Three-dimensional Fluorescence Spectra Research Articles

Enhancing anaerobic digestion of waste activated sludge by dielectric barrier discharge pretreatment: Nutrient release, sludge hydrolysis and microbial community succession

A dielectric barrier discharge (DBD) pretreatment of waste activated sludge (WAS) was developed for boosting the releasing of organic matter from floc structures and microbial cells. The changes of protein and polysaccharide in different extracellular polymeric substances layers of SCOD releasing from sludge were determined by using three-dimensional fluorescence spectra. Significantly improved cumulative methane production was achieved via enhancing anaerobic digestion, which was 83.5% higher than that of the control. The formed ∙OH radicals play a key role in sludge hydrolysis, thus improving the biodegradability of WAS. Furthermore, high-throughput sequencing analysis showed that DBD pretreatment improved the relative abundances of the main functional microbes with respect to sludge hydrolysis and anaerobic digestion. Therefore, this study verifies the feasibility of DBD pretreatment in sludge hydrolysis and is expected to provide a practical new technology for anaerobic digestion of WAS.

Noninvasive detection of diabetes mellitus based on skin fluorescence and diffuse reflectance spectroscopy.

There is an urgent need for a mass population screening tool for diabetes. Skin tissue contains a large number of endogenous fluorophores and physiological parameter markers related to diabetes. We built an excitation-emission spectrum measurement system with the excited light sources of 365, 395, 415, 430, and 455 nm to extract skin characteristics. The modeling experiment was carried out to design and verify the accuracy of the recovery of tissue intrinsic discrete three-dimensional fluorescence spectrum. Blood oxygen modeling experiment results indicated the accuracy of the physiological parameter extraction algorithm based on the diffuse reflectance spectrum. A community population cohort study was carried out. The tissue-reduced scattering coefficient and scattering power of the diabetes were significantly higher than normal control groups. The Gaussian multi-peak fitting was performed on each excitation-emission spectrum of the subject. A total of 63 fluorescence features containing information such as Gaussian spectral curve intensity, central wavelength position, and variance were obtained from each person. Logistic regression was used to construct the diabetes screening model. The results showed that the area under the receiver operating characteristic curve of the model for predicting diabetes was 0.816, indicating a high diagnostic value. As a rapid and non-invasive detection method, it is expected to have high clinical value.

Design, synthesis, biological evaluation, and docking study of new triazole-phenylacetamide derivatives as α-glucosidase inhibitors

To discover potent α-glucosidase inhibitors, a class of novel triazole-phenylacetamide derivatives (5a-5p) were designed, prepared, and tested for their α-glucosidase inhibitory effects. All tested compounds (5a-5p) displayed a strong α-glucosidase inhibitory activity (IC50 = 6.69 ± 0.18–113.65 ± 2.94 μM) in comparison with the positive control acarbose (IC50 = 723.06 ± 11.26 μM). Thereinto, 5g (IC50 = 6.69 ± 0.18 μM) showed the best anti-α-glucosidase activity and behaved as a mixed-type inhibitor with the value of Ki and Kis to be 1.65 μM and 4.54 μM, respectively. Besides, fluorescence quenching experiment, three-dimensional fluorescence spectra assay, circular dichroism analysis, and molecular docking studies indicated that 5g may inhibit α-glucosidase activity by binding with its active site as well as changing the secondary structure of α-glucosidase. Combined with the inhibition effect on the rise of postprandial blood glucose level and low cytotoxicity of 5g, it could be concluded that these title compounds may play a role as lead compounds to develop novel α-glucosidase inhibitors.

