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The ever-increasing algae biomass due to eutrophication brings an enormous destruction and potential threat to the ecosystem. Hydrothermal carbonization (HTC) is a potential means converting algae to value added products such as sustainable bioenergy and biomaterials. However, the waste aqueous phase (AP) produced during the HTC of algae biomass needs to be treated carefully in case of the second pollution to environment. In this study, a model microbe (E. coli) was adopted for the microbial pretreatment of AP, by which the bioavailability of AP could be improved, and the nutrients could be reclaimed though struvite precipitation. Three-dimensional fluorescence spectra and GC-MS results illustrated that E. coli pretreatment could convert a large number of organic nitrogenous compounds to ammonia nitrogen by degrading aromatic protein substances and deaminating nitrogenous heterocyclic compounds. Afterwards, a serious of characterizations confirmed that 81.13% of ammonia nitrogen could be recovered as struvite though precipitation. Life cycle assessment indicates the cost of the two-step treatment process was much lower than that of conventional wastewater treatment processes, and is beneficial to environment. This work provides an environment-friendly strategy for the comprehensive utilization of algae, which may contribute to alleviating the algal disasters and bring certain economic benefits though algal treatment.

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Existing general analysis methods using fluorescence spectra in wavelength units make it difficult to determine the internal molecular properties of contaminants owing to the neglect of the actual physical meanings of spectral data. In this study, the relationships between spectral data and internal molecular properties were studied, and a corresponding transform method was proposed. A series of transforms were conducted on three-dimensional fluorescence spectra for increased relevance to energy level transition; the horizontal and vertical coordinates represented the Stokes shift and absorptive energy in transition, respectively. Through theoretical analysis and experiments with eight common organic chemicals, it was found that more complex molecular structures caused larger Stokes shifts and the more conjugation led to lower absorptive energy. For convenience in water contaminant analysis, five parameters of volume integrals were presented in various spectral regions corresponding to individual categories of substances. The effectiveness and universality of this procedure for rapid water contaminant analysis was assessed through long-term monitoring of river water samples. The proposed method can provide additional information on contaminant types and molecular properties on the basis of transformed spectral data, which can improve the richness, authenticity, efficiency, and convenience of early water quality analysis.

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Rapid urbanization has a significant impact on dissolved organic matter (DOM) in water and sediment; thus, it is important to explore the distribution characteristics and influencing factors of DOM in watersheds. Xiaojia River is a typical urban area in Beilun District of Ningbo City, Yangtze River Delta. The spectral characteristics of DOM in the water and sediment in this river were studied to examine their sources and characteristics. The DOM was analyzed by three-dimensional fluorescence spectroscopy (EEM) coupled with the parallel factor analysis (PARAFAC) model. The following results were noted. ① Four fluorescence DOM components were derived by EEM-PARAFAC:C1 represents terrestrial humus with a high molecular weight; C2 represents terrestrial humus with a low molecular weight, which was produced by biodegradation; C3 represents protein-like substances that were sensitive in a microenvironment; and C4 is terrestrial humus. ② Both new-born endogenous and terrestrial sources have large impacts on DOM components. The humification degree was very weak with a low concentration of humus. The DOM in the sediments was derived mainly from terrestrial or soil sources with small endogenous contribution with high humification. The concentration of humus in the sediments was significantly higher than that in water. ③ Redundancy analysis (RDA) showed that farmland and urban land use were the dominant environmental factors and had relatively high correlation with the water indicators. Construction land, farmland, and wetland land use positively correlated with the sediment components. Among them, urban land use had the greatest influence on the concentration parameter Fn(355) of humus-like substance C4 and the humus-like substance in sediments.

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The subtropical zone in China is one of the regions most affected by nitrogen deposition. Soil dissolved organic matter (DOM) is considered to be an important indicator of soil organic matter. Nitrogen deposition may alter the quality and quantity of soil DOM by changing soil microbial activity. In this study, we explored the effects of nitrogen addition on soil DOM content, its spectral characteristics and microbial extraceller enzyme activity in the Moso bamboo plantations by setting control (CT), low-nitrogen (LN), and high-nitrogen (HN) addition levels for three-year nitrogen addition. The results showed that there was no significant change in soil pH, dissolved organic carbon, dissolved organic nitrogen, and aroma index following nitrogen addition, while the humification index increased significantly, microbial enzyme activities increased first and then decreased with the increases of nitrogen addition. Fourier transform infrared spectroscopy results showed that soil DOM had similar absorption peaks in seven regions, and that the absorption peaks of 1000 to 1260 cm-1 were the strongest, indicating an enhanced amount of polysaccharides, alcohols, carboxyl acids, and esters after nitrogen addition. The results of three-dimensional fluorescence spectroscopy showed that soil DOM structure significantly changed following nitrogen addition, with a decrease in low-molecular substances such as protein-like substances and microbial metabolites and a significant increase in high-molecular substances such as humus-like substances. In general, nitrogen addition made soil nitrogen compatible with microbial requirements. Microorganisms decompose substances that were easily degraded in DOM. The structure of soil DOM was more complex after nitrogen addition. Therefore, short-term nitrogen deposition might be conducive to preserving soil fertility.

