extracellular polymeric substances （EPS） matrix in mesophilic anaerobic digestion after ultrasonic pretreatment was studied. Characteristics of proteins （PN）, polysaccharides （PS）, excitation-emission matrix （EEM） fluorescence spectroscopy and molecular weight （MW） distribution of dissolved organic matters （DOM） in different EPS fractions were evaluated. The results showed that after ultrasonic pretreatment, the normalized capillary suction time （CST） decreased from 44.4 to 11.1 （sec·L）/g total suspended solids （TSS） during anaerobic digestion, indicating that sludge dewaterability was greatly improved. The normalized CST was significantly correlated with PN concentration （R2 = 0.92, p 〈 0.01） and the PN/PS ratio （R2 = 0.84, p 〈 0.01） in the loosely bound EPS （LB-EPS） fraction. Meanwhile, the average MW of DOM in the LB- EPS and tightly bound EPS （TB-EPS） fractions also had a good correlation with the normalized CST （R2 〉 0.66, p 〈 0.01）. According to EEM fluorescence spectroscopy, tryptophan-like substances intensities in the slime, LB-EPS and TB-EPS fractions were correlated with the normalized CST. The organic matters in the EPS matrix played an important role in influencing sludge dewaterability.
基金The authors thank the National Natural Science Foundation of China(No.21301166,21201159,61306081,and 61176016)Science and Technology Department of Jilin Province(No.20130522127JH)are gratefully acknowledged+1 种基金ZS thanks the support of the‘Hundred Talent Program’of CAS and Innovation and Entrepreneurship Program of JilinThe project was supported by Open Research Fund of State Key Laboratory of Polymer Physics and Chemistry and the open research fund program of the State Key Laboratory of Luminescence and Applications.
文摘Unlike inorganic quantum dots,fluorescent graphene quantum dots(GQDs)display excitation-dependent multiple color emission.In this study,we report N-doped GQDs(N-GQDs)with tailored single color emission by tuning p-conjugation degree,which is comparable to the inorganic quantum dot.Starting from citric acid and diethylenetriamine,as prepared N-GQDs display blue,green,and yellow light emission by changing the reaction solvent from water,dimethylformamide(DMF),and solvent free.The X-ray photoelectron spectroscopy,ultraviolet-visible spectra results clearly show the N-GQDs with blue emission(N-GQDs-B)have relatively short effective conjugation length and more carboxyl group because H_(2)O is a polar protic solvent,which tends to donate proton to the reagent to depress the H_(2)O elimination reaction.On the other hand,the polar aprotic solvent(DMF)cannot donate hydrogen,the elimination of H_(2)O is promoted and more nitrogen units enter GQD framework.With the increase of effective p-conjugation length and N content,the emission band of N-GQDS red-shifts to green and yellow.We also demonstrate that N-GQDs could be a potential great biomarker for fluorescent bioimaging.
基金supported by the National Natural Science Foundation of China (Nos.51290284 and 21477059)the Tsinghua University Initiative Scientific Research Program (No.20131089247)
文摘A sampling campaign was conducted monthly to investigate the occurrence of N-nitrosamines at a conventional water treatment plant in one city in North China.The yield of N-nitrosamines in the treated water indicated precursors changed greatly after the source water switching.Average concentrations of N-nitrosodimethylamine（NDMA）,N-nitrosomorpholine（NMOR）,and N-nitrosopyrrolidine（NPYR） in the finished water were6.9,3.3,and 3.1 ng/L,respectively,from June to October when the Luan River water was used as source water,while those of NDMA,N-nitrosomethylethylamine（NMEA）,and NPYR in the finished water were 10.1,4.9,and 4.7 ng/L,respectively,from November to next April when the Yellow River was used.NDMA concentration in the finished water was frequently over the 10 ng/L,i.e.,the notification level of California,USA,which indicated a considerable threat to public health.Weak correlations were observed between N-nitrosamine yield and typical water quality parameters except for the dissolved organic nitrogen.