Study on the Migration and Transformation of Nitrogen in Mine Water under the Action of Water–Coal Interactions

The coal pillar dam of underground reservoirs and residual coal in goaves have a direct impact on the quality of mine water. In this paper, the coal pillar dam of an underground reservoir and residual coal in the goaf and mine water in the Daliuta coal mine are used as research objects. The adsorption mechanism of residual coal with respect to NO3− in mine water was analyzed by carrying out adsorption experiments. The composition and variation of organic matter in mine water at different times were simulated using three-dimensional fluorescence spectrum analysis. The influence of residual coal and microorganisms in underground reservoirs on the change in NO3− contents in mine water was explored. Moreover, the mechanism of NO3− changes in the water body was clarified. The results showed that the concentration of NO3− in the water first decreased and then increased, showing a downward trend as a whole. The adsorption of NO3− by residual coal led to a decrease in its concentration, which conformed to a pseudo-second-order kinetic model and Freundlich isothermal adsorption model, indicating that the adsorption process of NO3− by residual coal is mainly carried out via chemical adsorption and multi-layer adsorption. The increase in NO3− concentration was caused by the hydrolysis of tryptophan and other protein-like substances in the water into nitrate under the action of microorganisms.

Surface microrelief induced by tillage management alters the pathway and composition of dissolved organic matter exports from soils to runoff during rainfall

Rainfall-runoff process mobilizes considerable dissolved organic matter (DOM) from soils to aquatic systems via surface and sub-surface flow pathways. Microrelief induced by tillage management can alter this flow partitioning and thus likely affect the associated pathway and composition of DOM exports during rainfall. This study conducted rainfall simulation experiments, combined with three-dimensional fluorescence spectra analysis and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) technology, to explore the effects of different surface microreliefs treatments on the quantity and composition of DOM exports at a plot scale. Four typical microrelief treatments (i.e., contour tillage (CP), longitudinal tillage (LP), artificial digging tillage (AP), and flat tillage (CK, as control)) were selected. Results showed that ratios of surface to sub-surface flow volume under four treatments were in order of LP (193:1)>CK (73:1)>AP (4.5:1)>CP (0.5:1). DOM concentrations in sub-surface flow (13.37∼33.50 mg L-1) were 7∼18 times of that in surface flow (0.03∼4.56 mg L-1). The total export fluxes of DOM were 134, 139, 563, and 1214 mg m-2 at LP, CK, AP, and CP treatments, respectively, with proportions of 8%, 17%, 82%, and 98% via sub-surface flow. Compared to surface flow, DOM molecular composition in sub-surface flow showed a significant feature of higher oxygen to carbon ratio, higher molecular weight, and lower hydrogen to carbon ratio. The findings indicated that microrelief with higher surface storage capacity tends to favor a large flux of DOM export, primarily via sub-surface flow, which might significantly affect the DOM cycling in the receiving aquatic ecosystems.

Combined effects of arsenate and benzene on Microcystis aeruginosa growth and arsenic metabolism

To comprehensively understand the ecological risks of the coexistence of organic pollutants benzene and inorganic arsenate (As(V)) in the aquatic environment, Microcystis aeruginosa, one of the dominant algal species in eutrophic waters, was taken as the experimental alga to explore their growth response, arsenic (As) metabolism and the dissolved organic matter (DOM) changes in water under individual and combined pollution for benzene and As, respectively. The results showed that the algal cells of M. aeruginosa could proliferate normally. No significant differences were found among treatments after 96 h exposure to benzene and As(V) individual or combined. Intracellular As(V) accumulation was the main metabolism path for this alga and was significantly correlated to As(V) concentration but not benzene in the environment under different treatments. Benzene could promote As accumulation in algae and the total As metabolism amount in an individual algal cell at low As(V) levels. Meanwhile, only low benzene concentration showed As accumulation promotion at high As(V) levels. Microcystins (MCs) release in media affected by As(V) was different with benzene concentrations. There were no significant differences of UV254 in media among different treatments which represented macromolecular organic matters and aromatic compounds containing CC and CO bonds. Total organic carbon (TOC) was relatively higher in benzene media than in other treatments. The infrared spectrum characteristics of dissolved organic matter (DOM) confirmed that benzene was degraded and converted obviously at high levels in media by algal cells. Meanwhile, the three-dimensional fluorescence spectrum analysis showed that benzene in media could restrict proteins released in DOM caused by algae cells. The results are of great significance to the application of microalgae in water bioremediation and the comprehensive understanding of the ecological effects and risks in aquatic ecosystems.