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The interaction between graphene oxide-sliver nanocomposites (GO-AgNCPs) and bovine serum albumin (BSA) in aqueous buffer solution was investigated by using several spectroscopic and imaging techniques. The visible absorbance intensity of GO-AgNCPs increased with increasing concentrations of BSA, and a slight redshift of the surface plasmon resonance band (SPR) occurred due to the absorption of BSA on the surface of GO-AgNCPs. Fluorescence data revealed a static quenching process of BSA caused by GO-AgNCPs. Thermodynamic parameters of the absorption process, including adsorption equilibrium constants, changes in Gibbs free energy (ΔG), enthalpy (ΔH) and entropy (ΔS), were evaluated at different temperatures. Negative values of ΔG showed that this process was spontaneous and the BSA-GO-AgNCPs complex might form in aqueous solution. Negative values of ΔH and ΔS suggested that the binding was mainly an enthalpy-driven process, and van der Waals forces and hydrogen bonding were the major force in the formation of the nanoparticle-protein corona. Analysis of synchronous, three dimensional (3D) fluorescence and circular dichroism (CD) spectra demonstrated that the conformation of BSA was slightly altered in the presence of GO-AgNCPs. The protein corona formed on the surface of GO-AgNCPs was directly observed by scanning probe microscopy (SPM).

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The interactions of triangular silver nanoprisms (TAgNPrs) with bovine serum albumin (BSA) were investigated using multiple spectroscopic techniques. A noticeable absorbance increase was noted in the peak ranges of 250 to 300 nm for BSA, and the intensity increased with the increasing concentration of TAgNPrs. Furthermore, a slight blue shift of the surface plasmon resonance band of TAgNPrs occurred, indicating that the protein absorbed on the TAgNPrs surface to form a bio-nano interface. Analysis of fluorescence quenching data using the Stern-Volmer method revealed that static quenching takes place with complex formation. Evaluation of thermodynamic parameter ΔG θ for the binding processes indicated that the binding reaction was exothermic. Furthermore, the values of binding constant K revealed that the size of nanoparticles can affect the binding degree. The order of binding affinity is 43.7 nm > 36.2 nm > 25.1 nm. The competitive experiments of site markers (flufenamic acid and phenylbutazone) suggested that the binding site of TAgNPrs on BSA was located in the region of subdomain IIIA (Sudlow site II). In addition, the conformational changes of BSA by TAgNPrs were analyzed by using synchronous fluorescence spectra, circular dichroism, and three-dimensional fluorescence spectra. Graphical abstract The protein absorbed on the TAgNPrs surface to form a nanoparticle-protein corona.

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An increasing amount of bisphenol A (BPA) is being produced and used, then discharged into sewage treatment plants and accumulated in sludge or soil, when the sludge is used as fertilizer. Accumulation of BPA in sludge or soil causes poisoning to the enzyme, which affects the biological treatment of sludge and the circulation and conversion of materials in soil. In this research, effect of BPA on sludge hydrolysis is studied from the respect of concentration and components of soluble organic matter in sludge, using three-dimensional fluorescence spectra. In order to illuminate the interaction mechanism, toxic effect of BPA on α-Amylase (a model of hydrolase in sludge) is investigated with multi-spectra, isothermal titration microcalorimetry and molecule docking at the molecular level. Results show that the secondary structure of α-Amylase and the microenvironment of amino acid residue in α-Amylase are changed. The molecular docking study and ITC results show that hydrophobic bond and hydrogen bond exist in the interaction between BPA and α-Amylase. Based on the above analysis and enzyme activity assay, sludge hydrolysis is inhibited due to the denaturation of α-Amylase with BPA exposure.