基金Supported by the Natural Science Foundation of Fujian Province, No. A0310018 and No. 2002F008the Scientific Research Program of Fujian Province, No. JA03041
文摘AIM: To investigate the autofluorescence spectroscopic differences in normal and adenomatous coionic tissues and to determine the optimal excitation wavelengths for subsequent study and clinical application. METHODS: Normal and adenomatous coionic tissues were obtained from patients during surgery. A FL/FS920 combined TCSPC spectrofluorimeter and a lifetime spectrometer system were used for fluorescence measurement. Fluorescence excitation wavelengths varying from 260 to 540 nm were used to induce the autofluorescence spectra, and the corresponding emission spectra were recorded from a range starting 20 nm above the excitation wavelength and extending to 800 nm. Emission spectra were assembled into a three-dimensional fluorescence spectroscopy and an excitation-emission matrix (EEM) to exploit endogenous fluorophores and diagnostic information. Then emission spectra of normal and adenomatous coionic tissues at certain excitation wavelengths were compared to determine the optimal excitation wavelengths for diagnosis of coionic cancer. RESULTS: When compared to normal tissues, low NAD (P)H and FAD, but high amino acids and endogenous phorphyrins of protoporphyrin IX characterized the high-grade malignant coionic tissues. The optimal excitation wavelengths for diagnosis of coionic cancer were about 340, 380, 460, and 540 nm. CONCLUSION: Significant differences in autofluorescence peaks and its intensities can be observed in normal and adenomatous coionic tissues. Autofluorescence EEMs are able to identify coionic tissues.
基金the National Natural Science Foundation of China(No.51778599)the Beijing Natural Science Foundation(No.LI82044)+1 种基金the CAS Strategic Priority Research Programmer(A)(No.XDA20050103)the Youth Innovation Promotion Association CAS(No.110500EA62)。
文摘The membrane bioreactor(MBR)technology is a rising star for wastewater treatment.The pollutant elimination and membrane fouling performances of MBRs are essentially related to the dissolved organic matter(DOM)in the system.Three-dimensional excitation-emission matrix(3D-EEM)fluorescence spectroscopy,a powerful tool for the rapid and sensitive characterization of DOM,has been extensively applied in MBR studies;however,only a limited portion of the EEM fingerprinting information was utilized.This paper revisits the principles and methods of fluorescence EEM,and reviews the recent progress in applying EEM to characterize DOM in MBR studies.We systematically introduced the information extracted from EEM by considering the fluorescence peak location/intensity,wavelength regional distribution,and spectral deconvolution(giving fluorescent component loadings/scores),and discussed how to use the information to interpret the chemical compositions,physiochemical properties,biological activities,membrane retention/fouling behaviors,and migration/transformation fates of DOM in MBR systems.In addition to conventional EEM indicators,novel fluorescent parameters are summarized for potential use,including quantum yield,Stokes shift,excited energy state,and fluorescence lifetime.The current limitations of EEM-based DOM characterization are also discussed,with possible measures proposed to improve applications in MBR monitoring.
基金Supported by the Science and Technology Research Project of Education Department of Hubei Province(Nos.Q20182502,D20152503)the Innovation Team Project of HBNU of Heavy Metal Pollution Mechanism and Ecological Restoration for Lake-Catchment System,Youth Project of Hubei Natural Science Foundation(No.2018CFB321)the Hubei Undergraduate Training Program for Innovation and Entrepreneurship(No.S201910513001)。
文摘Dissolved organic matter(DOM)plays a crucial role in both the carbon cycle and geochemical cycles of other nutrient elements,which is of importance to the management and protection of the aquatic environments.To achieve a more comprehensive understanding the characteristics of DOM in the Changjiang(Yangtze)River basin,water samples from four natural lakes(Xiandao,Baoan,Daye,and Qingshan)in southeastern Hubei Province in China with different eutrophication levels were collected and analyzed.The optical characteristics were analyzed using ultraviolet-visible spectrophotometry and excitation-emission matrix spectroscopy coupled with parallel factor analysis.The results show that:(1)two humic-like components(C1 and C2)and two protein-like substances(C3 and C4)of DOM were identified in all waterbodies;(2)C3 originated primarily from the degradation of microalgae and contributed substantially to humic-like components during transformation.C4 was widely present in the Changjiang River basin and its formation was related to microbial activity,rather than algal blooms or seasons.Influenced by the water mixing,the protein-like components were more likely to be transformed by microorganism,whereas humic-like components were more easily to be photobleached;(3)the concentration of DOM and the fluorescence intensity of humic-like components gradually increased with rising lake eutrophication levels.With respect to protein-like components,only C3 showed changes along the eutrophication gradients;(4)DOM showed a high affinity with permanganate index(COD Mn)and chlorophyll a(chl a)while the relationship was variable with phosphorus.This study helps us systematically understand the DOM characteristics,microbial activities,and pollutant transformation in the Changjiang River basin and provides reference to the ecological restoration of aquatic environments.