Discovery and experimental verification of the spectral characteristics at different growth stages of Aurelia

Under the dual pressure of human activities and global changes, jellyfish outbreaks have occurred frequently in China's offshore waters in recent years, with serious impacts on marine fisheries, coastal tourism, marine ecology and cooling water systems for coastal industries. In order to accurately identify the origin of Aurelia and to be more proactive in the prevention and control of Aurelia outbreaks, this article proposed the use of ultraviolet (UV) and fluorescence spectroscopy to detect the polyps, ephyrae and larvae of Aurelia at different growth stages. The AvaSpec-2048 UV visible fibre spectrometer and the F-7000 fluorescence spectrophotometer were used to focus on studying the UV absorption spectrum and three-dimensional fluorescence spectrum of the polyps, ephyrae, and larvae of Aurelia cultured under laboratory conditions. The research results showed that the three-dimensional fluorescence spectrum of the three different growth stages of Aurelia, namely polyps, ephyrae and larvae of Aurelia, had relatively similar fluorescence distributions, and the fluorescence intensity was different from each other. However, the absorption peaks of the three UV absorption spectrum appeared in different UV light bands and there were absorption peaks of different intensities. The different spectral characteristics at different growth stages of Aurelia provide new ideas and methods for exploring the birthplace of Aurelia.

Synthesis, Anti-Tyrosinase Activity, and Spectroscopic Inhibition Mechanism of Cinnamic Acid-Eugenol Esters.

Tyrosinase plays crucial roles in mediating the production of melanin pigment; thus, its inhibitors could be useful in preventing melanin-related diseases. To find potential tyrosinase inhibitors, a series of cinnamic acid-eugenol esters (c1~c29) was synthesized and their chemical structures were confirmed by 1H NMR, 13C NMR, HRMS, and FT-IR, respectively. The biological evaluation results showed that all compounds c1~c29 exhibited definite tyrosinase inhibitory activity; especially, compound c27 was the strongest tyrosinase inhibitor (IC50: 3.07 ± 0.26 μM), being ~4.6-fold stronger than the positive control, kojic acid (IC50: 14.15 ± 0.46 μM). Inhibition kinetic studies validated compound c27 as a reversible mixed-type inhibitor against tyrosinase. Three-dimensional fluorescence and circular dichroism (CD) spectra results indicated that compound c27 could change the conformation and secondary structure of tyrosinase. Fluorescence-quenching results showed that compound c27 quenched tyrosinase fluorescence in the static manner with one binding site. Molecular docking results also revealed the binding interactions between compound c27 and tyrosinase. Therefore, cinnamic acid-eugenol esters, especially c27, could be used as lead compounds to find potential tyrosinase inhibitors.

Novel insights into the mechanisms for Sb mobilization in groundwater in a mining area: A colloid field study

Colloids may play an important role in the geochemical cycle of antimony (Sb). However, the controlling behaviors of colloids on Sb fate in contaminated groundwater are not available. To investigate the effects of colloids on Sb mobility, groundwater samples from Xikuangshan Sb Mine's two main aquifers (the D3s2 aquifer and the D3x4 aquifer) were successively (ultra)filtered through progressively decreasing pore sizes (0.45 µm, 100 kDa, 50 kDa and 5 kDa). The results showed that 0.1–84.1% of Sb was adsorbed or carried by colloids, which corresponded to Sb concentration ranging between 0 and 2973 μg/L in the colloids (0.45 µm - 5 kDa). In both aquifers, Sb was closely associated with organic colloids (r = 0.72 p < 0.05 for the D3x4 aquifer, r = 0.94 p < 0.01 for the D3s2 aquifer). Parallel factor analysis of the three-dimensional fluorescence spectra determined that the protein-like substances in the D3x4 aquifer and the humus-like substances in the D3s2 aquifer controlled Sb behavior. X-ray absorption spectroscopy confirmed Sb complexing with organic substances. Competitive adsorption of As and Sb suppressed the complexation of colloids with Sb, particularly in the D3x4 aquifer (r = –0.71, p < 0.05). Sb mobility was also influenced by the redox of the groundwater system. As the oxidation-reduction potential and dissolved oxygen increased, Sb in the colloidal fractions decreased. These findings provide new insights into the mechanisms involved in Sb fate affected by colloids, establishing the theoretical basis for developing effective Sb and even metalloid pollution remediation strategies.