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An increasing amount of heavy metals (e.g., Cu2+) is being discharged into sewage treatment plants and is accumulating in sludge, which is toxic to the enzyme in sludge or soil when the sludge is used as fertilizer, resulting in unfavorable effect on the biological treatment of sludge and the circulation and conversion of materials in soil. In this research, effect of Cu2+ on sludge hydrolysis by α-amylase is studied from the respect of concentration and components of soluble organic matter in sludge, using three-dimensional fluorescence spectra. Results show that Cu2+ exposure not only inhibits the hydrolysis of sludge due to the denaturation of α-amylase but also affects the components of soluble organic matter in sludge. In order to illuminate the interaction mechanism between Cu2+ and α-amylase (a model of hydrolase in sludge), multi-spectra and isothermal titration microcalorimetry techniques are applied. Results show that the secondary structure of α-amylase is changed as that the α-helical content increases and the structure loosens. The microenvironment of amino acid residue in α-amylase is changed that the hydrophobicity decreases and the polarity increases with Cu2+ exposure. Isothermal titration calorimetry results show that Van der Waals force and hydrogen bond exist in the interaction between Cu2+ and α-amylase. Results from this research would favor the development of advanced process for the biological treatment of sludge containing heavy metals.

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Sewage sludge, as a very significant sources of BPS (up to 523mg/kg dw) introduction into the environment, must be handled properly. Therefore, it is important to access BPS removal and its effect on sludge treatment with the biological treatment. However, it is unclear for its effect on the hydrolysis of sludge. In this research, impact of BPS on sludge hydrolysis by α-Amylase is studied from the respect of component of soluble organic matter in sludge using three-dimensional fluorescence spectra. Enzyme activity assay suggests that sludge hydrolysis is inhibited due to the denaturation of α-Amylase with BPS exposure. In order to illuminate the interaction mechanism between BPS and α-Amylase, UV-vis, steady-state fluorescence, circular dichroism, synchronous fluorescence, light scattering spectra, enzyme activity assay and molecule docking techniques are applied. Results show that BPS interacts with α-Amylase by hydrophobic bond in the activity region of α-Amylase. This interaction not only causes an unfolding skeleton structure of α-Amylase and a less hydrophobic microenvironment of tyrosine and tryptophan residues, but also leads to a specific fluorophore quenching involving static and dynamic type. This work provides direct evidence about enzyme toxicity of BPS and establishes a new strategy to investigate the interaction between protein and BPS at a molecular level, which is helpful for clarifying the bioactivities of BPS.

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To study the effects of nitrogen deposition on the concentration and spectral characteristics of dissolved organic matter (DOM) in the forest soil solution from the subtropical Cunninghamia lanceolata plantation, using negative pressure sampling method, the dynamics of DOM in soil solutions from 0-15 and 15-30 cm soil layer was monitored for two years and the spectroscopic features of DOM were analyzed. The results showed that nitrogen deposition significantly reduced the concentration of dissolved organic carbon (DOC), and increased the aromatic index (AI) and the humic index (HIX), but had no significant effect on dissolved organic nitrogen (DON) concentration in both soil layers. There was obvious seasonal variation in DOM concentration of the soil solution, which was prominently higher in summer and autumn than in spring and winter.Fourier-transform infrared (FTIR) absorption spectrometry indicated that the DOM in forest soil solution had absorption peaks in the similar position of six regions, being the highest in wave number of 1145-1149 cm-1. Three-dimensional fluorescence spectra indicated that DOM was mainly consisted of protein-like substances (Ex/Em=230 nm/300 nm) and microbial degradation products (Ex/Em=275 nm/300 nm). The availability of protein-like substances from 0-15 cm soil layer was reduced in the nitrogen treatments. Nitrogen deposition significantly reduced the concentration of DOC in soil solution, maybe largely by reducing soil pH, inhibiting soil carbon mineralization and stimulating plant growth. In particular, the decline of DOC concentration in the surface layer was due to the production inhibition of the protein-like substances and carboxylic acids. Short-term nitrogen deposition might be beneficial to the maintenance of soil fertility, while the long-term accumulation of nitrogen deposition might lead to the hard utilization of soil nutrients.

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Edible blended vegetable oils are made from two or more refined oils. Blended oils can provide a wider range of essential fatty acids than single vegetable oils, which helps support good nutrition. Nutritional components in blended oils are related to the type and content of vegetable oils used, and a new, more accurate, method is proposed to identify and quantify the vegetable oils present using cluster analysis and a Quasi-Monte Carlo integral. Three-dimensional fluorescence spectra were obtained at 250-400nm (excitation) and 260-750nm (emission). Mixtures of sunflower, soybean and peanut oils were used as typical examples to validate the effectiveness of the method.