Dissolved organic matter evolution and straw decomposition rate characterization under different water and fertilizer conditions based on three-dimensional fluorescence spectrum and deep learning

Straw returning is a sustainable way to utilize agricultural solid waste resources. However, incomplete decomposition of straw will cause harm to crop growth and soil quality. Currently, there is a lack of technology to timely monitor the rate of straw decomposition. Dissolved organic matter (DOM) is the most active organic matter in soil and straw is mainly immersed in the soil in the form of DOM. In order to formulate reasonable straw returning management measures , a timely monitoring method of straw decomposition rate was developed in the study. Three water treatment (60%–65%, 70%–75% and 80%–85% maximum field capacity) and two fertilizer (organic fertilizer and chemical fertilizer) were set up in the management of straw returning to the field. Litterbag method was used to monitor the weight loss rate of straw decomposition under different water and fertilizer conditions in strawberry growth stage. The changes of DOM components were determined by three-dimensional fluorescence spectroscopy (3D-EEM). From the faster decomposition period to the slower decomposition period, the main components of DOM changed from protein-like components to humus-like components. At the end of the experiment, the relative content of humus-like components under the treatment of organic fertilizer and moderate water was the highest. Convolutional neural network (CNN) combined with 3D-EEM was used to identify the decomposition speed of straw. The classification precision of neural network validation set and test are 85.7% and 81.2%, respectively. In order to predict the decomposition rate of straw under different water and fertilizer conditions, 3D-EEM data of DOM were used as the input of CNN, parallel factor analysis (PARAFAC) and fluorescence region integral (FRI), and dissolved organic carbon data were used as the input of dissolved organic carbon linear prediction. The prediction model based on CNN had the best effect (R2 = 0.987). The results show that this method can effectively identify the spectral characteristics and predict the decomposition rate of straw under different conditions of water and fertilizer, which is helpful to promote the efficient decomposition of straw.

Inhibiting mechanisms of metal ion complexation on photogenerated reactive intermediates derived from dissolved black carbon

Dissolved black carbon (DBC), an important photosensitizer in surface waters, can influence the photodegradation of various organic micropollutants. In natural water systems, DBC often co-occurs with metal ions as DBC–metal ion complexes; however, the influence of metal ion complexation on the photochemical activity of DBC is still unclear. Herein, the effects of metal ion complexation were investigated using common metal ions (Mn2+, Cr3+, Cu2+, Fe3+, Zn2+, Al3+, Ca2+, and Mg2+). Complexation constants (logKM) derived from three-dimensional fluorescence spectra revealed that Mn2+, Cr3+, Cu2+, Fe3+, Zn2+, and Al3+ quenched the fluorescence components of DBC via static quenching. The steady-state radical experiment suggested that in the complex systems of DBC with various metal ions, Mn2+, Cr3+, Cu2+, Fe3+, Zn2+ and Al3+ inhibited the photogeneration of 3DBC* via dynamic quenching, which reduced the yields of 3DBC*-derived 1O2 and O2·-. Moreover, 3DBC* quenching by metal ions was associated with the complexation constant. A strong positive linear relationship existed between logKM and the dynamic quenching rate constant of metal ions. These results indicate that the strong complexation ability of metal ions enabled 3DBC quenching, which highlights the photochemical activity of DBC in natural aquatic environments enriched with metal ions.

Pyrolysis temperature dependent effects of biochar on shifting fluorescence spectrum characteristics of soil dissolved organic matter under warming