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Removal of conventional pollutants as well as genotoxicity was studied along a multistage A/O process, which was based on the monitoring data in a Municipal Wastewater Treatment Plant (MWWTP) of Yixing City. The results showed that the multistage A/O process removed (67.3±7.0)% of COD, (93.7±1.5)% of NH4+-N, (65.3±7.9)% of TN and (60.0±18.7)% of TP, respectively, which played a dominant role in the removal performance of the whole wastewater treatment process. The multistage A/O process showed significant ability to reduce alkanes, halogenated hydrocarbons and alcohols in the municipal wastewater, while it failed to remove the aromatic proteins which were the main fluorescent substances of this wastewater. Furthermore, the process removed 82.8% genotoxicity from its influent. Low organic load, single-phase influent and undesirable carbon source feeding pattern, which caused the downstream A/O stages being not fully utilized, were considered as the predominant reasons for the relatively low performance of the multistage A/O process. Multi-phase feeding and adjusting carbon source feeding pattern were thereby proposed. The results were considered to be helpful for improving the operational performance of the MWWTP and useful for performance evaluation of MWWTPs with similar process.

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Rayleigh and Raman scatterings inevitably appear in fluorescence measurements, which make the quantitative analysis more difficult, especially in the overlap of target signals and scattering signals. Based on the grayscale images of three-dimensional fluorescence spectra, the linear model with two selected Zernike moments was established for the determination of humic acid, and applied to the quantitative analysis of the real sample taken from the Yellow River. The correlation coefficient (R(2)) and leave-one-out cross validation correlation coefficient (R(2)cv) were up to 0.9994 and 0.9987, respectively. The average recoveries were reached 96.28%. Compared with N-way partial least square and alternating trilinear decomposition methods, our approach was immune from the scattering and noise signals owing to its powerful multi-resolution characteristic and the obtained results were more reliable and accurate, which could be applied in food analyses.

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To rapidly and efficiently detect the presence of adulterants in honey, three-dimensional fluorescence spectroscopy (3DFS) technique was employed with the help of multivariate calibration. The data of 3D fluorescence spectra were compressed using characteristic extraction and the principal component analysis (PCA). Then, partial least squares (PLS) and back propagation neural network (BP-ANN) algorithms were used for modeling. The model was optimized by cross validation, and its performance was evaluated according to root mean square error of prediction (RMSEP) and correlation coefficient (R) in prediction set. The results showed that BP-ANN model was superior to PLS models, and the optimum prediction results of the mixed group (sunflower±longan±buckwheat±rape) model were achieved as follow: RMSEP=0.0235 and R=0.9787 in the prediction set. The study demonstrated that the 3D fluorescence spectroscopy technique combined with multivariate calibration has high potential in rapid, nondestructive, and accurate quantitative analysis of honey adulteration.

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Mercury is a significant environmental pollutant that originates from industry. Mercury will bind with albumin and destroy biological functions in humans if it enters the blood. In this paper, the interaction between mercury (II) and bovine serum albumin (BSA) was investigated in vitro by fluorescence, UV-Vis absorption and circular dichroism (CD) under simulated physiological conditions. This study proves that the probable quenching mechanism of BSA by mercury (II) was mainly static quenching due to the formation of a mercury (II)-BSA complex. The quenching constant K(a) and the corresponding thermodynamic parameters (ΔH, ΔS and ΔG) at four different temperatures were calculated by a modified Stern-Volmer equation and the van't Hoff equation, respectively. The results revealed that the interaction between mercury (II) and BSA was mainly enthalpy-driven and that hydrogen bonding and van der Waals forces played a major role in the reaction. The obtained data for binding sites of n approximately equal to 1 indicated that there was a single class of binding site for the BSA with mercury (II). The value of the distance r (3.55 nm), determined by Föster's non-radioactive energy transfer theory, suggested that the energy transfer from BSA to mercury (II) occurred with a high probability. The conformational investigation from synchronous fluorescence, CD spectroscopy and three-dimensional fluorescence showed that the presence of mercury (II) resulted in micro-environmental and conformational changes of the BSA molecules, which may be responsible for the toxicity of mercury (II) in vivo.

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Fluorescence spectroscopy is a rapid and non-destructive method for monitoring water quality. In this work, wavelet analysis, together with independent component analysis (ICA), was applied for component recognition of seriously overlapped, multi-component, three dimensional fluorescence spectra. Wavelet analysis extracts the features of the spectra and amplifies differences among phenolic homologs. ICA analysis in blind signal separation was used to separate single component before multiple linear regression (MLR). The proposed method increases the correct classification rate and enriches the spectra library. As such, it is a useful alternative to traditional techniques in component recognition.

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