Biochar generally shift the content and molecular composition of soil dissolved organic matter (DOM) which represent the reactive components and have essential roles in coupling elemental cycling in soil. However, it is not clear how the effects of biochar on soil DOM composition is shifted under warming. This causes a knowledge gap to fully understand the fate of SOM affected by biochar application in a warming climate. To fill this gap, we conducted a simulated climate warming incubation of soil to study the influence of biochar with different pyrolysis temperatures and feedstock types on soil DOM components composition. Three-dimensional fluorescence spectrum analysis combining excitation emission matrix-parallel factor analysis (EEM-PARAFAC), fluorescence region integral (FRI), UV–vis spectrometry, principal component analysis (PCA), clustering analysis, Pearson correlation and multi-factor analysis of variance on fluorescence parameters (including FRI on Region I-V, FI, HIX, BIX, H/P) and soil DOC and DON content were analyzed for this purpose. Results showed that biochar shifted soil DOM composition and enhanced soil humification, which was dominantly pyrolysis-temperature dependent. Biochar shifted the soil DOM components composition probably through mediating soil microbial processing rather than direct input of their pristine DOM, and the influence of biochar on soil microbial processing was pyrolysis-temperature dependent and highly affected by warming. Medium-temperature biochar was more efficient for enhancing soil humification, by accelerating the transformation of protein-like components into humic-like components. Soil DOM composition presented a rapid response to warming, and long-term incubation may eliminate the effects of warming on shifting soil DOM composition. By revealing the heterogeneous effects of biochar with different pyrolysis temperatures on fluorescence characteristics of soil DOM components, our study provides a hint for the essential role of biochar on enhancing soil humification, and also suggests a vulnerability of biochar for soil carbon sequestration under warming.

Luminescence Characteristics of Green Grossular Garnets

Some light green grossular garnets exhibit orange-red luminescence under long-wave and short-wave ultraviolet light. To characterize their luminescence behavior, we studied seven grossular garnets with typical colors ranging from light yellowish-green to intense green by using photoluminescence (PL), ultraviolet–visible (UV–Vis) spectroscopy, electron paramagnetic resonance (EPR), Electron Probe Microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). In the PL spectra of these grossular garnets samples, a broad band exists at about 589 nm and three sharp peaks appear at 697, 702 and 716 nm. The three-dimensional fluorescence spectra reveal two luminescence emissions. They are (1) a broad band near 600 nm; and (2) a series of sharp peaks centered at 697, 702 and 716 nm. In the UV–Vis spectra, two prominent asymmetrical absorption bands near 430 and 605 nm are related to Cr3+ or Cr3+/V3+, and minor absorption peaks at 408 and 419/420 nm are related to Mn2+. EMPA and LA-ICP-MS analysis confirmed the existence of trace elements Ti, V, Cr and Mn. Furthermore, the EPR spectrum excluded the existence of V2+ and V4+ and confirmed the existence of Mn2+, Cr3+ and Fe3+. Regarding V, an interesting phenomenon was reported in which the intensity of luminescence could be suppressed in grossular garnets with higher concentrations of V. These results imply that chromium and manganese are the luminescence activators in grossular garnets, and vanadium is a powerful quencher.

Nicosulfuron on the Atrazine-degrading Arthrobacter sp. DNS10 by assays of intracellular accumulation of substrates, Zeta potential, EPS, and stress responses

Atrazine is often formulated with nicosulfuron as a commercial herbicide to enhance the weed control effect, however, the effect of nicosulfuron on the degradation of atrazine-degrading strain Arthrobacter sp. DNS10 was still unclear. In this study, the accumulation of atrazine in Arthrobacter sp. DNS10, as well as the cell surface characteristics (Zeta potential and extracellular polymers constitution) and antioxidant enzyme activity at different concentrations of nicosulfuron exposure for 48 h were measured. The results showed that the quantity of atrazine accumulation in strain DNS10 and the Zeta potential on strain cell surface were increased when nicosulfuron exposure level was increased. Three-dimensional fluorescence spectrum analysis found that nicosulfuron exposure could quench the peaks which represent the aromatic protein substances and soluble microbial metabolites in EPS of strain DNS10 In addition, the co-existed nicosulfuron could positively induce the activity of antioxidant enzymes (SOD and CAT) and malondialdehyde content, and also induce cell damage. This work proposes the mechanism by which nicosulfuron inhibits the biodegradation of atrazine, which is of great significance for improving the bioremediation of mixed herbicide contamination.

Identification of Oak-Barrel and Stainless Steel Tanks with Oak Chips Aged Wines in Ningxia Based on Three-Dimensional Fluorescence Spectroscopy Combined with Chemometrics.

With the increased incidence of wine fraud, a fast and reliable method for wine certification has become a necessary prerequisite for the vigorous development of the global wine industry. In this study, a classification strategy based on three-dimensional fluorescence spectroscopy combined with chemometrics was proposed for oak-barrel and stainless steel tanks with oak chips aged wines. Principal component analysis (PCA), partial least squares analysis (PLS-DA), and Fisher discriminant analysis (FDA) were used to distinguish and evaluate the data matrix of the three-dimensional fluorescence spectra of wines. The results showed that FDA was superior to PCA and PLS-DA in classifying oak-barrel and stainless steel tanks with oak chips aged wines. As a general conclusion, three-dimensional fluorescence spectroscopy can provide valuable fingerprint information for the identification of oak-barrel and stainless steel tanks with oak chips aged wines, while the study will provide some theoretical references and standards for the quality control and quality assessment of oak-barrel aged wines.

Synthesis of sulfur-chlorine-doped fluorescent carbon quantum dots from leachate membrane concentrate as a selective probe for Pd2+ detection

In this work, humic acid-based sulfur-chlorine-doped carbon quantum dots (L-CQDs) were synthesized by using a polyethylene glycol (PEG)-assisted hydrothermal technique using landfill leachate concentrate (LLC) as a carbon source. The prepared L-CQDs contain many oxygen-containing functional groups on the surface with a small average particle size of 4–6 nm, resulting in excellent hydrophilicity and dispensability. The three-dimensional fluorescence spectrum shows that the characteristic peak for humic acid for LLC is redshifted after adding PEG as an inactivator, indicating that L-CQDs are synthesized by PEG encapsulation and linkage. The optimum condition for preparing L-CQDs involves the addition of 0.5 g PEG (MW = 2000) into 20 mL LLC and reaction at 200 °C for 5 h, with the optimal L-CQD quantum yield reaching 5.32%. L-CQDs were used to prepare fluorescent nanoprobes for the detection of palladium ions (Pd2+). The obtained nanoprobe shows admirable performance in detecting Pd2+, with high selectivity, excellent water solubility and stability. The fluorescence intensity of the nanoprobe is selectively quenched through static quenching by Pd2+ in the concentration range of 5–40 μmol L−1. This work provides a simple, easy, and fast detection method for Pd2+ and opens up a way for the resource utilization of LLC.

A detection method of typical toxic mixed red tide algae in Qinhuangdao based on three-dimensional fluorescence spectroscopy

Red tides occur every year in the Qinhuangdao sea area of China, including a variety of toxic algae and non-toxic algae. Toxic red tide algae have caused great damage to the marine aquaculture industry in China and seriously endangered human health, but most of non-toxic algae are important bait for marine plankton. Therefore, it is very important to identify the type of mixed red tide algae in Qinhuangdao sea area. In this paper, three-dimensional fluorescence spectroscopy and chemometrics were applied to the identification of typical toxic mixed red tide algae in Qinhuangdao. Firstly, the three-dimensional fluorescence spectrum data of typical mixed red tide algae in Qinhuangdao sea area were measured by f-7000 fluorescence spectrometer, and the contour map of algae samples was obtained. Secondly, the contour spectrum analysis is carried out to find the excitation wavelength of the peak position of the three-dimensional fluorescence spectrum and form the new three-dimensional fluorescence spectrum data selected by the feature interval. Then, the new three-dimensional fluorescence spectrum data are extracted by principal component analysis (PCA). Finally, the feature extraction data and the data without feature extraction are used as the input of the genetic optimization support vector machine (GA-SVM) and particle swarm optimization support vector machine (PSO-SVM) classification models, respectively, to obtain the classification model of mixed red tide algae, and the two feature extraction analysis methods and two classification algorithms are compared. The results show that the classification accuracy of the test set using the principal component feature extraction and GA-SVM classification method is 92.97 %, when the excitation wavelengths are 420 nm, 440 nm, 480 nm, 500 nm and 580 nm, and the emission wavelengths are 650–750 nm. Therefore, it is feasible and effective to apply the three-dimensional fluorescence spectrum characteristics and genetic optimization support vector machine classification method to the identification of toxic mixed red tide algae in Qinhuangdao sea area.

Performance of resin adsorption and ozonation pretreatment in mitigating organic fouling of reverse osmosis membrane

Effective pretreatment of reverse osmosis (RO) influent is of great importance for reducing membrane fouling risks during coking wastewater desalination. In this study, the combined resin adsorption and ozonation pretreatment was investigated on alleviating RO membrane organic fouling. The performance of combined process was compared with only resin adsorption or ozonation, which was evaluated in terms of changes in chemical oxygen demand (COD), ultraviolet-visible index, and three-dimensional excitation-emission matrix fluorescence spectra. RO membrane fouling tests were conducted to examine the effects of pretreatment on flux decline and filtration resistance. The surface morphology and functional groups of membrane before and after fouling was characterized by scanning electron microscopy and infrared spectroscopy. The correlation between major organic matter in the wastewater and normalized RO membrane flux was established via multiple linear regression equations. The results showed that ozonation was more effective in removing COD and fluorescent organics than resin adsorption. Moreover, the combined bifunctional resin adsorption/ozonation unit showed the best performance, with COD and UV254 removal rates of 49.4 % and 88.0 %, respectively. The fluorescence intensity of each component decreased significantly. Meanwhile, the polysaccharide and protein components of the RO membrane fouling layer were effectively reduced by 67.2 % and 80.8 %, respectively. Most importantly, the combined pretreatment substantially reduced the decline in membrane flux and filtration resistance. Meanwhile, the fulvic acid-like organics in the wastewater showed high correlations with normalized membrane flux. The regression equation was beneficial for RO membrane fouling evaluation.

Investigations of the Interaction Mechanism Between Orphenadrine Hydrochloride and Bovine Serum Albumin by Spectroscopic and Voltammetric Techniques.

The interaction of orphenadrine hydrochloride (ORD) with the model protein, bovine serum albumin (BSA), was investigated using a variety of spectroscopic techniques such as steady-state fluorescence, ultraviolet-visible, Fourier transform infrared, 3-D spectroscopy, and electrochemical methods under physiological conditions. Stern-Volmer plots were used to calculate fluorescence quenching at various temperatures. The findings point to a static quenching mechanism between ORD and BSA. At various reaction times, the binding sites (n) and binding constants (K) of ORD to BSA were recorded. Thermodynamic parameters ∆H0, ∆S0 and ∆G0 between ORD and BSA were calculated and reported. The average binding distance (r) between the donor (BSA) and acceptor (ORD) molecules was predicted using Förster's theory. Three-dimensional fluorescence spectra, Fourier transform infrared spectra, and synchronous fluorescence studies all supported the alternations in protein structure following the interaction with ORD. A displacement study using site probes such as warfarin, ibuprofen, and digitoxin confirmed ORD binding at Sudlow's site I of BSA. The effect of common metal ions such as Cu2+, Ni2+, Ca2+, Co2+, and Zn2+ on binding constant values was investigated and reported.

The Influence of Aerated Irrigation on the Evolution of Dissolved Organic Matter Based on Three-Dimensional Fluorescence Spectrum

In order to unravel the effect of aerated irrigation on soil dissolved organic matter (DOM) fluorescence characteristics, and humification degree, a randomized block experiment was conducted with three factors and a two-level design, i.e., two irrigation rates (0.6 and 1.0 times of crop evaporation pan coefficient, W1 and W2), two nitrogen application rates (225 and 300 kg hm−2, N1 and N2), and two aeration rates (15% and 0% in control treatment, A1 and A0). Fluorescence regional integration (FRI) and correlation analysis methods were used to investigate the evolution characteristics of the soil DOM fluorescence spectrum. Under aerated and conventional subsurface irrigation, soil DOM components were dominated by humic acid-like substances, fulvic acid-like substances, tryptophan-like proteins, and supplemented by tyrosine-like proteins and dissolved microbial metabolites. Soil aeration could promote the consumption of soil DOM components under low irrigation rates and accelerate the consumption of soil DOM components under high irrigation rates. The humification index of AI treatments varied from 8.47 to 9.94 during the maturity growth stage of pepper, averagely increased by 31.59% compared with the non-aeration treatment. To sum up, aerated irrigation can promote the depletion of small molecular proteins and accelerate nutrient turnover and the accumulation of big molecular proteins.